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Timestamp:
Apr 15, 2016, 12:03:11 PM (10 years ago)
Author:
Thierry Delisle <tdelisle@…>
Branches:
ADT, aaron-thesis, arm-eh, ast-experimental, cleanup-dtors, ctor, deferred_resn, demangler, enum, forall-pointer-decay, gc_noraii, jacob/cs343-translation, jenkins-sandbox, master, memory, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, pthread-emulation, qualifiedEnum, resolv-new, stuck-waitfor-destruct, with_gc
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29ad0ac
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c5833e8 (diff), 37f0da8 (diff)
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Use the (diff) links above to see all the changes relative to each parent.
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Merge branch 'master' into gc_noraii

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  • doc/refrat/refrat.tex

    rc5833e8 r0f9e4403  
     1%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -*- Mode: Latex -*- %%%%%%%%%%%%%%%%%%%%%%%%%%%%
     2%%
     3%% Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
     4%%
     5%% The contents of this file are covered under the licence agreement in the
     6%% file "LICENCE" distributed with Cforall.
     7%%
     8%% refrat.tex --
     9%%
     10%% Author           : Peter A. Buhr
     11%% Created On       : Wed Apr  6 14:52:25 2016
     12%% Last Modified By : Peter A. Buhr
     13%% Last Modified On : Sat Apr  9 10:19:12 2016
     14%% Update Count     : 8
     15%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     16
    117% requires tex packages: texlive-base texlive-latex-base tex-common texlive-humanities texlive-latex-extra texlive-fonts-recommended
    218
     
    521
    622% Latex packages used in the document.
    7 
    823\usepackage{fullpage,times}
    924\usepackage{xspace}
     
    1126\usepackage{listings}
    1227\usepackage{comment}
    13 \usepackage{latexsym}                                   % \Box
    14 \usepackage{mathptmx}                                   % better math font with "times"
     28\usepackage{latexsym}                                   % \Box
     29\usepackage{mathptmx}                                   % better math font with "times"
    1530\usepackage[pagewise]{lineno}
    1631\renewcommand{\linenumberfont}{\scriptsize\sffamily}
    1732\usepackage[dvips,plainpages=false,pdfpagelabels,pdfpagemode=UseNone,colorlinks=true,pagebackref=true,linkcolor=blue,citecolor=blue,urlcolor=blue,pagebackref=true,breaklinks=true]{hyperref}
    1833\usepackage{breakurl}
    19 \urlstyle{sf}
     34\renewcommand{\UrlFont}{\small\sf}
    2035
    2136%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    2237
    23 % Names used in the document.
    24 
    25 \newcommand{\CFA}{Cforall\xspace}               % set language text name
    26 \newcommand{\CFAA}{C$\forall$\xspace}   % set language symbolic name
    27 \newcommand{\CC}{C\kern-.1em\hbox{+\kern-.25em+}\xspace} % CC symbolic name
    28 \def\c11{ISO/IEC C} % C11 name (cannot have numbers in latex command name)
     38% Bespoke macros used in the document.
     39\input{common}
    2940
    3041%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    3142
    32 % Bespoke macros used in the document.
    33 
    34 \makeatletter
    35 % index macros
    36 \newcommand{\italic}[1]{\emph{\hyperpage{#1}}}
    37 \newcommand{\definition}[1]{\textbf{\hyperpage{#1}}}
    38 \newcommand{\see}[1]{\emph{see} #1}
    39 
    40 % Define some commands that produce formatted index entries suitable for cross-references.
    41 % ``\spec'' produces entries for specifications of entities.  ``\impl'' produces entries for their
    42 % implementations, and ``\use'' for their uses.
    43 
    44 %  \newcommand{\bold}[1]{{\bf #1}}
    45 %  \def\spec{\@bsphack\begingroup
    46 %             \def\protect##1{\string##1\space}\@sanitize
    47 %             \@wrxref{|bold}}
    48 \def\impl{\@bsphack\begingroup
    49           \def\protect##1{\string##1\space}\@sanitize
    50           \@wrxref{|definition}}
    51 \newcommand{\indexcode}[1]{{\lstinline$#1$}}
    52 \def\use{\@bsphack\begingroup
    53          \def\protect##1{\string##1\space}\@sanitize
    54          \@wrxref{|hyperpage}}
    55 \def\@wrxref#1#2{\let\thepage\relax
    56     \xdef\@gtempa{\write\@indexfile{\string
    57     \indexentry{#2@{\lstinline$#2$}#1}{\thepage}}}\endgroup\@gtempa
    58     \if@nobreak \ifvmode\nobreak\fi\fi\@esphack}
    59 %\newcommand{\use}[1]{\index{#1@{\lstinline$#1$}}}
    60 %\newcommand{\impl}[1]{\index{\protect#1@{\lstinline$\protect#1$}|definition}}
    61 
    62 % text inline and lowercase index: \Index{Inline and index text}
    63 % text inline and as-in index: \Index{Inline and Index text}
    64 % text inline but index with different as-is text: \Index[index text]{inline text}
    65 \newcommand{\Index}{\@ifstar\@sIndex\@Index}
    66 \newcommand{\@Index}[2][\@empty]{\lowercase{\def\temp{#2}}#2\ifx#1\@empty\index{\temp}\else\index{#1@{\protect#2}}\fi}
    67 \newcommand{\@sIndex}[2][\@empty]{#2\ifx#1\@empty\index{#2}\else\index{#1@{\protect#2}}\fi}
    68 \makeatother
    69 
    70 % blocks and titles
    71 \newcommand{\define}[1]{\emph{#1\/}\index{#1}}
    72 \newenvironment{rationale}{%
    73   \begin{quotation}\noindent$\Box$\enspace
    74 }{%
    75   \hfill\enspace$\Box$\end{quotation}
    76 }%
    77 \newcommand{\rewrite}{\(\Rightarrow\)}
    78 \newcommand{\rewriterules}{\paragraph{Rewrite Rules}~\par\noindent}
    79 \newcommand{\examples}{\paragraph{Examples}~\par\noindent}
    80 \newcommand{\semantics}{\paragraph{Semantics}~\par\noindent}
    81 \newcommand{\constraints}{\paragraph{Constraints}~\par\noindent}
    82 \newcommand{\predefined}{\paragraph{Predefined Identifiers}~\par\noindent}
    83 
    84 % BNF macros
    85 \def\syntax{\paragraph{Syntax}\trivlist\parindent=.5in\item[\hskip.5in]}
    86 \let\endsyntax=\endtrivlist
    87 \newcommand{\lhs}[1]{\par{\emph{#1:}}\index{#1@{\emph{#1}}|italic}}
    88 \newcommand{\rhs}{\hfil\break\hbox{\hskip1in}}
    89 \newcommand{\oldlhs}[1]{\emph{#1: \ldots}\index{#1@{\emph{#1}}|italic}}
    90 \newcommand{\nonterm}[1]{\emph{#1\/}\index{#1@{\emph{#1}}|italic}}
    91 \newcommand{\opt}{$_{opt}$\ }
    92 
    93 % adjust varioref package with default "section" and "page" titles, and optional title with faraway page numbers
    94 % \VRef{label} => Section 2.7, \VPageref{label} => page 17
    95 % \VRef[Figure]{label} => Figure 3.4, \VPageref{label} => page 17
    96 \renewcommand{\reftextfaceafter}{\unskip}
    97 \renewcommand{\reftextfacebefore}{\unskip}
    98 \renewcommand{\reftextafter}{\unskip}
    99 \renewcommand{\reftextbefore}{\unskip}
    100 \renewcommand{\reftextfaraway}[1]{\unskip, p.~\pageref{#1}}
    101 \renewcommand{\reftextpagerange}[2]{\unskip, pp.~\pageref{#1}--\pageref{#2}}
    102 \newcommand{\VRef}[2][Section]{\ifx#1\@empty\else{#1}\nobreakspace\fi\vref{#2}}
    103 \newcommand{\VPageref}[2][page]{\ifx#1\@empty\else{#1}\nobreakspace\fi\pageref{#2}}
    104 
    105 % adjust listings macros
    106 \lstdefinelanguage{CFA}[ANSI]{C}%
    107 {morekeywords={asm,_Alignas,_Alignof,_At,_Atomic,_Bool,catch,catchResume,choose,_Complex,context,disable,dtype,enable,
    108         fallthru,finally,forall,ftype,_Generic,_Imaginary,inline,lvalue,_Noreturn,restrict,_Static_assert,
    109         _Thread_local,throw,throwResume,try,type,},
    110 }%
    111 
    112 \lstset{
    113 language=CFA,
    114 columns=flexible,
    115 basicstyle=\sf\small,
    116 tabsize=4,
    117 xleftmargin=\parindent,
    118 escapechar=@,
    119 keepspaces=true,
    120 %showtabs=true,
    121 %tab=\rightarrowfill,
    122 }%
    123 
    124 \makeatletter
    125 % replace/adjust listings characters that look bad in sanserif
    126 \lst@CCPutMacro
    127 \lst@ProcessOther{"2D}{\lst@ttfamily{-{}}{{\ttfamily\upshape -}}} % replace minus
    128 \lst@ProcessOther{"3C}{\lst@ttfamily{<}{\texttt{<}}} % replace less than
    129 \lst@ProcessOther{"3E}{\lst@ttfamily{<}{\texttt{>}}} % replace greater than
    130 \lst@ProcessOther{"5E}{\raisebox{0.4ex}{$\scriptstyle\land\,$}} % replace circumflex
    131 \lst@ProcessLetter{"5F}{\lst@ttfamily{\char95}{{\makebox[1.2ex][c]{\rule{1ex}{0.1ex}}}}} % replace underscore
    132 \lst@ProcessOther{"7E}{\raisebox{0.3ex}{$\scriptstyle\sim\,$}} % replace tilde
    133 %\lst@ProcessOther{"7E}{\raisebox{-.4ex}[1ex][0pt]{\textasciitilde}} % lower tilde
    134 \@empty\z@\@empty
    135 \makeatother
    136 
    137 \setcounter{secnumdepth}{3}     % number subsubsections
    138 \setcounter{tocdepth}{3}                % subsubsections in table of contents
     43\setcounter{secnumdepth}{3}                             % number subsubsections
     44\setcounter{tocdepth}{3}                                % subsubsections in table of contents
    13945\makeindex
    14046
     
    14349\begin{document}
    14450\pagestyle{headings}
    145 \linenumbers                                    % comment out to turn off line numbering
    146 
    147 \title{\CFA (\CFAA) Reference Manual and Rationale}
    148 \author{Glen Ditchfield \and Peter A. Buhr}
    149 \date{DRAFT\\\today}
     51\linenumbers                                            % comment out to turn off line numbering
     52
     53\title{\Huge
     54\vspace*{1in}
     55\CFA (\CFL) Reference Manual and Rationale
     56}% title
     57\author{\huge
     58Glen Ditchfield and Peter A. Buhr
     59}% author
     60\date{
     61DRAFT\\\today
     62}% date
    15063
    15164\pagenumbering{roman}
     
    15972\copyright\,2015 Glen Ditchfield \\ \\
    16073\noindent
    161 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a
    162 copy of this license, visit {\small\url{http://creativecommons.org/licenses/by/4.0}}.
     74This work is licensed under the Creative Commons Attribution 4.0 International License.
     75To view a copy of this license, visit {\small\url{http://creativecommons.org/licenses/by/4.0}}.
    16376\vspace*{1in}
    16477
     
    17386\chapter*{Introduction}\addcontentsline{toc}{chapter}{Introduction}
    17487
    175 This document is a reference manual and rationale for \CFA, a polymorphic extension of the C
    176 programming language. It makes frequent reference to the {\c11} standard \cite{ANS:C11}, and
    177 occasionally compares \CFA to {\CC} \cite{c++}.
    178 
    179 The manual deliberately imitates the ordering of the {\c11} standard (although the section numbering
    180 differs). Unfortunately, this means the manual contains more ``forward references'' than usual,
    181 making it harder to follow if the reader does not have a copy of the {\c11} standard. For a simple
    182 introduction to \CFA, see the companion document ``An Overview of \CFA''
     88This document is a reference manual and rationale for \CFA, a polymorphic extension of the C programming language.
     89It makes frequent reference to the {\c11} standard \cite{C11}, and occasionally compares \CFA to {\CC} \cite{C++}.
     90
     91The manual deliberately imitates the ordering of the {\c11} standard (although the section numbering differs).
     92Unfortunately, this means the manual contains more ``forward references'' than usual, making it harder to follow if the reader does not have a copy of the {\c11} standard.
     93For a simple introduction to \CFA, see the companion document ``An Overview of \CFA''
    18394\cite{Ditchfield96:Overview}.
    18495
    18596\begin{rationale}
    186 Commentary (like this) is quoted with quads. Commentary usually deals with subtle points, the
    187 rationale behind a rule, and design decisions.
     97Commentary (like this) is quoted with quads.
     98Commentary usually deals with subtle points, the rationale behind a rule, and design decisions.
    18899\end{rationale}
    189100
     
    194105\chapter{Terms, definitions, and symbols}
    195106
    196 Terms from the {\c11} standard used in this document have the same meaning as in the {\c11}
    197 standard.
     107Terms from the {\c11} standard used in this document have the same meaning as in the {\c11} standard.
    198108
    199109% No ``Conformance'' or ``Environment'' chapters yet.
     
    205115
    206116\section{Notation}
    207 The syntax notation used in this document is the same as in the {\c11} standard, with one exception:
    208 ellipsis in the definition of a nonterminal, as in ``\emph{declaration:} \ldots'', indicates that
    209 these rules extend a previous definition, which occurs in this document or in the {\c11} standard.
     117The syntax notation used in this document is the same as in the {\c11} standard, with one exception: ellipsis in the definition of a nonterminal, as in ``\emph{declaration:} \ldots'', indicates that these rules extend a previous definition, which occurs in this document or in the {\c11} standard.
    210118
    211119
     
    215123\subsection{Scopes of identifiers}\index{scopes}
    216124
    217 \CFA's scope rules differ from C's in one major respect: a declaration of an identifier may
    218 overload\index{overloading} outer declarations of lexically identical identifiers in the same
    219 \Index{name space}, instead of hiding them. The outer declaration is hidden if the two declarations
    220 have \Index{compatible type}, or if one declares an array type and the other declares a pointer type
    221 and the element type and pointed-at type are compatible, or if one has function type and the other
    222 is a pointer to a compatible function type, or if one declaration is a \lstinline$type$\use{type} or
     125\CFA's scope rules differ from C's in one major respect: a declaration of an identifier may overload\index{overloading} outer declarations of lexically identical identifiers in the same
     126\Index{name space}, instead of hiding them.
     127The outer declaration is hidden if the two declarations have \Index{compatible type}, or if one declares an array type and the other declares a pointer type and the element type and pointed-at type are compatible, or if one has function type and the other is a pointer to a compatible function type, or if one declaration is a \lstinline$type$\use{type} or
    223128\lstinline$typedef$\use{typedef} declaration and the other is not.  The outer declaration becomes
    224129\Index{visible} when the scope of the inner declaration terminates.
    225130\begin{rationale}
    226 Hence, a \CFA program can declare an \lstinline$int v$ and a \lstinline$float v$ in the same
    227 scope; a {\CC} program can not.
     131Hence, a \CFA program can declare an \lstinline$int v$ and a \lstinline$float v$ in the same scope;
     132a {\CC} program can not.
    228133\end{rationale}
    229134
     
    232137\index{linkage}
    233138
    234 \CFA's linkage rules differ from C's in only one respect: instances of a particular identifier with
    235 external or internal linkage do not necessarily denote the same object or function. Instead, in the
    236 set of translation units and libraries that constitutes an entire program, any two instances of a
    237 particular identifier with \Index{external linkage} denote the same object or function if they have
    238 \Index{compatible type}s, or if one declares an array type and the other declares a pointer type and
    239 the element type and pointed-at type are compatible, or if one has function type and the other is a
    240 pointer to a compatible function type. Within one translation unit, each instance of an identifier
    241 with \Index{internal linkage} denotes the same object or function in the same circumstances.
     139\CFA's linkage rules differ from C's in only one respect: instances of a particular identifier with external or internal linkage do not necessarily denote the same object or function.
     140Instead, in the set of translation units and libraries that constitutes an entire program, any two instances of a particular identifier with \Index{external linkage} denote the same object or function if they have
     141\Index{compatible type}s, or if one declares an array type and the other declares a pointer type and the element type and pointed-at type are compatible, or if one has function type and the other is a pointer to a compatible function type.
     142Within one translation unit, each instance of an identifier with \Index{internal linkage} denotes the same object or function in the same circumstances.
    242143Identifiers with \Index{no linkage} always denote unique entities.
    243144\begin{rationale}
    244 A \CFA program can declare an \lstinline$extern int v$ and an \lstinline$extern float v$; a C
    245 program cannot.
     145A \CFA program can declare an \lstinline$extern int v$ and an \lstinline$extern float v$;
     146a C program cannot.
    246147\end{rationale}
    247148
     
    253154\subsubsection{Semantics}
    254155
    255 \CFA provides a capability for generic types; using this capability a single "generic type
    256 generator" can be written that can represent multiple concrete type instantiations by substitution
    257 of the "type parameters" of the generic type for concrete types. Syntactically a generic type
    258 generator is represented by putting a forall specifier on a struct or union declaration, as defined
    259 in \VRef{forall}. An instantiation of the generic type is written by specifying the type parameters
    260 in parentheses after the name of the generic type generator:
    261 \begin{lstlisting}
    262 forall( type T | sumable( T ) ) struct pair {
     156\CFA provides a capability for generic types;
     157using this capability a single "generic type generator" can be written that can represent multiple concrete type instantiations by substitution of the "type parameters" of the generic type for concrete types.
     158Syntactically a generic type generator is represented by putting a forall specifier on a struct or union declaration, as defined in \VRef{forall}.
     159An instantiation of the generic type is written by specifying the type parameters in parentheses after the name of the generic type generator:
     160\begin{lstlisting}
     161forall( otype T | sumable( T ) ) struct pair {
    263162        T x;
    264163        T y;
     
    267166\end{lstlisting}
    268167
    269 The type parameters in an instantiation of a generic type must satisfy any constraints in the forall
    270 specifier on the type generator declaration, e.g., \lstinline$sumable$. The instantiation then has
    271 the semantics that would result if the type parameters were substituted into the type generator
    272 declaration by macro substitution.
    273 
    274 Polymorphic functions may have generic types as parameters, and those generic types may use type
    275 parameters of the polymorphic function as type parameters of the generic type:
    276 \begin{lstlisting}
    277 forall( type T ) void swap( pair(T) *p ) {
     168The type parameters in an instantiation of a generic type must satisfy any constraints in the forall specifier on the type generator declaration, e.g., \lstinline$sumable$.
     169The instantiation then has the semantics that would result if the type parameters were substituted into the type generator declaration by macro substitution.
     170
     171Polymorphic functions may have generic types as parameters, and those generic types may use type parameters of the polymorphic function as type parameters of the generic type:
     172\begin{lstlisting}
     173forall( otype T ) void swap( pair(T) *p ) {
    278174        T z = p->x;
    279175        p->x = p->y;
     
    285181\subsubsection{Constraints}
    286182
    287 To avoid unduly constraining implementors, the generic type generator definition must be visible at
    288 any point where it is instantiated.  Forward declarations of generic type generators are not
    289 forbidden, but the definition must be visible to instantiate the generic type.  Equivalently,
    290 instantiations of generic types are not allowed to be incomplete types.
     183To avoid unduly constraining implementors, the generic type generator definition must be visible at any point where it is instantiated.
     184Forward declarations of generic type generators are not forbidden, but the definition must be visible to instantiate the generic type.  Equivalently, instantiations of generic types are not allowed to be incomplete types.
    291185
    292186\examples
    293187\begin{lstlisting}
    294 forall( type T ) struct A;
    295 
    296 forall( type T ) struct B {
    297         A(T) *a;  // legal, but cannot instantiate B(T)
     188forall( otype T ) struct A;
     189
     190forall( otype T ) struct B {
     191        A(T) *a;                        // legal, but cannot instantiate B(T)
    298192};
    299193
    300 B(T) x; // illegal, *x.a is of an incomplete generic type
    301 
    302 forall( type T ) struct A {
     194B(T) x;                                 // illegal, *x.a is of an incomplete generic type
     195 
     196forall( otype T ) struct A {
    303197        B( T ) *b;
    304198};
    305199
    306 B( T ) y; // legal, *x.a is now of a complete generic type
    307 
     200B( T ) y;                               // legal, *x.a is now of a complete generic type
    308201
    309202// box.h:
    310         forall( type T ) struct box;
    311         forall( type T ) box( T ) *make_box( T );
    312         forall( type T ) void use_box( box( T ) *b );
     203        forall( otype T ) struct box;
     204        forall( otype T ) box( T ) *make_box( T );
     205        forall( otype T ) void use_box( box( T ) *b );
    313206       
    314207// main.c:
    315         box( int ) *b = make_box( 42 ); // illegal, def'n of box not visible
    316         use_box( b ); // illegal
     208        box( int ) *b = make_box( 42 ); // illegal, definition of box not visible
     209        use_box( b );           // illegal
    317210\end{lstlisting}
    318211
     
    320213\section{Conversions}
    321214\CFA defines situations where values of one type are automatically converted to another type.
    322 These conversions are called \define{implicit conversion}s. The programmer can request
     215These conversions are called \define{implicit conversion}s.
     216The programmer can request
    323217\define{explicit conversion}s using cast expressions.
    324218
     
    330224\subsubsection{Safe arithmetic conversions}
    331225
    332 In C, a pattern of conversions known as the \define{usual arithmetic conversion}s is used with most
    333 binary arithmetic operators to convert the operands to a common type and determine the type of the
    334 operator's result. In \CFA, these conversions play a role in overload resolution, and
    335 collectively are called the \define{safe arithmetic conversion}s.
    336 
    337 Let \(int_r\) and \(unsigned_r\) be the signed and unsigned integer types with integer conversion
    338 rank\index{integer conversion rank}\index{rank|see{integer conversion rank}} $r$. Let
    339 \(unsigned_{mr}\) be the unsigned integer type with maximal rank.
     226In C, a pattern of conversions known as the \define{usual arithmetic conversion}s is used with most binary arithmetic operators to convert the operands to a common type and determine the type of the operator's result.
     227In \CFA, these conversions play a role in overload resolution, and collectively are called the \define{safe arithmetic conversion}s.
     228
     229Let \(int_r\) and \(unsigned_r\) be the signed and unsigned integer types with integer conversion rank\index{integer conversion rank}\index{rank|see{integer conversion rank}} $r$.
     230Let \(unsigned_{mr}\) be the unsigned integer type with maximal rank.
    340231
    341232The following conversions are \emph{direct} safe arithmetic conversions.
     
    343234\item
    344235The \Index{integer promotion}s.
    345 
    346 \item
    347 For every rank $r$ greater than or equal to the rank of \lstinline$int$, conversion from \(int_r\)
    348 to \(unsigned_r\).
    349 
    350 \item
    351 For every rank $r$ greater than or equal to the rank of \lstinline$int$, where \(int_{r+1}\) exists
    352 and can represent all values of \(unsigned_r\), conversion from \(unsigned_r\) to \(int_{r+1}\).
    353 
     236\item
     237For every rank $r$ greater than or equal to the rank of \lstinline$int$, conversion from \(int_r\) to \(unsigned_r\).
     238\item
     239For every rank $r$ greater than or equal to the rank of \lstinline$int$, where \(int_{r+1}\) exists and can represent all values of \(unsigned_r\), conversion from \(unsigned_r\) to \(int_{r+1}\).
    354240\item
    355241Conversion from \(unsigned_{mr}\) to \lstinline$float$.
    356 
    357242\item
    358243Conversion from an enumerated type to its compatible integer type.
    359 
    360 \item
    361 Conversion from \lstinline$float$ to \lstinline$double$, and from \lstinline$double$ to
    362 \lstinline$long double$.
    363 
    364 \item
    365 Conversion from \lstinline$float _Complex$ to \lstinline$double _Complex$,
    366 and from \lstinline$double _Complex$ to \lstinline$long double _Complex$.
    367 
     244\item
     245Conversion from \lstinline$float$ to \lstinline$double$, and from \lstinline$double$ to \lstinline$long double$.
     246\item
     247Conversion from \lstinline$float _Complex$ to \lstinline$double _Complex$, and from \lstinline$double _Complex$ to \lstinline$long double _Complex$.
    368248\begin{sloppypar}
    369249\item
    370 Conversion from \lstinline$float _Imaginary$ to \lstinline$double _Imaginary$, and from
    371 \lstinline$double _Imaginary$ to \lstinline$long double$ \lstinline$_Imaginary$, if the
    372 implementation supports imaginary types.
     250Conversion from \lstinline$float _Imaginary$ to \lstinline$double _Imaginary$, and from \lstinline$double _Imaginary$ to \lstinline$long double$ \lstinline$_Imaginary$, if the implementation supports imaginary types.
    373251\end{sloppypar}
    374252\end{itemize}
    375253
    376 If type \lstinline$T$ can be converted to type \lstinline$U$ by a safe direct arithmetic conversion
    377 and type \lstinline$U$ can be converted to type \lstinline$V$ by a safe arithmetic conversion, then
    378 the conversion from \lstinline$T$ to type \lstinline$V$ is an \emph{indirect} safe arithmetic
    379 conversion.
    380 
    381 \begin{rationale}
    382 Note that {\c11} does not include conversion from \Index{real type}s to \Index{complex type}s in the
    383 usual arithmetic conversions, and \CFA does not include them as safe conversions.
     254If type \lstinline$T$ can be converted to type \lstinline$U$ by a safe direct arithmetic conversion and type \lstinline$U$ can be converted to type \lstinline$V$ by a safe arithmetic conversion, then the conversion from \lstinline$T$ to type \lstinline$V$ is an \emph{indirect} safe arithmetic conversion.
     255
     256\begin{rationale}
     257Note that {\c11} does not include conversion from \Index{real type}s to \Index{complex type}s in the usual arithmetic conversions, and \CFA does not include them as safe conversions.
    384258\end{rationale}
    385259
     
    393267
    394268If an expression's type is a pointer to a structure or union type that has a member that is an
    395 \Index{anonymous structure} or an \Index{anonymous union}, it can be implicitly
    396 converted\index{implicit conversion} to a pointer to the anonymous structure's or anonymous union's
    397 type. The result of the conversion is a pointer to the member.
     269\Index{anonymous structure} or an \Index{anonymous union}, it can be implicitly converted\index{implicit conversion} to a pointer to the anonymous structure's or anonymous union's type.
     270The result of the conversion is a pointer to the member.
    398271
    399272\examples
     
    402275        int x, y;
    403276};
    404 void move_by(struct point * p1, struct point * p2) {@\impl{move_by}@
     277void move_by( struct point * p1, struct point * p2 ) {@\impl{move_by}@
    405278        p1->x += p2.x;
    406279        p1->y += p2.y;
    407280}
    408 
    409281struct color_point {
    410282        enum { RED, BLUE, GREEN } color;
    411283        struct point;
    412284} cp1, cp2;
    413 move_to(&cp1, &cp2);
     285move_to( &cp1, &cp2 );
    414286\end{lstlisting}
    415287Thanks to implicit conversion, the two arguments that \lstinline$move_by()$ receives are pointers to
     
    418290
    419291\subsubsection{Specialization}
    420 A function or value whose type is polymorphic may be implicitly converted to one whose type is
    421 \Index{less polymorphic} by binding values to one or more of its \Index{inferred parameter}. Any
    422 value that is legal for the inferred parameter may be used, including other inferred parameters.
    423 
    424 If, after the inferred parameter binding, an \Index{assertion parameter} has no inferred parameters
    425 in its type, then an object or function must be visible at the point of the specialization that has
    426 the same identifier as the assertion parameter and has a type that is compatible\index{compatible
    427   type} with or can be specialized to the type of the assertion parameter.  The assertion parameter
    428 is bound to that object or function.
    429 
    430 The type of the specialization is the type of the original with the bound inferred parameters and
    431 the bound assertion parameters replaced by their bound values.
     292A function or value whose type is polymorphic may be implicitly converted to one whose type is \Index{less polymorphic} by binding values to one or more of its \Index{inferred parameter}.
     293Any value that is legal for the inferred parameter may be used, including other inferred parameters.
     294
     295If, after the inferred parameter binding, an \Index{assertion parameter} has no inferred parameters in its type, then an object or function must be visible at the point of the specialization that has the same identifier as the assertion parameter and has a type that is compatible\index{compatible type} with or can be specialized to the type of the assertion parameter.
     296The assertion parameter is bound to that object or function.
     297
     298The type of the specialization is the type of the original with the bound inferred parameters and the bound assertion parameters replaced by their bound values.
    432299
    433300\examples
    434301The type
    435302\begin{lstlisting}
    436 forall( type T, type U ) void (*)( T, U );
     303forall( otype T, otype U ) void (*)( T, U );
    437304\end{lstlisting}
    438305can be specialized to (among other things)
    439306\begin{lstlisting}
    440 forall( type T ) void (*)( T, T );              // U bound to T
    441 forall( type T ) void (*)( T, real );   // U bound to real
    442 forall( type U ) void (*)( real, U );   // T bound to real
     307forall( otype T ) void (*)( T, T );             // U bound to T
     308forall( otype T ) void (*)( T, real );  // U bound to real
     309forall( otype U ) void (*)( real, U );  // T bound to real
    443310void f( real, real );                                   // both bound to real
    444311\end{lstlisting}
     
    446313The type
    447314\begin{lstlisting}
    448 forall( type T | T ?+?( T, T )) T (*)( T );
     315forall( otype T | T ?+?( T, T ) ) T (*)( T );
    449316\end{lstlisting}
    450317can be specialized to (among other things)
    451318\begin{lstlisting}
    452 int (*)( int );                                         // T bound to int, and T ?+?(T, T ) bound to int ?+?( int, int )
     319int (*)( int );         // T bound to int, and T ?+?(T, T ) bound to int ?+?( int, int )
    453320\end{lstlisting}
    454321
     
    465332from a pointer to any non-\lstinline$void$ type to a pointer to \lstinline$void$;
    466333\item
    467 from a pointer to any type to a pointer to a more qualified version of the type\index{qualified
    468 type};
    469 \item
    470 from a pointer to a structure or union type to a pointer to the type of a member of the structure or
    471 union that is an \Index{anonymous structure} or an \Index{anonymous union};
    472 \item
    473 within the scope of an initialized \Index{type declaration}, conversions between a type and its
    474 implementation or between a pointer to a type and a pointer to its implementation.
     334from a pointer to any type to a pointer to a more qualified version of the type\index{qualified type};
     335\item
     336from a pointer to a structure or union type to a pointer to the type of a member of the structure or union that is an \Index{anonymous structure} or an \Index{anonymous union};
     337\item
     338within the scope of an initialized \Index{type declaration}, conversions between a type and its implementation or between a pointer to a type and a pointer to its implementation.
    475339\end{itemize}
    476340
    477341Conversions that are not safe conversions are \define{unsafe conversion}s.
    478342\begin{rationale}
    479 As in C, there is an implicit conversion from \lstinline$void *$ to any pointer type. This is
    480 clearly dangerous, and {\CC} does not have this implicit conversion.
    481 \CFA\index{deficiencies!void * conversion} keeps it, in the interest of remaining as pure a
    482 superset of C as possible, but discourages it by making it unsafe.
     343As in C, there is an implicit conversion from \lstinline$void *$ to any pointer type.
     344This is clearly dangerous, and {\CC} does not have this implicit conversion.
     345\CFA\index{deficiencies!void * conversion} keeps it, in the interest of remaining as pure a superset of C as possible, but discourages it by making it unsafe.
    483346\end{rationale}
    484347
     
    486349\subsection{Conversion cost}
    487350
    488 The \define{conversion cost} of a safe\index{safe conversion}
    489 conversion\footnote{Unsafe\index{unsafe conversion} conversions do not have defined conversion
    490 costs.} is a measure of how desirable or undesirable it is. It is defined as follows.
     351The \define{conversion cost} of a safe\index{safe conversion} conversion\footnote{Unsafe\index{unsafe conversion} conversions do not have defined conversion costs.} is a measure of how desirable or undesirable it is.
     352It is defined as follows.
    491353\begin{itemize}
    492354\item
     
    497359
    498360\item
    499 The cost of an indirect safe arithmetic conversion is the smallest number of direct conversions
    500 needed to make up the conversion.
     361The cost of an indirect safe arithmetic conversion is the smallest number of direct conversions needed to make up the conversion.
    501362\end{itemize}
    502363
     
    506367\begin{itemize}
    507368\item
    508 The cost of an implicit conversion from \lstinline$int$ to \lstinline$long$ is 1. The cost of an
    509 implicit conversion from \lstinline$long$ to \lstinline$double$ is 3, because it is defined in terms
    510 of conversions from \lstinline$long$ to \lstinline$unsigned long$, then to \lstinline$float$, and
    511 then to \lstinline$double$.
    512 
    513 \item
    514 If \lstinline$int$ can represent all the values of \lstinline$unsigned short$, then the cost of an
    515 implicit conversion from \lstinline$unsigned short$ to \lstinline$unsigned$ is 2:
    516 \lstinline$unsigned short$ to \lstinline$int$ to \lstinline$unsigned$. Otherwise,
    517 \lstinline$unsigned short$ is converted directly to \lstinline$unsigned$, and the cost is 1.
    518 
    519 \item
    520 If \lstinline$long$ can represent all the values of \lstinline$unsigned$, then the conversion cost
    521 of \lstinline$unsigned$ to \lstinline$long$ is 1. Otherwise, the conversion is an unsafe
    522 conversion, and its conversion cost is undefined.
     369The cost of an implicit conversion from \lstinline$int$ to \lstinline$long$ is 1.
     370The cost of an implicit conversion from \lstinline$long$ to \lstinline$double$ is 3, because it is defined in terms of conversions from \lstinline$long$ to \lstinline$unsigned long$, then to \lstinline$float$, and then to \lstinline$double$.
     371
     372\item
     373If \lstinline$int$ can represent all the values of \lstinline$unsigned short$, then the cost of an implicit conversion from \lstinline$unsigned short$ to \lstinline$unsigned$ is 2:
     374\lstinline$unsigned short$ to \lstinline$int$ to \lstinline$unsigned$.
     375Otherwise, \lstinline$unsigned short$ is converted directly to \lstinline$unsigned$, and the cost is 1.
     376
     377\item
     378If \lstinline$long$ can represent all the values of \lstinline$unsigned$, then the conversion cost of \lstinline$unsigned$ to \lstinline$long$ is 1.
     379Otherwise, the conversion is an unsafe conversion, and its conversion cost is undefined.
    523380\end{itemize}
    524381
     
    529386        \rhs \lstinline$forall$
    530387        \rhs \lstinline$lvalue$
    531         \rhs \lstinline$context$
     388        \rhs \lstinline$trait$
    532389        \rhs \lstinline$dtype$
    533390        \rhs \lstinline$ftype$
     
    538395\subsection{Identifiers}
    539396
    540 \CFA allows operator \Index{overloading} by associating operators with special function
    541 identifiers. Furthermore, the constants ``\lstinline$0$'' and ``\lstinline$1$'' have special status
    542 for many of C's data types (and for many programmer-defined data types as well), so \CFA treats them
    543 as overloadable identifiers. Programmers can use these identifiers to declare functions and objects
    544 that implement operators and constants for their own types.
     397\CFA allows operator \Index{overloading} by associating operators with special function identifiers.
     398Furthermore, the constants ``\lstinline$0$'' and ``\lstinline$1$'' have special status for many of C's data types (and for many programmer-defined data types as well), so \CFA treats them as overloadable identifiers.
     399Programmers can use these identifiers to declare functions and objects that implement operators and constants for their own types.
    545400
    546401
     
    554409\end{syntax}
    555410
    556 \index{constant identifiers}\index{identifiers!for constants} The tokens ``\lstinline$0$''\impl{0}
    557 and ``\lstinline$1$''\impl{1} are identifiers. No other tokens defined by the rules for integer
    558 constants are considered to be identifiers.
    559 \begin{rationale}
    560 Why ``\lstinline$0$'' and ``\lstinline$1$''? Those integers have special status in C. All scalar
    561 types can be incremented and decremented, which is defined in terms of adding or subtracting 1. The
    562 operations ``\lstinline$&&$'', ``\lstinline$||$'', and ``\lstinline$!$'' can be applied to any
    563 scalar arguments, and are defined in terms of comparison against 0. A \nonterm{constant-expression}
    564 that evaluates to 0 is effectively compatible with every pointer type.
    565 
    566 In C, the integer constants 0 and 1 suffice because the integer promotion rules can convert them to
    567 any arithmetic type, and the rules for pointer expressions treat constant expressions evaluating to
    568 0 as a special case. However, user-defined arithmetic types often need the equivalent of a 1 or 0
    569 for their functions or operators, polymorphic functions often need 0 and 1 constants of a type
    570 matching their polymorphic parameters, and user-defined pointer-like types may need a null value.
    571 Defining special constants for a user-defined type is more efficient than defining a conversion to
    572 the type from \lstinline$_Bool$.
    573 
    574 Why \emph{just} ``\lstinline$0$'' and ``\lstinline$1$''? Why not other integers? No other integers
    575 have special status in C. A facility that let programmers declare specific
    576 constants---``\lstinline$const Rational 12$'', for instance---would not be much of an improvement.
    577 Some facility for defining the creation of values of programmer-defined types from arbitrary integer
    578 tokens would be needed. The complexity of such a feature doesn't seem worth the gain.
     411\index{constant identifiers}\index{identifiers!for constants} The tokens ``\lstinline$0$''\impl{0} and ``\lstinline$1$''\impl{1} are identifiers.
     412No other tokens defined by the rules for integer constants are considered to be identifiers.
     413\begin{rationale}
     414Why ``\lstinline$0$'' and ``\lstinline$1$''? Those integers have special status in C.
     415All scalar types can be incremented and decremented, which is defined in terms of adding or subtracting 1.
     416The operations ``\lstinline$&&$'', ``\lstinline$||$'', and ``\lstinline$!$'' can be applied to any scalar arguments, and are defined in terms of comparison against 0.
     417A \nonterm{constant-expression} that evaluates to 0 is effectively compatible with every pointer type.
     418
     419In C, the integer constants 0 and 1 suffice because the integer promotion rules can convert them to any arithmetic type, and the rules for pointer expressions treat constant expressions evaluating to 0 as a special case.
     420However, user-defined arithmetic types often need the equivalent of a 1 or 0 for their functions or operators, polymorphic functions often need 0 and 1 constants of a type matching their polymorphic parameters, and user-defined pointer-like types may need a null value.
     421Defining special constants for a user-defined type is more efficient than defining a conversion to the type from \lstinline$_Bool$.
     422
     423Why \emph{just} ``\lstinline$0$'' and ``\lstinline$1$''? Why not other integers? No other integers have special status in C.
     424A facility that let programmers declare specific constants---``\lstinline$const Rational 12$'', for instance---would not be much of an improvement.
     425Some facility for defining the creation of values of programmer-defined types from arbitrary integer tokens would be needed.
     426The complexity of such a feature doesn't seem worth the gain.
    579427\end{rationale}
    580428
     
    582430\subsubsection{Operator identifiers}
    583431
    584 \index{operator identifiers}\index{identifiers!for operators} Table \ref{opids} lists the
    585 programmer-definable operator identifiers and the operations they are associated with. Functions
    586 that are declared with (or pointed at by function pointers that are declared with) these identifiers
    587 can be called by expressions that use the operator tokens and syntax, or the operator identifiers
    588 and ``function call'' syntax. The relationships between operators and function calls are discussed
    589 in descriptions of the operators.
     432\index{operator identifiers}\index{identifiers!for operators} Table \ref{opids} lists the programmer-definable operator identifiers and the operations they are associated with.
     433Functions that are declared with (or pointed at by function pointers that are declared with) these identifiers can be called by expressions that use the operator tokens and syntax, or the operator identifiers and ``function call'' syntax.
     434The relationships between operators and function calls are discussed in descriptions of the operators.
    590435
    591436\begin{table}[hbt]
     
    644489
    645490\begin{rationale}
    646 Operator identifiers are made up of the characters of the operator token, with question marks added
    647 to mark the positions of the arguments of operators. The question marks serve as mnemonic devices;
    648 programmers can not create new operators by arbitrarily mixing question marks and other
    649 non-alphabetic characters. Note that prefix and postfix versions of the increment and decrement
    650 operators are distinguished by the position of the question mark.
    651 \end{rationale}
    652 
    653 \begin{rationale}
    654 The use of ``\lstinline$?$'' in identifiers means that some C programs are not \CFA programs.  For
    655 instance, the sequence of characters ``\lstinline$(i < 0)?--i:i$'' is legal in a C program, but a
    656 \CFA compiler detects a syntax error because it treats ``\lstinline$?--$'' as an identifier, not
    657 as the two tokens ``\lstinline$?$'' and ``\lstinline$--$''.
     491Operator identifiers are made up of the characters of the operator token, with question marks added to mark the positions of the arguments of operators.
     492The question marks serve as mnemonic devices;
     493programmers can not create new operators by arbitrarily mixing question marks and other non-alphabetic characters.
     494Note that prefix and postfix versions of the increment and decrement operators are distinguished by the position of the question mark.
     495\end{rationale}
     496
     497\begin{rationale}
     498The use of ``\lstinline$?$'' in identifiers means that some C programs are not \CFA programs.  For instance, the sequence of characters ``\lstinline$(i < 0)?--i:i$'' is legal in a C program, but a
     499\CFA compiler detects a syntax error because it treats ``\lstinline$?--$'' as an identifier, not as the two tokens ``\lstinline$?$'' and ``\lstinline$--$''.
    658500\end{rationale}
    659501
     
    663505\item
    664506The logical operators ``\lstinline$&&$'' and ``\lstinline$||$'', and the conditional operator
    665 ``\lstinline$?:$''. These operators do not always evaluate their operands, and hence can not be
    666 properly defined by functions unless some mechanism like call-by-name is added to the language.
    667 Note that the definitions of ``\lstinline$&&$'' and ``\lstinline$||$'' say that they work by
    668 checking that their arguments are unequal to 0, so defining ``\lstinline$!=$'' and ``\lstinline$0$''
    669 for user-defined types is enough to allow them to be used in logical expressions.
    670 
    671 \item
    672 The comma operator\index{comma expression}. It is a control-flow operator like those above.
     507``\lstinline$?:$''.
     508These operators do not always evaluate their operands, and hence can not be properly defined by functions unless some mechanism like call-by-name is added to the language.
     509Note that the definitions of ``\lstinline$&&$'' and ``\lstinline$||$'' say that they work by checking that their arguments are unequal to 0, so defining ``\lstinline$!=$'' and ``\lstinline$0$'' for user-defined types is enough to allow them to be used in logical expressions.
     510
     511\item
     512The comma operator\index{comma expression}.
     513It is a control-flow operator like those above.
    673514Changing its meaning seems pointless and confusing.
    674515
    675516\item
    676 The ``address of'' operator. It would seem useful to define a unary ``\lstinline$&$'' operator that
    677 returns values of some programmer-defined pointer-like type. The problem lies with the type of the
    678 operator. Consider the expression ``\lstinline$p = &x$'', where \lstinline$x$ is of type
    679 \lstinline$T$ and \lstinline$p$ has the programmer-defined type \lstinline$T_ptr$. The expression
    680 might be treated as a call to the unary function ``\lstinline$&?$''. Now what is the type of the
    681 function's parameter? It can not be \lstinline$T$, because then \lstinline$x$ would be passed by
    682 value, and there is no way to create a useful pointer-like result from a value. Hence the parameter
    683 must have type \lstinline$T *$. But then the expression must be rewritten as ``\lstinline$p = &?( &x )$''
     517The ``address of'' operator.
     518It would seem useful to define a unary ``\lstinline$&$'' operator that returns values of some programmer-defined pointer-like type.
     519The problem lies with the type of the operator.
     520Consider the expression ``\lstinline$p = &x$'', where \lstinline$x$ is of type
     521\lstinline$T$ and \lstinline$p$ has the programmer-defined type \lstinline$T_ptr$.
     522The expression might be treated as a call to the unary function ``\lstinline$&?$''.
     523Now what is the type of the function's parameter? It can not be \lstinline$T$, because then \lstinline$x$ would be passed by value, and there is no way to create a useful pointer-like result from a value.
     524Hence the parameter must have type \lstinline$T *$.
     525But then the expression must be rewritten as ``\lstinline$p = &?( &x )$''
    684526---which doesn't seem like progress!
    685527
    686 The rule for address-of expressions would have to be something like ``keep applying address-of
    687 functions until you get one that takes a pointer argument, then use the built-in operator and
    688 stop''. It seems simpler to define a conversion function from \lstinline$T *$ to \lstinline$T_ptr$.
    689 
    690 \item
    691 The \lstinline$sizeof$ operator. It is already defined for every object type, and intimately tied
    692 into the language's storage allocation model. Redefining it seems pointless.
    693 
    694 \item
    695 The ``member of'' operators ``\lstinline$.$'' and ``\lstinline$->$''. These are not really infix
    696 operators, since their right ``operand'' is not a value or object.
    697 
    698 \item
    699 Cast operators\index{cast expression}. Anything that can be done with an explicit cast can be done
    700 with a function call. The difference in syntax is small.
     528The rule for address-of expressions would have to be something like ``keep applying address-of functions until you get one that takes a pointer argument, then use the built-in operator and stop''.
     529It seems simpler to define a conversion function from \lstinline$T *$ to \lstinline$T_ptr$.
     530
     531\item
     532The \lstinline$sizeof$ operator.
     533It is already defined for every object type, and intimately tied into the language's storage allocation model.
     534Redefining it seems pointless.
     535
     536\item
     537The ``member of'' operators ``\lstinline$.$'' and ``\lstinline$->$''.
     538These are not really infix operators, since their right ``operand'' is not a value or object.
     539
     540\item
     541Cast operators\index{cast expression}.
     542Anything that can be done with an explicit cast can be done with a function call.
     543The difference in syntax is small.
    701544\end{itemize}
    702545\end{rationale}
     
    705548\section{Expressions}
    706549
    707 \CFA allows operators and identifiers to be overloaded. Hence, each expression can have a number
    708 of \define{interpretation}s, each of which has a different type. The interpretations that are
    709 potentially executable are called \define{valid interpretation}s. The set of interpretations
    710 depends on the kind of expression and on the interpretations of the subexpressions that it contains.
    711 The rules for determining the valid interpretations of an expression are discussed below for each
    712 kind of expression. Eventually the context of the outermost expression chooses one interpretation
    713 of that expression.
    714 
    715 An \define{ambiguous interpretation} is an interpretation which does not specify the exact object or
    716 function denoted by every identifier in the expression. An expression can have some interpretations
    717 that are ambiguous and others that are unambiguous. An expression that is chosen to be executed
    718 shall not be ambiguous.
    719 
    720 The \define{best valid interpretations} are the valid interpretations that use the fewest
    721 unsafe\index{unsafe conversion} conversions. Of these, the best are those where the functions and
    722 objects involved are the least polymorphic\index{less polymorphic}. Of these, the best have the
    723 lowest total \Index{conversion cost}, including all implicit conversions in the argument
    724 expressions. Of these, the best have the highest total conversion cost for the implicit conversions
    725 (if any) applied to the argument expressions. If there is no single best valid interpretation, or if
    726 the best valid interpretation is ambiguous, then the resulting interpretation is
    727 ambiguous\index{ambiguous interpretation}.
    728 
    729 \begin{rationale}
    730 \CFA's rules for selecting the best interpretation are designed to allow overload resolution to
    731 mimic C's operator semantics. In C, the ``usual arithmetic conversions'' are applied to the
    732 operands of binary operators if necessary to convert the operands to types with a common real type.
    733 In \CFA, those conversions are ``safe''. The ``fewest unsafe conversions'' rule ensures that the
    734 usual conversions are done, if possible. The ``lowest total expression cost'' rule chooses the
    735 proper common type. The odd-looking ``highest argument conversion cost'' rule ensures that, when
    736 unary expressions must be converted, conversions of function results are preferred to conversion of
    737 function arguments: \lstinline$(double)-i$ will be preferred to \lstinline$-(double)i$.
    738 
    739 The ``least polymorphic'' rule reduces the number of polymorphic function calls, since such
    740 functions are presumably more expensive than monomorphic functions and since the more specific
    741 function is presumably more appropriate. It also gives preference to monomorphic values (such as the
     550\CFA allows operators and identifiers to be overloaded.
     551Hence, each expression can have a number of \define{interpretation}s, each of which has a different type.
     552The interpretations that are potentially executable are called \define{valid interpretation}s.
     553The set of interpretations depends on the kind of expression and on the interpretations of the subexpressions that it contains.
     554The rules for determining the valid interpretations of an expression are discussed below for each kind of expression.
     555Eventually the context of the outermost expression chooses one interpretation of that expression.
     556
     557An \define{ambiguous interpretation} is an interpretation which does not specify the exact object or function denoted by every identifier in the expression.
     558An expression can have some interpretations that are ambiguous and others that are unambiguous.
     559An expression that is chosen to be executed shall not be ambiguous.
     560
     561The \define{best valid interpretations} are the valid interpretations that use the fewest unsafe\index{unsafe conversion} conversions.
     562Of these, the best are those where the functions and objects involved are the least polymorphic\index{less polymorphic}.
     563Of these, the best have the lowest total \Index{conversion cost}, including all implicit conversions in the argument expressions.
     564Of these, the best have the highest total conversion cost for the implicit conversions
     565(if any) applied to the argument expressions.
     566If there is no single best valid interpretation, or if the best valid interpretation is ambiguous, then the resulting interpretation is ambiguous\index{ambiguous interpretation}.
     567
     568\begin{rationale}
     569\CFA's rules for selecting the best interpretation are designed to allow overload resolution to mimic C's operator semantics.
     570In C, the ``usual arithmetic conversions'' are applied to the operands of binary operators if necessary to convert the operands to types with a common real type.
     571In \CFA, those conversions are ``safe''.
     572The ``fewest unsafe conversions'' rule ensures that the usual conversions are done, if possible.
     573The ``lowest total expression cost'' rule chooses the proper common type.
     574The odd-looking ``highest argument conversion cost'' rule ensures that, when unary expressions must be converted, conversions of function results are preferred to conversion of function arguments: \lstinline$(double)-i$ will be preferred to \lstinline$-(double)i$.
     575
     576The ``least polymorphic'' rule reduces the number of polymorphic function calls, since such functions are presumably more expensive than monomorphic functions and since the more specific function is presumably more appropriate.
     577It also gives preference to monomorphic values (such as the
    742578\lstinline$int$ \lstinline$0$) over polymorphic values (such as the \Index{null pointer}
    743 \lstinline$0$\use{0}). However, interpretations that call polymorphic functions are preferred to
    744 interpretations that perform unsafe conversions, because those conversions potentially lose accuracy
    745 or violate strong typing.
     579\lstinline$0$\use{0}).
     580However, interpretations that call polymorphic functions are preferred to interpretations that perform unsafe conversions, because those conversions potentially lose accuracy or violate strong typing.
    746581
    747582There are two notable differences between \CFA's overload resolution rules and the rules for
    748 {\CC} defined in \cite{c++}. First, the result type of a function plays a role. In {\CC}, a
    749 function call must be completely resolved based on the arguments to the call in most circumstances.
    750 In \CFA, a function call may have several interpretations, each with a different result type, and
    751 the interpretations of the containing context choose among them. Second, safe conversions are used
    752 to choose among interpretations of all sorts of functions; in {\CC}, the ``usual arithmetic
    753 conversions'' are a separate set of rules that apply only to the built-in operators.
    754 \end{rationale}
    755 
    756 Expressions involving certain operators\index{operator identifiers} are considered to be equivalent
    757 to function calls. A transformation from ``operator'' syntax to ``function call'' syntax is defined
    758 by \define{rewrite rules}. Each operator has a set of predefined functions that overload its
    759 identifier. Overload resolution determines which member of the set is executed in a given
    760 expression. The functions have \Index{internal linkage} and are implicitly declared with \Index{file
    761 scope}. The predefined functions and rewrite rules are discussed below for each of these
    762 operators.
    763 \begin{rationale}
    764 Predefined functions and constants have internal linkage because that simplifies optimization in
    765 traditional compile-and-link environments. For instance, ``\lstinline$an_int + an_int$'' is
    766 equivalent to ``\lstinline$?+?(an_int, an_int)$''. If integer addition has not been redefined in
    767 the current scope, a compiler can generate code to perform the addition directly. If predefined
    768 functions had external linkage, this optimization would be difficult.
    769 \end{rationale}
    770 
    771 \begin{rationale}
    772 Since each subsection describes the interpretations of an expression in terms of the interpretations
    773 of its subexpressions, this chapter can be taken as describing an overload resolution algorithm that
    774 uses one bottom-up pass over an expression tree. Such an algorithm was first described (for Ada) by
    775 Baker~\cite{Bak:overload}. It is extended here to handle polymorphic functions and arithmetic
    776 conversions. The overload resolution rules and the predefined functions have been chosen so that, in
    777 programs that do not introduce overloaded declarations, expressions will have the same meaning in C
    778 and in \CFA.
    779 \end{rationale}
    780 
    781 \begin{rationale}
    782 Expression syntax is quoted from the {\c11} standard. The syntax itself defines the precedence and
    783 associativity of operators. The sections are arranged in decreasing order of precedence, with all
    784 operators in a section having the same precedence.
     583{\CC} defined in \cite{C++}.
     584First, the result type of a function plays a role.
     585In {\CC}, a function call must be completely resolved based on the arguments to the call in most circumstances.
     586In \CFA, a function call may have several interpretations, each with a different result type, and the interpretations of the containing context choose among them.
     587Second, safe conversions are used to choose among interpretations of all sorts of functions;
     588in {\CC}, the ``usual arithmetic conversions'' are a separate set of rules that apply only to the built-in operators.
     589\end{rationale}
     590
     591Expressions involving certain operators\index{operator identifiers} are considered to be equivalent to function calls.
     592A transformation from ``operator'' syntax to ``function call'' syntax is defined by \define{rewrite rules}.
     593Each operator has a set of predefined functions that overload its identifier.
     594Overload resolution determines which member of the set is executed in a given expression.
     595The functions have \Index{internal linkage} and are implicitly declared with \Index{file scope}.
     596The predefined functions and rewrite rules are discussed below for each of these operators.
     597\begin{rationale}
     598Predefined functions and constants have internal linkage because that simplifies optimization in traditional compile-and-link environments.
     599For instance, ``\lstinline$an_int + an_int$'' is equivalent to ``\lstinline$?+?(an_int, an_int)$''.
     600If integer addition has not been redefined in the current scope, a compiler can generate code to perform the addition directly.
     601If predefined functions had external linkage, this optimization would be difficult.
     602\end{rationale}
     603
     604\begin{rationale}
     605Since each subsection describes the interpretations of an expression in terms of the interpretations of its subexpressions, this chapter can be taken as describing an overload resolution algorithm that uses one bottom-up pass over an expression tree.
     606Such an algorithm was first described (for Ada) by Baker~\cite{Bak:overload}.
     607It is extended here to handle polymorphic functions and arithmetic conversions.
     608The overload resolution rules and the predefined functions have been chosen so that, in programs that do not introduce overloaded declarations, expressions will have the same meaning in C and in \CFA.
     609\end{rationale}
     610
     611\begin{rationale}
     612Expression syntax is quoted from the {\c11} standard.
     613The syntax itself defines the precedence and associativity of operators.
     614The sections are arranged in decreasing order of precedence, with all operators in a section having the same precedence.
    785615\end{rationale}
    786616
     
    801631const int 1;@\use{1}@
    802632const int 0;@\use{0}@
    803 forall( dtype DT ) DT *const 0;
    804 forall( ftype FT ) FT *const 0;
     633forall( dtype DT ) DT * const 0;
     634forall( ftype FT ) FT * const 0;
    805635\end{lstlisting}
    806636
    807637\semantics
    808 The \Index{valid interpretation} of an \nonterm{identifier} are given by the visible\index{visible}
    809 declarations of the identifier.
    810 
    811 A \nonterm{constant} or \nonterm{string-literal} has one valid interpretation, which has the type
    812 and value defined by {\c11}. The predefined integer identifiers ``\lstinline$1$'' and
    813 ``\lstinline$0$'' have the integer values 1 and 0, respectively. The other two predefined
    814 ``\lstinline$0$'' identifiers are bound to polymorphic pointer values that, when
    815 specialized\index{specialization} with a data type or function type respectively, produce a null
    816 pointer of that type.
     638The \Index{valid interpretation} of an \nonterm{identifier} are given by the visible\index{visible} declarations of the identifier.
     639
     640A \nonterm{constant} or \nonterm{string-literal} has one valid interpretation, which has the type and value defined by {\c11}.
     641The predefined integer identifiers ``\lstinline$1$'' and ``\lstinline$0$'' have the integer values 1 and 0, respectively.
     642The other two predefined ``\lstinline$0$'' identifiers are bound to polymorphic pointer values that, when specialized\index{specialization} with a data type or function type respectively, produce a null pointer of that type.
    817643
    818644A parenthesised expression has the same interpretations as the contained \nonterm{expression}.
    819645
    820646\examples
    821 The expression \lstinline$(void *)0$\use{0} specializes the (polymorphic) null pointer to a null
    822 pointer to \lstinline$void$. \lstinline$(const void *)0$ does the same, and also uses a safe
    823 conversion from \lstinline$void *$ to \lstinline$const void *$. In each case, the null pointer
    824 conversion is better\index{best valid interpretations} than the unsafe conversion of the integer
     647The expression \lstinline$(void *)0$\use{0} specializes the (polymorphic) null pointer to a null pointer to \lstinline$void$. \lstinline$(const void *)0$ does the same, and also uses a safe conversion from \lstinline$void *$ to \lstinline$const void *$.
     648In each case, the null pointer conversion is better\index{best valid interpretations} than the unsafe conversion of the integer
    825649\lstinline$0$ to a pointer.
    826650
     
    828652Note that the predefined identifiers have addresses.
    829653
    830 \CFA does not have C's concept of ``null pointer constants'', which are not typed values but
    831 special strings of tokens. The C token ``\lstinline$0$'' is an expression of type \lstinline$int$
    832 with the value ``zero'', and it \emph{also} is a null pointer constant. Similarly,
    833 ``\lstinline$(void *)0$ is an expression of type \lstinline$(void *)$ whose value is a null pointer,
    834 and it also is a null pointer constant. However, in C, ``\lstinline$(void *)(void *)0$'' is
    835 \emph{not} a null pointer constant, even though it is null-valued, a pointer, and constant! The
    836 semantics of C expressions contain many special cases to deal with subexpressions that are null
    837 pointer constants.
    838 
    839 \CFA handles these cases through overload resolution. The declaration
    840 \begin{lstlisting}
    841 forall( dtype DT ) DT *const 0;
    842 \end{lstlisting}
    843 means that \lstinline$0$ is a polymorphic object, and contains a value that can have \emph{any}
    844 pointer-to-object type or pointer-to-incomplete type. The only such value is the null pointer.
    845 Therefore the type \emph{alone} is enough to identify a null pointer. Where C defines an operator
    846 with a special case for the null pointer constant, \CFA defines predefined functions with a
    847 polymorphic object parameter.
     654\CFA does not have C's concept of ``null pointer constants'', which are not typed values but special strings of tokens.
     655The C token ``\lstinline$0$'' is an expression of type \lstinline$int$ with the value ``zero'', and it \emph{also} is a null pointer constant.
     656Similarly,
     657``\lstinline$(void *)0$ is an expression of type \lstinline$(void *)$ whose value is a null pointer, and it also is a null pointer constant.
     658However, in C, ``\lstinline$(void *)(void *)0$'' is
     659\emph{not} a null pointer constant, even though it is null-valued, a pointer, and constant! The semantics of C expressions contain many special cases to deal with subexpressions that are null pointer constants.
     660
     661\CFA handles these cases through overload resolution.
     662The declaration
     663\begin{lstlisting}
     664forall( dtype DT ) DT * const 0;
     665\end{lstlisting} means that \lstinline$0$ is a polymorphic object, and contains a value that can have \emph{any} pointer-to-object type or pointer-to-incomplete type.
     666The only such value is the null pointer.
     667Therefore the type \emph{alone} is enough to identify a null pointer.
     668Where C defines an operator with a special case for the null pointer constant, \CFA defines predefined functions with a polymorphic object parameter.
    848669\end{rationale}
    849670
     
    851672\subsubsection{Generic selection}
    852673
    853 \constraints The best interpretation of the controlling expression shall be
    854 unambiguous\index{ambiguous interpretation}, and shall have type compatible with at most one of the
    855 types named in its generic association list. If a generic selection has no \lstinline$default$
    856 generic association, the best interpretation of its controlling expression shall have type
    857 compatible with exactly one of the types named in its generic association list.
     674\constraints The best interpretation of the controlling expression shall be unambiguous\index{ambiguous interpretation}, and shall have type compatible with at most one of the types named in its generic association list.
     675If a generic selection has no \lstinline$default$ generic association, the best interpretation of its controlling expression shall have type compatible with exactly one of the types named in its generic association list.
    858676
    859677\semantics
     
    883701\rewriterules
    884702\begin{lstlisting}
    885 a[b] @\rewrite@ ?[?]( b, a ) // if a has integer type */@\use{?[?]}@
     703a[b] @\rewrite@ ?[?]( b, a ) // if a has integer type@\use{?[?]}@
    886704a[b] @\rewrite@ ?[?]( a, b ) // otherwise
    887 a( ${\em arguments }$ ) @\rewrite@ ?()( a, ${\em arguments} )$@\use{?()}@
     705a( @\emph{arguments}@ ) @\rewrite@ ?()( a, @\emph{arguments}@ )@\use{?()}@
    888706a++ @\rewrite@ ?++(&( a ))@\use{?++}@
    889707a-- @\rewrite@ ?--(&( a ))@\use{?--}@
     
    895713\predefined
    896714\begin{lstlisting}
    897 forall( type T ) lvalue T ?[?]( T *, ptrdiff_t );@\use{ptrdiff_t}@
    898 forall( type T ) lvalue _Atomic T ?[?]( _Atomic T *, ptrdiff_t );
    899 forall( type T ) lvalue const T ?[?]( const T *, ptrdiff_t );
    900 forall( type T ) lvalue restrict T ?[?]( restrict T *, ptrdiff_t );
    901 forall( type T ) lvalue volatile T ?[?]( volatile T *, ptrdiff_t );
    902 forall( type T ) lvalue _Atomic const T ?[?]( _Atomic const T *, ptrdiff_t );
    903 forall( type T ) lvalue _Atomic restrict T ?[?]( _Atomic restrict T *, ptrdiff_t );
    904 forall( type T ) lvalue _Atomic volatile T ?[?]( _Atomic volatile T *, ptrdiff_t );
    905 forall( type T ) lvalue const restrict T ?[?]( const restrict T *, ptrdiff_t );
    906 forall( type T ) lvalue const volatile T ?[?]( const volatile T *, ptrdiff_t );
    907 forall( type T ) lvalue restrict volatile T ?[?]( restrict volatile T *, ptrdiff_t );
    908 forall( type T ) lvalue _Atomic const restrict T ?[?]( _Atomic const restrict T *, ptrdiff_t );
    909 forall( type T ) lvalue _Atomic const volatile T ?[?]( _Atomic const volatile T *, ptrdiff_t );
    910 forall( type T ) lvalue _Atomic restrict volatile T ?[?]( _Atomic restrict volatile T *, ptrdiff_t );
    911 forall( type T ) lvalue const restrict volatile T ?[?]( const restrict volatile T *, ptrdiff_t );
    912 forall( type T ) lvalue _Atomic const restrict volatile T ?[?]( _Atomic const restrict volatile T *, ptrdiff_t );
     715forall( otype T ) lvalue T ?[?]( T *, ptrdiff_t );@\use{ptrdiff_t}@
     716forall( otype T ) lvalue _Atomic T ?[?]( _Atomic T *, ptrdiff_t );
     717forall( otype T ) lvalue const T ?[?]( const T *, ptrdiff_t );
     718forall( otype T ) lvalue restrict T ?[?]( restrict T *, ptrdiff_t );
     719forall( otype T ) lvalue volatile T ?[?]( volatile T *, ptrdiff_t );
     720forall( otype T ) lvalue _Atomic const T ?[?]( _Atomic const T *, ptrdiff_t );
     721forall( otype T ) lvalue _Atomic restrict T ?[?]( _Atomic restrict T *, ptrdiff_t );
     722forall( otype T ) lvalue _Atomic volatile T ?[?]( _Atomic volatile T *, ptrdiff_t );
     723forall( otype T ) lvalue const restrict T ?[?]( const restrict T *, ptrdiff_t );
     724forall( otype T ) lvalue const volatile T ?[?]( const volatile T *, ptrdiff_t );
     725forall( otype T ) lvalue restrict volatile T ?[?]( restrict volatile T *, ptrdiff_t );
     726forall( otype T ) lvalue _Atomic const restrict T ?[?]( _Atomic const restrict T *, ptrdiff_t );
     727forall( otype T ) lvalue _Atomic const volatile T ?[?]( _Atomic const volatile T *, ptrdiff_t );
     728forall( otype T ) lvalue _Atomic restrict volatile T ?[?]( _Atomic restrict volatile T *, ptrdiff_t );
     729forall( otype T ) lvalue const restrict volatile T ?[?]( const restrict volatile T *, ptrdiff_t );
     730forall( otype T ) lvalue _Atomic const restrict volatile T ?[?]( _Atomic const restrict volatile T *, ptrdiff_t );
    913731\end{lstlisting}
    914732\semantics
    915 The interpretations of subscript expressions are the interpretations of the corresponding function
    916 call expressions.
     733The interpretations of subscript expressions are the interpretations of the corresponding function call expressions.
    917734\begin{rationale}
    918735C defines subscripting as pointer arithmetic in a way that makes \lstinline$a[i]$ and
    919 \lstinline$i[a]$ equivalent. \CFA provides the equivalence through a rewrite rule to reduce the
    920 number of overloadings of \lstinline$?[?]$.
    921 
    922 Subscript expressions are rewritten as function calls that pass the first parameter by value. This
    923 is somewhat unfortunate, since array-like types tend to be large. The alternative is to use the
    924 rewrite rule ``\lstinline$a[b]$ \rewrite \lstinline$?[?](&(a), b)$''. However, C semantics forbid
    925 this approach: the \lstinline$a$ in ``\lstinline$a[b]$'' can be an arbitrary pointer value, which
    926 does not have an address.
     736\lstinline$i[a]$ equivalent. \CFA provides the equivalence through a rewrite rule to reduce the number of overloadings of \lstinline$?[?]$.
     737
     738Subscript expressions are rewritten as function calls that pass the first parameter by value.
     739This is somewhat unfortunate, since array-like types tend to be large.
     740The alternative is to use the rewrite rule ``\lstinline$a[b]$ \rewrite \lstinline$?[?](&(a), b)$''.
     741However, C semantics forbid this approach: the \lstinline$a$ in ``\lstinline$a[b]$'' can be an arbitrary pointer value, which does not have an address.
    927742
    928743The repetitive form of the predefined identifiers shows up a deficiency\index{deficiencies!pointers
    929  to qualified types} of \CFA's type system. Type qualifiers are not included in type values, so
    930 polymorphic functions that take pointers to arbitrary types often come in one flavor for each
    931 possible qualification of the pointed-at type.
     744 to qualified types} of \CFA's type system.
     745Type qualifiers are not included in type values, so polymorphic functions that take pointers to arbitrary types often come in one flavor for each possible qualification of the pointed-at type.
    932746\end{rationale}
    933747
     
    936750
    937751\semantics
    938 A \define{function designator} is an interpretation of an expression that has function type. The
    939 \nonterm{postfix-expression} in a function call may have some interpretations that are function
    940 designators and some that are not.
    941 
    942 For those interpretations of the \nonterm{postfix-expression} that are not function designators, the
    943 expression is rewritten and becomes a call of a function named ``\lstinline$?()$''. The valid
    944 interpretations of the rewritten expression are determined in the manner described below.
    945 
    946 Each combination of function designators and argument interpretations is considered. For those
    947 interpretations of the \nonterm{postfix-expression} that are \Index{monomorphic function}
    948 designators, the combination has a \Index{valid interpretation} if the function designator accepts
    949 the number of arguments given, and each argument interpretation matches the corresponding explicit
    950 parameter:
     752A \define{function designator} is an interpretation of an expression that has function type.
     753The
     754\nonterm{postfix-expression} in a function call may have some interpretations that are function designators and some that are not.
     755
     756For those interpretations of the \nonterm{postfix-expression} that are not function designators, the expression is rewritten and becomes a call of a function named ``\lstinline$?()$''.
     757The valid interpretations of the rewritten expression are determined in the manner described below.
     758
     759Each combination of function designators and argument interpretations is considered.
     760For those interpretations of the \nonterm{postfix-expression} that are \Index{monomorphic function} designators, the combination has a \Index{valid interpretation} if the function designator accepts the number of arguments given, and each argument interpretation matches the corresponding explicit parameter:
    951761\begin{itemize}
    952 \item
    953 if the argument corresponds to a parameter in the function designator's prototype, the argument
    954 interpretation must have the same type as the corresponding parameter, or be implicitly convertible
    955 to the parameter's type
    956 \item
    957 if the function designator's type does not include a prototype or if the argument corresponds to
     762\item if the argument corresponds to a parameter in the function designator's prototype, the argument interpretation must have the same type as the corresponding parameter, or be implicitly convertible to the parameter's type
     763\item if the function designator's type does not include a prototype or if the argument corresponds to
    958764``\lstinline$...$'' in a prototype, a \Index{default argument promotion} is applied to it.
    959765\end{itemize}
     
    961767
    962768For those combinations where the interpretation of the \nonterm{postfix-expression} is a
    963 \Index{polymorphic function} designator and the function designator accepts the number of arguments
    964 given, there shall be at least one set of \define{implicit argument}s for the implicit parameters
    965 such that
     769\Index{polymorphic function} designator and the function designator accepts the number of arguments given, there shall be at least one set of \define{implicit argument}s for the implicit parameters such that
    966770\begin{itemize}
    967771\item
    968 If the declaration of the implicit parameter uses \Index{type-class} \lstinline$type$\use{type}, the
    969 implicit argument must be an object type; if it uses \lstinline$dtype$, the implicit argument must
    970 be an object type or an incomplete type; and if it uses \lstinline$ftype$, the implicit argument
    971 must be a function type.
    972 
    973 \item
    974 if an explicit parameter's type uses any implicit parameters, then the corresponding explicit
    975 argument must have a type that is (or can be safely converted\index{safe conversion} to) the type
    976 produced by substituting the implicit arguments for the implicit parameters in the explicit
    977 parameter type.
    978 
    979 \item
    980 the remaining explicit arguments must match the remaining explicit parameters, as described for
    981 monomorphic function designators.
    982 
    983 \item
    984 for each \Index{assertion parameter} in the function designator's type, there must be an object or
    985 function with the same identifier that is visible at the call site and whose type is compatible with
    986 or can be specialized to the type of the assertion declaration.
     772If the declaration of the implicit parameter uses \Index{type-class} \lstinline$type$\use{type}, the implicit argument must be an object type;
     773if it uses \lstinline$dtype$, the implicit argument must be an object type or an incomplete type;
     774and if it uses \lstinline$ftype$, the implicit argument must be a function type.
     775
     776\item if an explicit parameter's type uses any implicit parameters, then the corresponding explicit argument must have a type that is (or can be safely converted\index{safe conversion} to) the type produced by substituting the implicit arguments for the implicit parameters in the explicit parameter type.
     777
     778\item the remaining explicit arguments must match the remaining explicit parameters, as described for monomorphic function designators.
     779
     780\item for each \Index{assertion parameter} in the function designator's type, there must be an object or function with the same identifier that is visible at the call site and whose type is compatible with or can be specialized to the type of the assertion declaration.
    987781\end{itemize}
    988 There is a valid interpretation for each such set of implicit parameters. The type of each valid
    989 interpretation is the return type of the function designator with implicit parameter values
    990 substituted for the implicit arguments.
    991 
    992 A valid interpretation is ambiguous\index{ambiguous interpretation} if the function designator or
    993 any of the argument interpretations is ambiguous.
    994 
    995 Every valid interpretation whose return type is not compatible with any other valid interpretation's
    996 return type is an interpretation of the function call expression.
    997 
    998 Every set of valid interpretations that have mutually compatible\index{compatible type} result types
    999 also produces an interpretation of the function call expression. The type of the interpretation is
    1000 the \Index{composite type} of the types of the valid interpretations, and the value of the
    1001 interpretation is that of the \Index{best valid interpretation}.
    1002 \begin{rationale}
    1003 One desirable property of a polymorphic programming language is \define{generalizability}: the
    1004 ability to replace an abstraction with a more general but equivalent abstraction without requiring
    1005 changes in any of the uses of the original\cite{Cormack90}. For instance, it should be possible to
    1006 replace a function ``\lstinline$int f( int );$'' with ``\lstinline$forall( type T ) T f( T );$''
    1007 without affecting any calls of \lstinline$f$.
     782There is a valid interpretation for each such set of implicit parameters.
     783The type of each valid interpretation is the return type of the function designator with implicit parameter values substituted for the implicit arguments.
     784
     785A valid interpretation is ambiguous\index{ambiguous interpretation} if the function designator or any of the argument interpretations is ambiguous.
     786
     787Every valid interpretation whose return type is not compatible with any other valid interpretation's return type is an interpretation of the function call expression.
     788
     789Every set of valid interpretations that have mutually compatible\index{compatible type} result types also produces an interpretation of the function call expression.
     790The type of the interpretation is the \Index{composite type} of the types of the valid interpretations, and the value of the interpretation is that of the \Index{best valid interpretation}.
     791\begin{rationale}
     792One desirable property of a polymorphic programming language is \define{generalizability}: the ability to replace an abstraction with a more general but equivalent abstraction without requiring changes in any of the uses of the original\cite{Cormack90}.
     793For instance, it should be possible to replace a function ``\lstinline$int f( int );$'' with ``\lstinline$forall( otype T ) T f( T );$'' without affecting any calls of \lstinline$f$.
    1008794
    1009795\CFA\index{deficiencies!generalizability} does not fully possess this property, because
     
    1015801float f;
    1016802double d;
    1017 f = g( f, f );  // (1)
    1018 f = g( i, f );  // (2) (safe conversion to float)
    1019 f = g( d, f );  // (3) (unsafe conversion to float)
    1020 \end{lstlisting}
    1021 If \lstinline$g$ was replaced by ``\lstinline$forall( type T ) T g( T, T );$'', the first and second
    1022 calls would be unaffected, but the third would change: \lstinline$f$ would be converted to
     803f = g( f, f );          // (1)
     804f = g( i, f );          // (2) (safe conversion to float)
     805f = g( d, f );          // (3) (unsafe conversion to float)
     806\end{lstlisting}
     807If \lstinline$g$ was replaced by ``\lstinline$forall( otype T ) T g( T, T );$'', the first and second calls would be unaffected, but the third would change: \lstinline$f$ would be converted to
    1023808\lstinline$double$, and the result would be a \lstinline$double$.
    1024809
    1025 Another example is the function ``\lstinline$void h( int *);$''. This function can be passed a
    1026 \lstinline$void *$ argument, but the generalization ``\lstinline$forall( type T ) void h( T *);$''
    1027 can not. In this case, \lstinline$void$ is not a valid value for \lstinline$T$ because it is not an
    1028 object type. If unsafe conversions were allowed, \lstinline$T$ could be inferred to be \emph{any}
    1029 object type, which is undesirable.
     810Another example is the function ``\lstinline$void h( int *);$''.
     811This function can be passed a
     812\lstinline$void *$ argument, but the generalization ``\lstinline$forall( otype T ) void h( T *);$'' can not.
     813In this case, \lstinline$void$ is not a valid value for \lstinline$T$ because it is not an object type.
     814If unsafe conversions were allowed, \lstinline$T$ could be inferred to be \emph{any} object type, which is undesirable.
    1030815\end{rationale}
    1031816
     
    1033818A function called ``\lstinline$?()$'' might be part of a numerical differentiation package.
    1034819\begin{lstlisting}
    1035 extern type Derivative;
     820extern otype Derivative;
    1036821extern double ?()( Derivative, double );
    1037822extern Derivative derivative_of( double (*f)( double ) );
     
    1045830For that interpretation, the function call is treated as ``\lstinline$?()( sin_dx, 12.9 )$''.
    1046831\begin{lstlisting}
    1047 int f( long );          // (1) 
    1048 int f( int, int );      // (2) 
     832int f( long );          // (1)
     833int f( int, int );      // (2)
    1049834int f( int *);          // (3)
    1050 
    1051835int i = f( 5 );         // calls (1)
    1052836\end{lstlisting}
    1053 Function (1) provides a valid interpretation of ``\lstinline$f( 5 )$'', using an implicit
    1054 \lstinline$int$ to \lstinline$long$ conversion. The other functions do not, since the second
    1055 requires two arguments, and since there is no implicit conversion from \lstinline$int$ to
    1056 \lstinline$int *$ that could be used with the third function.
    1057 
    1058 \begin{lstlisting}
    1059 forall( type T ) T h( T );
     837Function (1) provides a valid interpretation of ``\lstinline$f( 5 )$'', using an implicit \lstinline$int$ to \lstinline$long$ conversion.
     838The other functions do not, since the second requires two arguments, and since there is no implicit conversion from \lstinline$int$ to \lstinline$int *$ that could be used with the third function.
     839
     840\begin{lstlisting}
     841forall( otype T ) T h( T );
    1060842double d = h( 1.5 );
    1061843\end{lstlisting}
     
    1064846
    1065847\begin{lstlisting}
    1066 forall( type T, type U ) void g( T, U );        // (4)
    1067 forall( type T ) void g( T, T );                        // (5)
    1068 forall( type T ) void g( T, long );                     // (6)
    1069 void g( long, long );                                           // (7) 
     848forall( otype T, otype U ) void g( T, U );      // (4)
     849forall( otype T ) void g( T, T );                       // (5)
     850forall( otype T ) void g( T, long );                    // (6)
     851void g( long, long );                                           // (7)
    1070852double d;
    1071853int i;
    1072854int *p;
    1073 
    1074 g( d, d );                      // calls (5)
    1075 g( d, i );                      // calls (6)
    1076 g( i, i );                      // calls (7)
     855g( d, d );                      // calls (5)
     856g( d, i );                      // calls (6)
     857g( i, i );                      // calls (7)
    1077858g( i, p );                      // calls (4)
    1078859\end{lstlisting}
    1079 The first call has valid interpretations for all four versions of \lstinline$g$. (6) and (7) are
    1080 discarded because they involve unsafe \lstinline$double$-to-\lstinline$long$ conversions. (5) is
    1081 chosen because it is less polymorphic than (4).
    1082 
    1083 For the second call, (7) is again discarded. Of the remaining interpretations for (4), (5), and (6)
    1084 (with \lstinline$i$ converted to \lstinline$long$), (6) is chosen because it is the least
    1085 polymorphic.
    1086 
    1087 The third call has valid interpretations for all of the functions; (7) is chosen since it is not
    1088 polymorphic at all.
    1089 
    1090 The fourth call has no interpretation for (5), because its arguments must have compatible type. (4)
    1091 is chosen because it does not involve unsafe conversions.
    1092 \begin{lstlisting}
    1093 forall( type T ) T min( T, T );
     860The first call has valid interpretations for all four versions of \lstinline$g$. (6) and (7) are discarded because they involve unsafe \lstinline$double$-to-\lstinline$long$ conversions. (5) is chosen because it is less polymorphic than (4).
     861
     862For the second call, (7) is again discarded.
     863Of the remaining interpretations for (4), (5), and (6) (with \lstinline$i$ converted to \lstinline$long$), (6) is chosen because it is the least polymorphic.
     864
     865The third call has valid interpretations for all of the functions;
     866(7) is chosen since it is not polymorphic at all.
     867
     868The fourth call has no interpretation for (5), because its arguments must have compatible type. (4) is chosen because it does not involve unsafe conversions.
     869\begin{lstlisting}
     870forall( otype T ) T min( T, T );
    1094871double max( double, double );
    1095 context min_max( T ) {@\impl{min_max}@
     872trait min_max( T ) {@\impl{min_max}@
    1096873        T min( T, T );
    1097874        T max( T, T );
    1098875}
    1099 forall( type U | min_max( U ) ) void shuffle( U, U );
    1100 shuffle(9, 10);
    1101 \end{lstlisting}
    1102 The only possibility for \lstinline$U$ is \lstinline$double$, because that is the type used in the
    1103 only visible \lstinline$max$ function. 9 and 10 must be converted to \lstinline$double$, and
     876forall( otype U | min_max( U ) ) void shuffle( U, U );
     877shuffle( 9, 10 );
     878\end{lstlisting}
     879The only possibility for \lstinline$U$ is \lstinline$double$, because that is the type used in the only visible \lstinline$max$ function. 9 and 10 must be converted to \lstinline$double$, and
    1104880\lstinline$min$ must be specialized with \lstinline$T$ bound to \lstinline$double$.
    1105881\begin{lstlisting}
    1106 extern void q( int );           // (8) 
    1107 extern void q( void * );        // (9) 
     882extern void q( int );           // (8)
     883extern void q( void * );        // (9)
    1108884extern void r();
    1109885q( 0 );
    1110886r( 0 );
    1111887\end{lstlisting}
    1112 The \lstinline$int 0$ could be passed to (8), or the \lstinline$(void *)$ \Index{specialization} of
    1113 the null pointer\index{null pointer} \lstinline$0$\use{0} could be passed to (9). The former is
    1114 chosen because the \lstinline$int$ \lstinline$0$ is \Index{less polymorphic}. For
    1115 the same reason, \lstinline$int$ \lstinline$0$ is passed to \lstinline$r()$, even though it has
    1116 \emph{no} declared parameter types.
     888The \lstinline$int 0$ could be passed to (8), or the \lstinline$(void *)$ \Index{specialization} of the null pointer\index{null pointer} \lstinline$0$\use{0} could be passed to (9).
     889The former is chosen because the \lstinline$int$ \lstinline$0$ is \Index{less polymorphic}.
     890For the same reason, \lstinline$int$ \lstinline$0$ is passed to \lstinline$r()$, even though it has \emph{no} declared parameter types.
    1117891
    1118892
    1119893\subsubsection{Structure and union members}
    1120894
    1121 \semantics In the member selection expression ``\lstinline$s$.\lstinline$m$'', there shall be at
    1122 least one interpretation of \lstinline$s$ whose type is a structure type or union type containing a
    1123 member named \lstinline$m$. If two or more interpretations of \lstinline$s$ have members named
    1124 \lstinline$m$ with mutually compatible types, then the expression has an \Index{ambiguous
    1125 interpretation} whose type is the composite type of the types of the members. If an interpretation
    1126 of \lstinline$s$ has a member \lstinline$m$ whose type is not compatible with any other
    1127 \lstinline$s$'s \lstinline$m$, then the expression has an interpretation with the member's type. The
    1128 expression has no other interpretations.
     895\semantics In the member selection expression ``\lstinline$s$.\lstinline$m$'', there shall be at least one interpretation of \lstinline$s$ whose type is a structure type or union type containing a member named \lstinline$m$.
     896If two or more interpretations of \lstinline$s$ have members named
     897\lstinline$m$ with mutually compatible types, then the expression has an \Index{ambiguous interpretation} whose type is the composite type of the types of the members.
     898If an interpretation of \lstinline$s$ has a member \lstinline$m$ whose type is not compatible with any other
     899\lstinline$s$'s \lstinline$m$, then the expression has an interpretation with the member's type.
     900The expression has no other interpretations.
    1129901
    1130902The expression ``\lstinline$p->m$'' has the same interpretations as the expression
     
    1136908\predefined
    1137909\begin{lstlisting}
    1138 _Bool ?++( volatile _Bool * ),
    1139         ?++( _Atomic volatile _Bool * );
    1140 char ?++( volatile char * ),
    1141         ?++( _Atomic volatile char * );
    1142 signed char ?++( volatile signed char * ),
    1143         ?++( _Atomic volatile signed char * );
    1144 unsigned char ?++( volatile signed char * ),
    1145         ?++( _Atomic volatile signed char * );
    1146 short int ?++( volatile short int * ),
    1147         ?++( _Atomic volatile short int * );
    1148 unsigned short int ?++( volatile unsigned short int * ),
    1149         ?++( _Atomic volatile unsigned short int * );
    1150 int ?++( volatile int * ),
    1151         ?++( _Atomic volatile int * );
    1152 unsigned int ?++( volatile unsigned int * ),
    1153         ?++( _Atomic volatile unsigned int * );
    1154 long int ?++( volatile long int * ),
    1155         ?++( _Atomic volatile long int * );
    1156 long unsigned int ?++( volatile long unsigned int * ),
    1157         ?++( _Atomic volatile long unsigned int * );
    1158 long long int ?++( volatile long long int * ),
    1159         ?++( _Atomic volatile long long int * );
    1160 long long unsigned ?++( volatile long long unsigned int * ),
    1161         ?++( _Atomic volatile long long unsigned int * );
    1162 float ?++( volatile float * ),
    1163         ?++( _Atomic volatile float * );
    1164 double ?++( volatile double * ),
    1165         ?++( _Atomic volatile double * );
    1166 long double ?++( volatile long double * ),
    1167         ?++( _Atomic volatile long double * );
    1168 
    1169 forall( type T ) T * ?++( T * restrict volatile * ),
    1170         * ?++( T * _Atomic restrict volatile * );
    1171 
    1172 forall( type T ) _Atomic T * ?++( _Atomic T * restrict volatile * ),
    1173         * ?++( _Atomic T * _Atomic restrict volatile * );
    1174 
    1175 forall( type T ) const T * ?++( const T * restrict volatile * ),
    1176         * ?++( const T * _Atomic restrict volatile * );
    1177 
    1178 forall( type T ) volatile T * ?++( volatile T * restrict volatile * ),
    1179         * ?++( volatile T * _Atomic restrict volatile * );
    1180 
    1181 forall( type T ) restrict T * ?++( restrict T * restrict volatile * ),
    1182         * ?++( restrict T * _Atomic restrict volatile * );
    1183 
    1184 forall( type T ) _Atomic const T * ?++( _Atomic const T * restrict volatile * ),
     910_Bool ?++( volatile _Bool * ), ?++( _Atomic volatile _Bool * );
     911char ?++( volatile char * ), ?++( _Atomic volatile char * );
     912signed char ?++( volatile signed char * ), ?++( _Atomic volatile signed char * );
     913unsigned char ?++( volatile signed char * ), ?++( _Atomic volatile signed char * );
     914short int ?++( volatile short int * ), ?++( _Atomic volatile short int * );
     915unsigned short int ?++( volatile unsigned short int * ), ?++( _Atomic volatile unsigned short int * );
     916int ?++( volatile int * ), ?++( _Atomic volatile int * );
     917unsigned int ?++( volatile unsigned int * ), ?++( _Atomic volatile unsigned int * );
     918long int ?++( volatile long int * ), ?++( _Atomic volatile long int * );
     919long unsigned int ?++( volatile long unsigned int * ), ?++( _Atomic volatile long unsigned int * );
     920long long int ?++( volatile long long int * ), ?++( _Atomic volatile long long int * );
     921long long unsigned ?++( volatile long long unsigned int * ), ?++( _Atomic volatile long long unsigned int * );
     922float ?++( volatile float * ), ?++( _Atomic volatile float * );
     923double ?++( volatile double * ), ?++( _Atomic volatile double * );
     924long double ?++( volatile long double * ), ?++( _Atomic volatile long double * );
     925
     926forall( otype T ) T * ?++( T * restrict volatile * ), * ?++( T * _Atomic restrict volatile * );
     927forall( otype T ) _Atomic T * ?++( _Atomic T * restrict volatile * ), * ?++( _Atomic T * _Atomic restrict volatile * );
     928forall( otype T ) const T * ?++( const T * restrict volatile * ), * ?++( const T * _Atomic restrict volatile * );
     929forall( otype T ) volatile T * ?++( volatile T * restrict volatile * ), * ?++( volatile T * _Atomic restrict volatile * );
     930forall( otype T ) restrict T * ?++( restrict T * restrict volatile * ), * ?++( restrict T * _Atomic restrict volatile * );
     931forall( otype T ) _Atomic const T * ?++( _Atomic const T * restrict volatile * ),
    1185932        * ?++( _Atomic const T * _Atomic restrict volatile * );
    1186 
    1187 forall( type T ) _Atomic restrict T * ?++( _Atomic restrict T * restrict volatile * ),
     933forall( otype T ) _Atomic restrict T * ?++( _Atomic restrict T * restrict volatile * ),
    1188934        * ?++( _Atomic restrict T * _Atomic restrict volatile * );
    1189 
    1190 forall( type T ) _Atomic volatile T * ?++( _Atomic volatile T * restrict volatile * ),
     935forall( otype T ) _Atomic volatile T * ?++( _Atomic volatile T * restrict volatile * ),
    1191936        * ?++( _Atomic volatile T * _Atomic restrict volatile * );
    1192 
    1193 forall( type T ) const restrict T * ?++( const restrict T * restrict volatile * ),
     937forall( otype T ) const restrict T * ?++( const restrict T * restrict volatile * ),
    1194938        * ?++( const restrict T * _Atomic restrict volatile * );
    1195 
    1196 forall( type T ) const volatile T * ?++( const volatile T * restrict volatile * ),
     939forall( otype T ) const volatile T * ?++( const volatile T * restrict volatile * ),
    1197940        * ?++( const volatile T * _Atomic restrict volatile * );
    1198 
    1199 forall( type T ) restrict volatile T * ?++( restrict volatile T * restrict volatile * ),
     941forall( otype T ) restrict volatile T * ?++( restrict volatile T * restrict volatile * ),
    1200942        * ?++( restrict volatile T * _Atomic restrict volatile * );
    1201 
    1202 forall( type T ) _Atomic const restrict T * ?++( _Atomic const restrict T * restrict volatile * ),
     943forall( otype T ) _Atomic const restrict T * ?++( _Atomic const restrict T * restrict volatile * ),
    1203944        * ?++( _Atomic const restrict T * _Atomic restrict volatile * );
    1204 
    1205 forall( type T ) _Atomic const volatile T * ?++( _Atomic const volatile T * restrict volatile * ),
     945forall( otype T ) _Atomic const volatile T * ?++( _Atomic const volatile T * restrict volatile * ),
    1206946        * ?++( _Atomic const volatile T * _Atomic restrict volatile * );
    1207 
    1208 forall( type T ) _Atomic restrict volatile T * ?++( _Atomic restrict volatile T * restrict volatile * ),
     947forall( otype T ) _Atomic restrict volatile T * ?++( _Atomic restrict volatile T * restrict volatile * ),
    1209948        * ?++( _Atomic restrict volatile T * _Atomic restrict volatile * );
    1210 
    1211 forall( type T ) const restrict volatile T * ?++( const restrict volatile T * restrict volatile * ),
     949forall( otype T ) const restrict volatile T * ?++( const restrict volatile T * restrict volatile * ),
    1212950        * ?++( const restrict volatile T * _Atomic restrict volatile * );
    1213 
    1214 forall( type T ) _Atomic const restrict volatile T * ?++( _Atomic const restrict volatile T * restrict volatile * ),
     951forall( otype T ) _Atomic const restrict volatile T * ?++( _Atomic const restrict volatile T * restrict volatile * ),
    1215952        * ?++( _Atomic const restrict volatile T * _Atomic restrict volatile * );
    1216953
    1217 _Bool ?--( volatile _Bool * ),
    1218         ?--( _Atomic volatile _Bool * );
    1219 char ?--( volatile char * ),
    1220         ?--( _Atomic volatile char * );
    1221 signed char ?--( volatile signed char * ),
    1222         ?--( _Atomic volatile signed char * );
    1223 unsigned char ?--( volatile signed char * ),
    1224         ?--( _Atomic volatile signed char * );
    1225 short int ?--( volatile short int * ),
    1226         ?--( _Atomic volatile short int * );
    1227 unsigned short int ?--( volatile unsigned short int * ),
    1228         ?--( _Atomic volatile unsigned short int * );
    1229 int ?--( volatile int * ),
    1230         ?--( _Atomic volatile int * );
    1231 unsigned int ?--( volatile unsigned int * ),
    1232         ?--( _Atomic volatile unsigned int * );
    1233 long int ?--( volatile long int * ),
    1234         ?--( _Atomic volatile long int * );
    1235 long unsigned int ?--( volatile long unsigned int * ),
    1236         ?--( _Atomic volatile long unsigned int * );
    1237 long long int ?--( volatile long long int * ),
    1238         ?--( _Atomic volatile long long int * );
    1239 long long unsigned ?--( volatile long long unsigned int * ),
    1240         ?--( _Atomic volatile long long unsigned int * );
    1241 float ?--( volatile float * ),
    1242         ?--( _Atomic volatile float * );
    1243 double ?--( volatile double * ),
    1244         ?--( _Atomic volatile double * );
    1245 long double ?--( volatile long double * ),
    1246         ?--( _Atomic volatile long double * );
    1247 
    1248 forall( type T ) T * ?--( T * restrict volatile * ),
    1249         * ?--( T * _Atomic restrict volatile * );
    1250 
    1251 forall( type T ) _Atomic T * ?--( _Atomic T * restrict volatile * ),
    1252         * ?--( _Atomic T * _Atomic restrict volatile * );
    1253 
    1254 forall( type T ) const T * ?--( const T * restrict volatile * ),
    1255         * ?--( const T * _Atomic restrict volatile * );
    1256 
    1257 forall( type T ) volatile T * ?--( volatile T * restrict volatile * ),
    1258         * ?--( volatile T * _Atomic restrict volatile * );
    1259 
    1260 forall( type T ) restrict T * ?--( restrict T * restrict volatile * ),
    1261         * ?--( restrict T * _Atomic restrict volatile * );
    1262 
    1263 forall( type T ) _Atomic const T * ?--( _Atomic const T * restrict volatile * ),
     954_Bool ?--( volatile _Bool * ), ?--( _Atomic volatile _Bool * );
     955char ?--( volatile char * ), ?--( _Atomic volatile char * );
     956signed char ?--( volatile signed char * ), ?--( _Atomic volatile signed char * );
     957unsigned char ?--( volatile signed char * ), ?--( _Atomic volatile signed char * );
     958short int ?--( volatile short int * ), ?--( _Atomic volatile short int * );
     959unsigned short int ?--( volatile unsigned short int * ), ?--( _Atomic volatile unsigned short int * );
     960int ?--( volatile int * ), ?--( _Atomic volatile int * );
     961unsigned int ?--( volatile unsigned int * ), ?--( _Atomic volatile unsigned int * );
     962long int ?--( volatile long int * ), ?--( _Atomic volatile long int * );
     963long unsigned int ?--( volatile long unsigned int * ), ?--( _Atomic volatile long unsigned int * );
     964long long int ?--( volatile long long int * ), ?--( _Atomic volatile long long int * );
     965long long unsigned ?--( volatile long long unsigned int * ), ?--( _Atomic volatile long long unsigned int * );
     966float ?--( volatile float * ), ?--( _Atomic volatile float * );
     967double ?--( volatile double * ), ?--( _Atomic volatile double * );
     968long double ?--( volatile long double * ), ?--( _Atomic volatile long double * );
     969
     970forall( otype T ) T * ?--( T * restrict volatile * ), * ?--( T * _Atomic restrict volatile * );
     971forall( otype T ) _Atomic T * ?--( _Atomic T * restrict volatile * ), * ?--( _Atomic T * _Atomic restrict volatile * );
     972forall( otype T ) const T * ?--( const T * restrict volatile * ), * ?--( const T * _Atomic restrict volatile * );
     973forall( otype T ) volatile T * ?--( volatile T * restrict volatile * ), * ?--( volatile T * _Atomic restrict volatile * );
     974forall( otype T ) restrict T * ?--( restrict T * restrict volatile * ), * ?--( restrict T * _Atomic restrict volatile * );
     975forall( otype T ) _Atomic const T * ?--( _Atomic const T * restrict volatile * ),
    1264976        * ?--( _Atomic const T * _Atomic restrict volatile * );
    1265 
    1266 forall( type T ) _Atomic restrict T * ?--( _Atomic restrict T * restrict volatile * ),
     977forall( otype T ) _Atomic restrict T * ?--( _Atomic restrict T * restrict volatile * ),
    1267978        * ?--( _Atomic restrict T * _Atomic restrict volatile * );
    1268 
    1269 forall( type T ) _Atomic volatile T * ?--( _Atomic volatile T * restrict volatile * ),
     979forall( otype T ) _Atomic volatile T * ?--( _Atomic volatile T * restrict volatile * ),
    1270980        * ?--( _Atomic volatile T * _Atomic restrict volatile * );
    1271 
    1272 forall( type T ) const restrict T * ?--( const restrict T * restrict volatile * ),
     981forall( otype T ) const restrict T * ?--( const restrict T * restrict volatile * ),
    1273982        * ?--( const restrict T * _Atomic restrict volatile * );
    1274 
    1275 forall( type T ) const volatile T * ?--( const volatile T * restrict volatile * ),
     983forall( otype T ) const volatile T * ?--( const volatile T * restrict volatile * ),
    1276984        * ?--( const volatile T * _Atomic restrict volatile * );
    1277 
    1278 forall( type T ) restrict volatile T * ?--( restrict volatile T * restrict volatile * ),
     985forall( otype T ) restrict volatile T * ?--( restrict volatile T * restrict volatile * ),
    1279986        * ?--( restrict volatile T * _Atomic restrict volatile * );
    1280 
    1281 forall( type T ) _Atomic const restrict T * ?--( _Atomic const restrict T * restrict volatile * ),
     987forall( otype T ) _Atomic const restrict T * ?--( _Atomic const restrict T * restrict volatile * ),
    1282988        * ?--( _Atomic const restrict T * _Atomic restrict volatile * );
    1283 
    1284 forall( type T ) _Atomic const volatile T * ?--( _Atomic const volatile T * restrict volatile * ),
     989forall( otype T ) _Atomic const volatile T * ?--( _Atomic const volatile T * restrict volatile * ),
    1285990        * ?--( _Atomic const volatile T * _Atomic restrict volatile * );
    1286 
    1287 forall( type T ) _Atomic restrict volatile T * ?--( _Atomic restrict volatile T * restrict volatile * ),
     991forall( otype T ) _Atomic restrict volatile T * ?--( _Atomic restrict volatile T * restrict volatile * ),
    1288992        * ?--( _Atomic restrict volatile T * _Atomic restrict volatile * );
    1289 
    1290 forall( type T ) const restrict volatile T * ?--( const restrict volatile T * restrict volatile * ),
     993forall( otype T ) const restrict volatile T * ?--( const restrict volatile T * restrict volatile * ),
    1291994        * ?--( const restrict volatile T * _Atomic restrict volatile * );
    1292 
    1293 forall( type T ) _Atomic const restrict volatile T * ?--( _Atomic const restrict volatile T * restrict volatile * ),
     995forall( otype T ) _Atomic const restrict volatile T * ?--( _Atomic const restrict volatile T * restrict volatile * ),
    1294996        * ?--( _Atomic const restrict volatile T * _Atomic restrict volatile * );
    1295997\end{lstlisting}
     
    13081010
    13091011\begin{rationale}
    1310 Note that ``\lstinline$++$'' and ``\lstinline$--$'' are rewritten as function calls that are given a
    1311 pointer to that operand. (This is true of all operators that modify an operand.) As Hamish Macdonald
    1312 has pointed out, this forces the modified operand of such expressions to be an lvalue. This
    1313 partially enforces the C semantic rule that such operands must be \emph{modifiable} lvalues.
    1314 \end{rationale}
    1315 
    1316 \begin{rationale}
    1317 In C, a semantic rule requires that pointer operands of increment and decrement be pointers to
    1318 object types. Hence, \lstinline$void *$ objects cannot be incremented. In \CFA, the restriction
    1319 follows from the use of a \lstinline$type$ parameter in the predefined function definitions, as
    1320 opposed to \lstinline$dtype$, since only object types can be inferred arguments corresponding to the
    1321 type parameter \lstinline$T$.
     1012Note that ``\lstinline$++$'' and ``\lstinline$--$'' are rewritten as function calls that are given a pointer to that operand. (This is true of all operators that modify an operand.) As Hamish Macdonald has pointed out, this forces the modified operand of such expressions to be an lvalue.
     1013This partially enforces the C semantic rule that such operands must be \emph{modifiable} lvalues.
     1014\end{rationale}
     1015
     1016\begin{rationale}
     1017In C, a semantic rule requires that pointer operands of increment and decrement be pointers to object types.
     1018Hence, \lstinline$void *$ objects cannot be incremented.
     1019In \CFA, the restriction follows from the use of a \lstinline$type$ parameter in the predefined function definitions, as opposed to \lstinline$dtype$, since only object types can be inferred arguments corresponding to the type parameter \lstinline$T$.
    13221020\end{rationale}
    13231021
    13241022\semantics
    1325 First, each interpretation of the operand of an increment or decrement expression is considered
    1326 separately. For each interpretation that is a bit-field or is declared with the
    1327 \lstinline$register$\index{register@{\lstinline$register$}} \index{Itorage-class specifier}, the
    1328 expression has one valid interpretation, with the type of the operand, and the expression is
    1329 ambiguous if the operand is.
    1330 
    1331 For the remaining interpretations, the expression is rewritten, and the interpretations of the
    1332 expression are the interpretations of the corresponding function call. Finally, all interpretations
    1333 of the expression produced for the different interpretations of the operand are combined to produce
    1334 the interpretations of the expression as a whole; where interpretations have compatible result
    1335 types, the best interpretations are selected in the manner described for function call expressions.
     1023First, each interpretation of the operand of an increment or decrement expression is considered separately.
     1024For each interpretation that is a bit-field or is declared with the
     1025\lstinline$register$\index{register@{\lstinline$register$}} \index{Itorage-class specifier}, the expression has one valid interpretation, with the type of the operand, and the expression is ambiguous if the operand is.
     1026
     1027For the remaining interpretations, the expression is rewritten, and the interpretations of the expression are the interpretations of the corresponding function call.
     1028Finally, all interpretations of the expression produced for the different interpretations of the operand are combined to produce the interpretations of the expression as a whole; where interpretations have compatible result types, the best interpretations are selected in the manner described for function call expressions.
    13361029
    13371030\examples
     
    13461039\lstinline$vs++$ calls the \lstinline$?++$ function with the \lstinline$volatile short *$ parameter.
    13471040\lstinline$s++$ does the same, applying the safe conversion from \lstinline$short int *$ to
    1348 \lstinline$volatile short int *$. Note that there is no conversion that adds an \lstinline$_Atomic$
    1349 qualifier, so the \lstinline$_Atomic volatile short int$ overloading does not provide a valid
    1350 interpretation.
     1041\lstinline$volatile short int *$.
     1042Note that there is no conversion that adds an \lstinline$_Atomic$ qualifier, so the \lstinline$_Atomic volatile short int$ overloading does not provide a valid interpretation.
    13511043\end{sloppypar}
    13521044
    1353 There is no safe conversion from \lstinline$const short int *$ to \lstinline$volatile short int *$,
    1354 and no \lstinline$?++$ function that accepts a \lstinline$const *$ parameter, so \lstinline$cs++$
    1355 has no valid interpretations.
    1356 
    1357 The best valid interpretation of \lstinline$as++$ calls the \lstinline$short ?++$ function with the
    1358 \lstinline$_Atomic volatile short int *$ parameter, applying a safe conversion to add the
    1359 \lstinline$volatile$ qualifier.
    1360 
    1361 \begin{lstlisting}
    1362 char * const restrict volatile * restrict volatile pqpc; pqpc++
    1363 char * * restrict volatile ppc; ppc++;
    1364 \end{lstlisting}
    1365 Since \lstinline$&(pqpc)$ has type \lstinline$char * const restrict volatile * restrict volatile *$,
    1366 the best valid interpretation of \lstinline$pqpc++$ calls the polymorphic \lstinline$?++$ function
    1367 with the \lstinline$const restrict volatile T * restrict volatile *$ parameter, inferring
    1368 \lstinline$T$ to be \lstinline$char *$.
    1369 
    1370 \begin{sloppypar}
    1371 \lstinline$ppc++$ calls the same function, again inferring \lstinline$T$ to be \lstinline$char *$,
    1372 and using the safe conversions from \lstinline$T$ to \lstinline$T const restrict volatile$.
    1373 \end{sloppypar}
    1374 
    1375 \begin{rationale}
    1376 Increment and decrement expressions show up a deficiency of \CFA's type system. There is no such
    1377 thing as a pointer to a register object or bit-field\index{deficiencies!pointers to bit-fields}.
    1378 Therefore, there is no way to define a function that alters them, and hence no way to define
    1379 increment and decrement functions for them. As a result, the semantics of increment and decrement
    1380 expressions must treat them specially. This holds true for all of the operators that may modify
    1381 such objects.
    1382 \end{rationale}
    1383 
    1384 \begin{rationale}
    1385 The polymorphic overloadings for pointer increment and decrement can be understood by considering
    1386 increasingly complex types.
     1045There is no safe conversion from \lstinline$const short int *$ to \lstinline$volatile short int *$, and no \lstinline$?++$ function that accepts a \lstinline$const *$ parameter, so \lstinline$cs++$ has no valid interpretations.
     1046
     1047The best valid interpretation of \lstinline$as++$ calls the \lstinline$short ?++$ function with the \lstinline$_Atomic volatile short int *$ parameter, applying a safe conversion to add the \lstinline$volatile$ qualifier.
     1048\begin{lstlisting}
     1049char * const restrict volatile * restrict volatile pqpc;
     1050pqpc++
     1051char * * restrict volatile ppc;
     1052ppc++;
     1053\end{lstlisting}
     1054Since \lstinline$&(pqpc)$ has type \lstinline$char * const restrict volatile * restrict volatile *$, the best valid interpretation of \lstinline$pqpc++$ calls the polymorphic \lstinline$?++$ function with the \lstinline$const restrict volatile T * restrict volatile *$ parameter, inferring \lstinline$T$ to be \lstinline$char *$.
     1055
     1056\lstinline$ppc++$ calls the same function, again inferring \lstinline$T$ to be \lstinline$char *$, and using the safe conversions from \lstinline$T$ to \lstinline$T const$ \lstinline$restrict volatile$.
     1057
     1058\begin{rationale}
     1059Increment and decrement expressions show up a deficiency of \CFA's type system.
     1060There is no such thing as a pointer to a register object or bit-field\index{deficiencies!pointers to bit-fields}.
     1061Therefore, there is no way to define a function that alters them, and hence no way to define increment and decrement functions for them.
     1062As a result, the semantics of increment and decrement expressions must treat them specially.
     1063This holds true for all of the operators that may modify such objects.
     1064\end{rationale}
     1065
     1066\begin{rationale}
     1067The polymorphic overloadings for pointer increment and decrement can be understood by considering increasingly complex types.
    13871068\begin{enumerate}
    13881069\item
    1389 ``\lstinline$char * p; p++;$''. The argument to \lstinline$?++$ has type \lstinline$char * *$, and
    1390 the result has type \lstinline$char *$. The expression would be valid if \lstinline$?++$ were
    1391 declared by
    1392 \begin{lstlisting}
    1393 forall( type T ) T * ?++( T * * );
    1394 \end{lstlisting}
    1395 with \lstinline$T$ inferred to be \lstinline$char$.
    1396 
    1397 \item
    1398 ``\lstinline$char *restrict volatile qp; qp++$''. The result again has type \lstinline$char *$, but
    1399 the argument now has type \lstinline$char *restrict volatile *$, so it cannot be passed to the
    1400 hypothetical function declared in point 1. Hence the actual predefined function is
    1401 \begin{lstlisting}
    1402 forall( type T ) T * ?++( T * restrict volatile * );
    1403 \end{lstlisting}
    1404 which also accepts a \lstinline$char * *$ argument, because of the safe conversions that add
    1405 \lstinline$volatile$ and \lstinline$restrict$ qualifiers. (The parameter is not const-qualified, so
    1406 constant pointers cannot be incremented.)
    1407 
    1408 \item
    1409 ``\lstinline$char *_Atomic ap; ap++$''. The result again has type \lstinline$char *$, but no safe
    1410 conversion adds an \lstinline$_Atomic$ qualifier, so the function in point 2 is not applicable. A
    1411 separate overloading of \lstinline$?++$ is required.
    1412 
    1413 \item
    1414 ``\lstinline$char const volatile * pq; pq++$''. Here the result has type
     1070``\lstinline$char * p; p++;$''.
     1071The argument to \lstinline$?++$ has type \lstinline$char * *$, and the result has type \lstinline$char *$.
     1072The expression would be valid if \lstinline$?++$ were declared by
     1073\begin{lstlisting}
     1074forall( otype T ) T * ?++( T * * );
     1075\end{lstlisting} with \lstinline$T$ inferred to be \lstinline$char$.
     1076
     1077\item
     1078``\lstinline$char *restrict volatile qp; qp++$''.
     1079The result again has type \lstinline$char *$, but the argument now has type \lstinline$char *restrict volatile *$, so it cannot be passed to the hypothetical function declared in point 1.
     1080Hence the actual predefined function is
     1081\begin{lstlisting}
     1082forall( otype T ) T * ?++( T * restrict volatile * );
     1083\end{lstlisting} which also accepts a \lstinline$char * *$ argument, because of the safe conversions that add
     1084\lstinline$volatile$ and \lstinline$restrict$ qualifiers. (The parameter is not const-qualified, so constant pointers cannot be incremented.)
     1085
     1086\item
     1087``\lstinline$char *_Atomic ap; ap++$''.
     1088The result again has type \lstinline$char *$, but no safe conversion adds an \lstinline$_Atomic$ qualifier, so the function in point 2 is not applicable.
     1089A separate overloading of \lstinline$?++$ is required.
     1090
     1091\item
     1092``\lstinline$char const volatile * pq; pq++$''.
     1093Here the result has type
    14151094\lstinline$char const volatile *$, so a new overloading is needed:
    14161095\begin{lstlisting}
    1417 forall( type T ) T const volatile * ?++( T const volatile *restrict volatile * );
    1418 \end{lstlisting}
    1419 One overloading is needed for each combination of qualifiers in the pointed-at
    1420 type\index{deficiencies!pointers to qualified types}.
     1096forall( otype T ) T const volatile * ?++( T const volatile *restrict volatile * );
     1097\end{lstlisting}
     1098One overloading is needed for each combination of qualifiers in the pointed-at type\index{deficiencies!pointers to qualified types}.
    14211099 
    14221100\item
    1423 ``\lstinline$float *restrict * prp; prp++$''. The \lstinline$restrict$ qualifier is handled just
    1424 like \lstinline$const$ and \lstinline$volatile$ in the previous case:
    1425 \begin{lstlisting}
    1426 forall( type T ) T restrict * ?++( T restrict *restrict volatile * );
    1427 \end{lstlisting}
    1428 with \lstinline$T$ inferred to be \lstinline$float *$. This looks odd, because {\c11} contains a
    1429 constraint that requires restrict-qualified types to be pointer-to-object types, and \lstinline$T$
    1430 is not syntactically a pointer type. \CFA loosens the constraint.
     1101``\lstinline$float *restrict * prp; prp++$''.
     1102The \lstinline$restrict$ qualifier is handled just like \lstinline$const$ and \lstinline$volatile$ in the previous case:
     1103\begin{lstlisting}
     1104forall( otype T ) T restrict * ?++( T restrict *restrict volatile * );
     1105\end{lstlisting} with \lstinline$T$ inferred to be \lstinline$float *$.
     1106This looks odd, because {\c11} contains a constraint that requires restrict-qualified types to be pointer-to-object types, and \lstinline$T$ is not syntactically a pointer type. \CFA loosens the constraint.
    14311107\end{enumerate}
    14321108\end{rationale}
     
    14361112
    14371113\semantics
    1438 A compound literal has one interpretation, with the type given by the \nonterm{type-name} of the
    1439 compound literal.
     1114A compound literal has one interpretation, with the type given by the \nonterm{type-name} of the compound literal.
    14401115
    14411116
     
    14551130\rewriterules
    14561131\begin{lstlisting}
    1457 *a      @\rewrite@ *?(a) @\use{*?}@
    1458 +a      @\rewrite@ +?(a) @\use{+?}@
    1459 -a      @\rewrite@ -?(a) @\use{-?}@
    1460 ~a      @\rewrite@ ~?(a) @\use{~?}@
    1461 !a      @\rewrite@ !?(a) @\use{"!?}@
    1462 ++a     @\rewrite@ ++?(&(a)) @\use{++?}@
    1463 --a     @\rewrite@ --?(&(a)) @\use{--?}@
     1132*a      @\rewrite@ *?( a ) @\use{*?}@
     1133+a      @\rewrite@ +?( a ) @\use{+?}@
     1134-a      @\rewrite@ -?( a ) @\use{-?}@
     1135~a      @\rewrite@ ~?( a ) @\use{~?}@
     1136!a      @\rewrite@ !?( a ) @\use{"!?}@
     1137++a     @\rewrite@ ++?(&( a )) @\use{++?}@
     1138--a     @\rewrite@ --?(&( a )) @\use{--?}@
    14641139\end{lstlisting}
    14651140
     
    14691144\predefined
    14701145\begin{lstlisting}
    1471 _Bool ++?( volatile _Bool * ),
    1472         ++?( _Atomic volatile _Bool * );
    1473 char ++?( volatile char * ),
    1474         ++?( _Atomic volatile char * );
    1475 signed char ++?( volatile signed char * ),
    1476         ++?( _Atomic volatile signed char * );
    1477 unsigned char ++?( volatile signed char * ),
    1478         ++?( _Atomic volatile signed char * );
    1479 short int ++?( volatile short int * ),
    1480         ++?( _Atomic volatile short int * );
    1481 unsigned short int ++?( volatile unsigned short int * ),
    1482         ++?( _Atomic volatile unsigned short int * );
    1483 int ++?( volatile int * ),
    1484         ++?( _Atomic volatile int * );
    1485 unsigned int ++?( volatile unsigned int * ),
    1486         ++?( _Atomic volatile unsigned int * );
    1487 long int ++?( volatile long int * ),
    1488         ++?( _Atomic volatile long int * );
    1489 long unsigned int ++?( volatile long unsigned int * ),
    1490         ++?( _Atomic volatile long unsigned int * );
    1491 long long int ++?( volatile long long int * ),
    1492         ++?( _Atomic volatile long long int * );
    1493 long long unsigned ++?( volatile long long unsigned int * ),
    1494         ++?( _Atomic volatile long long unsigned int * );
    1495 float ++?( volatile float * ),
    1496         ++?( _Atomic volatile float * );
    1497 double ++?( volatile double * ),
    1498         ++?( _Atomic volatile double * );
    1499 long double ++?( volatile long double * ),
    1500         ++?( _Atomic volatile long double * );
    1501 
    1502 forall( type T ) T * ++?( T * restrict volatile * ),
    1503         * ++?( T * _Atomic restrict volatile * );
    1504 
    1505 forall( type T ) _Atomic T * ++?( _Atomic T * restrict volatile * ),
    1506         * ++?( _Atomic T * _Atomic restrict volatile * );
    1507 
    1508 forall( type T ) const T * ++?( const T * restrict volatile * ),
    1509         * ++?( const T * _Atomic restrict volatile * );
    1510 
    1511 forall( type T ) volatile T * ++?( volatile T * restrict volatile * ),
    1512         * ++?( volatile T * _Atomic restrict volatile * );
    1513 
    1514 forall( type T ) restrict T * ++?( restrict T * restrict volatile * ),
    1515         * ++?( restrict T * _Atomic restrict volatile * );
    1516 
    1517 forall( type T ) _Atomic const T * ++?( _Atomic const T * restrict volatile * ),
     1146_Bool ++?( volatile _Bool * ), ++?( _Atomic volatile _Bool * );
     1147char ++?( volatile char * ), ++?( _Atomic volatile char * );
     1148signed char ++?( volatile signed char * ), ++?( _Atomic volatile signed char * );
     1149unsigned char ++?( volatile signed char * ), ++?( _Atomic volatile signed char * );
     1150short int ++?( volatile short int * ), ++?( _Atomic volatile short int * );
     1151unsigned short int ++?( volatile unsigned short int * ), ++?( _Atomic volatile unsigned short int * );
     1152int ++?( volatile int * ), ++?( _Atomic volatile int * );
     1153unsigned int ++?( volatile unsigned int * ), ++?( _Atomic volatile unsigned int * );
     1154long int ++?( volatile long int * ), ++?( _Atomic volatile long int * );
     1155long unsigned int ++?( volatile long unsigned int * ), ++?( _Atomic volatile long unsigned int * );
     1156long long int ++?( volatile long long int * ), ++?( _Atomic volatile long long int * );
     1157long long unsigned ++?( volatile long long unsigned int * ), ++?( _Atomic volatile long long unsigned int * );
     1158float ++?( volatile float * ), ++?( _Atomic volatile float * );
     1159double ++?( volatile double * ), ++?( _Atomic volatile double * );
     1160long double ++?( volatile long double * ), ++?( _Atomic volatile long double * );
     1161
     1162forall( otype T ) T * ++?( T * restrict volatile * ), * ++?( T * _Atomic restrict volatile * );
     1163forall( otype T ) _Atomic T * ++?( _Atomic T * restrict volatile * ), * ++?( _Atomic T * _Atomic restrict volatile * );
     1164forall( otype T ) const T * ++?( const T * restrict volatile * ), * ++?( const T * _Atomic restrict volatile * );
     1165forall( otype T ) volatile T * ++?( volatile T * restrict volatile * ), * ++?( volatile T * _Atomic restrict volatile * );
     1166forall( otype T ) restrict T * ++?( restrict T * restrict volatile * ), * ++?( restrict T * _Atomic restrict volatile * );
     1167forall( otype T ) _Atomic const T * ++?( _Atomic const T * restrict volatile * ),
    15181168        * ++?( _Atomic const T * _Atomic restrict volatile * );
    1519 
    1520 forall( type T ) _Atomic volatile T * ++?( _Atomic volatile T * restrict volatile * ),
     1169forall( otype T ) _Atomic volatile T * ++?( _Atomic volatile T * restrict volatile * ),
    15211170        * ++?( _Atomic volatile T * _Atomic restrict volatile * );
    1522 
    1523 forall( type T ) _Atomic restrict T * ++?( _Atomic restrict T * restrict volatile * ),
     1171forall( otype T ) _Atomic restrict T * ++?( _Atomic restrict T * restrict volatile * ),
    15241172        * ++?( _Atomic restrict T * _Atomic restrict volatile * );
    1525 
    1526 forall( type T ) const volatile T * ++?( const volatile T * restrict volatile * ),
     1173forall( otype T ) const volatile T * ++?( const volatile T * restrict volatile * ),
    15271174        * ++?( const volatile T * _Atomic restrict volatile * );
    1528 
    1529 forall( type T ) const restrict T * ++?( const restrict T * restrict volatile * ),
     1175forall( otype T ) const restrict T * ++?( const restrict T * restrict volatile * ),
    15301176        * ++?( const restrict T * _Atomic restrict volatile * );
    1531 
    1532 forall( type T ) restrict volatile T * ++?( restrict volatile T * restrict volatile * ),
     1177forall( otype T ) restrict volatile T * ++?( restrict volatile T * restrict volatile * ),
    15331178        * ++?( restrict volatile T * _Atomic restrict volatile * );
    1534 
    1535 forall( type T ) _Atomic const volatile T * ++?( _Atomic const volatile T * restrict volatile * ),
     1179forall( otype T ) _Atomic const volatile T * ++?( _Atomic const volatile T * restrict volatile * ),
    15361180        * ++?( _Atomic const volatile T * _Atomic restrict volatile * );
    1537 
    1538 forall( type T ) _Atomic const restrict T * ++?( _Atomic const restrict T * restrict volatile * ),
     1181forall( otype T ) _Atomic const restrict T * ++?( _Atomic const restrict T * restrict volatile * ),
    15391182        * ++?( _Atomic const restrict T * _Atomic restrict volatile * );
    1540 
    1541 forall( type T ) _Atomic restrict volatile T * ++?( _Atomic restrict volatile T * restrict volatile * ),
     1183forall( otype T ) _Atomic restrict volatile T * ++?( _Atomic restrict volatile T * restrict volatile * ),
    15421184        * ++?( _Atomic restrict volatile T * _Atomic restrict volatile * );
    1543 
    1544 forall( type T ) const restrict volatile T * ++?( const restrict volatile T * restrict volatile * ),
     1185forall( otype T ) const restrict volatile T * ++?( const restrict volatile T * restrict volatile * ),
    15451186        * ++?( const restrict volatile T * _Atomic restrict volatile * );
    1546 
    1547 forall( type T ) _Atomic const restrict volatile T * ++?( _Atomic const restrict volatile T * restrict volatile * ),
     1187forall( otype T ) _Atomic const restrict volatile T * ++?( _Atomic const restrict volatile T * restrict volatile * ),
    15481188        * ++?( _Atomic const restrict volatile T * _Atomic restrict volatile * );
    15491189
    1550 _Bool --?( volatile _Bool * ),
    1551         --?( _Atomic volatile _Bool * );
    1552 char --?( volatile char * ),
    1553         --?( _Atomic volatile char * );
    1554 signed char --?( volatile signed char * ),
    1555         --?( _Atomic volatile signed char * );
    1556 unsigned char --?( volatile signed char * ),
    1557         --?( _Atomic volatile signed char * );
    1558 short int --?( volatile short int * ),
    1559         --?( _Atomic volatile short int * );
    1560 unsigned short int --?( volatile unsigned short int * ),
    1561         --?( _Atomic volatile unsigned short int * );
    1562 int --?( volatile int * ),
    1563         --?( _Atomic volatile int * );
    1564 unsigned int --?( volatile unsigned int * ),
    1565         --?( _Atomic volatile unsigned int * );
    1566 long int --?( volatile long int * ),
    1567         --?( _Atomic volatile long int * );
    1568 long unsigned int --?( volatile long unsigned int * ),
    1569         --?( _Atomic volatile long unsigned int * );
    1570 long long int --?( volatile long long int * ),
    1571         --?( _Atomic volatile long long int * );
    1572 long long unsigned --?( volatile long long unsigned int * ),
    1573         --?( _Atomic volatile long long unsigned int * );
    1574 float --?( volatile float * ),
    1575         --?( _Atomic volatile float * );
    1576 double --?( volatile double * ),
    1577         --?( _Atomic volatile double * );
    1578 long double --?( volatile long double * ),
    1579         --?( _Atomic volatile long double * );
    1580 
    1581 forall( type T ) T * --?( T * restrict volatile * ),
    1582         * --?( T * _Atomic restrict volatile * );
    1583 
    1584 forall( type T ) _Atomic T * --?( _Atomic T * restrict volatile * ),
    1585         * --?( _Atomic T * _Atomic restrict volatile * );
    1586 
    1587 forall( type T ) const T * --?( const T * restrict volatile * ),
    1588         * --?( const T * _Atomic restrict volatile * );
    1589 
    1590 forall( type T ) volatile T * --?( volatile T * restrict volatile * ),
    1591         * --?( volatile T * _Atomic restrict volatile * );
    1592 
    1593 forall( type T ) restrict T * --?( restrict T * restrict volatile * ),
    1594         * --?( restrict T * _Atomic restrict volatile * );
    1595 
    1596 forall( type T ) _Atomic const T * --?( _Atomic const T * restrict volatile * ),
     1190_Bool --?( volatile _Bool * ), --?( _Atomic volatile _Bool * );
     1191char --?( volatile char * ), --?( _Atomic volatile char * );
     1192signed char --?( volatile signed char * ), --?( _Atomic volatile signed char * );
     1193unsigned char --?( volatile signed char * ), --?( _Atomic volatile signed char * );
     1194short int --?( volatile short int * ), --?( _Atomic volatile short int * );
     1195unsigned short int --?( volatile unsigned short int * ), --?( _Atomic volatile unsigned short int * );
     1196int --?( volatile int * ), --?( _Atomic volatile int * );
     1197unsigned int --?( volatile unsigned int * ), --?( _Atomic volatile unsigned int * );
     1198long int --?( volatile long int * ), --?( _Atomic volatile long int * );
     1199long unsigned int --?( volatile long unsigned int * ), --?( _Atomic volatile long unsigned int * );
     1200long long int --?( volatile long long int * ), --?( _Atomic volatile long long int * );
     1201long long unsigned --?( volatile long long unsigned int * ), --?( _Atomic volatile long long unsigned int * );
     1202float --?( volatile float * ), --?( _Atomic volatile float * );
     1203double --?( volatile double * ), --?( _Atomic volatile double * );
     1204long double --?( volatile long double * ), --?( _Atomic volatile long double * );
     1205
     1206forall( otype T ) T * --?( T * restrict volatile * ), * --?( T * _Atomic restrict volatile * );
     1207forall( otype T ) _Atomic T * --?( _Atomic T * restrict volatile * ), * --?( _Atomic T * _Atomic restrict volatile * );
     1208forall( otype T ) const T * --?( const T * restrict volatile * ), * --?( const T * _Atomic restrict volatile * );
     1209forall( otype T ) volatile T * --?( volatile T * restrict volatile * ), * --?( volatile T * _Atomic restrict volatile * );
     1210forall( otype T ) restrict T * --?( restrict T * restrict volatile * ), * --?( restrict T * _Atomic restrict volatile * );
     1211forall( otype T ) _Atomic const T * --?( _Atomic const T * restrict volatile * ),
    15971212        * --?( _Atomic const T * _Atomic restrict volatile * );
    1598 
    1599 forall( type T ) _Atomic volatile T * --?( _Atomic volatile T * restrict volatile * ),
     1213forall( otype T ) _Atomic volatile T * --?( _Atomic volatile T * restrict volatile * ),
    16001214        * --?( _Atomic volatile T * _Atomic restrict volatile * );
    1601 
    1602 forall( type T ) _Atomic restrict T * --?( _Atomic restrict T * restrict volatile * ),
     1215forall( otype T ) _Atomic restrict T * --?( _Atomic restrict T * restrict volatile * ),
    16031216        * --?( _Atomic restrict T * _Atomic restrict volatile * );
    1604 
    1605 forall( type T ) const volatile T * --?( const volatile T * restrict volatile * ),
     1217forall( otype T ) const volatile T * --?( const volatile T * restrict volatile * ),
    16061218        * --?( const volatile T * _Atomic restrict volatile * );
    1607 
    1608 forall( type T ) const restrict T * --?( const restrict T * restrict volatile * ),
     1219forall( otype T ) const restrict T * --?( const restrict T * restrict volatile * ),
    16091220        * --?( const restrict T * _Atomic restrict volatile * );
    1610 
    1611 forall( type T ) restrict volatile T * --?( restrict volatile T * restrict volatile * ),
     1221forall( otype T ) restrict volatile T * --?( restrict volatile T * restrict volatile * ),
    16121222        * --?( restrict volatile T * _Atomic restrict volatile * );
    1613 
    1614 forall( type T ) _Atomic const volatile T * --?( _Atomic const volatile T * restrict volatile * ),
     1223forall( otype T ) _Atomic const volatile T * --?( _Atomic const volatile T * restrict volatile * ),
    16151224        * --?( _Atomic const volatile T * _Atomic restrict volatile * );
    1616 
    1617 forall( type T ) _Atomic const restrict T * --?( _Atomic const restrict T * restrict volatile * ),
     1225forall( otype T ) _Atomic const restrict T * --?( _Atomic const restrict T * restrict volatile * ),
    16181226        * --?( _Atomic const restrict T * _Atomic restrict volatile * );
    1619 
    1620 forall( type T ) _Atomic restrict volatile T * --?( _Atomic restrict volatile T * restrict volatile * ),
     1227forall( otype T ) _Atomic restrict volatile T * --?( _Atomic restrict volatile T * restrict volatile * ),
    16211228        * --?( _Atomic restrict volatile T * _Atomic restrict volatile * );
    1622 
    1623 forall( type T ) const restrict volatile T * --?( const restrict volatile T * restrict volatile * ),
     1229forall( otype T ) const restrict volatile T * --?( const restrict volatile T * restrict volatile * ),
    16241230        * --?( const restrict volatile T * _Atomic restrict volatile * );
    1625 
    1626 forall( type T ) _Atomic const restrict volatile T * --?( _Atomic const restrict volatile T * restrict volatile * ),
     1231forall( otype T ) _Atomic const restrict volatile T * --?( _Atomic const restrict volatile T * restrict volatile * ),
    16271232        * --?( _Atomic const restrict volatile T * _Atomic restrict volatile * );
    16281233\end{lstlisting}
     
    16451250
    16461251\semantics
    1647 The interpretations of prefix increment and decrement expressions are
    1648 determined in the same way as the interpretations of postfix increment and
    1649 decrement expressions.
     1252The interpretations of prefix increment and decrement expressions are determined in the same way as the interpretations of postfix increment and decrement expressions.
    16501253
    16511254
     
    16541257\predefined
    16551258\begin{lstlisting}
    1656 forall( type T ) lvalue T *?( T * );
    1657 forall( type T ) _Atomic lvalue T *?( _Atomic T * );
    1658 forall( type T ) const lvalue T *?( const T * );
    1659 forall( type T ) volatile lvalue T *?( volatile T * );
    1660 forall( type T ) restrict lvalue T *?( restrict T * );
    1661 forall( type T ) _Atomic const lvalue T *?( _Atomic const T * );
    1662 forall( type T ) _Atomic volatile lvalue T *?( _Atomic volatile T * );
    1663 forall( type T ) _Atomic restrict lvalue T *?( _Atomic restrict T * );
    1664 forall( type T ) const volatile lvalue T *?( const volatile T * );
    1665 forall( type T ) const restrict lvalue T *?( const restrict T * );
    1666 forall( type T ) restrict volatile lvalue T *?( restrict volatile T * );
    1667 forall( type T ) _Atomic const volatile lvalue T *?( _Atomic const volatile T * );
    1668 forall( type T ) _Atomic const restrict lvalue T *?( _Atomic const restrict T * );
    1669 forall( type T ) _Atomic restrict volatile lvalue T *?( _Atomic restrict volatile T * );
    1670 forall( type T ) const restrict volatile lvalue T *?( const restrict volatile T * );
    1671 forall( type T ) _Atomic const restrict volatile lvalue T *?( _Atomic const restrict volatile T * );
    1672 
     1259forall( otype T ) lvalue T *?( T * );
     1260forall( otype T ) _Atomic lvalue T *?( _Atomic T * );
     1261forall( otype T ) const lvalue T *?( const T * );
     1262forall( otype T ) volatile lvalue T *?( volatile T * );
     1263forall( otype T ) restrict lvalue T *?( restrict T * );
     1264forall( otype T ) _Atomic const lvalue T *?( _Atomic const T * );
     1265forall( otype T ) _Atomic volatile lvalue T *?( _Atomic volatile T * );
     1266forall( otype T ) _Atomic restrict lvalue T *?( _Atomic restrict T * );
     1267forall( otype T ) const volatile lvalue T *?( const volatile T * );
     1268forall( otype T ) const restrict lvalue T *?( const restrict T * );
     1269forall( otype T ) restrict volatile lvalue T *?( restrict volatile T * );
     1270forall( otype T ) _Atomic const volatile lvalue T *?( _Atomic const volatile T * );
     1271forall( otype T ) _Atomic const restrict lvalue T *?( _Atomic const restrict T * );
     1272forall( otype T ) _Atomic restrict volatile lvalue T *?( _Atomic restrict volatile T * );
     1273forall( otype T ) const restrict volatile lvalue T *?( const restrict volatile T * );
     1274forall( otype T ) _Atomic const restrict volatile lvalue T *?( _Atomic const restrict volatile T * );
    16731275forall( ftype FT ) FT *?( FT * );
    16741276\end{lstlisting}
     
    16821284\lstinline$T$ is the type of the operand.
    16831285
    1684 The interpretations of an indirection expression are the interpretations of the corresponding
    1685 function call.
     1286The interpretations of an indirection expression are the interpretations of the corresponding function call.
    16861287
    16871288
     
    16901291\predefined
    16911292\begin{lstlisting}
    1692 int
    1693         +?( int ),
    1694         -?( int ),
    1695         ~?( int );
    1696 unsigned int
    1697         +?( unsigned int ),
    1698         -?( unsigned int ),
    1699          ~?( unsigned int );
    1700 long int
    1701         +?( long int ),
    1702         -?( long int ),
    1703         ~?( long int );
    1704 long unsigned int
    1705         +?( long unsigned int ),
    1706         -?( long unsigned int ),
    1707         ~?( long unsigned int );
    1708 long long int
    1709         +?( long long int ),
    1710         -?( long long int ),
    1711         ~?( long long int );
    1712 long long unsigned int
    1713         +?( long long unsigned int ),
    1714         -?( long long unsigned int ),
    1715         ~?( long long unsigned int );
    1716 float
    1717         +?( float ),
    1718         -?( float );
    1719 double
    1720         +?( double ),
    1721         -?( double );
    1722 long double
    1723         +?( long double ),
    1724         -?( long double );
    1725 _Complex float
    1726         +?( _Complex float ),
    1727         -?( _Complex float );
    1728 _Complex double
    1729         +?( _Complex double ),
    1730         -?( _Complex double );
    1731 _Complex long double
    1732         +?( _Complex long double ),
    1733         -?( _Complex long double );
    1734 
    1735 int !?( int ),
    1736         !?( unsigned int ),
    1737         !?( long ),
    1738         !?( long unsigned int ),
    1739         !?( long long int ),
    1740         !?( long long unsigned int ),
    1741         !?( float ),
    1742         !?( double ),
    1743         !?( long double ),
    1744         !?( _Complex float ),
    1745         !?( _Complex double ),
    1746         !?( _Complex long double );
    1747 
     1293int     +?( int ), -?( int ), ~?( int );
     1294unsigned int +?( unsigned int ), -?( unsigned int ), ~?( unsigned int );
     1295long int +?( long int ), -?( long int ), ~?( long int );
     1296long unsigned int +?( long unsigned int ), -?( long unsigned int ), ~?( long unsigned int );
     1297long long int +?( long long int ), -?( long long int ), ~?( long long int );
     1298long long unsigned int +?( long long unsigned int ), -?( long long unsigned int ), ~?( long long unsigned int );
     1299float +?( float ), -?( float );
     1300double +?( double ), -?( double );
     1301long double +?( long double ), -?( long double );
     1302_Complex float +?( _Complex float ), -?( _Complex float );
     1303_Complex double +?( _Complex double ), -?( _Complex double );
     1304_Complex long double +?( _Complex long double ), -?( _Complex long double );
     1305int !?( int ), !?( unsigned int ), !?( long ), !?( long unsigned int ),
     1306        !?( long long int ), !?( long long unsigned int ),
     1307        !?( float ), !?( double ), !?( long double ),
     1308        !?( _Complex float ), !?( _Complex double ), !?( _Complex long double );
    17481309forall( dtype DT ) int !?( const restrict volatile DT * );
    17491310forall( dtype DT ) int !?( _Atomic const restrict volatile DT * );
    17501311forall( ftype FT ) int !?( FT * );
    17511312\end{lstlisting}
    1752 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    1753 rank of \lstinline$int$ there exist
     1313For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    17541314% Don't use predefined: keep this out of prelude.cf.
    17551315\begin{lstlisting}
     
    17591319
    17601320\semantics
    1761 The interpretations of a unary arithmetic expression are the interpretations of the corresponding
    1762 function call.
     1321The interpretations of a unary arithmetic expression are the interpretations of the corresponding function call.
    17631322
    17641323\examples
     
    17661325long int li;
    17671326void eat_double( double );@\use{eat_double}@
    1768 
    1769 eat_double(-li ); // @\rewrite@ eat_double( -?( li ) );
     1327eat_double(-li ); // @\rewrite@ eat_double( -?( li ) );
    17701328\end{lstlisting}
    17711329The valid interpretations of ``\lstinline$-li$'' (assuming no extended integer types exist) are
    17721330\begin{center}
    1773 \begin{tabular}{llc}
    1774 interpretation & result type & expression conversion cost \\
     1331\begin{tabular}{llc} interpretation & result type & expression conversion cost \\
    17751332\hline
    17761333\lstinline$-?( (int)li )$                                       & \lstinline$int$                                       & (unsafe) \\
     
    17881345\end{tabular}
    17891346\end{center}
    1790 The valid interpretations of the \lstinline$eat_double$ call, with the cost of the argument
    1791 conversion and the cost of the entire expression, are
     1347The valid interpretations of the \lstinline$eat_double$ call, with the cost of the argument conversion and the cost of the entire expression, are
    17921348\begin{center}
    1793 \begin{tabular}{lcc}
    1794 interpretation & argument cost & expression cost \\
     1349\begin{tabular}{lcc} interpretation & argument cost & expression cost \\
    17951350\hline
    17961351\lstinline$eat_double( (double)-?( (int)li) )$                                  & 7                     & (unsafe) \\
     
    18081363\end{tabular}
    18091364\end{center}
    1810 Each has result type \lstinline$void$, so the best must be selected. The interpretations involving
    1811 unsafe conversions are discarded. The remainder have equal expression conversion costs, so the
     1365Each has result type \lstinline$void$, so the best must be selected.
     1366The interpretations involving unsafe conversions are discarded.
     1367The remainder have equal expression conversion costs, so the
    18121368``highest argument conversion cost'' rule is invoked, and the chosen interpretation is
    18131369\lstinline$eat_double( (double)-?(li) )$.
     
    18201376\lstinline$dtype$, or \lstinline$ftype$.
    18211377
    1822 When the \lstinline$sizeof$\use{sizeof} operator is applied to an expression, the expression shall
    1823 have exactly one \Index{interpretation}\index{ambiguous interpretation}, which shall
    1824 be unambiguous. \semantics A \lstinline$sizeof$ or \lstinline$_Alignof$ expression has one
    1825 interpretation, of type \lstinline$size_t$.
     1378When the \lstinline$sizeof$\use{sizeof} operator is applied to an expression, the expression shall have exactly one \Index{interpretation}\index{ambiguous interpretation}, which shall be unambiguous. \semantics A \lstinline$sizeof$ or \lstinline$_Alignof$ expression has one interpretation, of type \lstinline$size_t$.
    18261379
    18271380When \lstinline$sizeof$ is applied to an identifier declared by a \nonterm{type-declaration} or a
    1828 \nonterm{type-parameter}, it yields the size in bytes of the type that implements the operand. When
    1829 the operand is an opaque type or an inferred type parameter\index{inferred parameter}, the
    1830 expression is not a constant expression.
     1381\nonterm{type-parameter}, it yields the size in bytes of the type that implements the operand.
     1382When the operand is an opaque type or an inferred type parameter\index{inferred parameter}, the expression is not a constant expression.
    18311383
    18321384When \lstinline$_Alignof$ is applied to an identifier declared by a \nonterm{type-declaration} or a
    1833 \nonterm{type-parameter}, it yields the alignment requirement of the type that implements the
    1834 operand. When the operand is an opaque type or an inferred type parameter\index{inferred
    1835 parameter}, the expression is not a constant expression.
    1836 \begin{rationale}
    1837 \begin{lstlisting}
    1838 type Pair = struct { int first, second; };
     1385\nonterm{type-parameter}, it yields the alignment requirement of the type that implements the operand.
     1386When the operand is an opaque type or an inferred type parameter\index{inferred parameter}, the expression is not a constant expression.
     1387\begin{rationale}
     1388\begin{lstlisting}
     1389otype Pair = struct { int first, second; };
    18391390size_t p_size = sizeof(Pair);           // constant expression
    1840 
    1841 extern type Rational;@\use{Rational}@
     1391extern otype Rational;@\use{Rational}@
    18421392size_t c_size = sizeof(Rational);       // non-constant expression
    1843 
    18441393forall(type T) T f(T p1, T p2) {
    18451394        size_t t_size = sizeof(T);              // non-constant expression
     
    18471396}
    18481397\end{lstlisting}
    1849 ``\lstinline$sizeof Rational$'', although not statically known, is fixed. Within \lstinline$f()$,
     1398``\lstinline$sizeof Rational$'', although not statically known, is fixed.
     1399Within \lstinline$f()$,
    18501400``\lstinline$sizeof(T)$'' is fixed for each call of \lstinline$f()$, but may vary from call to call.
    18511401\end{rationale}
     
    18671417
    18681418In a \Index{cast expression} ``\lstinline$($\nonterm{type-name}\lstinline$)e$'', if
    1869 \nonterm{type-name} is the type of an interpretation of \lstinline$e$, then that interpretation is
    1870 the only interpretation of the cast expression; otherwise, \lstinline$e$ shall have some
    1871 interpretation that can be converted to \nonterm{type-name}, and the interpretation of the cast
    1872 expression is the cast of the interpretation that can be converted at the lowest cost. The cast
    1873 expression's interpretation is ambiguous\index{ambiguous interpretation} if more than one
    1874 interpretation can be converted at the lowest cost or if the selected interpretation is ambiguous.
    1875 
    1876 \begin{rationale}
    1877 Casts can be used to eliminate ambiguity in expressions by selecting interpretations of
    1878 subexpressions, and to specialize polymorphic functions and values.
     1419\nonterm{type-name} is the type of an interpretation of \lstinline$e$, then that interpretation is the only interpretation of the cast expression;
     1420otherwise, \lstinline$e$ shall have some interpretation that can be converted to \nonterm{type-name}, and the interpretation of the cast expression is the cast of the interpretation that can be converted at the lowest cost.
     1421The cast expression's interpretation is ambiguous\index{ambiguous interpretation} if more than one interpretation can be converted at the lowest cost or if the selected interpretation is ambiguous.
     1422
     1423\begin{rationale}
     1424Casts can be used to eliminate ambiguity in expressions by selecting interpretations of subexpressions, and to specialize polymorphic functions and values.
    18791425\end{rationale}
    18801426
     
    18991445\predefined
    19001446\begin{lstlisting}
    1901 int?*?( int, int ),
    1902         ?/?( int, int ),
    1903         ?%?( int, int );
    1904 unsigned int?*?( unsigned int, unsigned int ),
    1905         ?/?( unsigned int, unsigned int ),
    1906         ?%?( unsigned int, unsigned int );
    1907 long int?*?( long int, long int ),
    1908         ?/?( long, long ),
    1909         ?%?( long, long );
     1447int?*?( int, int ), ?/?( int, int ), ?%?( int, int );
     1448unsigned int?*?( unsigned int, unsigned int ), ?/?( unsigned int, unsigned int ), ?%?( unsigned int, unsigned int );
     1449long int?*?( long int, long int ), ?/?( long, long ), ?%?( long, long );
    19101450long unsigned int?*?( long unsigned int, long unsigned int ),
    1911         ?/?( long unsigned int, long unsigned int ),
    1912         ?%?( long unsigned int, long unsigned int );
    1913 long long int?*?( long long int, long long int ),
    1914         ?/?( long long int, long long int ),
     1451        ?/?( long unsigned int, long unsigned int ), ?%?( long unsigned int, long unsigned int );
     1452long long int?*?( long long int, long long int ), ?/?( long long int, long long int ),
    19151453        ?%?( long long int, long long int );
    19161454long long unsigned int ?*?( long long unsigned int, long long unsigned int ),
    1917         ?/?( long long unsigned int, long long unsigned int ),
    1918         ?%?( long long unsigned int, long long unsigned int );
    1919 float?*?( float, float ),
    1920         ?/?( float, float );
    1921 double?*?( double, double ),
    1922         ?/?( double, double );
    1923 long double?*?( long double, long double ),
    1924         ?/?( long double, long double );
    1925 _Complex float?*?( float, _Complex float ),
    1926         ?/?( float, _Complex float ),
    1927         ?*?( _Complex float, float ),
    1928         ?/?( _Complex float, float ),
    1929         ?*?( _Complex float, _Complex float ),
    1930         ?/?( _Complex float, _Complex float );
    1931 _Complex double?*?( double, _Complex double ),
    1932         ?/?( double, _Complex double ),
    1933         ?*?( _Complex double, double ),
    1934         ?/?( _Complex double, double ),
    1935         ?*?( _Complex double, _Complex double ),
    1936         ?/?( _Complex double, _Complex double );
    1937 _Complex long double?*?( long double, _Complex long double ),
    1938         ?/?( long double, _Complex long double ),
    1939         ?*?( _Complex long double, long double ),
    1940         ?/?( _Complex long double, long double ),
    1941         ?*?( _Complex long double, _Complex long double ),
    1942         ?/?( _Complex long double, _Complex long double );
    1943 \end{lstlisting}
    1944 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    1945 rank of \lstinline$int$ there exist
     1455        ?/?( long long unsigned int, long long unsigned int ), ?%?( long long unsigned int, long long unsigned int );
     1456float?*?( float, float ), ?/?( float, float );
     1457double?*?( double, double ), ?/?( double, double );
     1458long double?*?( long double, long double ), ?/?( long double, long double );
     1459_Complex float?*?( float, _Complex float ), ?/?( float, _Complex float ),
     1460        ?*?( _Complex float, float ), ?/?( _Complex float, float ),
     1461        ?*?( _Complex float, _Complex float ), ?/?( _Complex float, _Complex float );
     1462_Complex double?*?( double, _Complex double ), ?/?( double, _Complex double ),
     1463        ?*?( _Complex double, double ), ?/?( _Complex double, double ),
     1464        ?*?( _Complex double, _Complex double ), ?/?( _Complex double, _Complex double );
     1465_Complex long double?*?( long double, _Complex long double ), ?/?( long double, _Complex long double ),
     1466        ?*?( _Complex long double, long double ), ?/?( _Complex long double, long double ),
     1467        ?*?( _Complex long double, _Complex long double ), ?/?( _Complex long double, _Complex long double );
     1468\end{lstlisting}
     1469For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    19461470% Don't use predefined: keep this out of prelude.cf.
    19471471\begin{lstlisting}
     
    19511475\begin{rationale}
    19521476{\c11} does not include conversions from the \Index{real type}s to \Index{complex type}s in the
    1953 \Index{usual arithmetic conversion}s.  Instead it specifies conversion of the result of binary
    1954 operations on arguments from mixed type domains. \CFA's predefined operators match that pattern.
     1477\Index{usual arithmetic conversion}s.  Instead it specifies conversion of the result of binary operations on arguments from mixed type domains. \CFA's predefined operators match that pattern.
    19551478\end{rationale}
    19561479
    19571480\semantics
    1958 The interpretations of multiplicative expressions are the interpretations of the corresponding
    1959 function call.
     1481The interpretations of multiplicative expressions are the interpretations of the corresponding function call.
    19601482
    19611483\examples
     
    19661488eat_double( li % i );
    19671489\end{lstlisting}
    1968 ``\lstinline$li % i$'' is rewritten as ``\lstinline$?%?(li, i )$''. The valid interpretations
    1969 of \lstinline$?%?(li, i )$, the cost\index{conversion cost} of converting their arguments, and
    1970 the cost of converting the result to \lstinline$double$ (assuming no extended integer types are
    1971 present ) are
     1490``\lstinline$li % i$'' is rewritten as ``\lstinline$?%?(li, i )$''.
     1491The valid interpretations of \lstinline$?%?(li, i )$, the cost\index{conversion cost} of converting their arguments, and the cost of converting the result to \lstinline$double$ (assuming no extended integer types are present ) are
    19721492\begin{center}
    1973 \begin{tabular}{lcc}
    1974 interpretation & argument cost & result cost \\
     1493\begin{tabular}{lcc} interpretation & argument cost & result cost \\
    19751494\hline
    19761495\lstinline$ ?%?( (int)li, i )$                                                                          & (unsafe)      & 6     \\
    19771496\lstinline$ ?%?( (unsigned)li,(unsigned)i )$                                            & (unsafe)      & 5     \\
    1978 \lstinline$ ?%?(li,(long)i )$                                                                           & 1                     & 4     \\
     1497\lstinline$ ?%?( li, (long)i )$                                                                         & 1                     & 4     \\
    19791498\lstinline$ ?%?( (long unsigned)li,(long unsigned)i )$                          & 3                     & 3     \\
    19801499\lstinline$ ?%?( (long long)li,(long long)i )$                                          & 5                     & 2     \\
     
    19831502\end{center}
    19841503The best interpretation of \lstinline$eat_double( li, i )$ is
    1985 \lstinline$eat_double( (double)?%?(li, (long)i ))$, which has no unsafe conversions and the
    1986 lowest total cost.
    1987 
    1988 \begin{rationale}
    1989 {\c11} defines most arithmetic operations to apply an \Index{integer promotion} to any argument that
    1990 belongs to a type that has an \Index{integer conversion rank} less than that of \lstinline$int$.If
     1504\lstinline$eat_double( (double)?%?(li, (long)i ))$, which has no unsafe conversions and the lowest total cost.
     1505
     1506\begin{rationale}
     1507{\c11} defines most arithmetic operations to apply an \Index{integer promotion} to any argument that belongs to a type that has an \Index{integer conversion rank} less than that of \lstinline$int$.If
    19911508\lstinline$s$ is a \lstinline$short int$, ``\lstinline$s *s$'' does not have type \lstinline$short int$;
    1992 it is treated as ``\lstinline$( (int)s ) * ( (int)s )$'', and has type \lstinline$int$. \CFA matches
    1993 that pattern; it does not predefine ``\lstinline$short ?*?( short, short )$''.
    1994 
    1995 These ``missing'' operators limit polymorphism. Consider
    1996 \begin{lstlisting}
    1997 forall( type T | T ?*?( T, T ) ) T square( T );
     1509it is treated as ``\lstinline$( (int)s ) * ( (int)s )$'', and has type \lstinline$int$. \CFA matches that pattern;
     1510it does not predefine ``\lstinline$short ?*?( short, short )$''.
     1511
     1512These ``missing'' operators limit polymorphism.
     1513Consider
     1514\begin{lstlisting}
     1515forall( otype T | T ?*?( T, T ) ) T square( T );
    19981516short s;
    19991517square( s );
     
    20011519Since \CFA does not define a multiplication operator for \lstinline$short int$,
    20021520\lstinline$square( s )$ is treated as \lstinline$square( (int)s )$, and the result has type
    2003 \lstinline$int$. This is mildly surprising, but it follows the {\c11} operator pattern.
     1521\lstinline$int$.
     1522This is mildly surprising, but it follows the {\c11} operator pattern.
    20041523
    20051524A more troubling example is
    20061525\begin{lstlisting}
    2007 forall( type T | ?*?( T, T ) ) T product( T[], int n );
     1526forall( otype T | ?*?( T, T ) ) T product( T[], int n );
    20081527short sa[5];
    20091528product( sa, 5);
    20101529\end{lstlisting}
    20111530This has no valid interpretations, because \CFA has no conversion from ``array of
    2012 \lstinline$short int$'' to ``array of \lstinline$int$''. The alternatives in such situations
    2013 include
     1531\lstinline$short int$'' to ``array of \lstinline$int$''.
     1532The alternatives in such situations include
    20141533\begin{itemize}
    20151534\item
     
    20201539\lstinline$product$.
    20211540\item
    2022 Defining \lstinline$product$ to take as an argument a conversion function from the ``small'' type to
    2023 the operator's argument type.
     1541Defining \lstinline$product$ to take as an argument a conversion function from the ``small'' type to the operator's argument type.
    20241542\end{itemize}
    20251543\end{rationale}
     
    20431561\predefined
    20441562\begin{lstlisting}
    2045 int?+?( int, int ),
    2046         ?-?( int, int );
    2047 unsigned int?+?( unsigned int, unsigned int ),
    2048         ?-?( unsigned int, unsigned int );
    2049 long int?+?( long int, long int ),
    2050         ?-?( long int, long int );
    2051 long unsigned int?+?( long unsigned int, long unsigned int ),
    2052         ?-?( long unsigned int, long unsigned int );
    2053 long long int?+?( long long int, long long int ),
    2054         ?-?( long long int, long long int );
     1563int?+?( int, int ), ?-?( int, int );
     1564unsigned int?+?( unsigned int, unsigned int ), ?-?( unsigned int, unsigned int );
     1565long int?+?( long int, long int ), ?-?( long int, long int );
     1566long unsigned int?+?( long unsigned int, long unsigned int ), ?-?( long unsigned int, long unsigned int );
     1567long long int?+?( long long int, long long int ), ?-?( long long int, long long int );
    20551568long long unsigned int ?+?( long long unsigned int, long long unsigned int ),
    20561569        ?-?( long long unsigned int, long long unsigned int );
    2057 float?+?( float, float ),
    2058         ?-?( float, float );
    2059 double?+?( double, double ),
    2060         ?-?( double, double );
    2061 long double?+?( long double, long double ),
    2062         ?-?( long double, long double );
    2063 _Complex float?+?( _Complex float, float ),
    2064         ?-?( _Complex float, float ),
    2065         ?+?( float, _Complex float ),
    2066         ?-?( float, _Complex float ),
    2067         ?+?( _Complex float, _Complex float ),
    2068         ?-?( _Complex float, _Complex float );
    2069 _Complex double?+?( _Complex double, double ),
    2070         ?-?( _Complex double, double ),
    2071         ?+?( double, _Complex double ),
    2072         ?-?( double, _Complex double ),
    2073         ?+?( _Complex double, _Complex double ),
    2074         ?-?( _Complex double, _Complex double );
    2075 _Complex long double?+?( _Complex long double, long double ),
    2076         ?-?( _Complex long double, long double ),
    2077         ?+?( long double, _Complex long double ),
    2078         ?-?( long double, _Complex long double ),
    2079         ?+?( _Complex long double, _Complex long double ),
    2080         ?-?( _Complex long double, _Complex long double );
    2081 
    2082 forall( type T ) T
    2083         * ?+?( T *, ptrdiff_t ),
    2084         * ?+?( ptrdiff_t, T * ),
    2085         * ?-?( T *, ptrdiff_t );
    2086 
    2087 forall( type T ) _Atomic T
    2088         * ?+?( _Atomic T *, ptrdiff_t ),
    2089         * ?+?( ptrdiff_t, _Atomic T * ),
     1570float?+?( float, float ), ?-?( float, float );
     1571double?+?( double, double ), ?-?( double, double );
     1572long double?+?( long double, long double ), ?-?( long double, long double );
     1573_Complex float?+?( _Complex float, float ), ?-?( _Complex float, float ),
     1574        ?+?( float, _Complex float ), ?-?( float, _Complex float ),
     1575        ?+?( _Complex float, _Complex float ), ?-?( _Complex float, _Complex float );
     1576_Complex double?+?( _Complex double, double ), ?-?( _Complex double, double ),
     1577        ?+?( double, _Complex double ), ?-?( double, _Complex double ),
     1578        ?+?( _Complex double, _Complex double ), ?-?( _Complex double, _Complex double );
     1579_Complex long double?+?( _Complex long double, long double ), ?-?( _Complex long double, long double ),
     1580        ?+?( long double, _Complex long double ), ?-?( long double, _Complex long double ),
     1581        ?+?( _Complex long double, _Complex long double ), ?-?( _Complex long double, _Complex long double );
     1582
     1583forall( otype T ) T * ?+?( T *, ptrdiff_t ), * ?+?( ptrdiff_t, T * ), * ?-?( T *, ptrdiff_t );
     1584forall( otype T ) _Atomic T * ?+?( _Atomic T *, ptrdiff_t ), * ?+?( ptrdiff_t, _Atomic T * ),
    20901585        * ?-?( _Atomic T *, ptrdiff_t );
    2091 
    2092 forall( type T ) const T
    2093         * ?+?( const T *, ptrdiff_t ),
    2094         * ?+?( ptrdiff_t, const T * ),
     1586forall( otype T ) const T * ?+?( const T *, ptrdiff_t ), * ?+?( ptrdiff_t, const T * ),
    20951587        * ?-?( const T *, ptrdiff_t );
    2096 
    2097 forall( type T ) restrict T
    2098         * ?+?( restrict T *, ptrdiff_t ),
    2099         * ?+?( ptrdiff_t, restrict T * ),
     1588forall( otype T ) restrict T * ?+?( restrict T *, ptrdiff_t ), * ?+?( ptrdiff_t, restrict T * ),
    21001589        * ?-?( restrict T *, ptrdiff_t );
    2101 
    2102 forall( type T ) volatile T
    2103         * ?+?( volatile T *, ptrdiff_t ),
    2104         * ?+?( ptrdiff_t, volatile T * ),
     1590forall( otype T ) volatile T * ?+?( volatile T *, ptrdiff_t ), * ?+?( ptrdiff_t, volatile T * ),
    21051591        * ?-?( volatile T *, ptrdiff_t );
    2106 
    2107 forall( type T ) _Atomic const T
    2108         * ?+?( _Atomic const T *, ptrdiff_t ),
    2109         * ?+?( ptrdiff_t, _Atomic const T * ),
     1592forall( otype T ) _Atomic const T * ?+?( _Atomic const T *, ptrdiff_t ), * ?+?( ptrdiff_t, _Atomic const T * ),
    21101593        * ?-?( _Atomic const T *, ptrdiff_t );
    2111 
    2112 forall( type T ) _Atomic restrict T
    2113         * ?+?( _Atomic restrict T *, ptrdiff_t ),
    2114         * ?+?( ptrdiff_t, _Atomic restrict T * ),
     1594forall( otype T ) _Atomic restrict T * ?+?( _Atomic restrict T *, ptrdiff_t ), * ?+?( ptrdiff_t, _Atomic restrict T * ),
    21151595        * ?-?( _Atomic restrict T *, ptrdiff_t );
    2116 
    2117 forall( type T ) _Atomic volatile T
    2118         * ?+?( _Atomic volatile T *, ptrdiff_t ),
    2119         * ?+?( ptrdiff_t, _Atomic volatile T * ),
     1596forall( otype T ) _Atomic volatile T * ?+?( _Atomic volatile T *, ptrdiff_t ), * ?+?( ptrdiff_t, _Atomic volatile T * ),
    21201597        * ?-?( _Atomic volatile T *, ptrdiff_t );
    2121 
    2122 forall( type T ) const restrict T
    2123         * ?+?( const restrict T *, ptrdiff_t ),
    2124         * ?+?( ptrdiff_t, const restrict T * ),
     1598forall( otype T ) const restrict T * ?+?( const restrict T *, ptrdiff_t ), * ?+?( ptrdiff_t, const restrict T * ),
    21251599        * ?-?( const restrict T *, ptrdiff_t );
    2126 
    2127 forall( type T ) const volatile T
    2128         * ?+?( const volatile T *, ptrdiff_t ),
    2129         * ?+?( ptrdiff_t, const volatile T * ),
     1600forall( otype T ) const volatile T * ?+?( const volatile T *, ptrdiff_t ), * ?+?( ptrdiff_t, const volatile T * ),
    21301601        * ?-?( const volatile T *, ptrdiff_t );
    2131 
    2132 forall( type T ) restrict volatile T
    2133         * ?+?( restrict volatile T *, ptrdiff_t ),
    2134         * ?+?( ptrdiff_t, restrict volatile T * ),
     1602forall( otype T ) restrict volatile T * ?+?( restrict volatile T *, ptrdiff_t ), * ?+?( ptrdiff_t, restrict volatile T * ),
    21351603        * ?-?( restrict volatile T *, ptrdiff_t );
    2136 
    2137 forall( type T ) _Atomic const restrict T
    2138         * ?+?( _Atomic const restrict T *, ptrdiff_t ),
     1604forall( otype T ) _Atomic const restrict T * ?+?( _Atomic const restrict T *, ptrdiff_t ),
    21391605        * ?+?( ptrdiff_t, _Atomic const restrict T * ),
    21401606        * ?-?( _Atomic const restrict T *, ptrdiff_t );
    2141 
    2142 forall( type T ) ptrdiff_t
     1607forall( otype T ) ptrdiff_t
    21431608        * ?-?( const restrict volatile T *, const restrict volatile T * ),
    21441609        * ?-?( _Atomic const restrict volatile T *, _Atomic const restrict volatile T * );
    21451610\end{lstlisting}
    2146 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2147 rank of \lstinline$int$ there exist
     1611For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    21481612% Don't use predefined: keep this out of prelude.cf.
    21491613\begin{lstlisting}
     
    21521616
    21531617\semantics
    2154 The interpretations of additive expressions are the interpretations of the corresponding function
    2155 calls.
    2156 
    2157 \begin{rationale}
    2158 \lstinline$ptrdiff_t$ is an implementation-defined identifier defined in \lstinline$<stddef.h>$ that
    2159 is synonymous with a signed integral type that is large enough to hold the difference between two
    2160 pointers. It seems reasonable to use it for pointer addition as well. (This is technically a
    2161 difference between \CFA and C, which only specifies that pointer addition uses an \emph{integral}
    2162 argument.) Hence it is also used for subscripting, which is defined in terms of pointer addition.
    2163 The {\c11} standard uses \lstinline$size_t$ in several cases where a library function takes an
    2164 argument that is used as a subscript, but \lstinline$size_t$ is unsuitable here because it is an
    2165 unsigned type.
     1618The interpretations of additive expressions are the interpretations of the corresponding function calls.
     1619
     1620\begin{rationale}
     1621\lstinline$ptrdiff_t$ is an implementation-defined identifier defined in \lstinline$<stddef.h>$ that is synonymous with a signed integral type that is large enough to hold the difference between two pointers.
     1622It seems reasonable to use it for pointer addition as well. (This is technically a difference between \CFA and C, which only specifies that pointer addition uses an \emph{integral} argument.) Hence it is also used for subscripting, which is defined in terms of pointer addition.
     1623The {\c11} standard uses \lstinline$size_t$ in several cases where a library function takes an argument that is used as a subscript, but \lstinline$size_t$ is unsuitable here because it is an unsigned type.
    21661624\end{rationale}
    21671625
     
    21841642\predefined
    21851643\begin{lstlisting}
    2186 int ?<<?( int, int ),
    2187          ?>>?( int, int );
    2188 unsigned int ?<<?( unsigned int, int ),
    2189          ?>>?( unsigned int, int );
    2190 long int ?<<?( long int, int ),
    2191          ?>>?( long int, int );
    2192 long unsigned int ?<<?( long unsigned int, int ),
    2193          ?>>?( long unsigned int, int );
    2194 long long int ?<<?( long long int, int ),
    2195          ?>>?( long long int, int );
    2196 long long unsigned int ?<<?( long long unsigned int, int ),
    2197          ?>>?( long long unsigned int, int);
    2198 \end{lstlisting}
    2199 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2200 rank of \lstinline$int$ there exist
     1644int ?<<?( int, int ), ?>>?( int, int );
     1645unsigned int ?<<?( unsigned int, int ), ?>>?( unsigned int, int );
     1646long int ?<<?( long int, int ), ?>>?( long int, int );
     1647long unsigned int ?<<?( long unsigned int, int ), ?>>?( long unsigned int, int );
     1648long long int ?<<?( long long int, int ), ?>>?( long long int, int );
     1649long long unsigned int ?<<?( long long unsigned int, int ), ?>>?( long long unsigned int, int);
     1650\end{lstlisting}
     1651For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    22011652% Don't use predefined: keep this out of prelude.cf.
    22021653\begin{lstlisting}
     
    22051656
    22061657\begin{rationale}
    2207 The bitwise shift operators break the usual pattern: they do not convert both operands to a common
    2208 type. The right operand only undergoes \Index{integer promotion}.
     1658The bitwise shift operators break the usual pattern: they do not convert both operands to a common type.
     1659The right operand only undergoes \Index{integer promotion}.
    22091660\end{rationale}
    22101661
    22111662\semantics
    2212 The interpretations of a bitwise shift expression are the interpretations of the corresponding
    2213 function calls.
     1663The interpretations of a bitwise shift expression are the interpretations of the corresponding function calls.
    22141664
    22151665
     
    22351685\predefined
    22361686\begin{lstlisting}
    2237 int ?<?( int, int ),
    2238         ?<=?( int, int ),
    2239         ?>?( int, int ),
    2240         ?>=?( int, int );
    2241 int ?<?( unsigned int, unsigned int ),
    2242         ?<=?( unsigned int, unsigned int ),
    2243         ?>?( unsigned int, unsigned int ),
    2244         ?>=?( unsigned int, unsigned int );
    2245 int ?<?( long int, long int ),
    2246         ?<=?( long int, long int ),
    2247         ?>?( long int, long int ),
    2248         ?>=?( long int, long int );
    2249 int ?<?( long unsigned int, long unsigned ),
    2250         ?<=?( long unsigned int, long unsigned ),
    2251         ?>?( long unsigned int, long unsigned ),
    2252         ?>=?( long unsigned int, long unsigned );
    2253 int ?<?( long long int, long long int ),
    2254         ?<=?( long long int, long long int ),
    2255         ?>?( long long int, long long int ),
    2256         ?>=?( long long int, long long int );
    2257 int ?<?( long long unsigned int, long long unsigned ),
    2258         ?<=?( long long unsigned int, long long unsigned ),
    2259         ?>?( long long unsigned int, long long unsigned ),
    2260         ?>=?( long long unsigned int, long long unsigned );
    2261 int ?<?( float, float ),
    2262         ?<=?( float, float ),
    2263         ?>?( float, float ),
    2264         ?>=?( float, float );
    2265 int ?<?( double, double ),
    2266         ?<=?( double, double ),
    2267         ?>?( double, double ),
    2268         ?>=?( double, double );
    2269 int ?<?( long double, long double ),
    2270         ?<=?( long double, long double ),
    2271         ?>?( long double, long double ),
    2272         ?>=?( long double, long double );
    2273 
    2274 forall( dtype DT ) int
    2275         ?<?( const restrict volatile DT *, const restrict volatile DT * ),
     1687int ?<?( int, int ), ?<=?( int, int ),
     1688        ?>?( int, int ), ?>=?( int, int );
     1689int ?<?( unsigned int, unsigned int ), ?<=?( unsigned int, unsigned int ),
     1690        ?>?( unsigned int, unsigned int ), ?>=?( unsigned int, unsigned int );
     1691int ?<?( long int, long int ), ?<=?( long int, long int ),
     1692        ?>?( long int, long int ), ?>=?( long int, long int );
     1693int ?<?( long unsigned int, long unsigned ), ?<=?( long unsigned int, long unsigned ),
     1694        ?>?( long unsigned int, long unsigned ), ?>=?( long unsigned int, long unsigned );
     1695int ?<?( long long int, long long int ), ?<=?( long long int, long long int ),
     1696        ?>?( long long int, long long int ), ?>=?( long long int, long long int );
     1697int ?<?( long long unsigned int, long long unsigned ), ?<=?( long long unsigned int, long long unsigned ),
     1698        ?>?( long long unsigned int, long long unsigned ), ?>=?( long long unsigned int, long long unsigned );
     1699int ?<?( float, float ), ?<=?( float, float ),
     1700        ?>?( float, float ), ?>=?( float, float );
     1701int ?<?( double, double ), ?<=?( double, double ),
     1702        ?>?( double, double ), ?>=?( double, double );
     1703int ?<?( long double, long double ), ?<=?( long double, long double ),
     1704        ?>?( long double, long double ), ?>=?( long double, long double );
     1705forall( dtype DT ) int ?<?( const restrict volatile DT *, const restrict volatile DT * ),
    22761706        ?<?( _Atomic const restrict volatile DT *, _Atomic const restrict volatile DT * ),
    22771707        ?<=?( const restrict volatile DT *, const restrict volatile DT * ),
     
    22821712        ?>=?( _Atomic const restrict volatile DT *, _Atomic const restrict volatile DT * );
    22831713\end{lstlisting}
    2284 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2285 rank of \lstinline$int$ there exist
     1714For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    22861715% Don't use predefined: keep this out of prelude.cf.
    22871716\begin{lstlisting}
     
    22931722
    22941723\semantics
    2295 The interpretations of a relational expression are the interpretations of the corresponding function
    2296 call.
     1724The interpretations of a relational expression are the interpretations of the corresponding function call.
    22971725
    22981726
     
    23141742\predefined
    23151743\begin{lstlisting}
    2316 int ?==?( int, int ),
    2317         ?!=?( int, int ),
    2318         ?==?( unsigned int, unsigned int ),
    2319         ?!=?( unsigned int, unsigned int ),
    2320         ?==?( long int, long int ),
    2321         ?!=?( long int, long int ),
    2322         ?==?( long unsigned int, long unsigned int ),
    2323         ?!=?( long unsigned int, long unsigned int ),
    2324         ?==?( long long int, long long int ),
    2325         ?!=?( long long int, long long int ),
    2326         ?==?( long long unsigned int, long long unsigned int ),
    2327         ?!=?( long long unsigned int, long long unsigned int ),
    2328         ?==?( float, float ),
    2329         ?!=?( float, float ),
    2330         ?==?( _Complex float, float ),
    2331         ?!=?( _Complex float, float ),
    2332         ?==?( float, _Complex float ),
    2333         ?!=?( float, _Complex float ),
    2334         ?==?( _Complex float, _Complex float ),
    2335         ?!=?( _Complex float, _Complex float ),
    2336         ?==?( double, double ),
    2337         ?!=?( double, double ),
    2338         ?==?( _Complex double, double ),
    2339         ?!=?( _Complex double, double ),
    2340         ?==?( double, _Complex double ),
    2341         ?!=?( double, _Complex double ),
    2342         ?==?( _Complex double, _Complex double ),
    2343         ?!=?( _Complex double, _Complex double ),
    2344         ?==?( long double, long double ),
    2345         ?!=?( long double, long double ),
    2346         ?==?( _Complex long double, long double ),
    2347         ?!=?( _Complex long double, long double ),
    2348         ?==?( long double, _Complex long double ),
    2349         ?!=?( long double, _Complex long double ),
    2350         ?==?( _Complex long double, _Complex long double ),
    2351         ?!=?( _Complex long double, _Complex long double );
    2352 
     1744int ?==?( int, int ), ?!=?( int, int ),
     1745        ?==?( unsigned int, unsigned int ), ?!=?( unsigned int, unsigned int ),
     1746        ?==?( long int, long int ), ?!=?( long int, long int ),
     1747        ?==?( long unsigned int, long unsigned int ), ?!=?( long unsigned int, long unsigned int ),
     1748        ?==?( long long int, long long int ), ?!=?( long long int, long long int ),
     1749        ?==?( long long unsigned int, long long unsigned int ), ?!=?( long long unsigned int, long long unsigned int ),
     1750        ?==?( float, float ), ?!=?( float, float ),
     1751        ?==?( _Complex float, float ), ?!=?( _Complex float, float ),
     1752        ?==?( float, _Complex float ), ?!=?( float, _Complex float ),
     1753        ?==?( _Complex float, _Complex float ), ?!=?( _Complex float, _Complex float ),
     1754        ?==?( double, double ), ?!=?( double, double ),
     1755        ?==?( _Complex double, double ), ?!=?( _Complex double, double ),
     1756        ?==?( double, _Complex double ), ?!=?( double, _Complex double ),
     1757        ?==?( _Complex double, _Complex double ), ?!=?( _Complex double, _Complex double ),
     1758        ?==?( long double, long double ), ?!=?( long double, long double ),
     1759        ?==?( _Complex long double, long double ), ?!=?( _Complex long double, long double ),
     1760        ?==?( long double, _Complex long double ), ?!=?( long double, _Complex long double ),
     1761        ?==?( _Complex long double, _Complex long double ), ?!=?( _Complex long double, _Complex long double );
    23531762forall( dtype DT ) int
    23541763        ?==?( const restrict volatile DT *, const restrict volatile DT * ),
     
    23751784        ?==?( forall( dtype DT2) const DT2*, _Atomic const restrict volatile DT * ),
    23761785        ?!=?( forall( dtype DT2) const DT2*, _Atomic const restrict volatile DT * );
    2377 
    23781786forall( ftype FT ) int
    2379         ?==?( FT *, FT * ),
    2380         ?!=?( FT *, FT * ),
    2381         ?==?( FT *, forall( ftype FT2) FT2 * ),
    2382         ?!=?( FT *, forall( ftype FT2) FT2 * ),
    2383         ?==?( forall( ftype FT2) FT2*, FT * ),
    2384         ?!=?( forall( ftype FT2) FT2*, FT * ),
    2385         ?==?( forall( ftype FT2) FT2*, forall( ftype FT3) FT3 * ),
    2386         ?!=?( forall( ftype FT2) FT2*, forall( ftype FT3) FT3 * );
    2387 \end{lstlisting}
    2388 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2389 rank of \lstinline$int$ there exist
     1787        ?==?( FT *, FT * ), ?!=?( FT *, FT * ),
     1788        ?==?( FT *, forall( ftype FT2) FT2 * ), ?!=?( FT *, forall( ftype FT2) FT2 * ),
     1789        ?==?( forall( ftype FT2) FT2*, FT * ), ?!=?( forall( ftype FT2) FT2*, FT * ),
     1790        ?==?( forall( ftype FT2) FT2*, forall( ftype FT3) FT3 * ), ?!=?( forall( ftype FT2) FT2*, forall( ftype FT3) FT3 * );
     1791\end{lstlisting}
     1792For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    23901793% Don't use predefined: keep this out of prelude.cf.
    23911794\begin{lstlisting}
     
    23951798
    23961799\begin{rationale}
    2397 The polymorphic equality operations come in three styles: comparisons between pointers of compatible
    2398 types, between pointers to \lstinline$void$ and pointers to object types or incomplete types, and
    2399 between the \Index{null pointer} constant and pointers to any type. In the last case, a special
    2400 constraint rule for null pointer constant operands has been replaced by a consequence of the \CFA
    2401 type system.
     1800The polymorphic equality operations come in three styles: comparisons between pointers of compatible types, between pointers to \lstinline$void$ and pointers to object types or incomplete types, and between the \Index{null pointer} constant and pointers to any type.
     1801In the last case, a special constraint rule for null pointer constant operands has been replaced by a consequence of the \CFA type system.
    24021802\end{rationale}
    24031803
    24041804\semantics
    2405 The interpretations of an equality expression are the interpretations of the corresponding function
    2406 call.
     1805The interpretations of an equality expression are the interpretations of the corresponding function call.
    24071806
    24081807\begin{sloppypar}
    2409 The result of an equality comparison between two pointers to predefined functions or predefined
    2410 values is implementation-defined.
     1808The result of an equality comparison between two pointers to predefined functions or predefined values is implementation-defined.
    24111809\end{sloppypar}
    24121810\begin{rationale}
    2413 The implementation-defined status of equality comparisons allows implementations to use one library
    2414 routine to implement many predefined functions. These optimization are particularly important when
    2415 the predefined functions are polymorphic, as is the case for most pointer operations
     1811The implementation-defined status of equality comparisons allows implementations to use one library routine to implement many predefined functions.
     1812These optimization are particularly important when the predefined functions are polymorphic, as is the case for most pointer operations
    24161813\end{rationale}
    24171814
     
    24391836long long unsigned int ?&?( long long unsigned int, long long unsigned int );
    24401837\end{lstlisting}
    2441 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2442 rank of \lstinline$int$ there exist
     1838For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    24431839% Don't use predefined: keep this out of prelude.cf.
    24441840\begin{lstlisting}
     
    24471843
    24481844\semantics
    2449 The interpretations of a bitwise AND expression are the interpretations of the corresponding
    2450 function call.
     1845The interpretations of a bitwise AND expression are the interpretations of the corresponding function call.
    24511846
    24521847
     
    24731868long long unsigned int ?^?( long long unsigned int, long long unsigned int );
    24741869\end{lstlisting}
    2475 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2476 rank of \lstinline$int$ there exist
     1870For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    24771871% Don't use predefined: keep this out of prelude.cf.
    24781872\begin{lstlisting}
     
    24811875
    24821876\semantics
    2483 The interpretations of a bitwise exclusive OR expression are the interpretations of the
    2484 corresponding function call.
     1877The interpretations of a bitwise exclusive OR expression are the interpretations of the corresponding function call.
    24851878
    24861879
     
    25071900long long unsigned int ?|?( long long unsigned int, long long unsigned int );
    25081901\end{lstlisting}
    2509 For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the
    2510 rank of \lstinline$int$ there exist
     1902For every extended integer type \lstinline$X$ with \Index{integer conversion rank} greater than the rank of \lstinline$int$ there exist
    25111903% Don't use predefined: keep this out of prelude.cf.
    25121904\begin{lstlisting}
     
    25151907
    25161908\semantics
    2517 The interpretations of a bitwise inclusive OR expression are the interpretations of the
    2518 corresponding function call.
     1909The interpretations of a bitwise inclusive OR expression are the interpretations of the corresponding function call.
    25191910
    25201911
     
    25281919
    25291920\semantics The operands of the expression ``\lstinline$a && b$'' are treated as
    2530 ``\lstinline$(int)((a)!=0)$'' and ``\lstinline$(int)((b)!=0)$'', which shall both be
    2531 unambiguous. The expression has only one interpretation, which is of type \lstinline$int$.
    2532 \begin{rationale}
    2533 When the operands of a logical expression are values of built-in types, and ``\lstinline$!=$'' has
    2534 not been redefined for those types, the compiler can optimize away the function calls.
     1921``\lstinline$(int)((a)!=0)$'' and ``\lstinline$(int)((b)!=0)$'', which shall both be unambiguous.
     1922The expression has only one interpretation, which is of type \lstinline$int$.
     1923\begin{rationale}
     1924When the operands of a logical expression are values of built-in types, and ``\lstinline$!=$'' has not been redefined for those types, the compiler can optimize away the function calls.
    25351925
    25361926A common C idiom omits comparisons to \lstinline$0$ in the controlling expressions of loops and
    2537 \lstinline$if$ statements. For instance, the loop below iterates as long as \lstinline$rp$ points
    2538 at a \lstinline$Rational$ value that is non-zero.
    2539 
    2540 \begin{lstlisting}
    2541 extern type Rational;@\use{Rational}@
     1927\lstinline$if$ statements.
     1928For instance, the loop below iterates as long as \lstinline$rp$ points at a \lstinline$Rational$ value that is non-zero.
     1929
     1930\begin{lstlisting}
     1931extern otype Rational;@\use{Rational}@
    25421932extern const Rational 0;@\use{0}@
    25431933extern int ?!=?( Rational, Rational );
    25441934Rational *rp;
    2545 
    25461935while ( rp && *rp ) { ... }
    25471936\end{lstlisting}
    2548 The logical expression calls the \lstinline$Rational$ inequality operator, passing
    2549 it \lstinline$*rp$ and the \lstinline$Rational 0$, and getting a 1 or 0 as a result. In
    2550 contrast, {\CC} would apply a programmer-defined \lstinline$Rational$-to-\lstinline$int$
    2551 conversion to \lstinline$*rp$ in the equivalent situation. The conversion to \lstinline$int$ would
    2552 produce a general integer value, which is unfortunate, and possibly dangerous if the conversion was
    2553 not written with this situation in mind.
     1937The logical expression calls the \lstinline$Rational$ inequality operator, passing it \lstinline$*rp$ and the \lstinline$Rational 0$, and getting a 1 or 0 as a result.
     1938In contrast, {\CC} would apply a programmer-defined \lstinline$Rational$-to-\lstinline$int$ conversion to \lstinline$*rp$ in the equivalent situation.
     1939The conversion to \lstinline$int$ would produce a general integer value, which is unfortunate, and possibly dangerous if the conversion was not written with this situation in mind.
    25541940\end{rationale}
    25551941
     
    25651951\semantics
    25661952
    2567 The operands of the expression ``\lstinline$a || b$'' are treated as ``\lstinline$(int)((a)!=0)$''
    2568 and ``\lstinline$(int)((b))!=0)$'', which shall both be unambiguous. The expression has only one
    2569 interpretation, which is of type \lstinline$int$.
     1953The operands of the expression ``\lstinline$a || b$'' are treated as ``\lstinline$(int)((a)!=0)$'' and ``\lstinline$(int)((b))!=0)$'', which shall both be unambiguous.
     1954The expression has only one interpretation, which is of type \lstinline$int$.
    25701955
    25711956
     
    25801965
    25811966\semantics
    2582 In the conditional expression\use{?:} ``\lstinline$a?b:c$'', if the second and
    2583 third operands both have an interpretation with \lstinline$void$ type, then the expression has an
    2584 interpretation with type \lstinline$void$, equivalent to
     1967In the conditional expression\use{?:} ``\lstinline$a?b:c$'', if the second and third operands both have an interpretation with \lstinline$void$ type, then the expression has an interpretation with type \lstinline$void$, equivalent to
    25851968\begin{lstlisting}
    25861969( int)(( a)!=0) ? ( void)( b) : ( void)( c)
    25871970\end{lstlisting}
    25881971
    2589 If the second and third operands both have interpretations with non-\lstinline$void$ types, the
    2590 expression is treated as if it were the call ``\lstinline$cond((a)!=0, b, c)$'',
    2591 with \lstinline$cond$ declared as
    2592 \begin{lstlisting}
    2593 forall( type T ) T cond( int, T, T );
    2594  
    2595 forall( dtype D ) void
    2596         * cond( int, D *, void * ),
    2597         * cond( int, void *, D * );
    2598        
    2599 forall( dtype D ) _atomic void
    2600         * cond( int, _Atomic D *, _Atomic void * ),
    2601         * cond( int, _Atomic void *, _Atomic D * );
    2602 
    2603 forall( dtype D ) const void
    2604         * cond( int, const D *, const void * ),
    2605         * cond( int, const void *, const D * );
    2606 
    2607 forall( dtype D ) restrict void
    2608         * cond( int, restrict D *, restrict void * ),
    2609         * cond( int, restrict void *, restrict D * );
    2610 
    2611 forall( dtype D ) volatile void
    2612         * cond( int, volatile D *, volatile void * ),
    2613         * cond( int, volatile void *, volatile D * );
    2614 
    2615 forall( dtype D ) _Atomic const void
    2616         * cond( int, _Atomic const D *, _Atomic const void * ),
    2617         * cond( int, _Atomic const void *, _Atomic const D * );
    2618 
    2619 forall( dtype D ) _Atomic restrict void
    2620         * cond( int, _Atomic restrict D *, _Atomic restrict void * ),
    2621         * cond( int, _Atomic restrict void *, _Atomic restrict D * );
    2622 
    2623 forall( dtype D ) _Atomic volatile void
    2624         * cond( int, _Atomic volatile D *, _Atomic volatile void * ),
    2625         * cond( int, _Atomic volatile void *, _Atomic volatile D * );
    2626 
    2627 forall( dtype D ) const restrict void
    2628         * cond( int, const restrict D *, const restrict void * ),
    2629         * cond( int, const restrict void *, const restrict D * );
    2630 
    2631 forall( dtype D ) const volatile void
    2632         * cond( int, const volatile D *, const volatile void * ),
    2633         * cond( int, const volatile void *, const volatile D * );
    2634 
    2635 forall( dtype D ) restrict volatile void
    2636         * cond( int, restrict volatile D *, restrict volatile void * ),
    2637         * cond( int, restrict volatile void *, restrict volatile D * );
    2638 
    2639 forall( dtype D ) _Atomic const restrict void
    2640         * cond( int, _Atomic const restrict D *, _Atomic const restrict void * ),
     1972If the second and third operands both have interpretations with non-\lstinline$void$ types, the expression is treated as if it were the call ``\lstinline$cond((a)!=0, b, c)$'', with \lstinline$cond$ declared as
     1973\begin{lstlisting}
     1974forall( otype T ) T cond( int, T, T );
     1975forall( dtype D ) void * cond( int, D *, void * ), * cond( int, void *, D * );
     1976forall( dtype D ) _atomic void * cond(
     1977        int, _Atomic D *, _Atomic void * ), * cond( int, _Atomic void *, _Atomic D * );
     1978forall( dtype D ) const void * cond(
     1979        int, const D *, const void * ), * cond( int, const void *, const D * );
     1980forall( dtype D ) restrict void * cond(
     1981        int, restrict D *, restrict void * ), * cond( int, restrict void *, restrict D * );
     1982forall( dtype D ) volatile void * cond(
     1983        int, volatile D *, volatile void * ), * cond( int, volatile void *, volatile D * );
     1984forall( dtype D ) _Atomic const void * cond(
     1985        int, _Atomic const D *, _Atomic const void * ), * cond( int, _Atomic const void *, _Atomic const D * );
     1986forall( dtype D ) _Atomic restrict void * cond(
     1987        int, _Atomic restrict D *, _Atomic restrict void * ), * cond( int, _Atomic restrict void *, _Atomic restrict D * );
     1988forall( dtype D ) _Atomic volatile void * cond(
     1989        int, _Atomic volatile D *, _Atomic volatile void * ), * cond( int, _Atomic volatile void *, _Atomic volatile D * );
     1990forall( dtype D ) const restrict void * cond(
     1991        int, const restrict D *, const restrict void * ), * cond( int, const restrict void *, const restrict D * );
     1992forall( dtype D ) const volatile void * cond(
     1993        int, const volatile D *, const volatile void * ), * cond( int, const volatile void *, const volatile D * );
     1994forall( dtype D ) restrict volatile void * cond(
     1995        int, restrict volatile D *, restrict volatile void * ), * cond( int, restrict volatile void *, restrict volatile D * );
     1996forall( dtype D ) _Atomic const restrict void * cond(
     1997        int, _Atomic const restrict D *, _Atomic const restrict void * ),
    26411998        * cond( int, _Atomic const restrict void *, _Atomic const restrict D * );
    2642 
    2643 forall( dtype D ) _Atomic const volatile void
    2644         * cond( int, _Atomic const volatile D *, _Atomic const volatile void * ),
     1999forall( dtype D ) _Atomic const volatile void * cond(
     2000        int, _Atomic const volatile D *, _Atomic const volatile void * ),
    26452001        * cond( int, _Atomic const volatile void *, _Atomic const volatile D * );
    2646 
    2647 forall( dtype D ) _Atomic restrict volatile void
    2648         * cond( int, _Atomic restrict volatile D *,
    2649          _Atomic restrict volatile void * ),
    2650         * cond( int, _Atomic restrict volatile void *,
    2651          _Atomic restrict volatile D * );
    2652 
    2653 forall( dtype D ) const restrict volatile void
    2654         * cond( int, const restrict volatile D *,
    2655          const restrict volatile void * ),
    2656         * cond( int, const restrict volatile void *,
    2657          const restrict volatile D * );
    2658 
    2659 forall( dtype D ) _Atomic const restrict volatile void
    2660         * cond( int, _Atomic const restrict volatile D *,
    2661          _Atomic const restrict volatile void * ),
    2662         * cond( int, _Atomic const restrict volatile void *,
    2663          _Atomic const restrict volatile D * );
    2664 \end{lstlisting}
    2665 
    2666 \begin{rationale}
    2667 The object of the above is to apply the \Index{usual arithmetic conversion}s when the second and
    2668 third operands have arithmetic type, and to combine the qualifiers of the second and third operands
    2669 if they are pointers.
     2002forall( dtype D ) _Atomic restrict volatile void * cond(
     2003        int, _Atomic restrict volatile D *, _Atomic restrict volatile void * ),
     2004        * cond( int, _Atomic restrict volatile void *, _Atomic restrict volatile D * );
     2005forall( dtype D ) const restrict volatile void * cond(
     2006        int, const restrict volatile D *, const restrict volatile void * ),
     2007        * cond( int, const restrict volatile void *, const restrict volatile D * );
     2008forall( dtype D ) _Atomic const restrict volatile void * cond(
     2009        int, _Atomic const restrict volatile D *, _Atomic const restrict volatile void * ),
     2010        * cond( int, _Atomic const restrict volatile void *, _Atomic const restrict volatile D * );
     2011\end{lstlisting}
     2012
     2013\begin{rationale}
     2014The object of the above is to apply the \Index{usual arithmetic conversion}s when the second and third operands have arithmetic type, and to combine the qualifiers of the second and third operands if they are pointers.
    26702015\end{rationale}
    26712016
     
    26852030rand() ? cip : vip;
    26862031\end{lstlisting}
    2687 The expression has type \lstinline$const volatile int *$, with safe conversions applied to the second
    2688 and third operands to add \lstinline$volatile$ and \lstinline$const$ qualifiers, respectively.
     2032The expression has type \lstinline$const volatile int *$, with safe conversions applied to the second and third operands to add \lstinline$volatile$ and \lstinline$const$ qualifiers, respectively.
    26892033
    26902034\begin{lstlisting}
     
    27082052
    27092053\rewriterules
    2710 Let ``\(\leftarrow\)'' be any of the assignment operators. Then
     2054Let ``\(\leftarrow\)'' be any of the assignment operators.
     2055Then
    27112056\use{?=?}\use{?*=?}\use{?/=?}\use{?%=?}\use{?+=?}\use{?-=?}
    27122057\use{?>>=?}\use{?&=?}\use{?^=?}\use{?"|=?}%use{?<<=?}
     
    27162061
    27172062\semantics
    2718 Each interpretation of the left operand of an assignment expression is considered separately. For
    2719 each interpretation that is a bit-field or is declared with the \lstinline$register$ storage class
    2720 specifier, the expression has one valid interpretation, with the type of the left operand. The
    2721 right operand is cast to that type, and the assignment expression is ambiguous if either operand is.
    2722 For the remaining interpretations, the expression is rewritten, and the interpretations of the
    2723 assignment expression are the interpretations of the corresponding function call. Finally, all
    2724 interpretations of the expression produced for the different interpretations of the left operand are
    2725 combined to produce the interpretations of the expression as a whole; where interpretations have
    2726 compatible result types, the best interpretations are selected in the manner described for function
    2727 call expressions.
     2063Each interpretation of the left operand of an assignment expression is considered separately.
     2064For each interpretation that is a bit-field or is declared with the \lstinline$register$ storage class specifier, the expression has one valid interpretation, with the type of the left operand.
     2065The right operand is cast to that type, and the assignment expression is ambiguous if either operand is.
     2066For the remaining interpretations, the expression is rewritten, and the interpretations of the assignment expression are the interpretations of the corresponding function call.
     2067Finally, all interpretations of the expression produced for the different interpretations of the left operand are combined to produce the interpretations of the expression as a whole;
     2068where interpretations have compatible result types, the best interpretations are selected in the manner described for function call expressions.
    27282069
    27292070
     
    27902131        ?=?( volatile _Complex long double *, _Complex long double ),
    27912132        ?=?( _Atomic volatile _Complex long double *, _Atomic _Complex long double );
    2792 
    27932133forall( ftype FT ) FT
    27942134        * ?=?( FT * volatile *, FT * ),
    27952135        * ?=?( FT * volatile *, forall( ftype F ) F * );
    2796 
    27972136forall( ftype FT ) FT const
    27982137        * ?=?( FT const * volatile *, FT const * ),
    27992138        * ?=?( FT const * volatile *, forall( ftype F ) F * );
    2800 
    28012139forall( ftype FT ) FT volatile
    28022140        * ?=?( FT volatile * volatile *, FT * ),
    28032141        * ?=?( FT volatile * volatile *, forall( ftype F ) F * );
    2804 
    28052142forall( ftype FT ) FT const
    28062143        * ?=?( FT const volatile * volatile *, FT const * ),
    28072144        * ?=?( FT const volatile * volatile *, forall( ftype F ) F * );
    2808 
    28092145forall( dtype DT ) DT
    28102146        * ?=?( DT * restrict volatile *, DT * ),
     
    28142150        * ?=?( DT * _Atomic restrict volatile *, void * ),
    28152151        * ?=?( DT * _Atomic restrict volatile *, forall( dtype D ) D * );
    2816 
    28172152forall( dtype DT ) DT _Atomic
    28182153        * ?=?( _Atomic DT * restrict volatile *, DT _Atomic * ),
     
    28222157        * ?=?( _Atomic DT * _Atomic restrict volatile *, void * ),
    28232158        * ?=?( _Atomic DT * _Atomic restrict volatile *, forall( dtype D ) D * );
    2824 
    28252159forall( dtype DT ) DT const
    28262160        * ?=?( DT const * restrict volatile *, DT const * ),
     
    28302164        * ?=?( DT const * _Atomic restrict volatile *, void const * ),
    28312165        * ?=?( DT const * _Atomic restrict volatile *, forall( dtype D ) D * );
    2832 
    28332166forall( dtype DT ) DT restrict
    28342167        * ?=?( restrict DT * restrict volatile *, DT restrict * ),
     
    28382171        * ?=?( restrict DT * _Atomic restrict volatile *, void * ),
    28392172        * ?=?( restrict DT * _Atomic restrict volatile *, forall( dtype D ) D * );
    2840 
    28412173forall( dtype DT ) DT volatile
    28422174        * ?=?( DT volatile * restrict volatile *, DT volatile * ),
     
    28462178        * ?=?( DT volatile * _Atomic restrict volatile *, void volatile * ),
    28472179        * ?=?( DT volatile * _Atomic restrict volatile *, forall( dtype D ) D * );
    2848 
    28492180forall( dtype DT ) DT _Atomic const
    28502181        * ?=?( DT _Atomic const * restrict volatile *, DT _Atomic const * ),
     
    28542185        * ?=?( DT _Atomic const * _Atomic restrict volatile *, void const * ),
    28552186        * ?=?( DT _Atomic const * _Atomic restrict volatile *, forall( dtype D ) D * );
    2856 
    28572187forall( dtype DT ) DT _Atomic restrict
    28582188        * ?=?( _Atomic restrict DT * restrict volatile *, DT _Atomic restrict * ),
     
    28622192        * ?=?( _Atomic restrict DT * _Atomic restrict volatile *, void * ),
    28632193        * ?=?( _Atomic restrict DT * _Atomic restrict volatile *, forall( dtype D ) D * );
    2864 
    28652194forall( dtype DT ) DT _Atomic volatile
    28662195        * ?=?( DT _Atomic volatile * restrict volatile *, DT _Atomic volatile * ),
     
    28702199        * ?=?( DT _Atomic volatile * _Atomic restrict volatile *, void volatile * ),
    28712200        * ?=?( DT _Atomic volatile * _Atomic restrict volatile *, forall( dtype D ) D * );
    2872 
    28732201forall( dtype DT ) DT const restrict
    28742202        * ?=?( DT const restrict * restrict volatile *, DT const restrict * ),
     
    28782206        * ?=?( DT const restrict * _Atomic restrict volatile *, void const * ),
    28792207        * ?=?( DT const restrict * _Atomic restrict volatile *, forall( dtype D ) D * );
    2880 
    28812208forall( dtype DT ) DT const volatile
    28822209        * ?=?( DT const volatile * restrict volatile *, DT const volatile * ),
     
    28862213        * ?=?( DT const volatile * _Atomic restrict volatile *, void const volatile * ),
    28872214        * ?=?( DT const volatile * _Atomic restrict volatile *, forall( dtype D ) D * );
    2888 
    28892215forall( dtype DT ) DT restrict volatile
    28902216        * ?=?( DT restrict volatile * restrict volatile *, DT restrict volatile * ),
     
    28942220        * ?=?( DT restrict volatile * _Atomic restrict volatile *, void volatile * ),
    28952221        * ?=?( DT restrict volatile * _Atomic restrict volatile *, forall( dtype D ) D * );
    2896 
    28972222forall( dtype DT ) DT _Atomic const restrict
    28982223        * ?=?( DT _Atomic const restrict * restrict volatile *,
     
    29082233        * ?=?( DT _Atomic const restrict * _Atomic restrict volatile *,
    29092234         forall( dtype D ) D * );
    2910 
    29112235forall( dtype DT ) DT _Atomic const volatile
    29122236        * ?=?( DT _Atomic const volatile * restrict volatile *,
     
    29222246        * ?=?( DT _Atomic const volatile * _Atomic restrict volatile *,
    29232247         forall( dtype D ) D * );
    2924 
    29252248forall( dtype DT ) DT _Atomic restrict volatile
    29262249        * ?=?( DT _Atomic restrict volatile * restrict volatile *,
     
    29362259        * ?=?( DT _Atomic restrict volatile * _Atomic restrict volatile *,
    29372260         forall( dtype D ) D * );
    2938 
    29392261forall( dtype DT ) DT const restrict volatile
    29402262        * ?=?( DT const restrict volatile * restrict volatile *,
     
    29502272        * ?=?( DT const restrict volatile * _Atomic restrict volatile *,
    29512273         forall( dtype D ) D * );
    2952 
    29532274forall( dtype DT ) DT _Atomic const restrict volatile
    29542275        * ?=?( DT _Atomic const restrict volatile * restrict volatile *,
     
    29642285        * ?=?( DT _Atomic const restrict volatile * _Atomic restrict volatile *,
    29652286         forall( dtype D ) D * );
    2966 
    29672287forall( dtype DT ) void
    29682288        * ?=?( void * restrict volatile *, DT * );
    2969 
    29702289forall( dtype DT ) void const
    29712290        * ?=?( void const * restrict volatile *, DT const * );
    2972 
    29732291forall( dtype DT ) void volatile
    29742292        * ?=?( void volatile * restrict volatile *, DT volatile * );
    2975 
    29762293forall( dtype DT ) void const volatile
    29772294        * ?=?( void const volatile * restrict volatile *, DT const volatile * );
    29782295\end{lstlisting}
    29792296\begin{rationale}
    2980 The pattern of overloadings for simple assignment resembles that of pointer increment and decrement,
    2981 except that the polymorphic pointer assignment functions declare a \lstinline$dtype$ parameter,
    2982 instead of a \lstinline$type$ parameter, because the left operand may be a pointer to an incomplete
    2983 type.
     2297The pattern of overloadings for simple assignment resembles that of pointer increment and decrement, except that the polymorphic pointer assignment functions declare a \lstinline$dtype$ parameter, instead of a \lstinline$type$ parameter, because the left operand may be a pointer to an incomplete type.
    29842298\end{rationale}
    29852299
     
    30062320
    30072321\semantics
    3008 The structure assignment functions provide member-wise assignment; each non-array member and each
    3009 element of each array member of the right argument is assigned to the corresponding member or
    3010 element of the left argument using the assignment function defined for its type. All other
    3011 assignment functions have the same effect as the corresponding C assignment expression.
    3012 \begin{rationale}
    3013 Note that, by default, union assignment\index{deficiencies!union assignment} uses C semantics---that
    3014 is, bitwise copy---even if some of the union members have programmer-defined assignment functions.
     2322The structure assignment functions provide member-wise assignment;
     2323each non-array member and each element of each array member of the right argument is assigned to the corresponding member or element of the left argument using the assignment function defined for its type.
     2324All other assignment functions have the same effect as the corresponding C assignment expression.
     2325\begin{rationale}
     2326Note that, by default, union assignment\index{deficiencies!union assignment} uses C semantics---that is, bitwise copy---even if some of the union members have programmer-defined assignment functions.
    30152327\end{rationale}
    30162328
     
    30202332\predefined
    30212333\begin{lstlisting}
    3022 forall( type T ) T
     2334forall( otype T ) T
    30232335        * ?+=?( T * restrict volatile *, ptrdiff_t ),
    30242336        * ?-=?( T * restrict volatile *, ptrdiff_t ),
    30252337        * ?+=?( T * _Atomic restrict volatile *, ptrdiff_t ),
    30262338        * ?-=?( T * _Atomic restrict volatile *, ptrdiff_t );
    3027 
    3028 forall( type T ) T _Atomic
     2339forall( otype T ) T _Atomic
    30292340        * ?+=?( T _Atomic * restrict volatile *, ptrdiff_t ),
    30302341        * ?-=?( T _Atomic * restrict volatile *, ptrdiff_t ),
    30312342        * ?+=?( T _Atomic * _Atomic restrict volatile *, ptrdiff_t ),
    30322343        * ?-=?( T _Atomic * _Atomic restrict volatile *, ptrdiff_t );
    3033 
    3034 forall( type T ) T const
     2344forall( otype T ) T const
    30352345        * ?+=?( T const * restrict volatile *, ptrdiff_t ),
    30362346        * ?-=?( T const * restrict volatile *, ptrdiff_t ),
    30372347        * ?+=?( T const * _Atomic restrict volatile *, ptrdiff_t ),
    30382348        * ?-=?( T const * _Atomic restrict volatile *, ptrdiff_t );
    3039 
    3040 forall( type T ) T restrict
     2349forall( otype T ) T restrict
    30412350        * ?+=?( T restrict * restrict volatile *, ptrdiff_t ),
    30422351        * ?-=?( T restrict * restrict volatile *, ptrdiff_t ),
    30432352        * ?+=?( T restrict * _Atomic restrict volatile *, ptrdiff_t ),
    30442353        * ?-=?( T restrict * _Atomic restrict volatile *, ptrdiff_t );
    3045 
    3046 forall( type T ) T volatile
     2354forall( otype T ) T volatile
    30472355        * ?+=?( T volatile * restrict volatile *, ptrdiff_t ),
    30482356        * ?-=?( T volatile * restrict volatile *, ptrdiff_t ),
    30492357        * ?+=?( T volatile * _Atomic restrict volatile *, ptrdiff_t ),
    30502358        * ?-=?( T volatile * _Atomic restrict volatile *, ptrdiff_t );
    3051 
    3052 forall( type T ) T _Atomic const
     2359forall( otype T ) T _Atomic const
    30532360        * ?+=?( T _Atomic const restrict volatile *, ptrdiff_t ),
    30542361        * ?-=?( T _Atomic const restrict volatile *, ptrdiff_t ),
    30552362        * ?+=?( T _Atomic const _Atomic restrict volatile *, ptrdiff_t ),
    30562363        * ?-=?( T _Atomic const _Atomic restrict volatile *, ptrdiff_t );
    3057 
    3058 forall( type T ) T _Atomic restrict
     2364forall( otype T ) T _Atomic restrict
    30592365        * ?+=?( T _Atomic restrict * restrict volatile *, ptrdiff_t ),
    30602366        * ?-=?( T _Atomic restrict * restrict volatile *, ptrdiff_t ),
    30612367        * ?+=?( T _Atomic restrict * _Atomic restrict volatile *, ptrdiff_t ),
    30622368        * ?-=?( T _Atomic restrict * _Atomic restrict volatile *, ptrdiff_t );
    3063 
    3064 forall( type T ) T _Atomic volatile
     2369forall( otype T ) T _Atomic volatile
    30652370        * ?+=?( T _Atomic volatile * restrict volatile *, ptrdiff_t ),
    30662371        * ?-=?( T _Atomic volatile * restrict volatile *, ptrdiff_t ),
    30672372        * ?+=?( T _Atomic volatile * _Atomic restrict volatile *, ptrdiff_t ),
    30682373        * ?-=?( T _Atomic volatile * _Atomic restrict volatile *, ptrdiff_t );
    3069 
    3070 forall( type T ) T const restrict
     2374forall( otype T ) T const restrict
    30712375        * ?+=?( T const restrict * restrict volatile *, ptrdiff_t ),
    30722376        * ?-=?( T const restrict * restrict volatile *, ptrdiff_t ),
    30732377        * ?+=?( T const restrict * _Atomic restrict volatile *, ptrdiff_t ),
    30742378        * ?-=?( T const restrict * _Atomic restrict volatile *, ptrdiff_t );
    3075 
    3076 forall( type T ) T const volatile
     2379forall( otype T ) T const volatile
    30772380        * ?+=?( T const volatile * restrict volatile *, ptrdiff_t ),
    30782381        * ?-=?( T const volatile * restrict volatile *, ptrdiff_t ),
    30792382        * ?+=?( T const volatile * _Atomic restrict volatile *, ptrdiff_t ),
    30802383        * ?-=?( T const volatile * _Atomic restrict volatile *, ptrdiff_t );
    3081 
    3082 forall( type T ) T restrict volatile
     2384forall( otype T ) T restrict volatile
    30832385        * ?+=?( T restrict volatile * restrict volatile *, ptrdiff_t ),
    30842386        * ?-=?( T restrict volatile * restrict volatile *, ptrdiff_t ),
    30852387        * ?+=?( T restrict volatile * _Atomic restrict volatile *, ptrdiff_t ),
    30862388        * ?-=?( T restrict volatile * _Atomic restrict volatile *, ptrdiff_t );
    3087 
    3088 forall( type T ) T _Atomic const restrict
     2389forall( otype T ) T _Atomic const restrict
    30892390        * ?+=?( T _Atomic const restrict * restrict volatile *, ptrdiff_t ),
    30902391        * ?-=?( T _Atomic const restrict * restrict volatile *, ptrdiff_t ),
    30912392        * ?+=?( T _Atomic const restrict * _Atomic restrict volatile *, ptrdiff_t ),
    30922393        * ?-=?( T _Atomic const restrict * _Atomic restrict volatile *, ptrdiff_t );
    3093 
    3094 forall( type T ) T _Atomic const volatile
     2394forall( otype T ) T _Atomic const volatile
    30952395        * ?+=?( T _Atomic const volatile * restrict volatile *, ptrdiff_t ),
    30962396        * ?-=?( T _Atomic const volatile * restrict volatile *, ptrdiff_t ),
    30972397        * ?+=?( T _Atomic const volatile * _Atomic restrict volatile *, ptrdiff_t ),
    30982398        * ?-=?( T _Atomic const volatile * _Atomic restrict volatile *, ptrdiff_t );
    3099 
    3100 forall( type T ) T _Atomic restrict volatile
     2399forall( otype T ) T _Atomic restrict volatile
    31012400        * ?+=?( T _Atomic restrict volatile * restrict volatile *, ptrdiff_t ),
    31022401        * ?-=?( T _Atomic restrict volatile * restrict volatile *, ptrdiff_t ),
    31032402        * ?+=?( T _Atomic restrict volatile * _Atomic restrict volatile *, ptrdiff_t ),
    31042403        * ?-=?( T _Atomic restrict volatile * _Atomic restrict volatile *, ptrdiff_t );
    3105 
    3106 forall( type T ) T const restrict volatile
     2404forall( otype T ) T const restrict volatile
    31072405        * ?+=?( T const restrict volatile * restrict volatile *, ptrdiff_t ),
    31082406        * ?-=?( T const restrict volatile * restrict volatile *, ptrdiff_t ),
    31092407        * ?+=?( T const restrict volatile * _Atomic restrict volatile *, ptrdiff_t ),
    31102408        * ?-=?( T const restrict volatile * _Atomic restrict volatile *, ptrdiff_t );
    3111 
    3112 forall( type T ) T _Atomic const restrict volatile
     2409forall( otype T ) T _Atomic const restrict volatile
    31132410        * ?+=?( T _Atomic const restrict volatile * restrict volatile *, ptrdiff_t ),
    31142411        * ?-=?( T _Atomic const restrict volatile * restrict volatile *, ptrdiff_t ),
     
    33212618\semantics
    33222619In the comma expression ``\lstinline$a, b$'', the first operand is interpreted as
    3323 ``\lstinline$( void )(a)$'', which shall be unambiguous\index{ambiguous interpretation}. The
    3324 interpretations of the expression are the interpretations of the second operand.
     2620``\lstinline$( void )(a)$'', which shall be unambiguous\index{ambiguous interpretation}.
     2621The interpretations of the expression are the interpretations of the second operand.
    33252622
    33262623
     
    33372634
    33382635\constraints
    3339 If an identifier has \Index{no linkage}, there shall be no more than one declaration of the
    3340 identifier ( in a declarator or type specifier ) with compatible types in the same scope and in the
    3341 same name space, except that:
     2636If an identifier has \Index{no linkage}, there shall be no more than one declaration of the identifier ( in a declarator or type specifier ) with compatible types in the same scope and in the same name space, except that:
    33422637\begin{itemize}
    3343 \item
    3344 a typedef name may be redefined to denote the same type as it currently does, provided that type is
    3345 not a variably modified type;
    3346 \item
    3347 tags may be redeclared as specified in section 6.7.2.3 of the {\c11} standard.
     2638\item a typedef name may be redefined to denote the same type as it currently does, provided that type is not a variably modified type;
     2639\item tags may be redeclared as specified in section 6.7.2.3 of the {\c11} standard.
    33482640\end{itemize}
    33492641\begin{rationale}
    3350 This constraint adds the phrase ``with compatible types'' to the {\c11} constraint, to allow
    3351 overloading.
    3352 \end{rationale}
    3353 
    3354 An identifier declared by a type declaration shall not be redeclared as a parameter in a function
    3355 definition whose declarator includes an identifier list.
    3356 \begin{rationale}
    3357 This restriction echos {\c11}'s ban on the redeclaration of typedef names as parameters. This
    3358 avoids an ambiguity between old-style function declarations and new-style function prototypes:
     2642This constraint adds the phrase ``with compatible types'' to the {\c11} constraint, to allow overloading.
     2643\end{rationale}
     2644
     2645An identifier declared by a type declaration shall not be redeclared as a parameter in a function definition whose declarator includes an identifier list.
     2646\begin{rationale}
     2647This restriction echos {\c11}'s ban on the redeclaration of typedef names as parameters.
     2648This avoids an ambiguity between old-style function declarations and new-style function prototypes:
    33592649\begin{lstlisting}
    33602650void f( Complex,        // ... 3000 characters ...
    33612651void g( Complex,        // ... 3000 characters ...
    3362 int Complex; { ... }
    3363 \end{lstlisting}
    3364 Without the rule, \lstinline$Complex$ would be a type in the first case, and a parameter name in the
    3365 second.
     2652int Complex;
     2653{ ... }
     2654\end{lstlisting}
     2655Without the rule, \lstinline$Complex$ would be a type in the first case, and a parameter name in the second.
    33662656\end{rationale}
    33672657
     
    33822672
    33832673\semantics
    3384 \CFA extends the {\c11} definition of \define{anonymous structure} to include structure
    3385 specifiers with tags, and extends the {\c11} definition of \define{anonymous union} to include union
    3386 specifiers with tags.
     2674\CFA extends the {\c11} definition of \define{anonymous structure} to include structure specifiers with tags, and extends the {\c11} definition of \define{anonymous union} to include union specifiers with tags.
    33872675\begin{rationale}
    33882676This extension imitates an extension in the Plan 9 C compiler \cite{Thompson90new}.
     
    34012689cp.x = 0;
    34022690cp.color = RED;
    3403 
    34042691struct literal {@\impl{literal}@
    34052692        enum { NUMBER, STRING } tag;
    34062693        union {
    3407          double n;
    3408          char *s;
     2694                double n;
     2695                char *s;
    34092696        };
    34102697};
     
    34282715\begin{comment}
    34292716\constraints
    3430 If the \nonterm{declaration-specifiers} of a declaration that contains a \nonterm{forall-specifier}
    3431 declares a structure or union tag, the types of the members of the structure or union shall not use
    3432 any of the type identifiers declared by the \nonterm{type-parameter-list}.
    3433 \begin{rationale}
    3434 This sort of declaration is illegal because the scope of the type identifiers ends at the end of the
    3435 declaration, but the scope of the structure tag does not.
    3436 \begin{lstlisting}
    3437 forall( type T ) struct Pair { T a, b; } mkPair( T, T ); // illegal
    3438 \end{lstlisting}
    3439 If an instance of \lstinline$struct Pair$ was declared later in the current scope, what would the
    3440 members' type be?
     2717If the \nonterm{declaration-specifiers} of a declaration that contains a \nonterm{forall-specifier} declares a structure or union tag, the types of the members of the structure or union shall not use any of the type identifiers declared by the \nonterm{type-parameter-list}.
     2718\begin{rationale}
     2719This sort of declaration is illegal because the scope of the type identifiers ends at the end of the declaration, but the scope of the structure tag does not.
     2720\begin{lstlisting}
     2721forall( otype T ) struct Pair { T a, b;
     2722} mkPair( T, T ); // illegal
     2723\end{lstlisting}
     2724If an instance of \lstinline$struct Pair$ was declared later in the current scope, what would the members' type be?
    34412725\end{rationale}
    34422726\end{comment}
    34432727
    34442728\semantics
    3445 The \nonterm{type-parameter-list}s and assertions of the \nonterm{forall-specifier}s declare type
    3446 identifiers, function and object identifiers with \Index{no linkage}.
     2729The \nonterm{type-parameter-list}s and assertions of the \nonterm{forall-specifier}s declare type identifiers, function and object identifiers with \Index{no linkage}.
    34472730
    34482731If, in the declaration ``\lstinline$T D$'', \lstinline$T$ contains \nonterm{forall-specifier}s and
     
    34502733\begin{lstlisting}
    34512734D( @\normalsize\nonterm{parameter-type-list}@ )
    3452 \end{lstlisting}
    3453 then a type identifier declared by one of the \nonterm{forall-specifier}s is an \define{inferred
    3454 parameter} of the function declarator if and only if it is not an inferred parameter of a function
    3455 declarator in \lstinline$D$, and it is used in the type of a parameter in the following
     2735\end{lstlisting} then a type identifier declared by one of the \nonterm{forall-specifier}s is an \define{inferred parameter} of the function declarator if and only if it is not an inferred parameter of a function declarator in \lstinline$D$, and it is used in the type of a parameter in the following
    34562736\nonterm{type-parameter-list} or it and an inferred parameter are used as arguments of a
    3457 \Index{specification} in one of the \nonterm{forall-specifier}s. The identifiers declared by
    3458 assertions that use an inferred parameter of a function declarator are \Index{assertion parameter}s
    3459 of that function declarator.
     2737\Index{specification} in one of the \nonterm{forall-specifier}s.
     2738The identifiers declared by assertions that use an inferred parameter of a function declarator are \Index{assertion parameter}s of that function declarator.
    34602739
    34612740\begin{comment}
    34622741\begin{rationale}
    3463 Since every inferred parameter is used by some parameter, inference can be understood as a single
    3464 bottom-up pass over the expression tree, that only needs to apply local reasoning at each node.
     2742Since every inferred parameter is used by some parameter, inference can be understood as a single bottom-up pass over the expression tree, that only needs to apply local reasoning at each node.
    34652743
    34662744If this restriction were lifted, it would be possible to write
    34672745\begin{lstlisting}
    3468 forall( type T ) T * alloc( void );@\use{alloc}@
    3469 int *p = alloc();
     2746forall( otype T ) T * alloc( void );@\use{alloc}@ int *p = alloc();
    34702747\end{lstlisting}
    34712748Here \lstinline$alloc()$ would receive \lstinline$int$ as an inferred argument, and return an
    3472 \lstinline$int *$. In general, if a call to \lstinline$alloc()$ is a subexpression of an expression
    3473 involving polymorphic functions and overloaded identifiers, there could be considerable distance
    3474 between the call and the subexpression that causes \lstinline$T$ to be bound.
     2749\lstinline$int *$.
     2750In general, if a call to \lstinline$alloc()$ is a subexpression of an expression involving polymorphic functions and overloaded identifiers, there could be considerable distance between the call and the subexpression that causes \lstinline$T$ to be bound.
    34752751
    34762752With the current restriction, \lstinline$alloc()$ must be given an argument that determines
    34772753\lstinline$T$:
    34782754\begin{lstlisting}
    3479 forall( type T ) T * alloc( T initial_value );@\use{alloc}@
     2755forall( otype T ) T * alloc( T initial_value );@\use{alloc}@
    34802756\end{lstlisting}
    34812757\end{rationale}
    34822758\end{comment}
    34832759
    3484 If a function declarator is part of a function definition, its inferred parameters and assertion
    3485 parameters have \Index{block scope}; otherwise, identifiers declared by assertions have a
     2760If a function declarator is part of a function definition, its inferred parameters and assertion parameters have \Index{block scope};
     2761otherwise, identifiers declared by assertions have a
    34862762\define{declaration scope}, which terminates at the end of the \nonterm{declaration}.
    34872763
    34882764A function type that has at least one inferred parameter is a \define{polymorphic function} type.
    3489 Function types with no inferred parameters are \define{monomorphic function} types. One function
    3490 type is \define{less polymorphic} than another if it has fewer inferred parameters, or if it has the
    3491 same number of inferred parameters and fewer of its explicit parameters have types that depend on an
    3492 inferred parameter.
    3493 
    3494 The names of inferred parameters and the order of identifiers in forall specifiers are not relevant
    3495 to polymorphic function type compatibility. Let $f$ and $g$ be two polymorphic function types with
    3496 the same number of inferred parameters, and let $f_i$ and $g_i$ be the inferred parameters of $f$
    3497 and $g$ in their order of occurance in the function types' \nonterm{parameter-type-list}s. Let $f'$
    3498 be $f$ with every occurrence of $f_i$ replaced by $g_i$, for all $i$. Then $f$ and $g$ are
    3499 \Index{compatible type}s if $f'$'s and $g$'s return types and parameter lists are compatible, and if
    3500 for every assertion parameter of $f'$ there is an assertion parameter in $g$ with the same
    3501 identifier and compatible type, and vice versa.
     2765Function types with no inferred parameters are \define{monomorphic function} types.
     2766One function type is \define{less polymorphic} than another if it has fewer inferred parameters, or if it has the same number of inferred parameters and fewer of its explicit parameters have types that depend on an inferred parameter.
     2767
     2768The names of inferred parameters and the order of identifiers in forall specifiers are not relevant to polymorphic function type compatibility.
     2769Let $f$ and $g$ be two polymorphic function types with the same number of inferred parameters, and let $f_i$ and $g_i$ be the inferred parameters of $f$ and $g$ in their order of occurance in the function types' \nonterm{parameter-type-list}s.
     2770Let $f'$ be $f$ with every occurrence of $f_i$ replaced by $g_i$, for all $i$.
     2771Then $f$ and $g$ are
     2772\Index{compatible type}s if $f'$'s and $g$'s return types and parameter lists are compatible, and if for every assertion parameter of $f'$ there is an assertion parameter in $g$ with the same identifier and compatible type, and vice versa.
    35022773
    35032774\examples
     
    35052776\begin{lstlisting}
    35062777int fi( int );
    3507 forall( type T ) T fT( T );
     2778forall( otype T ) T fT( T );
    35082779\end{lstlisting}
    35092780\lstinline$fi()$ takes an \lstinline$int$ and returns an \lstinline$int$. \lstinline$fT()$ takes a
     
    35112782\begin{lstlisting}
    35122783int (*pfi )( int ) = fi;
    3513 forall( type T ) T (*pfT )( T ) = fT;
    3514 \end{lstlisting}
    3515 \lstinline$pfi$ and \lstinline$pfT$ are pointers to functions. \lstinline$pfT$ is not
    3516 polymorphic, but the function it points at is.
     2784forall( otype T ) T (*pfT )( T ) = fT;
     2785\end{lstlisting}
     2786\lstinline$pfi$ and \lstinline$pfT$ are pointers to functions. \lstinline$pfT$ is not polymorphic, but the function it points at is.
    35172787\begin{lstlisting}
    35182788int (*fvpfi( void ))( int ) {
    35192789        return pfi;
    35202790}
    3521 forall( type T ) T (*fvpfT( void ))( T ) {
     2791forall( otype T ) T (*fvpfT( void ))( T ) {
    35222792        return pfT;
    35232793}
    35242794\end{lstlisting}
    3525 \lstinline$fvpfi()$ and \lstinline$fvpfT()$ are functions taking no arguments and returning pointers
    3526 to functions. \lstinline$fvpfT()$ is monomorphic, but the function that its return value points
    3527 at is polymorphic.
    3528 \begin{lstlisting}
    3529 forall( type T ) int ( *fTpfi( T ) )( int );
    3530 forall( type T ) T ( *fTpfT( T ) )( T );
    3531 forall( type T, type U ) U ( *fTpfU( T ) )( U );
    3532 \end{lstlisting}
    3533 \lstinline$fTpfi()$ is a polymorphic function that returns a pointer to a monomorphic function
    3534 taking an integer and returning an integer. It could return \lstinline$pfi$. \lstinline$fTpfT()$
    3535 is subtle: it is a polymorphic function returning a \emph{monomorphic} function taking and returning
    3536 \lstinline$T$, where \lstinline$T$ is an inferred parameter of \lstinline$fTpfT()$. For instance,
    3537 in the expression ``\lstinline$fTpfT(17)$'', \lstinline$T$ is inferred to be \lstinline$int$, and
    3538 the returned value would have type \lstinline$int ( * )( int )$. ``\lstinline$fTpfT(17)(13)$'' and
     2795\lstinline$fvpfi()$ and \lstinline$fvpfT()$ are functions taking no arguments and returning pointers to functions. \lstinline$fvpfT()$ is monomorphic, but the function that its return value points at is polymorphic.
     2796\begin{lstlisting}
     2797forall( otype T ) int ( *fTpfi( T ) )( int );
     2798forall( otype T ) T ( *fTpfT( T ) )( T );
     2799forall( otype T, otype U ) U ( *fTpfU( T ) )( U );
     2800\end{lstlisting}
     2801\lstinline$fTpfi()$ is a polymorphic function that returns a pointer to a monomorphic function taking an integer and returning an integer.
     2802It could return \lstinline$pfi$. \lstinline$fTpfT()$ is subtle: it is a polymorphic function returning a \emph{monomorphic} function taking and returning
     2803\lstinline$T$, where \lstinline$T$ is an inferred parameter of \lstinline$fTpfT()$.
     2804For instance, in the expression ``\lstinline$fTpfT(17)$'', \lstinline$T$ is inferred to be \lstinline$int$, and the returned value would have type \lstinline$int ( * )( int )$. ``\lstinline$fTpfT(17)(13)$'' and
    35392805``\lstinline$fTpfT("yes")("no")$'' are legal, but ``\lstinline$fTpfT(17)("no")$'' is illegal.
    3540 \lstinline$fTpfU()$ is polymorphic ( in type \lstinline$T$), and returns a pointer to a function that
    3541 is polymorphic ( in type \lstinline$U$). ``\lstinline$f5(17)("no")$'' is a legal expression of type
     2806\lstinline$fTpfU()$ is polymorphic ( in type \lstinline$T$), and returns a pointer to a function that is polymorphic ( in type \lstinline$U$). ``\lstinline$f5(17)("no")$'' is a legal expression of type
    35422807\lstinline$char *$.
    35432808\begin{lstlisting}
    3544 forall( type T, type U, type V ) U * f( T *, U, V * const );
    3545 forall( type U, type V, type W ) U * g( V *, U, W * const );
    3546 \end{lstlisting}
    3547 The functions \lstinline$f()$ and \lstinline$g()$ have compatible types. Let \(f\) and \(g\) be
    3548 their types; then \(f_1\) = \lstinline$T$, \(f_2\) = \lstinline$U$, \(f_3\) = \lstinline$V$, \(g_1\)
    3549 = \lstinline$V$, \(g_2\) = \lstinline$U$, and \(g_3\) = \lstinline$W$. Replacing every \(f_i\)
    3550 by \(g_i\) in \(f\) gives
    3551 \begin{lstlisting}
    3552 forall( type V, type U, type W ) U * f( V *, U, W * const );
    3553 \end{lstlisting}
    3554 which has a return type and parameter list that is compatible with \(g\).
    3555 \begin{rationale}
    3556 The word ``\lstinline$type$'' in a forall specifier is redundant at the moment, but I want to leave
    3557 room for inferred parameters of ordinary types in case parameterized types get added one day.
     2809forall( otype T, otype U, otype V ) U * f( T *, U, V * const );
     2810forall( otype U, otype V, otype W ) U * g( V *, U, W * const );
     2811\end{lstlisting}
     2812The functions \lstinline$f()$ and \lstinline$g()$ have compatible types.
     2813Let \(f\) and \(g\) be their types;
     2814then \(f_1\) = \lstinline$T$, \(f_2\) = \lstinline$U$, \(f_3\) = \lstinline$V$, \(g_1\)
     2815= \lstinline$V$, \(g_2\) = \lstinline$U$, and \(g_3\) = \lstinline$W$.
     2816Replacing every \(f_i\) by \(g_i\) in \(f\) gives
     2817\begin{lstlisting}
     2818forall( otype V, otype U, otype W ) U * f( V *, U, W * const );
     2819\end{lstlisting} which has a return type and parameter list that is compatible with \(g\).
     2820\begin{rationale}
     2821The word ``\lstinline$type$'' in a forall specifier is redundant at the moment, but I want to leave room for inferred parameters of ordinary types in case parameterized types get added one day.
    35582822
    35592823Even without parameterized types, I might try to allow
    35602824\begin{lstlisting}
    35612825forall( int n ) int sum( int vector[n] );
    3562 \end{lstlisting}
    3563 but C currently rewrites array parameters as pointer parameters, so the effects of such a change
    3564 require more thought.
    3565 \end{rationale}
    3566 
    3567 \begin{rationale}
    3568 A polymorphic declaration must do two things: it must introduce type parameters, and it must apply
    3569 assertions to those types. Adding this to existing C declaration syntax and semantics was delicate,
    3570 and not entirely successful.
    3571 
    3572 C depends on declaration-before-use, so a forall specifier must introduce type names before they can
    3573 be used in the declaration specifiers. This could be done by making the forall specifier part of
    3574 the declaration specifiers, or by making it a new introductory clause of declarations.
    3575 
    3576 Assertions are also part of polymorphic function types, because it must be clear which functions
    3577 have access to the assertion parameters declared by the assertions. All attempts to put assertions
    3578 inside an introductory clause produced complex semantics and confusing code. Building them into the
    3579 declaration specifiers could be done by placing them in the function's parameter list, or in a
    3580 forall specifier that is a declaration specifier. Assertions are also used with type parameters of
    3581 specifications, and by type declarations. For consistency's sake it seems best to attach assertions
    3582 to the type declarations in forall specifiers, which means that forall specifiers must be
    3583 declaration specifiers.
     2826\end{lstlisting} but C currently rewrites array parameters as pointer parameters, so the effects of such a change require more thought.
     2827\end{rationale}
     2828
     2829\begin{rationale}
     2830A polymorphic declaration must do two things: it must introduce type parameters, and it must apply assertions to those types.
     2831Adding this to existing C declaration syntax and semantics was delicate, and not entirely successful.
     2832
     2833C depends on declaration-before-use, so a forall specifier must introduce type names before they can be used in the declaration specifiers.
     2834This could be done by making the forall specifier part of the declaration specifiers, or by making it a new introductory clause of declarations.
     2835
     2836Assertions are also part of polymorphic function types, because it must be clear which functions have access to the assertion parameters declared by the assertions.
     2837All attempts to put assertions inside an introductory clause produced complex semantics and confusing code.
     2838Building them into the declaration specifiers could be done by placing them in the function's parameter list, or in a forall specifier that is a declaration specifier.
     2839Assertions are also used with type parameters of specifications, and by type declarations.
     2840For consistency's sake it seems best to attach assertions to the type declarations in forall specifiers, which means that forall specifiers must be declaration specifiers.
    35842841\end{rationale}
    35852842%HERE
     
    35952852
    35962853\constraints
    3597 \lstinline$restrict$\index{register@{\lstinline$restrict$}} Types other than type parameters and
    3598 pointer types whose referenced type is an object type shall not be restrict-qualified.
     2854\lstinline$restrict$\index{register@{\lstinline$restrict$}} Types other than type parameters and pointer types whose referenced type is an object type shall not be restrict-qualified.
    35992855
    36002856\semantics
    3601 An object's type may be a restrict-qualified type parameter. \lstinline$restrict$ does not
    3602 establish any special semantics in that case.
    3603 
    3604 \begin{rationale}
    3605 \CFA loosens the constraint on the restrict qualifier so that restrict-qualified pointers may be
    3606 passed to polymorphic functions.
    3607 \end{rationale}
    3608 
    3609 \lstinline$lvalue$ may be used to qualify the return type of a function type. Let \lstinline$T$ be
    3610 an unqualified version of a type; then the result of calling a function with return type
     2857An object's type may be a restrict-qualified type parameter. \lstinline$restrict$ does not establish any special semantics in that case.
     2858
     2859\begin{rationale}
     2860\CFA loosens the constraint on the restrict qualifier so that restrict-qualified pointers may be passed to polymorphic functions.
     2861\end{rationale}
     2862
     2863\lstinline$lvalue$ may be used to qualify the return type of a function type.
     2864Let \lstinline$T$ be an unqualified version of a type;
     2865then the result of calling a function with return type
    36112866\lstinline$lvalue T$ is a \Index{modifiable lvalue} of type \lstinline$T$.
    3612 \lstinline$const$\use{const} and \lstinline$volatile$\use{volatile} qualifiers may also be added to
    3613 indicate that the function result is a constant or volatile lvalue.
    3614 \begin{rationale}
    3615 The \lstinline$const$ and \lstinline$volatile$ qualifiers can only be sensibly used to qualify the
    3616 return type of a function if the \lstinline$lvalue$ qualifier is also used.
    3617 \end{rationale}
    3618 
    3619 An {lvalue}-qualified type may be used in a \Index{cast expression} if the operand is an lvalue; the
    3620 result of the expression is an lvalue.
    3621 
    3622 \begin{rationale}
    3623 \lstinline$lvalue$ provides some of the functionality of {\CC}'s ``\lstinline$T&$'' ( reference to
    3624 object of type \lstinline$T$) type. Reference types have four uses in {\CC}.
     2867\lstinline$const$\use{const} and \lstinline$volatile$\use{volatile} qualifiers may also be added to indicate that the function result is a constant or volatile lvalue.
     2868\begin{rationale}
     2869The \lstinline$const$ and \lstinline$volatile$ qualifiers can only be sensibly used to qualify the return type of a function if the \lstinline$lvalue$ qualifier is also used.
     2870\end{rationale}
     2871
     2872An {lvalue}-qualified type may be used in a \Index{cast expression} if the operand is an lvalue;
     2873the result of the expression is an lvalue.
     2874
     2875\begin{rationale}
     2876\lstinline$lvalue$ provides some of the functionality of {\CC}'s ``\lstinline$T&$'' ( reference to object of type \lstinline$T$) type.
     2877Reference types have four uses in {\CC}.
    36252878\begin{itemize}
    36262879\item
     
    36292882
    36302883\item
    3631 A reference can be used to define an alias for a complicated lvalue expression, as a way of getting
    3632 some of the functionality of the Pascal \lstinline$with$ statement. The following {\CC} code gives
    3633 an example.
     2884A reference can be used to define an alias for a complicated lvalue expression, as a way of getting some of the functionality of the Pascal \lstinline$with$ statement.
     2885The following {\CC} code gives an example.
    36342886\begin{lstlisting}
    36352887{
     
    36412893
    36422894\item
    3643 A reference parameter can be used to allow a function to modify an argument without forcing the
    3644 caller to pass the address of the argument. This is most useful for user-defined assignment
    3645 operators. In {\CC}, plain assignment is done by a function called ``\lstinline$operator=$'', and
    3646 the two expressions
     2895A reference parameter can be used to allow a function to modify an argument without forcing the caller to pass the address of the argument.
     2896This is most useful for user-defined assignment operators.
     2897In {\CC}, plain assignment is done by a function called ``\lstinline$operator=$'', and the two expressions
    36472898\begin{lstlisting}
    36482899a = b;
    36492900operator=( a, b );
    3650 \end{lstlisting}
    3651 are equivalent. If \lstinline$a$ and \lstinline$b$ are of type \lstinline$T$, then the first
    3652 parameter of \lstinline$operator=$ must have type ``\lstinline$T&$''. It cannot have type
     2901\end{lstlisting} are equivalent.
     2902If \lstinline$a$ and \lstinline$b$ are of type \lstinline$T$, then the first parameter of \lstinline$operator=$ must have type ``\lstinline$T&$''.
     2903It cannot have type
    36532904\lstinline$T$, because then assignment couldn't alter the variable, and it can't have type
    36542905``\lstinline$T *$'', because the assignment would have to be written ``\lstinline$&a = b;$''.
    36552906
    3656 In the case of user-defined operators, this could just as well be handled by using pointer types and
    3657 by changing the rewrite rules so that ``\lstinline$a = b;$'' is equivalent to
    3658 ``\lstinline$operator=(&( a), b )$''. Reference parameters of ``normal'' functions are Bad Things,
    3659 because they remove a useful property of C function calls: an argument can only be modified by a
    3660 function if it is preceded by ``\lstinline$&$''.
     2907In the case of user-defined operators, this could just as well be handled by using pointer types and by changing the rewrite rules so that ``\lstinline$a = b;$'' is equivalent to
     2908``\lstinline$operator=(&( a), b )$''.
     2909Reference parameters of ``normal'' functions are Bad Things, because they remove a useful property of C function calls: an argument can only be modified by a function if it is preceded by ``\lstinline$&$''.
    36612910
    36622911\item
     
    36682917void fiddle( const Thing & );
    36692918\end{lstlisting}
    3670 If the second form is used, then constructors and destructors are not invoked to create a temporary
    3671 variable at the call site ( and it is bad style for the caller to make any assumptions about such
    3672 things), and within \lstinline$fiddle$ the parameter is subject to the usual problems caused by
    3673 aliases. The reference form might be chosen for efficiency's sake if \lstinline$Thing$s are too
    3674 large or their constructors or destructors are too expensive. An implementation may switch between
    3675 them without causing trouble for well-behaved clients. This leaves the implementor to define ``too
    3676 large'' and ``too expensive''.
     2919If the second form is used, then constructors and destructors are not invoked to create a temporary variable at the call site ( and it is bad style for the caller to make any assumptions about such things), and within \lstinline$fiddle$ the parameter is subject to the usual problems caused by aliases.
     2920The reference form might be chosen for efficiency's sake if \lstinline$Thing$s are too large or their constructors or destructors are too expensive.
     2921An implementation may switch between them without causing trouble for well-behaved clients.
     2922This leaves the implementor to define ``too large'' and ``too expensive''.
    36772923
    36782924I propose to push this job onto the compiler by allowing it to implement
    36792925\begin{lstlisting}
    36802926void fiddle( const volatile Thing );
    3681 \end{lstlisting}
    3682 with call-by-reference. Since it knows all about the size of \lstinline$Thing$s and the parameter
    3683 passing mechanism, it should be able to come up with a better definition of ``too large'', and may
    3684 be able to make a good guess at ``too expensive''.
     2927\end{lstlisting} with call-by-reference.
     2928Since it knows all about the size of \lstinline$Thing$s and the parameter passing mechanism, it should be able to come up with a better definition of ``too large'', and may be able to make a good guess at ``too expensive''.
    36852929\end{itemize}
    36862930
    3687 In summary, since references are only really necessary for returning lvalues, I'll only provide
    3688 lvalue functions.
     2931In summary, since references are only really necessary for returning lvalues, I'll only provide lvalue functions.
    36892932\end{rationale}
    36902933
     
    36932936\subsection{Initialization}
    36942937
    3695 An expression that is used as an \nonterm{initializer} is treated as being cast to the type of the
    3696 object being initialized. An expression used in an \nonterm{initializer-list} is treated as being
    3697 cast to the type of the aggregate member that it initializes. In either case the cast must have a
    3698 single unambiguous \Index{interpretation}.
     2938An expression that is used as an \nonterm{initializer} is treated as being cast to the type of the object being initialized.
     2939An expression used in an \nonterm{initializer-list} is treated as being cast to the type of the aggregate member that it initializes.
     2940In either case the cast must have a single unambiguous \Index{interpretation}.
    36992941
    37002942
     
    37172959\end{syntax}
    37182960\begin{rationale}
    3719 The declarations allowed in a specification are much the same as those allowed in a structure,
    3720 except that bit fields are not allowed, and \Index{incomplete type}s and function types are allowed.
     2961The declarations allowed in a specification are much the same as those allowed in a structure, except that bit fields are not allowed, and \Index{incomplete type}s and function types are allowed.
    37212962\end{rationale}
    37222963
    37232964\semantics
    3724 A \define{specification definition} defines a name for a \define{specification}: a parameterized
    3725 collection of object and function declarations.
     2965A \define{specification definition} defines a name for a \define{specification}: a parameterized collection of object and function declarations.
    37262966
    37272967The declarations in a specification consist of the declarations in the
    37282968\nonterm{spec-declaration-list} and declarations produced by any assertions in the
    3729 \nonterm{spec-parameter-list}. If the collection contains two declarations that declare the same
    3730 identifier and have compatible types, they are combined into one declaration with the composite type
    3731 constructed from the two types.
     2969\nonterm{spec-parameter-list}.
     2970If the collection contains two declarations that declare the same identifier and have compatible types, they are combined into one declaration with the composite type constructed from the two types.
    37322971
    37332972
     
    37472986
    37482987\constraints
    3749 The \nonterm{identifier} in an assertion that is not a \nonterm{spec-declaration} shall be the name
    3750 of a specification. The \nonterm{type-name-list} shall contain one \nonterm{type-name} argument for
    3751 each \nonterm{type-parameter} in that specification's \nonterm{spec-parameter-list}. If the
    3752 \nonterm{type-parameter} uses type-class \lstinline$type$\use{type}, the argument shall be the type
    3753 name of an \Index{object type}; if it uses \lstinline$dtype$, the argument shall be the type name of
    3754 an object type or an \Index{incomplete type}; and if it uses \lstinline$ftype$, the argument shall
    3755 be the type name of a \Index{function type}.
     2988The \nonterm{identifier} in an assertion that is not a \nonterm{spec-declaration} shall be the name of a specification.
     2989The \nonterm{type-name-list} shall contain one \nonterm{type-name} argument for each \nonterm{type-parameter} in that specification's \nonterm{spec-parameter-list}.
     2990If the
     2991\nonterm{type-parameter} uses type-class \lstinline$type$\use{type}, the argument shall be the type name of an \Index{object type};
     2992if it uses \lstinline$dtype$, the argument shall be the type name of an object type or an \Index{incomplete type};
     2993and if it uses \lstinline$ftype$, the argument shall be the type name of a \Index{function type}.
    37562994
    37572995\semantics
     
    37592997\define{assertion parameters}.
    37602998
    3761 The assertion parameters produced by an assertion that applies the name of a specification to type
    3762 arguments are found by taking the declarations specified in the specification and treating each of
    3763 the specification's parameters as a synonym for the corresponding \nonterm{type-name} argument.
    3764 
    3765 The collection of assertion parameters produced by the \nonterm{assertion-list} are found by
    3766 combining the declarations produced by each assertion. If the collection contains two declarations
    3767 that declare the same identifier and have compatible types, they are combined into one declaration
    3768 with the \Index{composite type} constructed from the two types.
     2999The assertion parameters produced by an assertion that applies the name of a specification to type arguments are found by taking the declarations specified in the specification and treating each of the specification's parameters as a synonym for the corresponding \nonterm{type-name} argument.
     3000
     3001The collection of assertion parameters produced by the \nonterm{assertion-list} are found by combining the declarations produced by each assertion.
     3002If the collection contains two declarations that declare the same identifier and have compatible types, they are combined into one declaration with the \Index{composite type} constructed from the two types.
    37693003
    37703004\examples
    37713005\begin{lstlisting}
    3772 forall( type T | T ?*?( T, T ))@\use{?*?}@
     3006forall( otype T | T ?*?( T, T ))@\use{?*?}@
    37733007T square( T val ) {@\impl{square}@
    37743008        return val + val;
    37753009}
    3776 
    3777 context summable( type T ) {@\impl{summable}@
     3010trait summable( otype T ) {@\impl{summable}@
    37783011        T ?+=?( T *, T );@\use{?+=?}@
    37793012        const T 0;@\use{0}@
    37803013};
    3781 context list_of( type List, type Element ) {@\impl{list_of}@
     3014trait list_of( otype List, otype Element ) {@\impl{list_of}@
    37823015        Element car( List );
    37833016        List cdr( List );
     
    37863019        int is_nil( List );
    37873020};
    3788 context sum_list( type List, type Element | summable( Element ) | list_of( List, Element ) ) {};
    3789 \end{lstlisting}
    3790 \lstinline$sum_list$ contains seven declarations, which describe a list whose elements can be added
    3791 up. The assertion ``\lstinline$|sum_list( i_list, int )$''\use{sum_list} produces the assertion
    3792 parameters
     3021trait sum_list( otype List, otype Element | summable( Element ) | list_of( List, Element ) ) {};
     3022\end{lstlisting}
     3023\lstinline$sum_list$ contains seven declarations, which describe a list whose elements can be added up.
     3024The assertion ``\lstinline$|sum_list( i_list, int )$''\use{sum_list} produces the assertion parameters
    37933025\begin{lstlisting}
    37943026int ?+=?( int *, int );
     
    38253057
    38263058\constraints
    3827 If a type declaration has block scope, and the declared identifier has external or internal linkage,
    3828 the declaration shall have no initializer for the identifier.
     3059If a type declaration has block scope, and the declared identifier has external or internal linkage, the declaration shall have no initializer for the identifier.
    38293060
    38303061\semantics
    3831 A \nonterm{type-parameter} or a \nonterm{type-declarator} declares an identifier to be a \Index{type
    3832 name} for a type incompatible with all other types.
    3833 
    3834 An identifier declared by a \nonterm{type-parameter} has \Index{no linkage}. Identifiers declared
    3835 with type-class \lstinline$type$\use{type} are \Index{object type}s; those declared with type-class
    3836 \lstinline$dtype$\use{dtype} are \Index{incomplete type}s; and those declared with type-class
    3837 \lstinline$ftype$\use{ftype} are \Index{function type}s. The identifier has \Index{block scope} that
    3838 terminates at the end of the \nonterm{spec-declaration-list} or polymorphic function that contains
    3839 the \nonterm{type-parameter}.
    3840 
    3841 A \nonterm{type-declarator} with an \Index{initializer} is a \define{type definition}.  The declared
    3842 identifier is an \Index{incomplete type} within the initializer, and an \Index{object type} after
    3843 the end of the initializer. The type in the initializer is called the \define{implementation
    3844   type}. Within the scope of the declaration, \Index{implicit conversion}s can be performed between
    3845 the defined type and the implementation type, and between pointers to the defined type and pointers
    3846 to the implementation type.
    3847 
    3848 A type declaration without an \Index{initializer} and without a \Index{storage-class specifier} or
    3849 with storage-class specifier \lstinline$static$\use{static} defines an \Index{incomplete type}. If a
    3850 \Index{translation unit} or \Index{block} contains one or more such declarations for an identifier,
    3851 it must contain exactly one definition of the identifier ( but not in an enclosed block, which would
    3852 define a new type known only within that block).
     3062A \nonterm{type-parameter} or a \nonterm{type-declarator} declares an identifier to be a \Index{type name} for a type incompatible with all other types.
     3063
     3064An identifier declared by a \nonterm{type-parameter} has \Index{no linkage}.
     3065Identifiers declared with type-class \lstinline$type$\use{type} are \Index{object type}s;
     3066those declared with type-class
     3067\lstinline$dtype$\use{dtype} are \Index{incomplete type}s;
     3068and those declared with type-class
     3069\lstinline$ftype$\use{ftype} are \Index{function type}s.
     3070The identifier has \Index{block scope} that terminates at the end of the \nonterm{spec-declaration-list} or polymorphic function that contains the \nonterm{type-parameter}.
     3071
     3072A \nonterm{type-declarator} with an \Index{initializer} is a \define{type definition}.  The declared identifier is an \Index{incomplete type} within the initializer, and an \Index{object type} after the end of the initializer.
     3073The type in the initializer is called the \define{implementation
     3074  type}.
     3075Within the scope of the declaration, \Index{implicit conversion}s can be performed between the defined type and the implementation type, and between pointers to the defined type and pointers to the implementation type.
     3076
     3077A type declaration without an \Index{initializer} and without a \Index{storage-class specifier} or with storage-class specifier \lstinline$static$\use{static} defines an \Index{incomplete type}.
     3078If a
     3079\Index{translation unit} or \Index{block} contains one or more such declarations for an identifier, it must contain exactly one definition of the identifier ( but not in an enclosed block, which would define a new type known only within that block).
    38533080\begin{rationale}
    38543081Incomplete type declarations allow compact mutually-recursive types.
    38553082\begin{lstlisting}
    3856 type t1; // Incomplete type declaration.
    3857 type t2 = struct { t1 * p; ... };
    3858 type t1 = struct { t2 * p; ... };
    3859 \end{lstlisting}
    3860 Without them, mutual recursion could be handled by declaring mutually recursive structures, then
    3861 initializing the types to those structures.
     3083otype t1; // incomplete type declaration
     3084otype t2 = struct { t1 * p; ... };
     3085otype t1 = struct { t2 * p; ... };
     3086\end{lstlisting}
     3087Without them, mutual recursion could be handled by declaring mutually recursive structures, then initializing the types to those structures.
    38623088\begin{lstlisting}
    38633089struct s1;
    3864 type t2 = struct s2 { struct s1 * p; ... };
    3865 type t1 = struct s1 { struct s2 * p; ... };
    3866 \end{lstlisting}
    3867 This introduces extra names, and may force the programmer to cast between the types and their
    3868 implementations.
     3090otype t2 = struct s2 { struct s1 * p; ... };
     3091otype t1 = struct s1 { struct s2 * p; ... };
     3092\end{lstlisting}
     3093This introduces extra names, and may force the programmer to cast between the types and their implementations.
    38693094\end{rationale}
    38703095
    38713096A type declaration without an initializer and with \Index{storage-class specifier}
    3872 \lstinline$extern$\use{extern} is an \define{opaque type declaration}. Opaque types are
    3873 \Index{object type}s. An opaque type is not a \nonterm{constant-expression}; neither is a structure
    3874 or union that has a member whose type is not a \nonterm{constant-expression}.  Every other
    3875 \Index{object type} is a \nonterm{constant-expression}. Objects with static storage duration shall
    3876 be declared with a type that is a \nonterm{constant-expression}.
    3877 \begin{rationale}
    3878 Type declarations can declare identifiers with external linkage, whereas typedef declarations
    3879 declare identifiers that only exist within a translation unit. These opaque types can be used in
    3880 declarations, but the implementation of the type is not visible.
    3881 
    3882 Static objects can not have opaque types because space for them would have to be allocated at
    3883 program start-up. This is a deficiency\index{deficiencies!static opaque objects}, but I don't want
    3884 to deal with ``module initialization'' code just now.
    3885 \end{rationale}
    3886 
    3887 An \Index{incomplete type} which is not a qualified version\index{qualified type} of a type is a
    3888 value of \Index{type-class} \lstinline$dtype$. An object type\index{object types} which is not a
    3889 qualified version of a type is a value of type-classes \lstinline$type$ and \lstinline$dtype$. A
     3097\lstinline$extern$\use{extern} is an \define{opaque type declaration}.
     3098Opaque types are
     3099\Index{object type}s.
     3100An opaque type is not a \nonterm{constant-expression};
     3101neither is a structure or union that has a member whose type is not a \nonterm{constant-expression}.  Every other
     3102\Index{object type} is a \nonterm{constant-expression}.
     3103Objects with static storage duration shall be declared with a type that is a \nonterm{constant-expression}.
     3104\begin{rationale}
     3105Type declarations can declare identifiers with external linkage, whereas typedef declarations declare identifiers that only exist within a translation unit.
     3106These opaque types can be used in declarations, but the implementation of the type is not visible.
     3107
     3108Static objects can not have opaque types because space for them would have to be allocated at program start-up.
     3109This is a deficiency\index{deficiencies!static opaque objects}, but I don't want to deal with ``module initialization'' code just now.
     3110\end{rationale}
     3111
     3112An \Index{incomplete type} which is not a qualified version\index{qualified type} of a type is a value of \Index{type-class} \lstinline$dtype$.
     3113An object type\index{object types} which is not a qualified version of a type is a value of type-classes \lstinline$type$ and \lstinline$dtype$.
     3114A
    38903115\Index{function type} is a value of type-class \lstinline$ftype$.
    38913116\begin{rationale}
    3892 Syntactically, a type value is a \nonterm{type-name}, which is a declaration for an object which
    3893 omits the identifier being declared.
    3894 
    3895 Object types are precisely the types that can be instantiated. Type qualifiers are not included in
    3896 type values because the compiler needs the information they provide at compile time to detect
    3897 illegal statements or to produce efficient machine instructions. For instance, the code that a
    3898 compiler must generate to manipulate an object that has volatile-qualified type may be different
    3899 from the code to manipulate an ordinary object.
    3900 
    3901 Type qualifiers are a weak point of C's type system. Consider the standard library function
    3902 \lstinline$strchr()$ which, given a string and a character, returns a pointer to the first
    3903 occurrence of the character in the string.
     3117Syntactically, a type value is a \nonterm{type-name}, which is a declaration for an object which omits the identifier being declared.
     3118
     3119Object types are precisely the types that can be instantiated.
     3120Type qualifiers are not included in type values because the compiler needs the information they provide at compile time to detect illegal statements or to produce efficient machine instructions.
     3121For instance, the code that a compiler must generate to manipulate an object that has volatile-qualified type may be different from the code to manipulate an ordinary object.
     3122
     3123Type qualifiers are a weak point of C's type system.
     3124Consider the standard library function
     3125\lstinline$strchr()$ which, given a string and a character, returns a pointer to the first occurrence of the character in the string.
    39043126\begin{lstlisting}
    39053127char *strchr( const char *s, int c ) {@\impl{strchr}@
    39063128        char real_c = c; // done because c was declared as int.
    39073129        for ( ; *s != real_c; s++ )
    3908          if ( *s == '\0' ) return NULL;
     3130                if ( *s == '\0' ) return NULL;
    39093131        return ( char * )s;
    39103132}
    39113133\end{lstlisting}
    3912 The parameter \lstinline$s$ must be \lstinline$const char *$, because \lstinline$strchr()$ might be
    3913 used to search a constant string, but the return type must be \lstinline$char *$, because the result
    3914 might be used to modify a non-constant string. Hence the body must perform a cast, and ( even worse)
    3915 \lstinline$strchr()$ provides a type-safe way to attempt to modify constant strings. What is needed
    3916 is some way to say that \lstinline$s$'s type might contain qualifiers, and the result type has
    3917 exactly the same qualifiers. Polymorphic functions do not provide a fix for this
    3918 deficiency\index{deficiencies!pointers to qualified types}, because type qualifiers are not part of
    3919 type values. Instead, overloading can be used to define \lstinline$strchr()$ for each combination
    3920 of qualifiers.
    3921 \end{rationale}
    3922 
    3923 \begin{rationale}
    3924 Since \Index{incomplete type}s are not type values, they can not be used as the initializer in a
    3925 type declaration, or as the type of a structure or union member. This prevents the declaration of
    3926 types that contain each other.
    3927 \begin{lstlisting}
    3928 type t1;
    3929 type t2 = t1; // illegal: incomplete type t1.
    3930 type t1 = t2;
    3931 \end{lstlisting}
    3932 
    3933 The initializer in a file-scope declaration must be a constant expression. This means type
    3934 declarations can not build on opaque types, which is a deficiency\index{deficiencies!nesting opaque
     3134The parameter \lstinline$s$ must be \lstinline$const char *$, because \lstinline$strchr()$ might be used to search a constant string, but the return type must be \lstinline$char *$, because the result might be used to modify a non-constant string.
     3135Hence the body must perform a cast, and ( even worse)
     3136\lstinline$strchr()$ provides a type-safe way to attempt to modify constant strings.
     3137What is needed is some way to say that \lstinline$s$'s type might contain qualifiers, and the result type has exactly the same qualifiers.
     3138Polymorphic functions do not provide a fix for this deficiency\index{deficiencies!pointers to qualified types}, because type qualifiers are not part of type values.
     3139Instead, overloading can be used to define \lstinline$strchr()$ for each combination of qualifiers.
     3140\end{rationale}
     3141
     3142\begin{rationale}
     3143Since \Index{incomplete type}s are not type values, they can not be used as the initializer in a type declaration, or as the type of a structure or union member.
     3144This prevents the declaration of types that contain each other.
     3145\begin{lstlisting}
     3146otype t1;
     3147otype t2 = t1; // illegal: incomplete type t1
     3148otype t1 = t2;
     3149\end{lstlisting}
     3150
     3151The initializer in a file-scope declaration must be a constant expression.
     3152This means type declarations can not build on opaque types, which is a deficiency\index{deficiencies!nesting opaque
    39353153 types}.
    39363154\begin{lstlisting}
    3937 extern type Huge; // extended-precision integer type.
    3938 type Rational = struct {
     3155extern otype Huge; // extended-precision integer type
     3156otype Rational = struct {
    39393157        Huge numerator, denominator;    // illegal
    39403158};
     
    39443162\end{lstlisting}
    39453163Without this restriction, \CFA might require ``module initialization'' code ( since
    3946 \lstinline$Rational$ has external linkage, it must be created before any other translation unit
    3947 instantiates it), and would force an ordering on the initialization of the translation unit that
    3948 defines \lstinline$Huge$ and the translation that declares \lstinline$Rational$.
    3949 
    3950 A benefit of the restriction is that it prevents the declaration in separate translation units of
    3951 types that contain each other, which would be hard to prevent otherwise.
     3164\lstinline$Rational$ has external linkage, it must be created before any other translation unit instantiates it), and would force an ordering on the initialization of the translation unit that defines \lstinline$Huge$ and the translation that declares \lstinline$Rational$.
     3165
     3166A benefit of the restriction is that it prevents the declaration in separate translation units of types that contain each other, which would be hard to prevent otherwise.
    39523167\begin{lstlisting}
    39533168//  File a.c:
     
    39623177\begin{rationale}
    39633178Since a \nonterm{type-declaration} is a \nonterm{declaration} and not a
    3964 \nonterm{struct-declaration}, type declarations can not be structure members. The form of
     3179\nonterm{struct-declaration}, type declarations can not be structure members.
     3180The form of
    39653181\nonterm{type-declaration} forbids arrays of, pointers to, and functions returning \lstinline$type$.
    3966 Hence the syntax of \nonterm{type-specifier} does not have to be extended to allow type-valued
    3967 expressions. It also side-steps the problem of type-valued expressions producing different values
    3968 in different declarations.
    3969 
    3970 Since a type declaration is not a \nonterm{parameter-declaration}, functions can not have explicit
    3971 type parameters. This may be too restrictive, but it attempts to make compilation simpler. Recall
    3972 that when traditional C scanners read in an identifier, they look it up in the symbol table to
    3973 determine whether or not it is a typedef name, and return a ``type'' or ``identifier'' token
    3974 depending on what they find. A type parameter would add a type name to the current scope. The
    3975 scope manipulations involved in parsing the declaration of a function that takes function pointer
    3976 parameters and returns a function pointer may just be too complicated.
    3977 
    3978 Explicit type parameters don't seem to be very useful, anyway, because their scope would not include
    3979 the return type of the function. Consider the following attempt to define a type-safe memory
    3980 allocation function.
     3182Hence the syntax of \nonterm{type-specifier} does not have to be extended to allow type-valued expressions.
     3183It also side-steps the problem of type-valued expressions producing different values in different declarations.
     3184
     3185Since a type declaration is not a \nonterm{parameter-declaration}, functions can not have explicit type parameters.
     3186This may be too restrictive, but it attempts to make compilation simpler.
     3187Recall that when traditional C scanners read in an identifier, they look it up in the symbol table to determine whether or not it is a typedef name, and return a ``type'' or ``identifier'' token depending on what they find.
     3188A type parameter would add a type name to the current scope.
     3189The scope manipulations involved in parsing the declaration of a function that takes function pointer parameters and returns a function pointer may just be too complicated.
     3190
     3191Explicit type parameters don't seem to be very useful, anyway, because their scope would not include the return type of the function.
     3192Consider the following attempt to define a type-safe memory allocation function.
    39813193\begin{lstlisting}
    39823194#include <stdlib.h>
    3983 T * new( type T ) { return ( T * )malloc( sizeof( T) ); };
    3984 @\ldots@
    3985 int * ip = new( int );
    3986 \end{lstlisting}
    3987 This looks sensible, but \CFA's declaration-before-use rules mean that ``\lstinline$T$'' in the
    3988 function body refers to the parameter, but the ``\lstinline$T$'' in the return type refers to the
    3989 meaning of \lstinline$T$ in the scope that contains \lstinline$new$; it could be undefined, or a
    3990 type name, or a function or variable name. Nothing good can result from such a situation.
     3195T * new( otype T ) { return ( T * )malloc( sizeof( T) ); };
     3196@\ldots@ int * ip = new( int );
     3197\end{lstlisting}
     3198This looks sensible, but \CFA's declaration-before-use rules mean that ``\lstinline$T$'' in the function body refers to the parameter, but the ``\lstinline$T$'' in the return type refers to the meaning of \lstinline$T$ in the scope that contains \lstinline$new$;
     3199it could be undefined, or a type name, or a function or variable name.
     3200Nothing good can result from such a situation.
    39913201\end{rationale}
    39923202
     
    39943204Since type declarations create new types, instances of types are always passed by value.
    39953205\begin{lstlisting}
    3996 type A1 = int[2];
     3206otype A1 = int[2];
    39973207void f1( A1 a ) { a[0] = 0; };
    3998 typedef int A2[2];
     3208otypedef int A2[2];
    39993209void f2( A2 a ) { a[0] = 0; };
    40003210A1 v1;
     
    40033213f2( v2 );
    40043214\end{lstlisting}
    4005 \lstinline$V1$ is passed by value, so \lstinline$f1()$'s assignment to \lstinline$a[0]$ does not
    4006 modify v1.  \lstinline$V2$ is converted to a pointer, so \lstinline$f2()$ modifies
    4007 \lstinline$v2[0]$.
     3215\lstinline$V1$ is passed by value, so \lstinline$f1()$'s assignment to \lstinline$a[0]$ does not modify v1.  \lstinline$V2$ is converted to a pointer, so \lstinline$f2()$ modifies \lstinline$v2[0]$.
    40083216
    40093217A translation unit containing the declarations
    40103218\begin{lstlisting}
    4011 extern type Complex;@\use{Complex}@ // opaque type declaration.
     3219extern type Complex;@\use{Complex}@ // opaque type declaration
    40123220extern float abs( Complex );@\use{abs}@
    4013 \end{lstlisting}
    4014 can contain declarations of complex numbers, which can be passed to \lstinline$abs$. Some other
    4015 translation unit must implement \lstinline$Complex$ and \lstinline$abs$. That unit might contain
    4016 the declarations
    4017 \begin{lstlisting}
    4018 type Complex = struct { float re, im; };@\impl{Complex}@
     3221\end{lstlisting} can contain declarations of complex numbers, which can be passed to \lstinline$abs$.
     3222Some other translation unit must implement \lstinline$Complex$ and \lstinline$abs$.
     3223That unit might contain the declarations
     3224\begin{lstlisting}
     3225otype Complex = struct { float re, im; };@\impl{Complex}@
    40193226Complex cplx_i = { 0.0, 1.0 };@\impl{cplx_i}@
    40203227float abs( Complex c ) {@\impl{abs( Complex )}@
     
    40223229}
    40233230\end{lstlisting}
    4024 Note that \lstinline$c$ is implicitly converted to a \lstinline$struct$ so that its components can
    4025 be retrieved.
    4026 
    4027 \begin{lstlisting}
    4028 type Time_of_day = int;@\impl{Time_of_day}@ // seconds since midnight.
     3231Note that \lstinline$c$ is implicitly converted to a \lstinline$struct$ so that its components can be retrieved.
     3232
     3233\begin{lstlisting}
     3234otype Time_of_day = int;@\impl{Time_of_day}@ // seconds since midnight.
    40293235Time_of_day ?+?( Time_of_day t1, int seconds ) {@\impl{?+?}@
    40303236        return (( int)t1 + seconds ) % 86400;
     
    40343240
    40353241\begin{rationale}
    4036 Within the scope of a type definition, an instance of the type can be viewed as having that type or
    4037 as having the implementation type. In the \lstinline$Time_of_day$ example, the difference is
    4038 important. Different languages have treated the distinction between the abstraction and the
    4039 implementation in different ways.
     3242Within the scope of a type definition, an instance of the type can be viewed as having that type or as having the implementation type.
     3243In the \lstinline$Time_of_day$ example, the difference is important.
     3244Different languages have treated the distinction between the abstraction and the implementation in different ways.
    40403245\begin{itemize}
    40413246\item
    4042 Inside a Clu cluster \cite{clu}, the declaration of an instance states which view applies. Two
    4043 primitives called \lstinline$up$ and \lstinline$down$ can be used to convert between the views.
    4044 \item
    4045 The Simula class \cite{Simula87} is essentially a record type. Since the only operations on a
    4046 record are member selection and assignment, which can not be overloaded, there is never any
    4047 ambiguity as to whether the abstraction or the implementation view is being used. In {\CC}
    4048 \cite{c++}, operations on class instances include assignment and ``\lstinline$&$'', which can be
    4049 overloaded. A ``scope resolution'' operator can be used inside the class to specify whether the
    4050 abstract or implementation version of the operation should be used.
    4051 \item
    4052 An Ada derived type definition \cite{ada} creates a new type from an old type, and also implicitly
    4053 declares derived subprograms that correspond to the existing subprograms that use the old type as a
    4054 parameter type or result type. The derived subprograms are clones of the existing subprograms with
    4055 the old type replaced by the derived type. Literals and aggregates of the old type are also cloned.
     3247Inside a Clu cluster \cite{CLU}, the declaration of an instance states which view applies.
     3248Two primitives called \lstinline$up$ and \lstinline$down$ can be used to convert between the views.
     3249\item
     3250The Simula class \cite{SIMULA87} is essentially a record type.
     3251Since the only operations on a record are member selection and assignment, which can not be overloaded, there is never any ambiguity as to whether the abstraction or the implementation view is being used.
     3252In {\CC}
     3253\cite{C++}, operations on class instances include assignment and ``\lstinline$&$'', which can be overloaded.
     3254A ``scope resolution'' operator can be used inside the class to specify whether the abstract or implementation version of the operation should be used.
     3255\item
     3256An Ada derived type definition \cite{Ada} creates a new type from an old type, and also implicitly declares derived subprograms that correspond to the existing subprograms that use the old type as a parameter type or result type.
     3257The derived subprograms are clones of the existing subprograms with the old type replaced by the derived type.
     3258Literals and aggregates of the old type are also cloned.
    40563259In other words, the abstract view provides exactly the same operations as the implementation view.
    40573260This allows the abstract view to be used in all cases.
    40583261
    4059 The derived subprograms can be replaced by programmer-specified subprograms. This is an exception
    4060 to the normal scope rules, which forbid duplicate definitions of a subprogram in a scope. In this
    4061 case, explicit conversions between the derived type and the old type can be used.
     3262The derived subprograms can be replaced by programmer-specified subprograms.
     3263This is an exception to the normal scope rules, which forbid duplicate definitions of a subprogram in a scope.
     3264In this case, explicit conversions between the derived type and the old type can be used.
    40623265\end{itemize}
    4063 \CFA's rules are like Clu's, except that implicit conversions and
    4064 conversion costs allow it to do away with most uses of \lstinline$up$ and \lstinline$down$.
     3266\CFA's rules are like Clu's, except that implicit conversions and conversion costs allow it to do away with most uses of \lstinline$up$ and \lstinline$down$.
    40653267\end{rationale}
    40663268
     
    40703272A declaration\index{type declaration} of a type identifier \lstinline$T$ with type-class
    40713273\lstinline$type$ implicitly declares a \define{default assignment} function
    4072 \lstinline$T ?=?( T *, T )$\use{?=?}, with the same \Index{scope} and \Index{linkage} as the
    4073 identifier \lstinline$T$.
    4074 \begin{rationale}
    4075 Assignment is central to C's imperative programming style, and every existing C object type has
    4076 assignment defined for it ( except for array types, which are treated as pointer types for purposes
    4077 of assignment). Without this rule, nearly every inferred type parameter would need an accompanying
    4078 assignment assertion parameter. If a type parameter should not have an assignment operation,
    4079 \lstinline$dtype$ should be used. If a type should not have assignment defined, the user can define
    4080 an assignment function that causes a run-time error, or provide an external declaration but no
    4081 definition and thus cause a link-time error.
    4082 \end{rationale}
    4083 
    4084 A definition\index{type definition} of a type identifier \lstinline$T$ with \Index{implementation
    4085 type} \lstinline$I$ and type-class \lstinline$type$ implicitly defines a default assignment
    4086 function. A definition\index{type definition} of a type identifier \lstinline$T$ with implementation
    4087 type \lstinline$I$ and an assertion list implicitly defines \define{default function}s and
    4088 \define{default object}s as declared by the assertion declarations. The default objects and
    4089 functions have the same \Index{scope} and \Index{linkage} as the identifier \lstinline$T$. Their
    4090 values are determined as follows:
     3274\lstinline$T ?=?( T *, T )$\use{?=?}, with the same \Index{scope} and \Index{linkage} as the identifier \lstinline$T$.
     3275\begin{rationale}
     3276Assignment is central to C's imperative programming style, and every existing C object type has assignment defined for it ( except for array types, which are treated as pointer types for purposes of assignment).
     3277Without this rule, nearly every inferred type parameter would need an accompanying assignment assertion parameter.
     3278If a type parameter should not have an assignment operation,
     3279\lstinline$dtype$ should be used.
     3280If a type should not have assignment defined, the user can define an assignment function that causes a run-time error, or provide an external declaration but no definition and thus cause a link-time error.
     3281\end{rationale}
     3282
     3283A definition\index{type definition} of a type identifier \lstinline$T$ with \Index{implementation type} \lstinline$I$ and type-class \lstinline$type$ implicitly defines a default assignment function.
     3284A definition\index{type definition} of a type identifier \lstinline$T$ with implementation type \lstinline$I$ and an assertion list implicitly defines \define{default function}s and
     3285\define{default object}s as declared by the assertion declarations.
     3286The default objects and functions have the same \Index{scope} and \Index{linkage} as the identifier \lstinline$T$.
     3287Their values are determined as follows:
    40913288\begin{itemize}
    40923289\item
    4093 If at the definition of \lstinline$T$ there is visible a declaration of an object with the same name
    4094 as the default object, and if the type of that object with all occurrence of \lstinline$I$ replaced
    4095 by \lstinline$T$ is compatible with the type of the default object, then the default object is
    4096 initialized with that object. Otherwise the scope of the declaration of \lstinline$T$ must contain
    4097 a definition of the default object.
     3290If at the definition of \lstinline$T$ there is visible a declaration of an object with the same name as the default object, and if the type of that object with all occurrence of \lstinline$I$ replaced by \lstinline$T$ is compatible with the type of the default object, then the default object is initialized with that object.
     3291Otherwise the scope of the declaration of \lstinline$T$ must contain a definition of the default object.
    40983292
    40993293\item
    4100 If at the definition of \lstinline$T$ there is visible a declaration of a function with the same
    4101 name as the default function, and if the type of that function with all occurrence of \lstinline$I$
    4102 replaced by \lstinline$T$ is compatible with the type of the default function, then the default
    4103 function calls that function after converting its arguments and returns the converted result.
    4104 
    4105 Otherwise, if \lstinline$I$ contains exactly one anonymous member\index{anonymous member} such that
    4106 at the definition of \lstinline$T$ there is visible a declaration of a function with the same name
    4107 as the default function, and the type of that function with all occurrences of the anonymous
    4108 member's type in its parameter list replaced by \lstinline$T$ is compatible with the type of the
    4109 default function, then the default function calls that function after converting its arguments and
    4110 returns the result.
    4111 
    4112 Otherwise the scope of the declaration of \lstinline$T$ must contain a definition of the default
    4113 function.
     3294If at the definition of \lstinline$T$ there is visible a declaration of a function with the same name as the default function, and if the type of that function with all occurrence of \lstinline$I$ replaced by \lstinline$T$ is compatible with the type of the default function, then the default function calls that function after converting its arguments and returns the converted result.
     3295
     3296Otherwise, if \lstinline$I$ contains exactly one anonymous member\index{anonymous member} such that at the definition of \lstinline$T$ there is visible a declaration of a function with the same name as the default function, and the type of that function with all occurrences of the anonymous member's type in its parameter list replaced by \lstinline$T$ is compatible with the type of the default function, then the default function calls that function after converting its arguments and returns the result.
     3297
     3298Otherwise the scope of the declaration of \lstinline$T$ must contain a definition of the default function.
    41143299\end{itemize}
    41153300\begin{rationale}
    4116 Note that a pointer to a default function will not compare as equal to a pointer to the inherited
    4117 function.
    4118 \end{rationale}
    4119 
    4120 A function or object with the same type and name as a default function or object that is declared
    4121 within the scope of the definition of \lstinline$T$ replaces the default function or object.
     3301Note that a pointer to a default function will not compare as equal to a pointer to the inherited function.
     3302\end{rationale}
     3303
     3304A function or object with the same type and name as a default function or object that is declared within the scope of the definition of \lstinline$T$ replaces the default function or object.
    41223305
    41233306\examples
    41243307\begin{lstlisting}
    4125 context s( type T ) {
     3308trait s( otype T ) {
    41263309        T a, b;
    4127 }
    4128 struct impl { int left, right; } a = { 0, 0 };
    4129 type Pair | s( Pair ) = struct impl;
     3310} struct impl { int left, right; } a = { 0, 0 };
     3311otype Pair | s( Pair ) = struct impl;
    41303312Pair b = { 1, 1 };
    41313313\end{lstlisting}
    41323314The definition of \lstinline$Pair$ implicitly defines two objects \lstinline$a$ and \lstinline$b$.
    4133 \lstinline$Pair a$ inherits its value from the \lstinline$struct impl a$. The definition of
    4134 \lstinline$Pair b$ is compulsory because there is no \lstinline$struct impl b$ to construct a value
    4135 from.
    4136 \begin{lstlisting}
    4137 context ss( type T ) {
     3315\lstinline$Pair a$ inherits its value from the \lstinline$struct impl a$.
     3316The definition of
     3317\lstinline$Pair b$ is compulsory because there is no \lstinline$struct impl b$ to construct a value from.
     3318\begin{lstlisting}
     3319trait ss( otype T ) {
    41383320        T clone( T );
    41393321        void munge( T * );
    41403322}
    4141 type Whatsit | ss( Whatsit );@\use{Whatsit}@
    4142 type Doodad | ss( Doodad ) = struct doodad {@\use{Doodad}@
     3323otype Whatsit | ss( Whatsit );@\use{Whatsit}@
     3324otype Doodad | ss( Doodad ) = struct doodad {@\use{Doodad}@
    41433325        Whatsit; // anonymous member
    41443326        int extra;
     
    41523334void munge( Doodad * );
    41533335\end{lstlisting}
    4154 The assignment function inherits \lstinline$struct doodad$'s assignment function because the types
    4155 match when \lstinline$struct doodad$ is replaced by \lstinline$Doodad$ throughout.
     3336The assignment function inherits \lstinline$struct doodad$'s assignment function because the types match when \lstinline$struct doodad$ is replaced by \lstinline$Doodad$ throughout.
    41563337\lstinline$munge()$ inherits \lstinline$Whatsit$'s \lstinline$munge()$ because the types match when
    4157 \lstinline$Whatsit$ is replaced by \lstinline$Doodad$ in the parameter list. \lstinline$clone()$
    4158 does \emph{not} inherit \lstinline$Whatsit$'s \lstinline$clone()$: replacement in the parameter
    4159 list yields ``\lstinline$Whatsit clone( Doodad )$'', which is not compatible with
    4160 \lstinline$Doodad$'s \lstinline$clone()$'s type. Hence the definition of
     3338\lstinline$Whatsit$ is replaced by \lstinline$Doodad$ in the parameter list. \lstinline$clone()$ does \emph{not} inherit \lstinline$Whatsit$'s \lstinline$clone()$: replacement in the parameter list yields ``\lstinline$Whatsit clone( Doodad )$'', which is not compatible with
     3339\lstinline$Doodad$'s \lstinline$clone()$'s type.
     3340Hence the definition of
    41613341``\lstinline$Doodad clone( Doodad )$'' is necessary.
    41623342
    41633343Default functions and objects are subject to the normal scope rules.
    41643344\begin{lstlisting}
    4165 type T = @\ldots@;
     3345otype T = @\ldots@;
    41663346T a_T = @\ldots@;               // Default assignment used.
    41673347T ?=?( T *, T );
     
    41733353
    41743354\begin{rationale}
    4175 The \emph{class} construct of object-oriented programming languages performs three independent
    4176 functions. It \emph{encapsulates} a data structure; it defines a \emph{subtype} relationship, whereby
    4177 instances of one class may be used in contexts that require instances of another; and it allows one
    4178 class to \emph{inherit} the implementation of another.
    4179 
    4180 In \CFA, encapsulation is provided by opaque types and the scope rules, and subtyping is provided
    4181 by specifications and assertions. Inheritance is provided by default functions and objects.
     3355The \emph{class} construct of object-oriented programming languages performs three independent functions.
     3356It \emph{encapsulates} a data structure;
     3357it defines a \emph{subtype} relationship, whereby instances of one class may be used in contexts that require instances of another;
     3358and it allows one class to \emph{inherit} the implementation of another.
     3359
     3360In \CFA, encapsulation is provided by opaque types and the scope rules, and subtyping is provided by specifications and assertions.
     3361Inheritance is provided by default functions and objects.
    41823362\end{rationale}
    41833363
     
    41903370\end{syntax}
    41913371
    4192 Many statements contain expressions, which may have more than one interpretation. The following
    4193 sections describe how the \CFA translator selects an interpretation. In all cases the result of the
    4194 selection shall be a single unambiguous \Index{interpretation}.
     3372Many statements contain expressions, which may have more than one interpretation.
     3373The following sections describe how the \CFA translator selects an interpretation.
     3374In all cases the result of the selection shall be a single unambiguous \Index{interpretation}.
    41953375
    41963376
     
    42393419switch ( E ) ...
    42403420choose ( E ) ...
    4241 \end{lstlisting}
    4242 may have more than one interpretation, but it shall have only one interpretation with an integral type.
     3421\end{lstlisting} may have more than one interpretation, but it shall have only one interpretation with an integral type.
    42433422An \Index{integer promotion} is performed on the expression if necessary.
    42443423The constant expressions in \lstinline$case$ statements with the switch are converted to the promoted type.
     
    42843463while ( E ) ...
    42853464do ... while ( E );
    4286 \end{lstlisting}
    4287 is treated as ``\lstinline$( int )((E)!=0)$''.
     3465\end{lstlisting} is treated as ``\lstinline$( int )((E)!=0)$''.
    42883466
    42893467The statement
    42903468\begin{lstlisting}
    42913469for ( a; b; c ) @\ldots@
    4292 \end{lstlisting}
    4293 is treated as
     3470\end{lstlisting} is treated as
    42943471\begin{lstlisting}
    42953472for ( ( void )( a ); ( int )(( b )!=0); ( void )( c ) ) ...
     
    44133590
    44143591The implementation shall define the macro names \lstinline$__LINE__$, \lstinline$__FILE__$,
    4415 \lstinline$__DATE__$, and \lstinline$__TIME__$, as in the {\c11} standard. It shall not define the
    4416 macro name \lstinline$__STDC__$.
    4417 
    4418 In addition, the implementation shall define the macro name \lstinline$__CFORALL__$ to be the
    4419 decimal constant 1.
     3592\lstinline$__DATE__$, and \lstinline$__TIME__$, as in the {\c11} standard.
     3593It shall not define the macro name \lstinline$__STDC__$.
     3594
     3595In addition, the implementation shall define the macro name \lstinline$__CFORALL__$ to be the decimal constant 1.
    44203596
    44213597
     
    44273603
    44283604\section{C types}
    4429 This section gives example specifications for some groups of types that are important in the C
    4430 language, in terms of the predefined operations that can be applied to those types.
     3605This section gives example specifications for some groups of types that are important in the C language, in terms of the predefined operations that can be applied to those types.
    44313606
    44323607
    44333608\subsection{Scalar, arithmetic, and integral types}
    44343609
    4435 The pointer, integral, and floating-point types are all \define{scalar types}. All of these types
    4436 can be logically negated and compared. The assertion ``\lstinline$scalar( Complex )$'' should be read
    4437 as ``type \lstinline$Complex$ is scalar''.
    4438 \begin{lstlisting}
    4439 context scalar( type T ) {@\impl{scalar}@
     3610The pointer, integral, and floating-point types are all \define{scalar types}.
     3611All of these types can be logically negated and compared.
     3612The assertion ``\lstinline$scalar( Complex )$'' should be read as ``type \lstinline$Complex$ is scalar''.
     3613\begin{lstlisting}
     3614trait scalar( otype T ) {@\impl{scalar}@
    44403615        int !?( T );
    44413616        int ?<?( T, T ), ?<=?( T, T ), ?==?( T, T ), ?>=?( T, T ), ?>?( T, T ), ?!=?( T, T );
     
    44433618\end{lstlisting}
    44443619
    4445 The integral and floating-point types are \define{arithmetic types}, which support the basic
    4446 arithmetic operators. The use of an assertion in the \nonterm{spec-parameter-list} declares that,
    4447 in order to be arithmetic, a type must also be scalar ( and hence that scalar operations are
    4448 available ). This is equivalent to inheritance of specifications.
    4449 \begin{lstlisting}
    4450 context arithmetic( type T | scalar( T ) ) {@\impl{arithmetic}@@\use{scalar}@
     3620The integral and floating-point types are \define{arithmetic types}, which support the basic arithmetic operators.
     3621The use of an assertion in the \nonterm{spec-parameter-list} declares that, in order to be arithmetic, a type must also be scalar ( and hence that scalar operations are available ).
     3622This is equivalent to inheritance of specifications.
     3623\begin{lstlisting}
     3624trait arithmetic( otype T | scalar( T ) ) {@\impl{arithmetic}@@\use{scalar}@
    44513625        T +?( T ), -?( T );
    44523626        T ?*?( T, T ), ?/?( T, T ), ?+?( T, T ), ?-?( T, T );
     
    44573631\define{integral types}.
    44583632\begin{lstlisting}
    4459 context integral( type T | arithmetic( T ) ) {@\impl{integral}@@\use{arithmetic}@
     3633trait integral( otype T | arithmetic( T ) ) {@\impl{integral}@@\use{arithmetic}@
    44603634        T ~?( T );
    44613635        T ?&?( T, T ), ?|?( T, T ), ?^?( T, T );
     
    44713645The only operation that can be applied to all modifiable lvalues is simple assignment.
    44723646\begin{lstlisting}
    4473 context m_lvalue( type T ) {@\impl{m_lvalue}@
     3647trait m_lvalue( otype T ) {@\impl{m_lvalue}@
    44743648        T ?=?( T *, T );
    44753649};
     
    44773651
    44783652Modifiable scalar lvalues are scalars and are modifiable lvalues, and assertions in the
    4479 \nonterm{spec-parameter-list} reflect those relationships. This is equivalent to multiple
    4480 inheritance of specifications. Scalars can also be incremented and decremented.
    4481 \begin{lstlisting}
    4482 context m_l_scalar( type T | scalar( T ) | m_lvalue( T ) ) {@\impl{m_l_scalar}@
     3653\nonterm{spec-parameter-list} reflect those relationships.
     3654This is equivalent to multiple inheritance of specifications.
     3655Scalars can also be incremented and decremented.
     3656\begin{lstlisting}
     3657trait m_l_scalar( otype T | scalar( T ) | m_lvalue( T ) ) {@\impl{m_l_scalar}@
    44833658        T ?++( T * ), ?--( T * );@\use{scalar}@@\use{m_lvalue}@
    44843659        T ++?( T * ), --?( T * );
     
    44863661\end{lstlisting}
    44873662
    4488 Modifiable arithmetic lvalues are both modifiable scalar lvalues and arithmetic. Note that this
    4489 results in the ``inheritance'' of \lstinline$scalar$ along both paths.
    4490 \begin{lstlisting}
    4491 context m_l_arithmetic( type T | m_l_scalar( T ) | arithmetic( T ) ) {@\impl{m_l_arithmetic}@
     3663Modifiable arithmetic lvalues are both modifiable scalar lvalues and arithmetic.
     3664Note that this results in the ``inheritance'' of \lstinline$scalar$ along both paths.
     3665\begin{lstlisting}
     3666trait m_l_arithmetic( otype T | m_l_scalar( T ) | arithmetic( T ) ) {@\impl{m_l_arithmetic}@
    44923667        T ?/=?( T *, T ), ?*=?( T *, T );@\use{m_l_scalar}@@\use{arithmetic}@
    44933668        T ?+=?( T *, T ), ?-=?( T *, T );
    44943669};
    4495 
    4496 context m_l_integral( type T | m_l_arithmetic( T ) | integral( T ) ) {@\impl{m_l_integral}@
     3670trait m_l_integral( otype T | m_l_arithmetic( T ) | integral( T ) ) {@\impl{m_l_integral}@
    44973671        T ?&=?( T *, T ), ?|=?( T *, T ), ?^=?( T *, T );@\use{m_l_arithmetic}@
    44983672        T ?%=?( T *, T ), ?<<=?( T *, T ), ?>>=?( T *, T );@\use{integral}@
     
    45033677\subsection{Pointer and array types}
    45043678
    4505 Array types can barely be said to exist in {\c11}, since in most cases an array name is treated as a
    4506 constant pointer to the first element of the array, and the subscript expression
     3679Array types can barely be said to exist in {\c11}, since in most cases an array name is treated as a constant pointer to the first element of the array, and the subscript expression
    45073680``\lstinline$a[i]$'' is equivalent to the dereferencing expression ``\lstinline$(*( a+( i )))$''.
    45083681Technically, pointer arithmetic and pointer comparisons other than ``\lstinline$==$'' and
    4509 ``\lstinline$!=$'' are only defined for pointers to array elements, but the type system does not
    4510 enforce those restrictions. Consequently, there is no need for a separate ``array type''
    4511 specification.
    4512 
    4513 Pointer types are scalar types. Like other scalar types, they have ``\lstinline$+$'' and
     3682``\lstinline$!=$'' are only defined for pointers to array elements, but the type system does not enforce those restrictions.
     3683Consequently, there is no need for a separate ``array type'' specification.
     3684
     3685Pointer types are scalar types.
     3686Like other scalar types, they have ``\lstinline$+$'' and
    45143687``\lstinline$-$'' operators, but the types do not match the types of the operations in
    45153688\lstinline$arithmetic$, so these operators cannot be consolidated in \lstinline$scalar$.
    45163689\begin{lstlisting}
    4517 context pointer( type P | scalar( P ) ) {@\impl{pointer}@@\use{scalar}@
     3690trait pointer( type P | scalar( P ) ) {@\impl{pointer}@@\use{scalar}@
    45183691        P ?+?( P, long int ), ?+?( long int, P ), ?-?( P, long int );
    45193692        ptrdiff_t ?-?( P, P );
    45203693};
    4521 
    4522 context m_l_pointer( type P | pointer( P ) | m_l_scalar( P ) ) {@\impl{m_l_pointer}@
     3694trait m_l_pointer( type P | pointer( P ) | m_l_scalar( P ) ) {@\impl{m_l_pointer}@
    45233695        P ?+=?( P *, long int ), ?-=?( P *, long int );
    45243696        P ?=?( P *, void * );
     
    45273699\end{lstlisting}
    45283700
    4529 Specifications that define the dereference operator ( or subscript operator ) require two
    4530 parameters, one for the pointer type and one for the pointed-at ( or element ) type. Different
    4531 specifications are needed for each set of \Index{type qualifier}s, because qualifiers are not
    4532 included in types. The assertion ``\lstinline$|ptr_to( Safe_pointer, int )$'' should be read as
     3701Specifications that define the dereference operator ( or subscript operator ) require two parameters, one for the pointer type and one for the pointed-at ( or element ) type.
     3702Different specifications are needed for each set of \Index{type qualifier}s, because qualifiers are not included in types.
     3703The assertion ``\lstinline$|ptr_to( Safe_pointer, int )$'' should be read as
    45333704``\lstinline$Safe_pointer$ acts like a pointer to \lstinline$int$''.
    45343705\begin{lstlisting}
    4535 context ptr_to( type P | pointer( P ), type T ) {@\impl{ptr_to}@@\use{pointer}@
    4536         lvalue T *?( P ); lvalue T ?[?]( P, long int );
     3706trait ptr_to( otype P | pointer( P ), otype T ) {@\impl{ptr_to}@@\use{pointer}@
     3707        lvalue T *?( P );
     3708        lvalue T ?[?]( P, long int );
    45373709};
    4538 
    4539 context ptr_to_const( type P | pointer( P ), type T ) {@\impl{ptr_to_const}@
    4540         const lvalue T *?( P ); const lvalue T ?[?]( P, long int );@\use{pointer}@
     3710trait ptr_to_const( otype P | pointer( P ), otype T ) {@\impl{ptr_to_const}@
     3711        const lvalue T *?( P );
     3712        const lvalue T ?[?]( P, long int );@\use{pointer}@
    45413713};
    4542 
    4543 context ptr_to_volatile( type P | pointer( P ), type T ) }@\impl{ptr_to_volatile}@
    4544         volatile lvalue T *?( P ); volatile lvalue T ?[?]( P, long int );@\use{pointer}@
     3714trait ptr_to_volatile( otype P | pointer( P ), otype T ) }@\impl{ptr_to_volatile}@
     3715        volatile lvalue T *?( P );
     3716        volatile lvalue T ?[?]( P, long int );@\use{pointer}@
    45453717};
    4546 \end{lstlisting}
    4547 \begin{lstlisting}
    4548 context ptr_to_const_volatile( type P | pointer( P ), type T ) }@\impl{ptr_to_const_volatile}@
     3718trait ptr_to_const_volatile( otype P | pointer( P ), otype T ) }@\impl{ptr_to_const_volatile}@
    45493719        const volatile lvalue T *?( P );@\use{pointer}@
    45503720        const volatile lvalue T ?[?]( P, long int );
     
    45523722\end{lstlisting}
    45533723
    4554 Assignment to pointers is more complicated than is the case with other types, because the target's
    4555 type can have extra type qualifiers in the pointed-at type: a ``\lstinline$T *$'' can be assigned to
    4556 a ``\lstinline$const T *$'', a ``\lstinline$volatile T *$'', and a ``\lstinline$const volatile T *$''.
     3724Assignment to pointers is more complicated than is the case with other types, because the target's type can have extra type qualifiers in the pointed-at type: a ``\lstinline$T *$'' can be assigned to a ``\lstinline$const T *$'', a ``\lstinline$volatile T *$'', and a ``\lstinline$const volatile T *$''.
    45573725Again, the pointed-at type is passed in, so that assertions can connect these specifications to the
    45583726``\lstinline$ptr_to$'' specifications.
    45593727\begin{lstlisting}
    4560 context m_l_ptr_to( type P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to}@ type T | ptr_to( P, T )@\use{ptr_to}@ {
     3728trait m_l_ptr_to( otype P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to}@ otype T | ptr_to( P, T )@\use{ptr_to}@ {
    45613729        P ?=?( P *, T * );
    45623730        T * ?=?( T **, P );
    45633731};
    4564 
    4565 context m_l_ptr_to_const( type P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to_const}@ type T | ptr_to_const( P, T )@\use{ptr_to_const}@) {
     3732trait m_l_ptr_to_const( otype P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to_const}@ otype T | ptr_to_const( P, T )@\use{ptr_to_const}@) {
    45663733        P ?=?( P *, const T * );
    45673734        const T * ?=?( const T **, P );
    45683735};
    4569 
    4570 context m_l_ptr_to_volatile( type P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to_volatile}@ type T | ptr_to_volatile( P, T )) {@\use{ptr_to_volatile}@
     3736trait m_l_ptr_to_volatile( otype P | m_l_pointer( P ),@\use{m_l_pointer}@@\impl{m_l_ptr_to_volatile}@ otype T | ptr_to_volatile( P, T )) {@\use{ptr_to_volatile}@
    45713737        P ?=?( P *, volatile T * );
    45723738        volatile T * ?=?( volatile T **, P );
    45733739};
    4574 
    4575 context m_l_ptr_to_const_volatile( type P | ptr_to_const_volatile( P ),@\use{ptr_to_const_volatile}@@\impl{m_l_ptr_to_const_volatile}@
    4576                 type T | m_l_ptr_to_volatile( P, T ) | m_l_ptr_to_const( P )) {@\use{m_l_ptr_to_const}@@\use{m_l_ptr_to_volatile}@
     3740trait m_l_ptr_to_const_volatile( otype P | ptr_to_const_volatile( P ),@\use{ptr_to_const_volatile}@@\impl{m_l_ptr_to_const_volatile}@
     3741                otype T | m_l_ptr_to_volatile( P, T ) | m_l_ptr_to_const( P )) {@\use{m_l_ptr_to_const}@@\use{m_l_ptr_to_volatile}@
    45773742        P ?=?( P *, const volatile T * );
    45783743        const volatile T * ?=?( const volatile T **, P );
     
    45803745\end{lstlisting}
    45813746
    4582 Note the regular manner in which type qualifiers appear in those specifications. An alternative
    4583 specification can make use of the fact that qualification of the pointed-at type is part of a
    4584 pointer type to capture that regularity.
    4585 \begin{lstlisting}
    4586 context m_l_ptr_like( type MyP | m_l_pointer( MyP ),@\use{m_l_pointer}@@\impl{m_l_ptr_like}@ type CP | m_l_pointer( CP ) ) {
     3747Note the regular manner in which type qualifiers appear in those specifications.
     3748An alternative specification can make use of the fact that qualification of the pointed-at type is part of a pointer type to capture that regularity.
     3749\begin{lstlisting}
     3750trait m_l_ptr_like( type MyP | m_l_pointer( MyP ),@\use{m_l_pointer}@@\impl{m_l_ptr_like}@ type CP | m_l_pointer( CP ) ) {
    45873751        MyP ?=?( MyP *, CP );
    45883752        CP ?=?( CP *, MyP );
     
    45903754\end{lstlisting}
    45913755The assertion ``\lstinline$| m_l_ptr_like( Safe_ptr, const int * )$'' should be read as
    4592 ``\lstinline$Safe_ptr$ is a pointer type like \lstinline$const int *$''. This specification has two
    4593 defects, compared to the original four: there is no automatic assertion that dereferencing a
     3756``\lstinline$Safe_ptr$ is a pointer type like \lstinline$const int *$''.
     3757This specification has two defects, compared to the original four: there is no automatic assertion that dereferencing a
    45943758\lstinline$MyP$ produces an lvalue of the type that \lstinline$CP$ points at, and the
    4595 ``\lstinline$|m_l_pointer( CP )$'' assertion provides only a weak assurance that the argument passed
    4596 to \lstinline$CP$ really is a pointer type.
     3759``\lstinline$|m_l_pointer( CP )$'' assertion provides only a weak assurance that the argument passed to \lstinline$CP$ really is a pointer type.
    45973760
    45983761
    45993762\section{Relationships between operations}
    46003763
    4601 Different operators often have related meanings; for instance, in C, ``\lstinline$+$'',
     3764Different operators often have related meanings;
     3765for instance, in C, ``\lstinline$+$'',
    46023766``\lstinline$+=$'', and the two versions of ``\lstinline$++$'' perform variations of addition.
    4603 Languages like {\CC} and Ada allow programmers to define operators for new types, but do not
    4604 require that these relationships be preserved, or even that all of the operators be implemented.
    4605 Completeness and consistency is left to the good taste and discretion of the programmer. It is
    4606 possible to encourage these attributes by providing generic operator functions, or member functions
    4607 of abstract classes, that are defined in terms of other, related operators.
    4608 
    4609 In \CFA, polymorphic functions provide the equivalent of these generic operators, and
    4610 specifications explicitly define the minimal implementation that a programmer should provide. This
    4611 section shows a few examples.
     3767Languages like {\CC} and Ada allow programmers to define operators for new types, but do not require that these relationships be preserved, or even that all of the operators be implemented.
     3768Completeness and consistency is left to the good taste and discretion of the programmer.
     3769It is possible to encourage these attributes by providing generic operator functions, or member functions of abstract classes, that are defined in terms of other, related operators.
     3770
     3771In \CFA, polymorphic functions provide the equivalent of these generic operators, and specifications explicitly define the minimal implementation that a programmer should provide.
     3772This section shows a few examples.
    46123773
    46133774
    46143775\subsection{Relational and equality operators}
    46153776
    4616 The different comparison operators have obvious relationships, but there is no obvious subset of the
    4617 operations to use in the implementation of the others. However, it is usually convenient to
    4618 implement a single comparison function that returns a negative integer, 0, or a positive integer if
    4619 its first argument is respectively less than, equal to, or greater than its second argument; the
    4620 library function \lstinline$strcmp$ is an example.
    4621 
    4622 C and \CFA have an extra, non-obvious comparison operator: ``\lstinline$!$'', logical negation,
    4623 returns 1 if its operand compares equal to 0, and 0 otherwise.
    4624 \begin{lstlisting}
    4625 context comparable( type T ) {
     3777The different comparison operators have obvious relationships, but there is no obvious subset of the operations to use in the implementation of the others.
     3778However, it is usually convenient to implement a single comparison function that returns a negative integer, 0, or a positive integer if its first argument is respectively less than, equal to, or greater than its second argument;
     3779the library function \lstinline$strcmp$ is an example.
     3780
     3781C and \CFA have an extra, non-obvious comparison operator: ``\lstinline$!$'', logical negation, returns 1 if its operand compares equal to 0, and 0 otherwise.
     3782\begin{lstlisting}
     3783trait comparable( otype T ) {
    46263784        const T 0;
    46273785        int compare( T, T );
    46283786}
    4629 
    4630 forall( type T | comparable( T ) ) int ?<?( T l, T r ) {
     3787forall( otype T | comparable( T ) ) int ?<?( T l, T r ) {
    46313788        return compare( l, r ) < 0;
    46323789}
    46333790// ... similarly for <=, ==, >=, >, and !=.
    4634 
    4635 forall( type T | comparable( T ) ) int !?( T operand ) {
     3791forall( otype T | comparable( T ) ) int !?( T operand ) {
    46363792        return !compare( operand, 0 );
    46373793}
     
    46413797\subsection{Arithmetic and integer operations}
    46423798
    4643 A complete arithmetic type would provide the arithmetic operators and the corresponding assignment
    4644 operators. Of these, the assignment operators are more likely to be implemented directly, because
    4645 it is usually more efficient to alter the contents of an existing object than to create and return a
    4646 new one. Similarly, a complete integral type would provide integral operations based on integral
    4647 assignment operations.
    4648 \begin{lstlisting}
    4649 context arith_base( type T ) {
     3799A complete arithmetic type would provide the arithmetic operators and the corresponding assignment operators.
     3800Of these, the assignment operators are more likely to be implemented directly, because it is usually more efficient to alter the contents of an existing object than to create and return a new one.
     3801Similarly, a complete integral type would provide integral operations based on integral assignment operations.
     3802\begin{lstlisting}
     3803trait arith_base( otype T ) {
    46503804        const T 1;
    46513805        T ?+=?( T *, T ), ?-=?( T *, T ), ?*=?( T *, T ), ?/=?( T *, T );
    46523806}
    4653 
    4654 forall( type T | arith_base( T ) ) T ?+?( T l, T r ) {
     3807forall( otype T | arith_base( T ) ) T ?+?( T l, T r ) {
    46553808        return l += r;
    46563809}
    4657 
    4658 forall( type T | arith_base( T ) ) T ?++( T * operand ) {
     3810forall( otype T | arith_base( T ) ) T ?++( T * operand ) {
    46593811        T temporary = *operand;
    46603812        *operand += 1;
    46613813        return temporary;
    46623814}
    4663 
    4664 forall( type T | arith_base( T ) ) T ++?( T * operand ) {
     3815forall( otype T | arith_base( T ) ) T ++?( T * operand ) {
    46653816        return *operand += 1;
    46663817}
    46673818// ... similarly for -, --, *, and /.
    4668 
    4669 context int_base( type T ) {
     3819trait int_base( otype T ) {
    46703820        T ?&=?( T *, T ), ?|=?( T *, T ), ?^=?( T *, T );
    46713821        T ?%=?( T *, T ), ?<<=?( T *, T ), ?>>=?( T *, T );
    46723822}
    4673 
    4674 forall( type T | int_base( T ) ) T ?&?( T l, T r ) {
     3823forall( otype T | int_base( T ) ) T ?&?( T l, T r ) {
    46753824        return l &= r;
    46763825}
     
    46783827\end{lstlisting}
    46793828
    4680 Note that, although an arithmetic type would certainly provide comparison functions, and an integral
    4681 type would provide arithmetic operations, there does not have to be any relationship among
    4682 \lstinline$int_base$, \lstinline$arith_base$ and \lstinline$comparable$. Note also that these
    4683 declarations provide guidance and assistance, but they do not define an absolutely minimal set of
    4684 requirements. A truly minimal implementation of an arithmetic type might only provide
     3829Note that, although an arithmetic type would certainly provide comparison functions, and an integral type would provide arithmetic operations, there does not have to be any relationship among
     3830\lstinline$int_base$, \lstinline$arith_base$ and \lstinline$comparable$.
     3831Note also that these declarations provide guidance and assistance, but they do not define an absolutely minimal set of requirements.
     3832A truly minimal implementation of an arithmetic type might only provide
    46853833\lstinline$0$, \lstinline$1$, and \lstinline$?-=?$, which would be used by polymorphic
    46863834\lstinline$?+=?$, \lstinline$?*=?$, and \lstinline$?/=?$ functions.
     
    46923840Review index entries.
    46933841
    4694 Restrict allowed to qualify anything, or type/dtype parameters, but only affects pointers. This gets
    4695 into \lstinline$noalias$ territory. Qualifying anything (``\lstinline$short restrict rs$'') means
    4696 pointer parameters of \lstinline$?++$, etc, would need restrict qualifiers.
    4697 
    4698 Enumerated types. Constants are not ints. Overloading. Definition should be ``representable as an
    4699 integer type'', not ``as an int''. C11 usual conversions freely convert to and from ordinary
    4700 integer types via assignment, which works between any integer types. Does enum Color ?*?( enum
     3842Restrict allowed to qualify anything, or type/dtype parameters, but only affects pointers.
     3843This gets into \lstinline$noalias$ territory.
     3844Qualifying anything (``\lstinline$short restrict rs$'') means pointer parameters of \lstinline$?++$, etc, would need restrict qualifiers.
     3845
     3846Enumerated types.
     3847Constants are not ints.
     3848Overloading.
     3849Definition should be ``representable as an integer type'', not ``as an int''.
     3850C11 usual conversions freely convert to and from ordinary integer types via assignment, which works between any integer types.
     3851Does enum Color ?*?( enum
    47013852Color, enum Color ) really make sense? ?++ does, but it adds (int)1.
    47023853
    4703 Operators on {,signed,unsigned} char and other small types. ?<? harmless; ?*? questionable for
    4704 chars. Generic selections make these choices visible. Safe conversion operators? Predefined
     3854Operators on {,signed,unsigned} char and other small types. ?<? harmless;
     3855?*? questionable for chars.
     3856Generic selections make these choices visible.
     3857Safe conversion operators? Predefined
    47053858``promotion'' function?
    47063859
    4707 \lstinline$register$ assignment might be handled as assignment to a temporary with copying back and
    4708 forth, but copying must not be done by assignment.
     3860\lstinline$register$ assignment might be handled as assignment to a temporary with copying back and forth, but copying must not be done by assignment.
    47093861
    47103862Don't use ptrdiff\_t by name in the predefineds.
    47113863
    4712 Polymorphic objects. Polymorphic typedefs and type declarations.
     3864Polymorphic objects.
     3865Polymorphic typedefs and type declarations.
    47133866
    47143867
    47153868\bibliographystyle{plain}
    4716 \bibliography{refrat}
     3869\bibliography{cfa}
    47173870
    47183871
    47193872\addcontentsline{toc}{chapter}{\indexname} % add index name to table of contents
    47203873\begin{theindex}
    4721 Italic page numbers give the location of the main entry for the referenced term. Plain page numbers
    4722 denote uses of the indexed term. Entries for grammar non-terminals are italicized. A typewriter
    4723 font is used for grammar terminals and program identifiers.
     3874Italic page numbers give the location of the main entry for the referenced term.
     3875Plain page numbers denote uses of the indexed term.
     3876Entries for grammar non-terminals are italicized.
     3877A typewriter font is used for grammar terminals and program identifiers.
    47243878\indexspace
    47253879\input{refrat.ind}
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