Changeset 95b3a9c for doc/user/user.tex
- Timestamp:
- Feb 17, 2021, 12:45:36 PM (3 years ago)
- Branches:
- ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum
- Children:
- e7c077a
- Parents:
- 5e99a9a (diff), 9fb1367 (diff)
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doc/user/user.tex
r5e99a9a r95b3a9c 11 11 %% Created On : Wed Apr 6 14:53:29 2016 12 12 %% Last Modified By : Peter A. Buhr 13 %% Last Modified On : Mon Oct 5 08:57:29 202014 %% Update Count : 399813 %% Last Modified On : Mon Feb 15 13:48:53 2021 14 %% Update Count : 4452 15 15 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 16 16 … … 37 37 \usepackage{mathptmx} % better math font with "times" 38 38 \usepackage[usenames]{color} 39 \usepackage[dvips,plainpages=false,pdfpagelabels,pdfpagemode=UseNone,colorlinks=true,pagebackref=true,linkcolor=blue,citecolor=blue,urlcolor=blue,pagebackref=true,breaklinks=true]{hyperref} 40 \usepackage{breakurl} 41 42 \renewcommand\footnoterule{\kern -3pt\rule{0.3\linewidth}{0.15pt}\kern 2pt} 43 44 \usepackage[pagewise]{lineno} 45 \renewcommand{\linenumberfont}{\scriptsize\sffamily} 46 \usepackage[firstpage]{draftwatermark} 47 \SetWatermarkLightness{0.9} 48 49 % Default underscore is too low and wide. Cannot use lstlisting "literate" as replacing underscore 50 % removes it as a variable-name character so keywords in variables are highlighted. MUST APPEAR 51 % AFTER HYPERREF. 52 \renewcommand{\textunderscore}{\leavevmode\makebox[1.2ex][c]{\rule{1ex}{0.075ex}}} 53 54 \setlength{\topmargin}{-0.45in} % move running title into header 55 \setlength{\headsep}{0.25in} 56 57 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 58 39 59 \newcommand{\CFALatin}{} 40 60 % inline code ©...© (copyright symbol) emacs: C-q M-) … … 46 66 % math escape $...$ (dollar symbol) 47 67 \input{common} % common CFA document macros 48 \usepackage[dvips,plainpages=false,pdfpagelabels,pdfpagemode=UseNone,colorlinks=true,pagebackref=true,linkcolor=blue,citecolor=blue,urlcolor=blue,pagebackref=true,breaklinks=true]{hyperref}49 \usepackage{breakurl}50 51 \renewcommand\footnoterule{\kern -3pt\rule{0.3\linewidth}{0.15pt}\kern 2pt}52 53 \usepackage[pagewise]{lineno}54 \renewcommand{\linenumberfont}{\scriptsize\sffamily}55 \usepackage[firstpage]{draftwatermark}56 \SetWatermarkLightness{0.9}57 58 % Default underscore is too low and wide. Cannot use lstlisting "literate" as replacing underscore59 % removes it as a variable-name character so keywords in variables are highlighted. MUST APPEAR60 % AFTER HYPERREF.61 \renewcommand{\textunderscore}{\leavevmode\makebox[1.2ex][c]{\rule{1ex}{0.075ex}}}62 63 \setlength{\topmargin}{-0.45in} % move running title into header64 \setlength{\headsep}{0.25in}65 66 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%67 68 68 \CFAStyle % use default CFA format-style 69 \lstset{language=CFA} % CFA default lnaguage 69 70 \lstnewenvironment{C++}[1][] % use C++ style 70 {\lstset{language=C++,moredelim=**[is][\protect\color{red}]{ ®}{®},#1}}71 {\lstset{language=C++,moredelim=**[is][\protect\color{red}]{@}{@},#1}} 71 72 {} 72 73 … … 81 82 \newcommand{\Emph}[2][red]{{\color{#1}\textbf{\emph{#2}}}} 82 83 \newcommand{\R}[1]{\Textbf{#1}} 84 \newcommand{\RC}[1]{\Textbf{\LstBasicStyle{#1}}} 83 85 \newcommand{\B}[1]{{\Textbf[blue]{#1}}} 84 86 \newcommand{\G}[1]{{\Textbf[OliveGreen]{#1}}} … … 103 105 104 106 \author{ 105 \huge \CFA Team \medskip \\ 106 \Large Andrew Beach, Richard Bilson, Peter A. Buhr, Thierry Delisle, \smallskip \\ 107 \Large Glen Ditchfield, Rodolfo G. Esteves, Aaron Moss, Rob Schluntz 107 \huge \CFA Team (past and present) \medskip \\ 108 \Large Andrew Beach, Richard Bilson, Michael Brooks, Peter A. Buhr, Thierry Delisle, \smallskip \\ 109 \Large Glen Ditchfield, Rodolfo G. Esteves, Aaron Moss, Colby Parsons, Rob Schluntz, \smallskip \\ 110 \Large Fangren Yu, Mubeen Zulfiqar 108 111 }% author 109 112 … … 126 129 \vspace*{\fill} 127 130 \noindent 128 \copyright\,2016 \CFA Project \\ \\131 \copyright\,2016, 2018, 2021 \CFA Project \\ \\ 129 132 \noindent 130 133 This work is licensed under the Creative Commons Attribution 4.0 International License. … … 144 147 \section{Introduction} 145 148 146 \CFA{}\index{cforall@\CFA}\footnote{Pronounced ``\Index*{C-for-all}'', and written \CFA, CFA, or \CFL.} is a modern general-purpose programming-language, designed as an evolutionary step forward for the C programming language.149 \CFA{}\index{cforall@\CFA}\footnote{Pronounced ``\Index*{C-for-all}'', and written \CFA, CFA, or \CFL.} is a modern general-purpose concurrent programming-language, designed as an evolutionary step forward for the C programming language. 147 150 The syntax of \CFA builds from C and should look immediately familiar to C/\Index*[C++]{\CC{}} programmers. 148 151 % Any language feature that is not described here can be assumed to be using the standard \Celeven syntax. 149 \CFA adds many modern programming-languagefeatures that directly lead to increased \emph{\Index{safety}} and \emph{\Index{productivity}}, while maintaining interoperability with existing C programs and achieving similar performance.152 \CFA adds many modern features that directly lead to increased \emph{\Index{safety}} and \emph{\Index{productivity}}, while maintaining interoperability with existing C programs and achieving similar performance. 150 153 Like C, \CFA is a statically typed, procedural (non-\Index{object-oriented}) language with a low-overhead runtime, meaning there is no global \Index{garbage-collection}, but \Index{regional garbage-collection}\index{garbage-collection!regional} is possible. 151 154 The primary new features include polymorphic routines and types, exceptions, concurrency, and modules. … … 157 160 instead, a programmer evolves a legacy program into \CFA by incrementally incorporating \CFA features. 158 161 As well, new programs can be written in \CFA using a combination of C and \CFA features. 162 In many ways, \CFA is to C as \Index{Scala}~\cite{Scala} is to Java, providing a vehicle for new typing and control-flow capabilities on top of a highly popular programming language allowing immediate dissemination. 159 163 160 164 \Index*[C++]{\CC{}}~\cite{c++:v1} had a similar goal 30 years ago, allowing object-oriented programming to be incrementally added to C. … … 165 169 For example, the following programs compare the C, \CFA, and \CC I/O mechanisms, where the programs output the same result. 166 170 \begin{center} 167 \begin{tabular}{@{}l@{\hspace{1 .5em}}l@{\hspace{1.5em}}l@{}}168 \multicolumn{1}{c@{\hspace{1 .5em}}}{\textbf{C}} & \multicolumn{1}{c}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{\CC}} \\169 \begin{cfa} 170 #include <stdio.h> §\indexc{stdio.h}§171 \begin{tabular}{@{}l@{\hspace{1em}}l@{\hspace{1em}}l@{}} 172 \multicolumn{1}{c@{\hspace{1em}}}{\textbf{C}} & \multicolumn{1}{c}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{\CC}} \\ 173 \begin{cfa} 174 #include <stdio.h>$\indexc{stdio.h}$ 171 175 172 176 int main( void ) { 173 177 int x = 0, y = 1, z = 2; 174 ®printf( "%d %d %d\n", x, y, z );®178 @printf( "%d %d %d\n", x, y, z );@ 175 179 } 176 180 \end{cfa} 177 181 & 178 182 \begin{cfa} 179 #include <fstream> §\indexc{fstream}§183 #include <fstream>$\indexc{fstream}$ 180 184 181 185 int main( void ) { 182 186 int x = 0, y = 1, z = 2; 183 ®sout | x | y | z;®§\indexc{sout}§187 @sout | x | y | z;@$\indexc{sout}$ 184 188 } 185 189 \end{cfa} 186 190 & 187 191 \begin{cfa} 188 #include <iostream> §\indexc{iostream}§192 #include <iostream>$\indexc{iostream}$ 189 193 using namespace std; 190 194 int main() { 191 195 int x = 0, y = 1, z = 2; 192 ®cout<<x<<" "<<y<<" "<<z<<endl;®196 @cout<<x<<" "<<y<<" "<<z<<endl;@ 193 197 } 194 198 \end{cfa} 195 199 \end{tabular} 196 200 \end{center} 197 While the \CFA I/O looks similar to the \Index*[C++]{\CC{}} output style, there are important differences, such as automatic spacing between variables as in \Index*{Python} (see~\VRef{s:IOLibrary}).201 While \CFA I/O \see{\VRef{s:StreamIOLibrary}} looks similar to \Index*[C++]{\CC{}}, there are important differences, such as automatic spacing between variables and an implicit newline at the end of the expression list, similar to \Index*{Python}~\cite{Python}. 198 202 199 203 … … 210 214 \section{Why fix C?} 211 215 212 The C programming language is a foundational technology for modern computing with millions of lines of code implementing everything from hobby projects to commercial operating-systems.216 The C programming language is a foundational technology for modern computing with billions of lines of code implementing everything from hobby projects to commercial operating-systems. 213 217 This installation base and the programmers producing it represent a massive software-engineering investment spanning decades and likely to continue for decades more. 214 218 Even with all its problems, C continues to be popular because it allows writing software at virtually any level in a computer system without restriction. 215 For system programming, where direct access to hardware, storage management, and real-time issues are a requirement, C is usuallythe only language of choice.216 The TIOBE index~\cite{TIOBE} for February 202 0 ranks the top six most \emph{popular} programming languages as \Index*{Java} 17.4\%, C 16.8\%, Python 9.3\%, \Index*[C++]{\CC{}} 6.2\%, \Csharp 5.9\%, Visual Basic 5.9\% = 61.5\%, where the next 50 languages are less than 2\% each, with a long tail.219 For system programming, where direct access to hardware, storage management, and real-time issues are a requirement, C is the only language of choice. 220 The TIOBE index~\cite{TIOBE} for February 2021 ranks the top six most \emph{popular} programming languages as C 17.4\%, \Index*{Java} 12\%, Python 12\%, \Index*[C++]{\CC{}} 7.6\%, \Csharp 4\%, Visual Basic 3.8\% = 56.8\%, where the next 50 languages are less than 2\% each, with a long tail. 217 221 The top 4 rankings over the past 35 years are: 218 222 \begin{center} 219 223 \setlength{\tabcolsep}{10pt} 220 224 \begin{tabular}{@{}rcccccccc@{}} 221 & 202 0 & 2015 & 2010 & 2005 & 2000 & 1995 & 1990 & 1985\\ \hline222 Java & 1 & 2 & 1 & 2 & 3 & - & - & -\\223 \R{C} & \R{2} & \R{1} & \R{2} & \R{1} & \R{1} & \R{2} & \R{1} & \R{1}\\224 Python & 3 & 7 & 6 & 6 & 22 & 21& - & - \\225 \CC & 4 & 4 & 4 & 3 & 2 & 1 & 2 & 12\\225 & 2021 & 2016 & 2011 & 2006 & 2001 & 1996 & 1991 & 1986 \\ \hline 226 \R{C} & \R{1} & \R{2} & \R{2} & \R{1} & \R{1} & \R{1} & \R{1} & \R{1} \\ 227 Java & 2 & 1 & 1 & 2 & 3 & 28 & - & - \\ 228 Python & 3 & 5 & 6 & 7 & 23 & 13 & - & - \\ 229 \CC & 4 & 3 & 3 & 3 & 2 & 2 & 2 & 8 \\ 226 230 \end{tabular} 227 231 \end{center} … … 232 236 As stated, the goal of the \CFA project is to engineer modern language-features into C in an evolutionary rather than revolutionary way. 233 237 \CC~\cite{C++14,C++} is an example of a similar project; 234 however, it largely extended the C language, and did not address m ostof C's existing problems.\footnote{%238 however, it largely extended the C language, and did not address many of C's existing problems.\footnote{% 235 239 Two important existing problems addressed were changing the type of character literals from ©int© to ©char© and enumerator from ©int© to the type of its enumerators.} 236 240 \Index*{Fortran}~\cite{Fortran08}, \Index*{Ada}~\cite{Ada12}, and \Index*{Cobol}~\cite{Cobol14} are examples of programming languages that took an evolutionary approach, where modern language-features (\eg objects, concurrency) are added and problems fixed within the framework of the existing language. … … 241 245 242 246 The result of this project is a language that is largely backwards compatible with \Index*[C11]{\Celeven{}}~\cite{C11}, but fixes many of the well known C problems while adding modern language-features. 243 To achieve these goals required a significant engineering exercise, where we had to ``think inside the existing C box''. 244 Without these significant extension to C, it is unable to cope with the needs of modern programming problems and programmers; 245 as a result, it will fade into disuse. 246 Considering the large body of existing C code and programmers, there is significant impetus to ensure C is transformed into a modern programming language. 247 To achieve these goals required a significant engineering exercise, \ie ``thinking \emph{inside} the C box''. 248 Considering the large body of existing C code and programmers, there is significant impetus to ensure C is transformed into a modern language. 247 249 While \Index*[C11]{\Celeven{}} made a few simple extensions to the language, nothing was added to address existing problems in the language or to augment the language with modern language-features. 248 250 While some may argue that modern language-features may make C complex and inefficient, it is clear a language without modern capabilities is insufficient for the advanced programming problems existing today. … … 251 253 \section{History} 252 254 253 The \CFA project started with \Index*{Dave Till}\index{Till, Dave}'s \Index*{K-W C}~\cite{Buhr94a,Till89}, which extended C with new declaration syntax, multiple return values from routines, and advanced assignment capabilities using the notion of tuples. 254 (See~\cite{Werther96} for similar work in \Index*[C++]{\CC{}}.) 255 The \CFA project started with \Index*{Dave Till}\index{Till, Dave}'s \Index*{K-W C}~\cite{Buhr94a,Till89}, which extended C with new declaration syntax, multiple return values from routines, and advanced assignment capabilities using the notion of tuples \see{\cite{Werther96} for similar work in \Index*[C++]{\CC{}}}. 255 256 The first \CFA implementation of these extensions was by \Index*{Rodolfo Esteves}\index{Esteves, Rodolfo}~\cite{Esteves04}. 256 257 257 258 The signature feature of \CFA is \emph{\Index{overload}able} \Index{parametric-polymorphic} functions~\cite{forceone:impl,Cormack90,Duggan96} with functions generalized using a ©forall© clause (giving the language its name): 258 259 \begin{cfa} 259 ®forall( otype T )®T identity( T val ) { return val; }260 int forty_two = identity( 42 ); §\C{// T is bound to int, forty\_two == 42}§260 @forall( otype T )@ T identity( T val ) { return val; } 261 int forty_two = identity( 42 ); $\C{// T is bound to int, forty\_two == 42}$ 261 262 \end{cfa} 262 263 % extending the C type system with parametric polymorphism and overloading, as opposed to the \Index*[C++]{\CC{}} approach of object-oriented extensions. 263 264 \CFA{}\hspace{1pt}'s polymorphism was originally formalized by \Index*{Glen Ditchfield}\index{Ditchfield, Glen}~\cite{Ditchfield92}, and first implemented by \Index*{Richard Bilson}\index{Bilson, Richard}~\cite{Bilson03}. 264 265 However, at that time, there was little interesting in extending C, so work did not continue. 265 As the saying goes, ``\Index*{What goes around, comes around.}'', and there is now renewed interest in the C programming language because of legacy code-bases, so the \CFA project has been restarted.266 As the saying goes, ``\Index*{What goes around, comes around.}'', and there is now renewed interest in the C programming language because of the legacy code-base, so the \CFA project was restarted in 2015. 266 267 267 268 … … 273 274 This feature allows \CFA programmers to take advantage of the existing panoply of C libraries to access thousands of external software features. 274 275 Language developers often state that adequate \Index{library support} takes more work than designing and implementing the language itself. 275 Fortunately, \CFA, like \Index*[C++]{\CC{}}, starts with immediate access to all exiting C libraries, and in many cases, can easily wrap library routines with simpler and safer interfaces, at very low cost.276 Fortunately, \CFA, like \Index*[C++]{\CC{}}, starts with immediate access to all exiting C libraries, and in many cases, can easily wrap library routines with simpler and safer interfaces, at zero or very low cost. 276 277 Hence, \CFA begins by leveraging the large repository of C libraries, and than allows programmers to incrementally augment their C programs with modern \Index{backward-compatible} features. 277 278 … … 286 287 287 288 double key = 5.0, vals[10] = { /* 10 sorted floating values */ }; 288 double * val = (double *)bsearch( &key, vals, 10, sizeof(vals[0]), comp ); §\C{// search sorted array}§289 double * val = (double *)bsearch( &key, vals, 10, sizeof(vals[0]), comp ); $\C{// search sorted array}$ 289 290 \end{cfa} 290 291 which can be augmented simply with a polymorphic, type-safe, \CFA-overloaded wrappers: … … 295 296 296 297 forall( otype T | { int ?<?( T, T ); } ) unsigned int bsearch( T key, const T * arr, size_t size ) { 297 T * result = bsearch( key, arr, size ); §\C{// call first version}§298 return result ? result - arr : size; } §\C{// pointer subtraction includes sizeof(T)}§299 300 double * val = bsearch( 5.0, vals, 10 ); §\C{// selection based on return type}§298 T * result = bsearch( key, arr, size ); $\C{// call first version}$ 299 return result ? result - arr : size; } $\C{// pointer subtraction includes sizeof(T)}$ 300 301 double * val = bsearch( 5.0, vals, 10 ); $\C{// selection based on return type}$ 301 302 int posn = bsearch( 5.0, vals, 10 ); 302 303 \end{cfa} … … 310 311 \begin{cfa} 311 312 forall( dtype T | sized(T) ) T * malloc( void ) { return (T *)malloc( sizeof(T) ); } 312 int * ip = malloc(); §\C{// select type and size from left-hand side}§313 int * ip = malloc(); $\C{// select type and size from left-hand side}$ 313 314 double * dp = malloc(); 314 315 struct S {...} * sp = malloc(); … … 319 320 However, it is necessary to differentiate between C and \CFA code because of name \Index{overload}ing, as for \CC. 320 321 For example, the C math-library provides the following routines for computing the absolute value of the basic types: ©abs©, ©labs©, ©llabs©, ©fabs©, ©fabsf©, ©fabsl©, ©cabsf©, ©cabs©, and ©cabsl©. 321 Whereas, \CFA wraps each of these routines into ones with the overloaded name ©abs©: 322 \begin{cfa} 323 char ®abs®( char ); 324 extern "C" { int ®abs®( int ); } §\C{// use default C routine for int}§ 325 long int ®abs®( long int ); 326 long long int ®abs®( long long int ); 327 float ®abs®( float ); 328 double ®abs®( double ); 329 long double ®abs®( long double ); 330 float _Complex ®abs®( float _Complex ); 331 double _Complex ®abs®( double _Complex ); 332 long double _Complex ®abs®( long double _Complex ); 333 \end{cfa} 334 The problem is the name clash between the library routine ©abs© and the \CFA names ©abs©. 335 Hence, names appearing in an ©extern "C"© block have \newterm*{C linkage}. 336 Then overloading polymorphism uses a mechanism called \newterm{name mangling}\index{mangling!name} to create unique names that are different from C names, which are not mangled. 337 Hence, there is the same need, as in \CC, to know if a name is a C or \CFA name, so it can be correctly formed. 338 There is no way around this problem, other than C's approach of creating unique names for each pairing of operation and types. 339 340 This example strongly illustrates a core idea in \CFA: \emph{the \Index{power of a name}}. 322 Whereas, \CFA wraps each of these routines into one overloaded name ©abs©: 323 \begin{cfa} 324 char @abs@( char ); 325 extern "C" { int @abs@( int ); } $\C{// use default C routine for int}$ 326 long int @abs@( long int ); 327 long long int @abs@( long long int ); 328 float @abs@( float ); 329 double @abs@( double ); 330 long double @abs@( long double ); 331 float _Complex @abs@( float _Complex ); 332 double _Complex @abs@( double _Complex ); 333 long double _Complex @abs@( long double _Complex ); 334 \end{cfa} 335 The problem is \Index{name clash} between the C name ©abs© and the \CFA names ©abs©, resulting in two name linkages\index{C linkage}: ©extern "C"© and ©extern "Cforall"© (default). 336 Overloaded names must use \newterm{name mangling}\index{mangling!name} to create unique names that are different from unmangled C names. 337 Hence, there is the same need as in \CC to know if a name is a C or \CFA name, so it can be correctly formed. 338 The only way around this problem is C's approach of creating unique names for each pairing of operation and type. 339 340 This example illustrates a core idea in \CFA: \emph{the \Index{power of a name}}. 341 341 The name ``©abs©'' evokes the notion of absolute value, and many mathematical types provide the notion of absolute value. 342 342 Hence, knowing the name ©abs© is sufficient to apply it to any type where it is applicable. … … 344 344 345 345 346 \section [Compiling a CFA Program]{Compiling a \CFA Program}346 \section{\CFA Compilation} 347 347 348 348 The command ©cfa© is used to compile a \CFA program and is based on the \Index{GNU} \Indexc{gcc} command, \eg: 349 349 \begin{cfa} 350 cfa§\indexc{cfa}\index{compilation!cfa@©cfa©}§ [ gcc-options ] [ C/§\CFA{}§ source-files ] [ assembler/loader files ] 351 \end{cfa} 352 \CFA programs having the following ©gcc© flags turned on: 353 \begin{description} 350 cfa$\indexc{cfa}\index{compilation!cfa@©cfa©}$ [ gcc/$\CFA{}$-options ] [ C/$\CFA{}$ source-files ] [ assembler/loader files ] 351 \end{cfa} 352 There is no ordering among options (flags) and files, unless an option has an argument, which must appear immediately after the option possibly with or without a space separating option and argument. 353 354 \CFA has the following ©gcc© flags turned on: 355 \begin{description}[topsep=0pt] 354 356 \item 355 357 \Indexc{-std=gnu11}\index{compilation option!-std=gnu11@{©-std=gnu11©}} … … 359 361 Use the traditional GNU semantics for inline routines in C11 mode, which allows inline routines in header files. 360 362 \end{description} 361 The following new \CFA options are available: 362 \begin{description} 363 364 \CFA has the following new options: 365 \begin{description}[topsep=0pt] 363 366 \item 364 367 \Indexc{-CFA}\index{compilation option!-CFA@©-CFA©} 365 Only the C preprocessor and the \CFA translator steps are performed and the transformed program is written to standard output, which makes it possible to examine the code generated by the \CFA translator.368 Only the C preprocessor (flag ©-E©) and the \CFA translator steps are performed and the transformed program is written to standard output, which makes it possible to examine the code generated by the \CFA translator. 366 369 The generated code starts with the standard \CFA \Index{prelude}. 370 371 \item 372 \Indexc{-XCFA}\index{compilation option!-XCFA@©-XCFA©} 373 Pass next flag as-is to the ©cfa-cpp© translator (see details below). 367 374 368 375 \item 369 376 \Indexc{-debug}\index{compilation option!-debug@©-debug©} 370 377 The program is linked with the debugging version of the runtime system. 371 The debug version performs runtime checks to help duringthe debugging phase of a \CFA program, but can substantially slow program execution.378 The debug version performs runtime checks to aid the debugging phase of a \CFA program, but can substantially slow program execution. 372 379 The runtime checks should only be removed after the program is completely debugged. 373 380 \textbf{This option is the default.} … … 399 406 \item 400 407 \Indexc{-no-include-stdhdr}\index{compilation option!-no-include-stdhdr@©-no-include-stdhdr©} 401 Do not supply ©extern "C"© wrappers for \Celeven standard include files (see~\VRef{s:StandardHeaders}).408 Do not supply ©extern "C"© wrappers for \Celeven standard include files \see{\VRef{s:StandardHeaders}}. 402 409 \textbf{This option is \emph{not} the default.} 403 410 \end{comment} … … 430 437 \begin{cfa} 431 438 #ifndef __CFORALL__ 432 #include <stdio.h> §\indexc{stdio.h}§ §\C{// C header file}§439 #include <stdio.h>$\indexc{stdio.h}$ $\C{// C header file}$ 433 440 #else 434 #include <fstream> §\indexc{fstream}§ §\C{// \CFA header file}§441 #include <fstream>$\indexc{fstream}$ $\C{// \CFA header file}$ 435 442 #endif 436 443 \end{cfa} … … 438 445 439 446 The \CFA translator has multiple steps. 440 The following flags control how the tran lator works, the stages run, and printing within a stage.447 The following flags control how the translator works, the stages run, and printing within a stage. 441 448 The majority of these flags are used by \CFA developers, but some are occasionally useful to programmers. 449 Each option must be escaped with \Indexc{-XCFA}\index{translator option!-XCFA@{©-XCFA©}} to direct it to the compiler step, similar to the ©-Xlinker© flag for the linker, \eg: 450 \begin{lstlisting}[language=sh] 451 cfa $test$.cfa -CFA -XCFA -p # print translated code without printing the standard prelude 452 cfa $test$.cfa -XCFA -P -XCFA parse -XCFA -n # show program parse without prelude 453 \end{lstlisting} 442 454 \begin{description}[topsep=5pt,itemsep=0pt,parsep=0pt] 443 455 \item 444 \Indexc{-h}\index{translator option!-h@{©-h©}}, \Indexc{--help}\index{translator option!--help@{©--help©}} \, print help message 445 \item 446 \Indexc{-l}\index{translator option!-l@{©-l©}}, \Indexc{--libcfa}\index{translator option!--libcfa@{©--libcfa©}} \, generate libcfa.c 456 \Indexc{-c}\index{translator option!-c@{©-c©}}, \Indexc{--colors}\index{translator option!--colors@{©--colors©}} \, diagnostic color: ©never©, ©always©, \lstinline[deletekeywords=auto]{auto} 457 \item 458 \Indexc{-g}\index{translator option!-g@{©-g©}}, \Indexc{--gdb}\index{translator option!--gdb@{©--gdb©}} \, wait for gdb to attach 459 \item 460 \Indexc{-h}\index{translator option!-h@{©-h©}}, \Indexc{--help}\index{translator option!--help@{©--help©}} \, print translator help message 461 \item 462 \Indexc{-l}\index{translator option!-l@{©-l©}}, \Indexc{--libcfa}\index{translator option!--libcfa@{©--libcfa©}} \, generate ©libcfa.c© 447 463 \item 448 464 \Indexc{-L}\index{translator option!-L@{©-L©}}, \Indexc{--linemarks}\index{translator option!--linemarks@{©--linemarks©}} \, generate line marks … … 454 470 \Indexc{-n}\index{translator option!-n@{©-n©}}, \Indexc{--no-prelude}\index{translator option!--no-prelude@{©--no-prelude©}} \, do not read prelude 455 471 \item 456 \Indexc{-p}\index{translator option!-p@{©-p©}}, \Indexc{--prototypes}\index{translator option!--prototypes@{©--prototypes©}} \, generate prototypes for prelude functions 472 \Indexc{-p}\index{translator option!-p@{©-p©}}, \Indexc{--prototypes}\index{translator option!--prototypes@{©--prototypes©}} \, do not generate prelude prototypes $\Rightarrow$ prelude not printed 473 \item 474 \Indexc{-d}\index{translator option!-d@{©-d©}}, \Indexc{--deterministic-out}\index{translator option!--deterministic-out@{©--deterministic-out©}} \, only print deterministic output 457 475 \item 458 476 \Indexc{-P}\index{translator option!-P@{©-P©}}, \Indexc{--print}\index{translator option!--print@{©--print©}} \, one of: 459 477 \begin{description}[topsep=0pt,itemsep=0pt,parsep=0pt] 460 478 \item 479 \Indexc{ascodegen}\index{translator option!-P@{©-P©}!©ascodegen©}\index{translator option!--print@{©-print©}!©ascodegen©} \, as codegen rather than AST 480 \item 481 \Indexc{asterr}\index{translator option!-P@{©-P©}!©asterr©}\index{translator option!--print@{©-print©}!©asterr©} \, AST on error 482 \item 483 \Indexc{declstats}\index{translator option!-P@{©-P©}!©declstats©}\index{translator option!--print@{©-print©}!©declstats©} \, code property statistics 484 \item 485 \Indexc{parse}\index{translator option!-P@{©-P©}!©parse©}\index{translator option!--print@{©-print©}!©parse©} \, yacc (parsing) debug information 486 \item 487 \Indexc{pretty}\index{translator option!-P@{©-P©}!©pretty©}\index{translator option!--print@{©-print©}!©pretty©} \, prettyprint for ©ascodegen© flag 488 \item 489 \Indexc{rproto}\index{translator option!-P@{©-P©}!©rproto©}\index{translator option!--print@{©-print©}!©rproto©} \, resolver-proto instance 490 \item 491 \Indexc{rsteps}\index{translator option!-P@{©-P©}!©rsteps©}\index{translator option!--print@{©-print©}!©rsteps©} \, resolver steps 492 \item 493 \Indexc{tree}\index{translator option!-P@{©-P©}!©tree©}\index{translator option!--print@{©-print©}!©tree©} \, parse tree 494 \item 495 \Indexc{ast}\index{translator option!-P@{©-P©}!©ast©}\index{translator option!--print@{©-print©}!©ast©} \, AST after parsing 496 \item 497 \Indexc{symevt}\index{translator option!-P@{©-P©}!©symevt©}\index{translator option!--print@{©-print©}!©symevt©} \, symbol table events 498 \item 461 499 \Indexc{altexpr}\index{translator option!-P@{©-P©}!©altexpr©}\index{translator option!--print@{©-print©}!©altexpr©} \, alternatives for expressions 462 500 \item 463 \Indexc{ascodegen}\index{translator option!-P@{©-P©}!©ascodegen©}\index{translator option!--print@{©-print©}!©ascodegen©} \, as codegen rather than AST464 \item465 \Indexc{ast}\index{translator option!-P@{©-P©}!©ast©}\index{translator option!--print@{©-print©}!©ast©} \, AST after parsing466 \item467 501 \Indexc{astdecl}\index{translator option!-P@{©-P©}!©astdecl©}\index{translator option!--print@{©-print©}!©astdecl©} \, AST after declaration validation pass 468 502 \item 469 \Indexc{ asterr}\index{translator option!-P@{©-P©}!©asterr©}\index{translator option!--print@{©-print©}!©asterr©} \, AST on error503 \Indexc{resolver}\index{translator option!-P@{©-P©}!©resolver©}\index{translator option!--print@{©-print©}!©resolver©} \, before resolver step 470 504 \item 471 505 \Indexc{astexpr}\index{translator option!-P@{©-P©}!©astexpr©}\index{translator option!--print@{©-print©}!©altexpr©} \, AST after expression analysis 472 506 \item 507 \Indexc{ctordtor}\index{translator option!-P@{©-P©}!©ctordtor©}\index{translator option!--print@{©-print©}!©ctordtor©} \, after ctor/dtor are replaced 508 \item 509 \Indexc{tuple}\index{translator option!-P@{©-P©}!©tuple©}\index{translator option!--print@{©-print©}!©tuple©} \, after tuple expansion 510 \item 473 511 \Indexc{astgen}\index{translator option!-P@{©-P©}!©astgen©}\index{translator option!--print@{©-print©}!©astgen©} \, AST after instantiate generics 474 512 \item 475 513 \Indexc{box}\index{translator option!-P@{©-P©}!©box©}\index{translator option!--print@{©-print©}!©box©} \, before box step 476 514 \item 477 \Indexc{ctordtor}\index{translator option!-P@{©-P©}!©ctordtor©}\index{translator option!--print@{©-print©}!©ctordtor©} \, after ctor/dtor are replaced478 \item479 515 \Indexc{codegen}\index{translator option!-P@{©-P©}!©codegen©}\index{translator option!--print@{©-print©}!©codegen©} \, before code generation 480 \item481 \Indexc{declstats}\index{translator option!-P@{©-P©}!©declstats©}\index{translator option!--print@{©-print©}!©declstats©} \, code property statistics482 \item483 \Indexc{parse}\index{translator option!-P@{©-P©}!©parse©}\index{translator option!--print@{©-print©}!©parse©} \, yacc (parsing) debug information484 \item485 \Indexc{pretty}\index{translator option!-P@{©-P©}!©pretty©}\index{translator option!--print@{©-print©}!©pretty©} \, prettyprint for ascodegen flag486 \item487 \Indexc{resolver}\index{translator option!-P@{©-P©}!©resolver©}\index{translator option!--print@{©-print©}!©resolver©} \, before resolver step488 \item489 \Indexc{rproto}\index{translator option!-P@{©-P©}!©rproto©}\index{translator option!--print@{©-print©}!©rproto©} \, resolver-proto instance490 \item491 \Indexc{rsteps}\index{translator option!-P@{©-P©}!©rsteps©}\index{translator option!--print@{©-print©}!©rsteps©} \, resolver steps492 \item493 \Indexc{symevt}\index{translator option!-P@{©-P©}!©symevt©}\index{translator option!--print@{©-print©}!©symevt©} \, symbol table events494 \item495 \Indexc{tree}\index{translator option!-P@{©-P©}!©tree©}\index{translator option!--print@{©-print©}!©tree©} \, parse tree496 \item497 \Indexc{tuple}\index{translator option!-P@{©-P©}!©tuple©}\index{translator option!--print@{©-print©}!©tuple©} \, after tuple expansion498 516 \end{description} 499 517 \item 500 518 \Indexc{--prelude-dir} <directory> \, prelude directory for debug/nodebug 501 519 \item 502 \Indexc{-S}\index{translator option!-S@{©-S©}!©counters,heap,time,all,none©}, \Indexc{--statistics}\index{translator option!--statistics@{©--statistics©}!©counters,heap,time,all,none©} <option-list> \, enable profiling information: 503 \begin{description}[topsep=0pt,itemsep=0pt,parsep=0pt] 504 \item 505 \Indexc{counters,heap,time,all,none} 506 \end{description} 520 \Indexc{-S}\index{translator option!-S@{©-S©}!©counters,heap,time,all,none©}, \Indexc{--statistics}\index{translator option!--statistics@{©--statistics©}!©counters,heap,time,all,none©} <option-list> \, enable profiling information: ©counters©, ©heap©, ©time©, ©all©, ©none© 507 521 \item 508 522 \Indexc{-t}\index{translator option!-t@{©-t©}}, \Indexc{--tree}\index{translator option!--tree@{©--tree©}} build in tree … … 513 527 \label{s:BackquoteIdentifiers} 514 528 515 \CFA introduces several new keywords (see \VRef{s:CFAKeywords})that can clash with existing C variable-names in legacy code.529 \CFA introduces several new keywords \see{\VRef{s:CFAKeywords}} that can clash with existing C variable-names in legacy code. 516 530 Keyword clashes are accommodated by syntactic transformations using the \CFA backquote escape-mechanism: 517 531 \begin{cfa} 518 int ®``®otype = 3; §\C{// make keyword an identifier}§519 double ®``®forall = 3.5;532 int @``@otype = 3; $\C{// make keyword an identifier}$ 533 double @``@forall = 3.5; 520 534 \end{cfa} 521 535 522 536 Existing C programs with keyword clashes can be converted by enclosing keyword identifiers in backquotes, and eventually the identifier name can be changed to a non-keyword name. 523 \VRef[Figure]{f:HeaderFileInterposition} shows how clashes in existing C header-files (see~\VRef{s:StandardHeaders})can be handled using preprocessor \newterm{interposition}: ©#include_next© and ©-I filename©.537 \VRef[Figure]{f:HeaderFileInterposition} shows how clashes in existing C header-files \see{\VRef{s:StandardHeaders}} can be handled using preprocessor \newterm{interposition}: ©#include_next© and ©-I filename©. 524 538 Several common C header-files with keyword clashes are fixed in the standard \CFA header-library, so there is a seamless programming-experience. 525 539 … … 527 541 \begin{cfa} 528 542 // include file uses the CFA keyword "with". 529 #if ! defined( with ) §\C{// nesting ?}§530 #define with ®``®with §\C{// make keyword an identifier}§543 #if ! defined( with ) $\C{// nesting ?}$ 544 #define with @``@with $\C{// make keyword an identifier}$ 531 545 #define __CFA_BFD_H__ 532 546 #endif 533 §{\color{red}\#\textbf{include\_next} <bfdlink.h>}§ §\C{// must have internal check for multiple expansion}§ 534 #if defined( with ) && defined( __CFA_BFD_H__ ) §\C{// reset only if set}§547 $\R{\#include\_next} <bfdlink.h>$ $\C{// must have internal check for multiple expansion}$ 548 #if defined( with ) && defined( __CFA_BFD_H__ ) $\C{// reset only if set}$ 535 549 #undef with 536 550 #undef __CFA_BFD_H__ … … 544 558 \section{Constant Underscores} 545 559 546 Numeric constants are extended to allow \Index{underscore}s\index{constant!underscore} , \eg:547 \begin{cfa} 548 2 ®_®147®_®483®_®648; §\C{// decimal constant}§549 56 ®_®ul; §\C{// decimal unsigned long constant}§550 0 ®_®377; §\C{// octal constant}§551 0x ®_®ff®_®ff; §\C{// hexadecimal constant}§552 0x ®_®ef3d®_®aa5c; §\C{// hexadecimal constant}§553 3.141 ®_®592®_®654; §\C{// floating constant}§554 10 ®_®e®_®+1®_®00; §\C{// floating constant}§555 0x ®_®ff®_®ff®_®p®_®3; §\C{// hexadecimal floating}§556 0x ®_®1.ffff®_®ffff®_®p®_®128®_®l; §\C{// hexadecimal floating long constant}§557 L ®_®§"\texttt{\textbackslash{x}}§®_®§\texttt{ff}§®_®§\texttt{ee}"§; §\C{// wide character constant}§560 Numeric constants are extended to allow \Index{underscore}s\index{constant!underscore} as a separator, \eg: 561 \begin{cfa} 562 2@_@147@_@483@_@648; $\C{// decimal constant}$ 563 56@_@ul; $\C{// decimal unsigned long constant}$ 564 0@_@377; $\C{// octal constant}$ 565 0x@_@ff@_@ff; $\C{// hexadecimal constant}$ 566 0x@_@ef3d@_@aa5c; $\C{// hexadecimal constant}$ 567 3.141@_@592@_@654; $\C{// floating constant}$ 568 10@_@e@_@+1@_@00; $\C{// floating constant}$ 569 0x@_@ff@_@ff@_@p@_@3; $\C{// hexadecimal floating}$ 570 0x@_@1.ffff@_@ffff@_@p@_@128@_@l; $\C{// hexadecimal floating long constant}$ 571 L@_@$"\texttt{\textbackslash{x}}$@_@$\texttt{ff}$@_@$\texttt{ee}"$; $\C{// wide character constant}$ 558 572 \end{cfa} 559 573 The rules for placement of underscores are: … … 574 588 It is significantly easier to read and enter long constants when they are broken up into smaller groupings (many cultures use comma and/or period among digits for the same purpose). 575 589 This extension is backwards compatible, matches with the use of underscore in variable names, and appears in \Index*{Ada} and \Index*{Java} 8. 590 \CC uses the single quote (©'©) as a separator, restricted within a sequence of digits, \eg ©0xaa©©'©©ff©, ©3.141©©'©©592E1©©'©©1©. 576 591 577 592 578 593 \section{Exponentiation Operator} 579 594 580 C, \CC, and Java (and manyother programming languages) have no exponentiation operator\index{exponentiation!operator}\index{operator!exponentiation}, \ie $x^y$, and instead use a routine, like \Indexc{pow(x,y)}, to perform the exponentiation operation.581 \CFA extends the basic operators with the exponentiation operator ©? ®\®?©\index{?\\?@©?®\®?©} and ©?\=?©\index{?\\=?@©®\®=?©}, as in, ©x ®\® y© and ©x ®\®= y©, which means $x^y$ and $x \leftarrow x^y$.582 The priority of the exponentiation operator is between the cast and multiplicative operators, so that ©w * (int)x \ (int)y * z© is parenthesized as ©( (w * (((int)x) \ ((int)y))) * z)©.595 C, \CC, and Java (and other programming languages) have no exponentiation operator\index{exponentiation!operator}\index{operator!exponentiation}, \ie $x^y$, and instead use a routine, like \Indexc{pow(x,y)}, to perform the exponentiation operation. 596 \CFA extends the basic operators with the exponentiation operator ©?©\R{©\\©}©?©\index{?\\?@©?@\@?©} and ©?©\R{©\\©}©=?©\index{?\\=?@©@\@=?©}, as in, ©x ©\R{©\\©}© y© and ©x ©\R{©\\©}©= y©, which means $x^y$ and $x \leftarrow x^y$. 597 The priority of the exponentiation operator is between the cast and multiplicative operators, so that ©w * (int)x \ (int)y * z© is parenthesized as ©(w * (((int)x) \ ((int)y))) * z©. 583 598 584 599 There are exponentiation operators for integral and floating types, including the builtin \Index{complex} types. … … 587 602 Floating exponentiation\index{exponentiation!floating} is performed using \Index{logarithm}s\index{exponentiation!logarithm}, so the exponent cannot be negative. 588 603 \begin{cfa} 589 sout | 1 ®\® 0 | 1 ®\® 1 | 2 ®\® 8 | -4 ®\® 3 | 5 ®\® 3 | 5 ®\® 32 | 5L ®\® 32 | 5L ®\® 64 | -4 ®\® -3 | -4.0 ®\® -3 | 4.0 ®\®2.1590 | (1.0f+2.0fi) ®\®(3.0f+2.0fi);591 1 1 256 -64 125 ®0® 3273344365508751233 ®0® ®0®-0.015625 18.3791736799526 0.264715-1.1922i604 sout | 1 @\@ 0 | 1 @\@ 1 | 2 @\@ 8 | -4 @\@ 3 | 5 @\@ 3 | 5 @\@ 32 | 5L @\@ 32 | 5L @\@ 64 | -4 @\@ -3 | -4.0 @\@ -3 | 4.0 @\@ 2.1 605 | (1.0f+2.0fi) @\@ (3.0f+2.0fi); 606 1 1 256 -64 125 @0@ 3273344365508751233 @0@ @0@ -0.015625 18.3791736799526 0.264715-1.1922i 592 607 \end{cfa} 593 608 Note, ©5 \ 32© and ©5L \ 64© overflow, and ©-4 \ -3© is a fraction but stored in an integer so all three computations generate an integral zero. 594 Parenthesis are necessary for complex constants or the expression is parsed as ©1.0f+®(®2.0fi \ 3.0f®)®+2.0fi©. 609 Because exponentiation has higher priority than ©+©, parenthesis are necessary for exponentiation of \Index{complex constant}s or the expression is parsed as ©1.0f+©\R{©(©}©2.0fi \ 3.0f©\R{©)©}©+2.0fi©, requiring \R{©(©}©1.0f+2.0fi©\R{©)©}© \ ©\R{©(©}©3.0f+2.0fi©\R{©)©}. 610 595 611 The exponentiation operator is available for all the basic types, but for user-defined types, only the integral-computation version is available. 596 612 \begin{cfa} 597 forall( otype OT | { void ?{}( OT & this, one_t ); OT ?*?( OT, OT ); } )598 OT ?®\®?( OT ep, unsigned int y );599 forall( otype OT | { void ?{}( OT & this, one_t ); OT ?*?( OT, OT ); } )600 OT ?®\®?( OT ep, unsigned long int y );613 forall( otype T | { void ?{}( T & this, one_t ); T ?*?( T, T ); } ) 614 T ?@\@?( T ep, unsigned int y ); 615 forall( otype T | { void ?{}( T & this, one_t ); T ?*?( T, T ); } ) 616 T ?@\@?( T ep, unsigned long int y ); 601 617 \end{cfa} 602 618 The user type ©T© must define multiplication, one (©1©), and ©*©. … … 609 625 610 626 %\subsection{\texorpdfstring{\protect\lstinline@if@/\protect\lstinline@while@ Statement}{if Statement}} 611 \subsection{\texorpdfstring{\LstKeywordStyle{if}/\LstKeywordStyle{while} Statement}{if/while Statement}} 612 613 The ©if©/©while© expression allows declarations, similar to ©for© declaration expression. 614 (Does not make sense for ©do©-©while©.) 615 \begin{cfa} 616 if ( ®int x = f()® ) ... §\C{// x != 0}§ 617 if ( ®int x = f(), y = g()® ) ... §\C{// x != 0 \&\& y != 0}§ 618 if ( ®int x = f(), y = g(); x < y® ) ... §\C{// relational expression}§ 619 if ( ®struct S { int i; } x = { f() }; x.i < 4® ) §\C{// relational expression}§ 620 621 while ( ®int x = f()® ) ... §\C{// x != 0}§ 622 while ( ®int x = f(), y = g()® ) ... §\C{// x != 0 \&\& y != 0}§ 623 while ( ®int x = f(), y = g(); x < y® ) ... §\C{// relational expression}§ 624 while ( ®struct S { int i; } x = { f() }; x.i < 4® ) ... §\C{// relational expression}§ 625 \end{cfa} 626 Unless a relational expression is specified, each variable is compared not equal to 0, which is the standard semantics for the ©if©/©while© expression, and the results are combined using the logical ©&&© operator.\footnote{\CC only provides a single declaration always compared not equal to 0.} 627 The scope of the declaration(s) is local to the @if@ statement but exist within both the ``then'' and ``else'' clauses. 627 \subsection{\texorpdfstring{\LstKeywordStyle{if} / \LstKeywordStyle{while} Statement}{if / while Statement}} 628 629 The ©if©/©while© expression allows declarations, similar to ©for© declaration expression.\footnote{ 630 Declarations in the ©do©-©while© condition are not useful because they appear after the loop body.} 631 \begin{cfa} 632 if ( @int x = f()@ ) ... $\C{// x != 0}$ 633 if ( @int x = f(), y = g()@ ) ... $\C{// x != 0 \&\& y != 0}$ 634 if ( @int x = f(), y = g(); x < y@ ) ... $\C{// relational expression}$ 635 if ( @struct S { int i; } x = { f() }; x.i < 4@ ) $\C{// relational expression}$ 636 637 while ( @int x = f()@ ) ... $\C{// x != 0}$ 638 while ( @int x = f(), y = g()@ ) ... $\C{// x != 0 \&\& y != 0}$ 639 while ( @int x = f(), y = g(); x < y@ ) ... $\C{// relational expression}$ 640 while ( @struct S { int i; } x = { f() }; x.i < 4@ ) ... $\C{// relational expression}$ 641 \end{cfa} 642 Unless a relational expression is specified, each variable is compared not equal to 0, which is the standard semantics for the ©if©/©while© expression, and the results are combined using the logical ©&&© operator. 643 The scope of the declaration(s) is local to the ©if© statement but exist within both the \emph{then} and \emph{else} clauses. 644 \CC only provides a single declaration always compared ©!=© to 0. 628 645 629 646 630 647 %\section{\texorpdfstring{\protect\lstinline@case@ Clause}{case Clause}} 631 648 \subsection{\texorpdfstring{\LstKeywordStyle{case} Clause}{case Clause}} 649 \label{s:caseClause} 632 650 633 651 C restricts the ©case© clause of a ©switch© statement to a single value. … … 640 658 \begin{cfa} 641 659 switch ( i ) { 642 case ®1, 3, 5®:660 case @1, 3, 5@: 643 661 ... 644 case ®2, 4, 6®:662 case @2, 4, 6@: 645 663 ... 646 664 } … … 670 688 \begin{cfa} 671 689 switch ( i ) { 672 case ®1~5:® §\C{// 1, 2, 3, 4, 5}§690 case @1~5:@ $\C{// 1, 2, 3, 4, 5}$ 673 691 ... 674 case ®10~15:® §\C{// 10, 11, 12, 13, 14, 15}§692 case @10~15:@ $\C{// 10, 11, 12, 13, 14, 15}$ 675 693 ... 676 694 } … … 678 696 Lists of subranges are also allowed. 679 697 \begin{cfa} 680 case ®1~5, 12~21, 35~42®:698 case @1~5, 12~21, 35~42@: 681 699 \end{cfa} 682 700 … … 722 740 if ( argc == 3 ) { 723 741 // open output file 724 ®// open input file725 ®} else if ( argc == 2 ) {726 ®// open input file (duplicate)727 728 ®} else {742 @// open input file 743 @} else if ( argc == 2 ) { 744 @// open input file (duplicate) 745 746 @} else { 729 747 // usage message 730 748 } … … 733 751 \end{cquote} 734 752 In this example, case 2 is always done if case 3 is done. 735 This control flow is difficult to simulate with ifstatements or a ©switch© statement without fall-through as code must be duplicated or placed in a separate routine.753 This control flow is difficult to simulate with ©if© statements or a ©switch© statement without fall-through as code must be duplicated or placed in a separate routine. 736 754 C also uses fall-through to handle multiple case-values resulting in the same action: 737 755 \begin{cfa} 738 756 switch ( i ) { 739 ®case 1: case 3: case 5:®// odd values757 @case 1: case 3: case 5:@ // odd values 740 758 // odd action 741 759 break; 742 ®case 2: case 4: case 6:®// even values760 @case 2: case 4: case 6:@ // even values 743 761 // even action 744 762 break; 745 763 } 746 764 \end{cfa} 747 However, this situation is handled in other languages without fall-through by allowing a list of case values.748 While fall-through itself is not a problem, the problem occurs when fall-through is the default, as this semantics is unintuitive to many programmers and is different from virtually all otherprogramming languages with a ©switch© statement.765 This situation better handled without fall-through by allowing a list of case values \see{\VRef{s:caseClause}}. 766 While fall-through itself is not a problem, the problem occurs when fall-through is the default, as this semantics is unintuitive to many programmers and is different from most programming languages with a ©switch© statement. 749 767 Hence, default fall-through semantics results in a large number of programming errors as programmers often \emph{forget} the ©break© statement at the end of a ©case© clause, resulting in inadvertent fall-through. 750 768 … … 756 774 if ( j < k ) { 757 775 ... 758 ®case 1:®// transfer into "if" statement776 @case 1:@ // transfer into "if" statement 759 777 ... 760 778 } // if … … 762 780 while ( j < 5 ) { 763 781 ... 764 ®case 3:®// transfer into "while" statement782 @case 3:@ // transfer into "while" statement 765 783 ... 766 784 } // while 767 785 } // switch 768 786 \end{cfa} 769 Th e problem with this usage is branchinginto control structures, which is known to cause both comprehension and technical difficulties.770 The comprehension problem occurs from the inability to determine how control reaches a particular point due to the number of branches leading to it.787 This usage branches into control structures, which is known to cause both comprehension and technical difficulties. 788 The comprehension problem results from the inability to determine how control reaches a particular point due to the number of branches leading to it. 771 789 The technical problem results from the inability to ensure declaration and initialization of variables when blocks are not entered at the beginning. 772 There are no positivearguments for this kind of control flow, and therefore, there is a strong impetus to eliminate it.790 There are few arguments for this kind of control flow, and therefore, there is a strong impetus to eliminate it. 773 791 Nevertheless, C does have an idiom where this capability is used, known as ``\Index*{Duff's device}''~\cite{Duff83}: 774 792 \begin{cfa} … … 794 812 \item 795 813 It is possible to place the ©default© clause anywhere in the list of labelled clauses for a ©switch© statement, rather than only at the end. 796 Virtually allprogramming languages with a ©switch© statement require the ©default© clause to appear last in the case-clause list.814 Most programming languages with a ©switch© statement require the ©default© clause to appear last in the case-clause list. 797 815 The logic for this semantics is that after checking all the ©case© clauses without success, the ©default© clause is selected; 798 816 hence, physically placing the ©default© clause at the end of the ©case© clause list matches with this semantics. … … 803 821 \begin{cfa} 804 822 switch ( x ) { 805 ®int y = 1;® §\C{// unreachable initialization}§806 ®x = 7;® §\C{// unreachable code without label/branch}§823 @int y = 1;@ $\C{// unreachable initialization}$ 824 @x = 7;@ $\C{// unreachable code without label/branch}$ 807 825 case 0: ... 808 826 ... 809 ®int z = 0;® §\C{// unreachable initialization, cannot appear after case}§827 @int z = 0;@ $\C{// unreachable initialization, cannot appear after case}$ 810 828 z = 2; 811 829 case 1: 812 ®x = z;® §\C{// without fall through, z is uninitialized}§830 @x = z;@ $\C{// without fall through, z is uninitialized}$ 813 831 } 814 832 \end{cfa} 815 833 While the declaration of the local variable ©y© is useful with a scope across all ©case© clauses, the initialization for such a variable is defined to never be executed because control always transfers over it. 816 Furthermore, any statements before the first ©case© clause can only be executed if labelled and transferred to using a ©goto©, either from outside or inside of the ©switch©, both of which are problematic.817 As well, the declaration of ©z© cannot occur after the ©case© because a label can only be attached to a statement, and without a fall 818 The key observation is that the ©switch© statement branches into control structure, \ie there are multiple entry points into its statement body.834 Furthermore, any statements before the first ©case© clause can only be executed if labelled and transferred to using a ©goto©, either from outside or inside of the ©switch©, where both are problematic. 835 As well, the declaration of ©z© cannot occur after the ©case© because a label can only be attached to a statement, and without a fall-through to case 3, ©z© is uninitialized. 836 The key observation is that the ©switch© statement branches into a control structure, \ie there are multiple entry points into its statement body. 819 837 \end{enumerate} 820 838 … … 842 860 Therefore, to preserve backwards compatibility, it is necessary to introduce a new kind of ©switch© statement, called ©choose©, with no implicit fall-through semantics and an explicit fall-through if the last statement of a case-clause ends with the new keyword ©fallthrough©/©fallthru©, \eg: 843 861 \begin{cfa} 844 ®choose®( i ) {862 @choose@ ( i ) { 845 863 case 1: case 2: case 3: 846 864 ... 847 ®// implicit end of switch (break)848 ®case 5:865 @// implicit end of switch (break) 866 @case 5: 849 867 ... 850 ®fallthru®; §\C{// explicit fall through}§868 @fallthru@; $\C{// explicit fall through}$ 851 869 case 7: 852 870 ... 853 ®break® §\C{// explicit end of switch (redundant)}§871 @break@ $\C{// explicit end of switch (redundant)}$ 854 872 default: 855 873 j = 3; 856 874 } 857 875 \end{cfa} 858 Like the ©switch© statement, the ©choose© statement retains the fall-through semantics for a list of ©case© clauses ;876 Like the ©switch© statement, the ©choose© statement retains the fall-through semantics for a list of ©case© clauses. 859 877 An implicit ©break© is applied only at the end of the \emph{statements} following a ©case© clause. 860 878 An explicit ©fallthru© is retained because it is a C-idiom most C programmers expect, and its absence might discourage programmers from using the ©choose© statement. … … 872 890 \begin{cfa} 873 891 switch ( x ) { 874 ®int i = 0;® §\C{// allowed only at start}§892 @int i = 0;@ $\C{// allowed only at start}$ 875 893 case 0: 876 894 ... 877 ®int j = 0;® §\C{// disallowed}§895 @int j = 0;@ $\C{// disallowed}$ 878 896 case 1: 879 897 { 880 ®int k = 0;® §\C{// allowed at different nesting levels}§898 @int k = 0;@ $\C{// allowed at different nesting levels}$ 881 899 ... 882 ®case 2:® §\C{// disallow case in nested statements}§900 @case 2:@ $\C{// disallow case in nested statements}$ 883 901 } 884 902 ... … … 897 915 case 3: 898 916 if ( ... ) { 899 ... ®fallthru;®// goto case 4917 ... @fallthru;@ // goto case 4 900 918 } else { 901 919 ... … … 912 930 choose ( ... ) { 913 931 case 3: 914 ... ®fallthrough common;®932 ... @fallthrough common;@ 915 933 case 4: 916 ... ®fallthrough common;®917 918 ®common:®// below fallthrough934 ... @fallthrough common;@ 935 936 @common:@ // below fallthrough 919 937 // at case-clause level 920 938 ... // common code for cases 3/4 … … 932 950 for ( ... ) { 933 951 // multi-level transfer 934 ... ®fallthru common;®952 ... @fallthru common;@ 935 953 } 936 954 ... 937 955 } 938 956 ... 939 ®common:®// below fallthrough957 @common:@ // below fallthrough 940 958 // at case-clause level 941 959 \end{cfa} … … 948 966 949 967 \begin{figure} 950 \begin{tabular}{@{}l |l@{}}951 \multicolumn{1}{ c|}{loop control} & \multicolumn{1}{c}{output} \\968 \begin{tabular}{@{}l@{\hspace{25pt}}|l@{}} 969 \multicolumn{1}{@{}c@{\hspace{25pt}}|}{loop control} & \multicolumn{1}{c@{}}{output} \\ 952 970 \hline 953 \begin{cfa} [xleftmargin=0pt]954 while ®()®{ sout | "empty"; break; }955 do { sout | "empty"; break; } while ®()®;956 for ®()®{ sout | "empty"; break; }957 for ( ®0®) { sout | "A"; } sout | "zero";958 for ( ®1®) { sout | "A"; }959 for ( ®10®) { sout | "A"; }960 for ( ®= 10®) { sout | "A"; }961 for ( ®1 ~= 10 ~ 2®) { sout | "B"; }962 for ( ®10 -~= 1 ~ 2®) { sout | "C"; }963 for ( ®0.5 ~ 5.5®) { sout | "D"; }964 for ( ®5.5 -~ 0.5®) { sout | "E"; }965 for ( ®i; 10®) { sout | i; }966 for ( ®i; = 10®) { sout | i; }967 for ( ®i; 1 ~= 10 ~ 2®) { sout | i; }968 for ( ®i; 10 -~= 1 ~ 2®) { sout | i; }969 for ( ®i; 0.5 ~ 5.5®) { sout | i; }970 for ( ®i; 5.5 -~ 0.5®) { sout | i; }971 for ( ®ui; 2u ~= 10u ~ 2u®) { sout | ui; }972 for ( ®ui; 10u -~= 2u ~ 2u®) { sout | ui; }971 \begin{cfa} 972 while @($\,$)@ { sout | "empty"; break; } 973 do { sout | "empty"; break; } while @($\,$)@; 974 for @($\,$)@ { sout | "empty"; break; } 975 for ( @0@ ) { sout | "A"; } sout | "zero"; 976 for ( @1@ ) { sout | "A"; } 977 for ( @10@ ) { sout | "A"; } 978 for ( @= 10@ ) { sout | "A"; } 979 for ( @1 ~= 10 ~ 2@ ) { sout | "B"; } 980 for ( @10 -~= 1 ~ 2@ ) { sout | "C"; } 981 for ( @0.5 ~ 5.5@ ) { sout | "D"; } 982 for ( @5.5 -~ 0.5@ ) { sout | "E"; } 983 for ( @i; 10@ ) { sout | i; } 984 for ( @i; = 10@ ) { sout | i; } 985 for ( @i; 1 ~= 10 ~ 2@ ) { sout | i; } 986 for ( @i; 10 -~= 1 ~ 2@ ) { sout | i; } 987 for ( @i; 0.5 ~ 5.5@ ) { sout | i; } 988 for ( @i; 5.5 -~ 0.5@ ) { sout | i; } 989 for ( @ui; 2u ~= 10u ~ 2u@ ) { sout | ui; } 990 for ( @ui; 10u -~= 2u ~ 2u@ ) { sout | ui; } 973 991 enum { N = 10 }; 974 for ( ®N®) { sout | "N"; }975 for ( ®i; N®) { sout | i; }976 for ( ®i; N -~ 0®) { sout | i; }992 for ( @N@ ) { sout | "N"; } 993 for ( @i; N@ ) { sout | i; } 994 for ( @i; N -~ 0@ ) { sout | i; } 977 995 const int start = 3, comp = 10, inc = 2; 978 for ( ®i; start ~ comp ~ inc + 1®) { sout | i; }979 for ( i; 1 ~ ®@®) { if ( i > 10 ) break; sout | i; }980 for ( i; 10 -~ ®@®) { if ( i < 0 ) break; sout | i; }981 for ( i; 2 ~ ®@®~ 2 ) { if ( i > 10 ) break; sout | i; }982 for ( i; 2.1 ~ ®@® ~ ®@®) { if ( i > 10.5 ) break; sout | i; i += 1.7; }983 for ( i; 10 -~ ®@®~ 2 ) { if ( i < 0 ) break; sout | i; }984 for ( i; 12.1 ~ ®@® ~ ®@®) { if ( i < 2.5 ) break; sout | i; i -= 1.7; }985 for ( i; 5 ®:® j; -5 ~ @) { sout | i | j; }986 for ( i; 5 ®:® j; -5 -~ @) { sout | i | j; }987 for ( i; 5 ®:® j; -5 ~ @~ 2 ) { sout | i | j; }988 for ( i; 5 ®:® j; -5 -~ @~ 2 ) { sout | i | j; }989 for ( i; 5 ®:® j; -5 ~ @) { sout | i | j; }990 for ( i; 5 ®:® j; -5 -~ @) { sout | i | j; }991 for ( i; 5 ®:® j; -5 ~ @~ 2 ) { sout | i | j; }992 for ( i; 5 ®:® j; -5 -~ @~ 2 ) { sout | i | j; }993 for ( i; 5 ®:® j; -5 -~ @ ~ 2 ®:® k; 1.5 ~ @) { sout | i | j | k; }994 for ( i; 5 ®:® j; -5 -~ @ ~ 2 ®:® k; 1.5 ~ @) { sout | i | j | k; }995 for ( i; 5 ®:® k; 1.5 ~ @ ®:® j; -5 -~ @~ 2 ) { sout | i | j | k; }996 for ( @i; start ~ comp ~ inc + 1@ ) { sout | i; } 997 for ( i; 1 ~ $\R{@}$ ) { if ( i > 10 ) break; sout | i; } 998 for ( i; 10 -~ $\R{@}$ ) { if ( i < 0 ) break; sout | i; } 999 for ( i; 2 ~ $\R{@}$ ~ 2 ) { if ( i > 10 ) break; sout | i; } 1000 for ( i; 2.1 ~ $\R{@}$ ~ $\R{@}$ ) { if ( i > 10.5 ) break; sout | i; i += 1.7; } 1001 for ( i; 10 -~ $\R{@}$ ~ 2 ) { if ( i < 0 ) break; sout | i; } 1002 for ( i; 12.1 ~ $\R{@}$ ~ $\R{@}$ ) { if ( i < 2.5 ) break; sout | i; i -= 1.7; } 1003 for ( i; 5 @:@ j; -5 ~ $@$ ) { sout | i | j; } 1004 for ( i; 5 @:@ j; -5 -~ $@$ ) { sout | i | j; } 1005 for ( i; 5 @:@ j; -5 ~ $@$ ~ 2 ) { sout | i | j; } 1006 for ( i; 5 @:@ j; -5 -~ $@$ ~ 2 ) { sout | i | j; } 1007 for ( i; 5 @:@ j; -5 ~ $@$ ) { sout | i | j; } 1008 for ( i; 5 @:@ j; -5 -~ $@$ ) { sout | i | j; } 1009 for ( i; 5 @:@ j; -5 ~ $@$ ~ 2 ) { sout | i | j; } 1010 for ( i; 5 @:@ j; -5 -~ $@$ ~ 2 ) { sout | i | j; } 1011 for ( i; 5 @:@ j; -5 -~ $@$ ~ 2 @:@ k; 1.5 ~ $@$ ) { sout | i | j | k; } 1012 for ( i; 5 @:@ j; -5 -~ $@$ ~ 2 @:@ k; 1.5 ~ $@$ ) { sout | i | j | k; } 1013 for ( i; 5 @:@ k; 1.5 ~ $@$ @:@ j; -5 -~ $@$ ~ 2 ) { sout | i | j | k; } 996 1014 \end{cfa} 997 1015 & … … 1056 1074 \subsection{Loop Control} 1057 1075 1058 The ©for©/©while©/©do-while© loop-control allows empty or simplified ranges (see Figure~\ref{f:LoopControlExamples}). 1059 \begin{itemize} 1076 Looping a fixed number of times, possibly with a loop index, occurs frequently. 1077 \CFA condenses simply looping to facilitate coding speed and safety. 1078 The ©for©/©while©/©do-while© loop-control is augmented as follows \see{examples in \VRef[Figure]{f:LoopControlExamples}}: 1079 \begin{itemize}[itemsep=0pt] 1080 \item 1081 ©0© is the implicit start value; 1082 \item 1083 ©1© is the implicit increment value. 1084 \item 1085 The up-to range uses operator ©+=© for increment; 1086 \item 1087 The down-to range uses operator ©-=© for decrement. 1060 1088 \item 1061 1089 The loop index is polymorphic in the type of the comparison value N (when the start value is implicit) or the start value M. 1090 \begin{cfa} 1091 for ( i; @5@ ) $\C[2.5in]{// typeof(5) i; 5 is comparison value}$ 1092 for ( i; @1.5@~5.5~0.5 ) $\C{// typeof(1.5) i; 1.5 is start value}$ 1093 \end{cfa} 1062 1094 \item 1063 1095 An empty conditional implies comparison value of ©1© (true). 1064 \item 1065 A comparison N is implicit up-to exclusive range [0,N©®)®©. 1066 \item 1067 A comparison ©=© N is implicit up-to inclusive range [0,N©®]®©. 1068 \item 1069 The up-to range M ©~©\index{~@©~©} N means exclusive range [M,N©®)®©. 1070 \item 1071 The up-to range M ©~=©\index{~=@©~=©} N means inclusive range [M,N©®]®©. 1072 \item 1073 The down-to range M ©-~©\index{-~@©-~©} N means exclusive range [N,M©®)®©. 1074 \item 1075 The down-to range M ©-~=©\index{-~=@©-~=©} N means inclusive range [N,M©®]®©. 1076 \item 1077 ©0© is the implicit start value; 1078 \item 1079 ©1© is the implicit increment value. 1080 \item 1081 The up-to range uses operator ©+=© for increment; 1082 \item 1083 The down-to range uses operator ©-=© for decrement. 1096 \begin{cfa} 1097 while ( $\R{/*empty*/}$ ) $\C{// while ( true )}$ 1098 for ( $\R{/*empty*/}$ ) $\C{// for ( ; true; )}$ 1099 do ... while ( $\R{/*empty*/}$ ) $\C{// do ... while ( true )}$ 1100 \end{cfa} 1101 \item 1102 A comparison N is implicit up-to exclusive range [0,N\R{)}. 1103 \begin{cfa} 1104 for ( @5@ ) $\C{// for ( typeof(5) i; i < 5; i += 1 )}$ 1105 \end{cfa} 1106 \item 1107 A comparison ©=© N is implicit up-to inclusive range [0,N\R{]}. 1108 \begin{cfa} 1109 for ( @=@5 ) $\C{// for ( typeof(5) i; i <= 5; i += 1 )}$ 1110 \end{cfa} 1111 \item 1112 The up-to range M ©~©\index{~@©~©} N means exclusive range [M,N\R{)}. 1113 \begin{cfa} 1114 for ( 1@~@5 ) $\C{// for ( typeof(1) i = 1; i < 5; i += 1 )}$ 1115 \end{cfa} 1116 \item 1117 The up-to range M ©~=©\index{~=@©~=©} N means inclusive range [M,N\R{]}. 1118 \begin{cfa} 1119 for ( 1@~=@5 ) $\C{// for ( typeof(1) i = 1; i <= 5; i += 1 )}$ 1120 \end{cfa} 1121 \item 1122 The down-to range M ©-~©\index{-~@©-~©} N means exclusive range [N,M\R{)}. 1123 \begin{cfa} 1124 for ( 1@-~@5 ) $\C{// for ( typeof(1) i = 5; i > 0; i -= 1 )}$ 1125 \end{cfa} 1126 \item 1127 The down-to range M ©-~=©\index{-~=@©-~=©} N means inclusive range [N,M\R{]}. 1128 \begin{cfa} 1129 for ( 1@-~=@5 ) $\C{// for ( typeof(1) i = 5; i >= 0; i -= 1 )}$ 1130 \end{cfa} 1084 1131 \item 1085 1132 ©@© means put nothing in this field. 1133 \begin{cfa} 1134 for ( 1~$\R{@}$~2 ) $\C{// for ( typeof(1) i = 1; /*empty*/; i += 2 )}$ 1135 \end{cfa} 1086 1136 \item 1087 1137 ©:© means start another index. 1138 \begin{cfa} 1139 for ( i; 5 @:@ j; 2~12~3 ) $\C{// for ( typeof(i) i = 1, j = 2; i < 5 \&\& j < 12; i += 1, j += 3 )}\CRT$ 1140 \end{cfa} 1088 1141 \end{itemize} 1089 1142 … … 1092 1145 \subsection{\texorpdfstring{Labelled \LstKeywordStyle{continue} / \LstKeywordStyle{break} Statement}{Labelled continue / break Statement}} 1093 1146 1094 While C provides ©continue© and ©break© statements for altering control flow, bothare restricted to one level of nesting for a particular control structure.1095 Unfortunately, this restriction forces programmers to use \Indexc{goto} to achieve the equivalent control-flow for more than one level of nesting.1147 C ©continue© and ©break© statements, for altering control flow, are restricted to one level of nesting for a particular control structure. 1148 This restriction forces programmers to use \Indexc{goto} to achieve the equivalent control-flow for more than one level of nesting. 1096 1149 To prevent having to switch to the ©goto©, \CFA extends the \Indexc{continue}\index{continue@©continue©!labelled}\index{labelled!continue@©continue©} and \Indexc{break}\index{break@©break©!labelled}\index{labelled!break@©break©} with a target label to support static multi-level exit\index{multi-level exit}\index{static multi-level exit}~\cite{Buhr85}, as in Java. 1097 1150 For both ©continue© and ©break©, the target label must be directly associated with a ©for©, ©while© or ©do© statement; 1098 1151 for ©break©, the target label can also be associated with a ©switch©, ©if© or compound (©{}©) statement. 1099 \VRef[Figure]{f:MultiLevelExit} shows ©continue© and ©break© indicating the specific control structure, and the corresponding C program using only©goto© and labels.1152 \VRef[Figure]{f:MultiLevelExit} shows a comparison between labelled ©continue© and ©break© and the corresponding C equivalent using ©goto© and labels. 1100 1153 The innermost loop has 8 exit points, which cause continuation or termination of one or more of the 7 \Index{nested control-structure}s. 1101 1154 … … 1104 1157 \begin{lrbox}{\myboxA} 1105 1158 \begin{cfa}[tabsize=3] 1106 ®Compound:®{1107 ®Try:®try {1108 ®For:®for ( ... ) {1109 ®While:®while ( ... ) {1110 ®Do:®do {1111 ®If:®if ( ... ) {1112 ®Switch:®switch ( ... ) {1159 @Compound:@ { 1160 @Try:@ try { 1161 @For:@ for ( ... ) { 1162 @While:@ while ( ... ) { 1163 @Do:@ do { 1164 @If:@ if ( ... ) { 1165 @Switch:@ switch ( ... ) { 1113 1166 case 3: 1114 ®break Compound®;1115 ®break Try®;1116 ®break For®; /* or */ ®continue For®;1117 ®break While®; /* or */ ®continue While®;1118 ®break Do®; /* or */ ®continue Do®;1119 ®break If®;1120 ®break Switch®;1167 @break Compound@; 1168 @break Try@; 1169 @break For@; /* or */ @continue For@; 1170 @break While@; /* or */ @continue While@; 1171 @break Do@; /* or */ @continue Do@; 1172 @break If@; 1173 @break Switch@; 1121 1174 } // switch 1122 1175 } else { 1123 ... ®break If®; ... // terminate if1176 ... @break If@; ... // terminate if 1124 1177 } // if 1125 1178 } while ( ... ); // do 1126 1179 } // while 1127 1180 } // for 1128 } ®finally®{ // always executed1181 } @finally@ { // always executed 1129 1182 } // try 1130 1183 } // compound … … 1136 1189 { 1137 1190 1138 ®ForC:®for ( ... ) {1139 ®WhileC:®while ( ... ) {1140 ®DoC:®do {1191 @ForC:@ for ( ... ) { 1192 @WhileC:@ while ( ... ) { 1193 @DoC:@ do { 1141 1194 if ( ... ) { 1142 1195 switch ( ... ) { 1143 1196 case 3: 1144 ®goto Compound®;1145 ®goto Try®;1146 ®goto ForB®; /* or */ ®goto ForC®;1147 ®goto WhileB®; /* or */ ®goto WhileC®;1148 ®goto DoB®; /* or */ ®goto DoC®;1149 ®goto If®;1150 ®goto Switch®;1151 } ®Switch:®;1197 @goto Compound@; 1198 @goto Try@; 1199 @goto ForB@; /* or */ @goto ForC@; 1200 @goto WhileB@; /* or */ @goto WhileC@; 1201 @goto DoB@; /* or */ @goto DoC@; 1202 @goto If@; 1203 @goto Switch@; 1204 } @Switch:@ ; 1152 1205 } else { 1153 ... ®goto If®; ... // terminate if1154 } ®If:®;1155 } while ( ... ); ®DoB:®;1156 } ®WhileB:®;1157 } ®ForB:®;1158 1159 1160 } ®Compound:®;1206 ... @goto If@; ... // terminate if 1207 } @If:@; 1208 } while ( ... ); @DoB:@ ; 1209 } @WhileB:@ ; 1210 } @ForB:@ ; 1211 1212 1213 } @Compound:@ ; 1161 1214 \end{cfa} 1162 1215 \end{lrbox} 1163 1216 1164 1217 \subfloat[\CFA]{\label{f:CFibonacci}\usebox\myboxA} 1165 \hspace{ 2pt}1218 \hspace{3pt} 1166 1219 \vrule 1167 \hspace{ 2pt}1220 \hspace{3pt} 1168 1221 \subfloat[C]{\label{f:CFAFibonacciGen}\usebox\myboxB} 1169 1222 \caption{Multi-level Exit} … … 1180 1233 This restriction prevents missing declarations and/or initializations at the start of a control structure resulting in undefined behaviour. 1181 1234 \end{itemize} 1182 The advantage of the labelled ©continue©/©break© is allowing static multi-level exits without having to use the ©goto© statement, and tying control flow to the target control structure rather than an arbitrary point in a program .1235 The advantage of the labelled ©continue©/©break© is allowing static multi-level exits without having to use the ©goto© statement, and tying control flow to the target control structure rather than an arbitrary point in a program via a label. 1183 1236 Furthermore, the location of the label at the \emph{beginning} of the target control structure informs the reader (\Index{eye candy}) that complex control-flow is occurring in the body of the control structure. 1184 1237 With ©goto©, the label is at the end of the control structure, which fails to convey this important clue early enough to the reader. … … 1187 1240 1188 1241 1189 %\s ection{\texorpdfstring{\protect\lstinline@with@ Statement}{with Statement}}1190 \s ection{\texorpdfstring{\LstKeywordStyle{with} Statement}{with Statement}}1242 %\subsection{\texorpdfstring{\protect\lstinline@with@ Statement}{with Statement}} 1243 \subsection{\texorpdfstring{\LstKeywordStyle{with} Statement}{with Statement}} 1191 1244 \label{s:WithStatement} 1192 1245 1193 Grouping heterogeneous data into \newterm{aggregate}s (structure/union) is a common programming practice, and an aggregate can be further organized into more complex structures, such as arrays and containers:1194 \begin{cfa} 1195 struct S { §\C{// aggregate}§1196 char c; §\C{// fields}§1197 int i;1198 double d;1246 Grouping heterogeneous data into an \newterm{aggregate} (structure/union) is a common programming practice, and aggregates may be nested: 1247 \begin{cfa} 1248 struct Person { $\C{// aggregate}$ 1249 struct Name { char first[20], last[20]; } name $\C{// nesting}$ 1250 struct Address { ... } address $\C{// nesting}$ 1251 int sex; 1199 1252 }; 1200 S s, as[10]; 1201 \end{cfa} 1202 However, functions manipulating aggregates must repeat the aggregate name to access its containing fields: 1203 \begin{cfa} 1204 void f( S s ) { 1205 ®s.®c; ®s.®i; ®s.®d; §\C{// access containing fields}§ 1206 } 1207 \end{cfa} 1208 which extends to multiple levels of qualification for nested aggregates. 1209 A similar situation occurs in object-oriented programming, \eg \CC: 1253 \end{cfa} 1254 Functions manipulating aggregates must repeat the aggregate name to access its containing fields. 1255 \begin{cfa} 1256 Person p 1257 @p.@name; @p.@address; @p.@sex; $\C{// access containing fields}$ 1258 \end{cfa} 1259 which extends to multiple levels of qualification for nested aggregates and multiple aggregates. 1260 \begin{cfa} 1261 struct Ticket { ... } t; 1262 @p.name@.first; @p.address@.street; $\C{// access nested fields}$ 1263 @t.@departure; @t.@cost; $\C{// access multiple aggregate}$ 1264 \end{cfa} 1265 Repeated aggregate qualification is tedious and makes code difficult to read. 1266 Therefore, reducing aggregate qualification is a useful language design goal. 1267 1268 C allows unnamed nested aggregates that open their scope into the containing aggregate. 1269 This feature is used to group fields for attributes and/or with ©union© aggregates. 1270 \begin{cfa} 1271 struct S { 1272 struct { int g, h; } __attribute__(( aligned(64) )); 1273 int tag; 1274 union { 1275 struct { char c1, c2; } __attribute__(( aligned(128) )); 1276 struct { int i1, i2; }; 1277 struct { double d1, d2; }; 1278 }; 1279 }; 1280 s.g; s.h; s.tag; s.c1; s.c2; s.i1; s.i2; s.d1; s.d2; 1281 \end{cfa} 1282 1283 Object-oriented languages reduce qualification for class variables within member functions, \eg \CC: 1210 1284 \begin{C++} 1211 1285 struct S { 1212 char c; §\C{// fields}§ 1213 int i; 1214 double d; 1215 void f() { §\C{// implicit ``this'' aggregate}§ 1216 ®this->®c; ®this->®i; ®this->®d; §\C{// access containing fields}§ 1286 char @c@; int @i@; double @d@; 1287 void f( /* S * this */ ) { $\C{// implicit ``this'' parameter}$ 1288 @c@; @i@; @d@; $\C{// this->c; this->i; this->d;}$ 1217 1289 } 1218 1290 } 1219 1291 \end{C++} 1220 Object-oriented nesting of member functions in a \lstinline[language=C++]@class/struct@ allows eliding \lstinline[language=C++]@this->@ because of lexical scoping. 1221 However, for other aggregate parameters, qualification is necessary: 1222 \begin{cfa} 1223 struct T { double m, n; }; 1224 int S::f( T & t ) { §\C{// multiple aggregate parameters}§ 1225 c; i; d; §\C{\color{red}// this--{\textgreater}.c, this--{\textgreater}.i, this--{\textgreater}.d}§ 1226 ®t.®m; ®t.®n; §\C{// must qualify}§ 1227 } 1228 \end{cfa} 1229 1230 To simplify the programmer experience, \CFA provides a ©with© statement (see Pascal~\cite[\S~4.F]{Pascal}) to elide aggregate qualification to fields by opening a scope containing the field identifiers. 1231 Hence, the qualified fields become variables with the side-effect that it is easier to optimizing field references in a block. 1232 \begin{cfa} 1233 void f( S & this ) ®with ( this )® { §\C{// with statement}§ 1234 c; i; d; §\C{\color{red}// this.c, this.i, this.d}§ 1292 In general, qualification is elided for the variables and functions in the lexical scopes visible from a member function. 1293 However, qualification is necessary for name shadowing and explicit aggregate parameters. 1294 \begin{cfa} 1295 struct T { 1296 char @m@; int @i@; double @n@; $\C{// derived class variables}$ 1297 }; 1298 struct S : public T { 1299 char @c@; int @i@; double @d@; $\C{// class variables}$ 1300 void g( double @d@, T & t ) { 1301 d; @t@.m; @t@.i; @t@.n; $\C{// function parameter}$ 1302 c; i; @this->@d; @S::@d; $\C{// class S variables}$ 1303 m; @T::@i; n; $\C{// class T variables}$ 1304 } 1305 }; 1306 \end{cfa} 1307 Note the three different forms of qualification syntax in \CC, ©.©, ©->©, ©::©, which is confusing. 1308 1309 Since \CFA in not object-oriented, it has no implicit parameter with its implicit qualification. 1310 Instead \CFA introduces a general mechanism using the ©with© statement \see{Pascal~\cite[\S~4.F]{Pascal}} to explicitly elide aggregate qualification by opening a scope containing the field identifiers. 1311 Hence, the qualified fields become variables with the side-effect that it is simpler to write, easier to read, and optimize field references in a block. 1312 \begin{cfa} 1313 void f( S & this ) @with ( this )@ { $\C{// with statement}$ 1314 @c@; @i@; @d@; $\C{// this.c, this.i, this.d}$ 1235 1315 } 1236 1316 \end{cfa} 1237 1317 with the generality of opening multiple aggregate-parameters: 1238 1318 \begin{cfa} 1239 void f( S & s, T & t ) ®with ( s, t )® { §\C{// multiple aggregate parameters}§ 1240 c; i; d; §\C{\color{red}// s.c, s.i, s.d}§ 1241 m; n; §\C{\color{red}// t.m, t.n}§ 1242 } 1243 \end{cfa} 1244 1245 In detail, the ©with© statement has the form: 1246 \begin{cfa} 1247 §\emph{with-statement}§: 1248 'with' '(' §\emph{expression-list}§ ')' §\emph{compound-statement}§ 1249 \end{cfa} 1250 and may appear as the body of a function or nested within a function body. 1251 Each expression in the expression-list provides a type and object. 1252 The type must be an aggregate type. 1319 void g( S & s, T & t ) @with ( s, t )@ { $\C{// multiple aggregate parameters}$ 1320 c; @s.@i; d; $\C{// s.c, s.i, s.d}$ 1321 m; @t.@i; n; $\C{// t.m, t.i, t.n}$ 1322 } 1323 \end{cfa} 1324 where qualification is only necessary to disambiguate the shadowed variable ©i©. 1325 1326 In detail, the ©with© statement may appear as the body of a function or nested within a function body. 1327 The ©with© clause takes a list of expressions, where each expression provides an aggregate type and object. 1253 1328 (Enumerations are already opened.) 1254 The object is the implicit qualifier for the open structure-fields. 1255 1329 To open a pointer type, the pointer must be dereferenced to obtain a reference to the aggregate type. 1330 \begin{cfa} 1331 S * sp; 1332 with ( *sp ) { ... } 1333 \end{cfa} 1334 The expression object is the implicit qualifier for the open structure-fields. 1335 \CFA's ability to overload variables \see{\VRef{s:VariableOverload}} and use the left-side of assignment in type resolution means most fields with the same name but different types are automatically disambiguated, eliminating qualification. 1256 1336 All expressions in the expression list are open in parallel within the compound statement. 1257 1337 This semantic is different from Pascal, which nests the openings from left to right. 1258 1338 The difference between parallel and nesting occurs for fields with the same name and type: 1259 1339 \begin{cfa} 1260 struct S { int ®i®; int j; double m; } s, w; 1261 struct T { int ®i®; int k; int m; } t, w; 1262 with ( s, t ) { 1263 j + k; §\C{// unambiguous, s.j + t.k}§ 1264 m = 5.0; §\C{// unambiguous, t.m = 5.0}§ 1265 m = 1; §\C{// unambiguous, s.m = 1}§ 1266 int a = m; §\C{// unambiguous, a = s.i }§ 1267 double b = m; §\C{// unambiguous, b = t.m}§ 1268 int c = s.i + t.i; §\C{// unambiguous, qualification}§ 1269 (double)m; §\C{// unambiguous, cast}§ 1270 } 1271 \end{cfa} 1272 For parallel semantics, both ©s.i© and ©t.i© are visible, so ©i© is ambiguous without qualification; 1273 for nested semantics, ©t.i© hides ©s.i©, so ©i© implies ©t.i©. 1274 \CFA's ability to overload variables means fields with the same name but different types are automatically disambiguated, eliminating most qualification when opening multiple aggregates. 1275 Qualification or a cast is used to disambiguate. 1276 1277 There is an interesting problem between parameters and the function-body ©with©, \eg: 1278 \begin{cfa} 1279 void ?{}( S & s, int i ) with ( s ) { §\C{// constructor}§ 1280 ®s.i = i;® j = 3; m = 5.5; §\C{// initialize fields}§ 1340 struct Q { int @i@; int k; int @m@; } q, w; 1341 struct R { int @i@; int j; double @m@; } r, w; 1342 with ( r, q ) { 1343 j + k; $\C{// unambiguous, r.j + q.k}$ 1344 m = 5.0; $\C{// unambiguous, q.m = 5.0}$ 1345 m = 1; $\C{// unambiguous, r.m = 1}$ 1346 int a = m; $\C{// unambiguous, a = r.i }$ 1347 double b = m; $\C{// unambiguous, b = q.m}$ 1348 int c = r.i + q.i; $\C{// disambiguate with qualification}$ 1349 (double)m; $\C{// disambiguate with cast}$ 1350 } 1351 \end{cfa} 1352 For parallel semantics, both ©r.i© and ©q.i© are visible, so ©i© is ambiguous without qualification; 1353 for nested semantics, ©q.i© hides ©r.i©, so ©i© implies ©q.i©. 1354 Pascal nested-semantics is possible by nesting ©with© statements. 1355 \begin{cfa} 1356 with ( r ) { 1357 i; $\C{// unambiguous, r.i}$ 1358 with ( q ) { 1359 i; $\C{// unambiguous, q.i}$ 1360 } 1361 } 1362 \end{cfa} 1363 A cast or qualification can be used to disambiguate variables within a ©with© \emph{statement}. 1364 A cast can be used to disambiguate among overload variables in a ©with© \emph{expression}: 1365 \begin{cfa} 1366 with ( w ) { ... } $\C{// ambiguous, same name and no context}$ 1367 with ( (Q)w ) { ... } $\C{// unambiguous, cast}$ 1368 \end{cfa} 1369 Because there is no left-side in the ©with© expression to implicitly disambiguate between the ©w© variables, it is necessary to explicitly disambiguate by casting ©w© to type ©Q© or ©R©. 1370 1371 Finally, there is an interesting problem between parameters and the function-body ©with©, \eg: 1372 \begin{cfa} 1373 void ?{}( S & s, int i ) with ( s ) { $\C{// constructor}$ 1374 @s.i = i;@ j = 3; m = 5.5; $\C{// initialize fields}$ 1281 1375 } 1282 1376 \end{cfa} … … 1291 1385 and implicitly opened \emph{after} a function-body open, to give them higher priority: 1292 1386 \begin{cfa} 1293 void ?{}( S & s, int ®i® ) with ( s ) ®with( §\emph{\color{red}params}§ )® { 1294 s.i = ®i®; j = 3; m = 5.5; 1295 } 1296 \end{cfa} 1297 Finally, a cast may be used to disambiguate among overload variables in a ©with© expression: 1298 \begin{cfa} 1299 with ( w ) { ... } §\C{// ambiguous, same name and no context}§ 1300 with ( (S)w ) { ... } §\C{// unambiguous, cast}§ 1301 \end{cfa} 1302 and ©with© expressions may be complex expressions with type reference (see Section~\ref{s:References}) to aggregate: 1303 % \begin{cfa} 1304 % struct S { int i, j; } sv; 1305 % with ( sv ) { §\C{// implicit reference}§ 1306 % S & sr = sv; 1307 % with ( sr ) { §\C{// explicit reference}§ 1308 % S * sp = &sv; 1309 % with ( *sp ) { §\C{// computed reference}§ 1310 % i = 3; j = 4; §\C{\color{red}// sp--{\textgreater}i, sp--{\textgreater}j}§ 1311 % } 1312 % i = 2; j = 3; §\C{\color{red}// sr.i, sr.j}§ 1313 % } 1314 % i = 1; j = 2; §\C{\color{red}// sv.i, sv.j}§ 1315 % } 1316 % \end{cfa} 1317 1318 In \Index{object-oriented} programming, there is an implicit first parameter, often names \textbf{©self©} or \textbf{©this©}, which is elided. 1319 \begin{C++} 1320 class C { 1321 int i, j; 1322 int mem() { §\C{\color{red}// implicit "this" parameter}§ 1323 i = 1; §\C{\color{red}// this->i}§ 1324 j = 2; §\C{\color{red}// this->j}§ 1325 } 1326 } 1327 \end{C++} 1328 Since \CFA is non-object-oriented, the equivalent object-oriented program looks like: 1329 \begin{cfa} 1330 struct S { int i, j; }; 1331 int mem( S & ®this® ) { §\C{// explicit "this" parameter}§ 1332 ®this.®i = 1; §\C{// "this" is not elided}§ 1333 ®this.®j = 2; 1334 } 1335 \end{cfa} 1336 but it is cumbersome having to write ``©this.©'' many times in a member. 1337 1338 \CFA provides a ©with© clause/statement (see Pascal~\cite[\S~4.F]{Pascal}) to elided the "©this.©" by opening a scope containing field identifiers, changing the qualified fields into variables and giving an opportunity for optimizing qualified references. 1339 \begin{cfa} 1340 int mem( S & this ) ®with( this )® { §\C{// with clause}§ 1341 i = 1; §\C{\color{red}// this.i}§ 1342 j = 2; §\C{\color{red}// this.j}§ 1343 } 1344 \end{cfa} 1345 which extends to multiple routine parameters: 1346 \begin{cfa} 1347 struct T { double m, n; }; 1348 int mem2( S & this1, T & this2 ) ®with( this1, this2 )® { 1349 i = 1; j = 2; 1350 m = 1.0; n = 2.0; 1351 } 1352 \end{cfa} 1353 1354 The statement form is used within a block: 1355 \begin{cfa} 1356 int foo() { 1357 struct S1 { ... } s1; 1358 struct S2 { ... } s2; 1359 ®with( s1 )® { §\C{// with statement}§ 1360 // access fields of s1 without qualification 1361 ®with s2® { §\C{// nesting}§ 1362 // access fields of s1 and s2 without qualification 1363 } 1364 } 1365 ®with s1, s2® { 1366 // access unambiguous fields of s1 and s2 without qualification 1367 } 1368 } 1369 \end{cfa} 1370 1371 When opening multiple structures, fields with the same name and type are ambiguous and must be fully qualified. 1372 For fields with the same name but different type, context/cast can be used to disambiguate. 1373 \begin{cfa} 1374 struct S { int i; int j; double m; } a, c; 1375 struct T { int i; int k; int m } b, c; 1376 with( a, b ) 1377 { 1378 } 1379 \end{cfa} 1380 1381 \begin{comment} 1382 The components in the "with" clause 1383 1384 with a, b, c { ... } 1385 1386 serve 2 purposes: each component provides a type and object. The type must be a 1387 structure type. Enumerations are already opened, and I think a union is opened 1388 to some extent, too. (Or is that just unnamed unions?) The object is the target 1389 that the naked structure-fields apply to. The components are open in "parallel" 1390 at the scope of the "with" clause/statement, so opening "a" does not affect 1391 opening "b", etc. This semantic is different from Pascal, which nests the 1392 openings. 1393 1394 Having said the above, it seems reasonable to allow a "with" component to be an 1395 expression. The type is the static expression-type and the object is the result 1396 of the expression. Again, the type must be an aggregate. Expressions require 1397 parenthesis around the components. 1398 1399 with( a, b, c ) { ... } 1400 1401 Does this now make sense? 1402 1403 Having written more CFA code, it is becoming clear to me that I *really* want 1404 the "with" to be implemented because I hate having to type all those object 1405 names for fields. It's a great way to drive people away from the language. 1406 \end{comment} 1387 void ?{}( S & s, int @i@ ) with ( s ) @with( $\emph{\R{params}}$ )@ { // syntax not allowed, illustration only 1388 s.i = @i@; j = 3; m = 5.5; 1389 } 1390 \end{cfa} 1391 This implicit semantic matches with programmer expectation. 1392 1407 1393 1408 1394 … … 1414 1400 Non-local transfer can cause stack unwinding, \ie non-local routine termination, depending on the kind of raise. 1415 1401 \begin{cfa} 1416 exception_t E {}; §\C{// exception type}§1402 exception_t E {}; $\C{// exception type}$ 1417 1403 void f(...) { 1418 ... throw E{}; ... §\C{// termination}§1419 ... throwResume E{}; ... §\C{// resumption}§1404 ... throw E{}; ... $\C{// termination}$ 1405 ... throwResume E{}; ... $\C{// resumption}$ 1420 1406 } 1421 1407 try { 1422 1408 f(...); 1423 } catch( E e ; §boolean-predicate§ ) { §\C{// termination handler}§1409 } catch( E e ; $boolean-predicate$ ) { $\C{// termination handler}$ 1424 1410 // recover and continue 1425 } catchResume( E e ; §boolean-predicate§ ) { §\C{// resumption handler}§1411 } catchResume( E e ; $boolean-predicate$ ) { $\C{// resumption handler}$ 1426 1412 // repair and return 1427 1413 } finally { … … 1430 1416 \end{cfa} 1431 1417 The kind of raise and handler match: ©throw© with ©catch© and ©throwResume© with ©catchResume©. 1432 Then the exception type must match along with any addit onal predicate must be true.1418 Then the exception type must match along with any additional predicate must be true. 1433 1419 The ©catch© and ©catchResume© handlers may appear in any oder. 1434 1420 However, the ©finally© clause must appear at the end of the ©try© statement. … … 1483 1469 For example, a routine returning a \Index{pointer} to an array of integers is defined and used in the following way: 1484 1470 \begin{cfa} 1485 int ®(*®f®())[®5®]® {...}; §\C{// definition}§1486 ... ®(*®f®())[®3®]® += 1; §\C{// usage}§1471 int @(*@f@())[@5@]@ {...}; $\C{// definition}$ 1472 ... @(*@f@())[@3@]@ += 1; $\C{// usage}$ 1487 1473 \end{cfa} 1488 1474 Essentially, the return type is wrapped around the routine name in successive layers (like an \Index{onion}). … … 1499 1485 \begin{tabular}{@{}l@{\hspace{3em}}l@{}} 1500 1486 \multicolumn{1}{c@{\hspace{3em}}}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{C}} \\ 1501 \begin{cfa} 1502 ß[5] *ß ®int®x1;1503 ß* [5]ß ®int®x2;1504 ß[* [5] int]ß f®( int p )®;1487 \begin{cfa}[moredelim={**[is][\color{blue}]{\#}{\#}}] 1488 #[5] *# @int@ x1; 1489 #* [5]# @int@ x2; 1490 #[* [5] int]# f@( int p )@; 1505 1491 \end{cfa} 1506 1492 & 1507 \begin{cfa} 1508 ®int® ß*ß x1 ß[5]ß;1509 ®int® ß(*ßx2ß)[5]ß;1510 ßint (*ßf®( int p )®ß)[5]ß;1493 \begin{cfa}[moredelim={**[is][\color{blue}]{\#}{\#}}] 1494 @int@ #*# x1 #[5]#; 1495 @int@ #(*#x2#)[5]#; 1496 #int (*#f@( int p )@#)[5]#; 1511 1497 \end{cfa} 1512 1498 \end{tabular} … … 1520 1506 \multicolumn{1}{c@{\hspace{3em}}}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{C}} \\ 1521 1507 \begin{cfa} 1522 ®*®int x, y;1508 @*@ int x, y; 1523 1509 \end{cfa} 1524 1510 & 1525 1511 \begin{cfa} 1526 int ®*®x, ®*®y;1512 int @*@x, @*@y; 1527 1513 \end{cfa} 1528 1514 \end{tabular} … … 1533 1519 \multicolumn{1}{c@{\hspace{3em}}}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{C}} \\ 1534 1520 \begin{cfa} 1535 ®*®int x;1521 @*@ int x; 1536 1522 int y; 1537 1523 \end{cfa} 1538 1524 & 1539 1525 \begin{cfa} 1540 int ®*®x, y;1526 int @*@x, y; 1541 1527 1542 1528 \end{cfa} … … 1647 1633 1648 1634 \section{Pointer / Reference} 1635 \label{s:PointerReference} 1649 1636 1650 1637 C provides a \newterm{pointer type}; … … 1673 1660 & 1674 1661 \begin{cfa} 1675 int * ®const®x = (int *)1001662 int * @const@ x = (int *)100 1676 1663 *x = 3; // implicit dereference 1677 int * ®const®y = (int *)104;1664 int * @const@ y = (int *)104; 1678 1665 *y = *x; // implicit dereference 1679 1666 \end{cfa} … … 1713 1700 \begin{tabular}{@{}l@{\hspace{2em}}l@{}} 1714 1701 \begin{cfa} 1715 int x, y, ®*® p1, ®*® p2, ®**®p3;1716 p1 = ®&®x; // p1 points to x1702 int x, y, @*@ p1, @*@ p2, @**@ p3; 1703 p1 = @&@x; // p1 points to x 1717 1704 p2 = p1; // p2 points to x 1718 p1 = ®&®y; // p1 points to y1705 p1 = @&@y; // p1 points to y 1719 1706 p3 = &p2; // p3 points to p2 1720 1707 \end{cfa} … … 1728 1715 For example, \Index*{Algol68}~\cite{Algol68} infers pointer dereferencing to select the best meaning for each pointer usage 1729 1716 \begin{cfa} 1730 p2 = p1 + x; §\C{// compiler infers *p2 = *p1 + x;}§1717 p2 = p1 + x; $\C{// compiler infers *p2 = *p1 + x;}$ 1731 1718 \end{cfa} 1732 1719 Algol68 infers the following dereferencing ©*p2 = *p1 + x©, because adding the arbitrary integer value in ©x© to the address of ©p1© and storing the resulting address into ©p2© is an unlikely operation. … … 1736 1723 In C, objects of pointer type always manipulate the pointer object's address: 1737 1724 \begin{cfa} 1738 p1 = p2; §\C{// p1 = p2\ \ rather than\ \ *p1 = *p2}§1739 p2 = p1 + x; §\C{// p2 = p1 + x\ \ rather than\ \ *p2 = *p1 + x}§1725 p1 = p2; $\C{// p1 = p2\ \ rather than\ \ *p1 = *p2}$ 1726 p2 = p1 + x; $\C{// p2 = p1 + x\ \ rather than\ \ *p2 = *p1 + x}$ 1740 1727 \end{cfa} 1741 1728 even though the assignment to ©p2© is likely incorrect, and the programmer probably meant: 1742 1729 \begin{cfa} 1743 p1 = p2; §\C{// pointer address assignment}§1744 ®*®p2 = ®*®p1 + x; §\C{// pointed-to value assignment / operation}§ 1730 p1 = p2; $\C{// pointer address assignment}$ 1731 @*@p2 = @*@p1 + x; $\C{// pointed-to value assignment / operation}$ 1745 1732 \end{cfa} 1746 1733 The C semantics work well for situations where manipulation of addresses is the primary meaning and data is rarely accessed, such as storage management (©malloc©/©free©). … … 1758 1745 To support this common case, a reference type is introduced in \CFA, denoted by ©&©, which is the opposite dereference semantics to a pointer type, making the value at the pointed-to location the implicit semantics for dereferencing (similar but not the same as \CC \Index{reference type}s). 1759 1746 \begin{cfa} 1760 int x, y, ®&® r1, ®&® r2, ®&&®r3;1761 ®&®r1 = &x; §\C{// r1 points to x}§ 1762 ®&®r2 = &r1; §\C{// r2 points to x}§ 1763 ®&®r1 = &y; §\C{// r1 points to y}§ 1764 ®&&®r3 = ®&®&r2; §\C{// r3 points to r2}§ 1765 r2 = ((r1 + r2) * (r3 - r1)) / (r3 - 15); §\C{// implicit dereferencing}§1747 int x, y, @&@ r1, @&@ r2, @&&@ r3; 1748 @&@r1 = &x; $\C{// r1 points to x}$ 1749 @&@r2 = &r1; $\C{// r2 points to x}$ 1750 @&@r1 = &y; $\C{// r1 points to y}$ 1751 @&&@r3 = @&@&r2; $\C{// r3 points to r2}$ 1752 r2 = ((r1 + r2) * (r3 - r1)) / (r3 - 15); $\C{// implicit dereferencing}$ 1766 1753 \end{cfa} 1767 1754 Except for auto-dereferencing by the compiler, this reference example is the same as the previous pointer example. … … 1769 1756 One way to conceptualize a reference is via a rewrite rule, where the compiler inserts a dereference operator before the reference variable for each reference qualifier in a declaration, so the previous example becomes: 1770 1757 \begin{cfa} 1771 ®*®r2 = ((®*®r1 + ®*®r2) ®*® (®**®r3 - ®*®r1)) / (®**®r3 - 15);1758 @*@r2 = ((@*@r1 + @*@r2) @*@ (@**@r3 - @*@r1)) / (@**@r3 - 15); 1772 1759 \end{cfa} 1773 1760 When a reference operation appears beside a dereference operation, \eg ©&*©, they cancel out. … … 1778 1765 For a \CFA reference type, the cancellation on the left-hand side of assignment leaves the reference as an address (\Index{lvalue}): 1779 1766 \begin{cfa} 1780 (& ®*®)r1 = &x; §\C{// (\&*) cancel giving address in r1 not variable pointed-to by r1}§1767 (&@*@)r1 = &x; $\C{// (\&*) cancel giving address in r1 not variable pointed-to by r1}$ 1781 1768 \end{cfa} 1782 1769 Similarly, the address of a reference can be obtained for assignment or computation (\Index{rvalue}): 1783 1770 \begin{cfa} 1784 (&(& ®*®)®*®)r3 = &(&®*®)r2; §\C{// (\&*) cancel giving address in r2, (\&(\&*)*) cancel giving address in r3}§1771 (&(&@*@)@*@)r3 = &(&@*@)r2; $\C{// (\&*) cancel giving address in r2, (\&(\&*)*) cancel giving address in r3}$ 1785 1772 \end{cfa} 1786 1773 Cancellation\index{cancellation!pointer/reference}\index{pointer!cancellation} works to arbitrary depth. … … 1790 1777 int x, *p1 = &x, **p2 = &p1, ***p3 = &p2, 1791 1778 &r1 = x, &&r2 = r1, &&&r3 = r2; 1792 ***p3 = 3; §\C{// change x}§1793 r3 = 3; §\C{// change x, ***r3}§1794 **p3 = ...; §\C{// change p1}§1795 &r3 = ...; §\C{// change r1, (\&*)**r3, 1 cancellation}§1796 *p3 = ...; §\C{// change p2}§1797 &&r3 = ...; §\C{// change r2, (\&(\&*)*)*r3, 2 cancellations}§1798 &&&r3 = p3; §\C{// change r3 to p3, (\&(\&(\&*)*)*)r3, 3 cancellations}§1779 ***p3 = 3; $\C{// change x}$ 1780 r3 = 3; $\C{// change x, ***r3}$ 1781 **p3 = ...; $\C{// change p1}$ 1782 &r3 = ...; $\C{// change r1, (\&*)**r3, 1 cancellation}$ 1783 *p3 = ...; $\C{// change p2}$ 1784 &&r3 = ...; $\C{// change r2, (\&(\&*)*)*r3, 2 cancellations}$ 1785 &&&r3 = p3; $\C{// change r3 to p3, (\&(\&(\&*)*)*)r3, 3 cancellations}$ 1799 1786 \end{cfa} 1800 1787 Furthermore, both types are equally performant, as the same amount of dereferencing occurs for both types. … … 1803 1790 As for a pointer type, a reference type may have qualifiers: 1804 1791 \begin{cfa} 1805 const int cx = 5; §\C{// cannot change cx;}§1806 const int & cr = cx; §\C{// cannot change what cr points to}§1807 ®&®cr = &cx; §\C{// can change cr}§ 1808 cr = 7; §\C{// error, cannot change cx}§1809 int & const rc = x; §\C{// must be initialized}§1810 ®&®rc = &x; §\C{// error, cannot change rc}§ 1811 const int & const crc = cx; §\C{// must be initialized}§1812 crc = 7; §\C{// error, cannot change cx}§1813 ®&®crc = &cx; §\C{// error, cannot change crc}§ 1792 const int cx = 5; $\C{// cannot change cx;}$ 1793 const int & cr = cx; $\C{// cannot change what cr points to}$ 1794 @&@cr = &cx; $\C{// can change cr}$ 1795 cr = 7; $\C{// error, cannot change cx}$ 1796 int & const rc = x; $\C{// must be initialized}$ 1797 @&@rc = &x; $\C{// error, cannot change rc}$ 1798 const int & const crc = cx; $\C{// must be initialized}$ 1799 crc = 7; $\C{// error, cannot change cx}$ 1800 @&@crc = &cx; $\C{// error, cannot change crc}$ 1814 1801 \end{cfa} 1815 1802 Hence, for type ©& const©, there is no pointer assignment, so ©&rc = &x© is disallowed, and \emph{the address value cannot be the null pointer unless an arbitrary pointer is coerced\index{coercion} into the reference}: 1816 1803 \begin{cfa} 1817 int & const cr = *0; §\C{// where 0 is the int * zero}§1804 int & const cr = *0; $\C{// where 0 is the int * zero}$ 1818 1805 \end{cfa} 1819 1806 Note, constant reference-types do not prevent \Index{addressing errors} because of explicit storage-management: … … 1822 1809 cr = 5; 1823 1810 free( &cr ); 1824 cr = 7; §\C{// unsound pointer dereference}§1811 cr = 7; $\C{// unsound pointer dereference}$ 1825 1812 \end{cfa} 1826 1813 1827 1814 The position of the ©const© qualifier \emph{after} the pointer/reference qualifier causes confuse for C programmers. 1828 1815 The ©const© qualifier cannot be moved before the pointer/reference qualifier for C style-declarations; 1829 \CFA-style declarations (see \VRef{s:AlternativeDeclarations})attempt to address this issue:1816 \CFA-style declarations \see{\VRef{s:AlternativeDeclarations}} attempt to address this issue: 1830 1817 \begin{cquote} 1831 1818 \begin{tabular}{@{}l@{\hspace{3em}}l@{}} 1832 1819 \multicolumn{1}{c@{\hspace{3em}}}{\textbf{\CFA}} & \multicolumn{1}{c}{\textbf{C}} \\ 1833 1820 \begin{cfa} 1834 ®const® * ®const®* const int ccp;1835 ®const® & ®const®& const int ccr;1821 @const@ * @const@ * const int ccp; 1822 @const@ & @const@ & const int ccr; 1836 1823 \end{cfa} 1837 1824 & 1838 1825 \begin{cfa} 1839 const int * ®const® * ®const®ccp;1826 const int * @const@ * @const@ ccp; 1840 1827 1841 1828 \end{cfa} … … 1846 1833 Finally, like pointers, references are usable and composable with other type operators and generators. 1847 1834 \begin{cfa} 1848 int w, x, y, z, & ar[3] = { x, y, z }; §\C{// initialize array of references}§1849 &ar[1] = &w; §\C{// change reference array element}§1850 typeof( ar[1] ) p; §\C{// (gcc) is int, \ie the type of referenced object}§1851 typeof( &ar[1] ) q; §\C{// (gcc) is int \&, \ie the type of reference}§1852 sizeof( ar[1] ) == sizeof( int ); §\C{// is true, \ie the size of referenced object}§1853 sizeof( &ar[1] ) == sizeof( int *) §\C{// is true, \ie the size of a reference}§1835 int w, x, y, z, & ar[3] = { x, y, z }; $\C{// initialize array of references}$ 1836 &ar[1] = &w; $\C{// change reference array element}$ 1837 typeof( ar[1] ) p; $\C{// (gcc) is int, \ie the type of referenced object}$ 1838 typeof( &ar[1] ) q; $\C{// (gcc) is int \&, \ie the type of reference}$ 1839 sizeof( ar[1] ) == sizeof( int ); $\C{// is true, \ie the size of referenced object}$ 1840 sizeof( &ar[1] ) == sizeof( int *) $\C{// is true, \ie the size of a reference}$ 1854 1841 \end{cfa} 1855 1842 1856 1843 In contrast to \CFA reference types, \Index*[C++]{\CC{}}'s reference types are all ©const© references, preventing changes to the reference address, so only value assignment is possible, which eliminates half of the \Index{address duality}. 1857 1844 Also, \CC does not allow \Index{array}s\index{array!reference} of reference\footnote{ 1858 The reason for disallowing arrays of reference is unknown, but possibly comes from references being ethereal (like a textual macro), and hence, replaceable by the refer ant object.}1845 The reason for disallowing arrays of reference is unknown, but possibly comes from references being ethereal (like a textual macro), and hence, replaceable by the referent object.} 1859 1846 \Index*{Java}'s reference types to objects (all Java objects are on the heap) are like C pointers, which always manipulate the address, and there is no (bit-wise) object assignment, so objects are explicitly cloned by shallow or deep copying, which eliminates half of the address duality. 1860 1847 … … 1868 1855 Therefore, for pointer/reference initialization, the initializing value must be an address not a value. 1869 1856 \begin{cfa} 1870 int * p = &x; §\C{// assign address of x}§1871 ®int * p = x;® §\C{// assign value of x}§ 1872 int & r = x; §\C{// must have address of x}§1857 int * p = &x; $\C{// assign address of x}$ 1858 @int * p = x;@ $\C{// assign value of x}$ 1859 int & r = x; $\C{// must have address of x}$ 1873 1860 \end{cfa} 1874 1861 Like the previous example with C pointer-arithmetic, it is unlikely assigning the value of ©x© into a pointer is meaningful (again, a warning is usually given). … … 1879 1866 Similarly, when a reference type is used for a parameter/return type, the call-site argument does not require a reference operator for the same reason. 1880 1867 \begin{cfa} 1881 int & f( int & r ); §\C{// reference parameter and return}§1882 z = f( x ) + f( y ); §\C{// reference operator added, temporaries needed for call results}§1868 int & f( int & r ); $\C{// reference parameter and return}$ 1869 z = f( x ) + f( y ); $\C{// reference operator added, temporaries needed for call results}$ 1883 1870 \end{cfa} 1884 1871 Within routine ©f©, it is possible to change the argument by changing the corresponding parameter, and parameter ©r© can be locally reassigned within ©f©. … … 1893 1880 When a pointer/reference parameter has a ©const© value (immutable), it is possible to pass literals and expressions. 1894 1881 \begin{cfa} 1895 void f( ®const®int & cr );1896 void g( ®const®int * cp );1897 f( 3 ); g( ®&®3 );1898 f( x + y ); g( ®&®(x + y) );1882 void f( @const@ int & cr ); 1883 void g( @const@ int * cp ); 1884 f( 3 ); g( @&@3 ); 1885 f( x + y ); g( @&@(x + y) ); 1899 1886 \end{cfa} 1900 1887 Here, the compiler passes the address to the literal 3 or the temporary for the expression ©x + y©, knowing the argument cannot be changed through the parameter. … … 1907 1894 void f( int & r ); 1908 1895 void g( int * p ); 1909 f( 3 ); g( ®&®3 ); §\C{// compiler implicit generates temporaries}§1910 f( x + y ); g( ®&®(x + y) ); §\C{// compiler implicit generates temporaries}§1896 f( 3 ); g( @&@3 ); $\C{// compiler implicit generates temporaries}$ 1897 f( x + y ); g( @&@(x + y) ); $\C{// compiler implicit generates temporaries}$ 1911 1898 \end{cfa} 1912 1899 Essentially, there is an implicit \Index{rvalue} to \Index{lvalue} conversion in this case.\footnote{ … … 1919 1906 \begin{cfa} 1920 1907 void f( int i ); 1921 void (* fp)( int ); §\C{// routine pointer}§1922 fp = f; §\C{// reference initialization}§1923 fp = &f; §\C{// pointer initialization}§1924 fp = *f; §\C{// reference initialization}§1925 fp(3); §\C{// reference invocation}§1926 (*fp)(3); §\C{// pointer invocation}§1908 void (* fp)( int ); $\C{// routine pointer}$ 1909 fp = f; $\C{// reference initialization}$ 1910 fp = &f; $\C{// pointer initialization}$ 1911 fp = *f; $\C{// reference initialization}$ 1912 fp(3); $\C{// reference invocation}$ 1913 (*fp)(3); $\C{// pointer invocation}$ 1927 1914 \end{cfa} 1928 1915 While C's treatment of routine objects has similarity to inferring a reference type in initialization contexts, the examples are assignment not initialization, and all possible forms of assignment are possible (©f©, ©&f©, ©*f©) without regard for type. 1929 1916 Instead, a routine object should be referenced by a ©const© reference: 1930 1917 \begin{cfa} 1931 ®const® void (®&® fr)( int ) = f; §\C{// routine reference}§ 1932 fr = ... §\C{// error, cannot change code}§1933 &fr = ...; §\C{// changing routine reference}§1934 fr( 3 ); §\C{// reference call to f}§1935 (*fr)(3); §\C{// error, incorrect type}§1918 @const@ void (@&@ fr)( int ) = f; $\C{// routine reference}$ 1919 fr = ... $\C{// error, cannot change code}$ 1920 &fr = ...; $\C{// changing routine reference}$ 1921 fr( 3 ); $\C{// reference call to f}$ 1922 (*fr)(3); $\C{// error, incorrect type}$ 1936 1923 \end{cfa} 1937 1924 because the value of the routine object is a routine literal, \ie the routine code is normally immutable during execution.\footnote{ … … 1946 1933 \begin{itemize} 1947 1934 \item 1948 if ©R© is an \Index{rvalue} of type ©T &©$_1\cdots$ ©&©$_r$, where $r \ge 1$ references (©&© symbols), than ©&R© has type ©T ®*®&©$_{\color{red}2}\cdots$ ©&©$_{\color{red}r}$, \ie ©T© pointer with $r-1$ references (©&© symbols).1949 1950 \item 1951 if ©L© is an \Index{lvalue} of type ©T &©$_1\cdots$ ©&©$_l$, where $l \ge 0$ references (©&© symbols), than ©&L© has type ©T ®*®&©$_{\color{red}1}\cdots$ ©&©$_{\color{red}l}$, \ie ©T© pointer with $l$ references (©&© symbols).1935 if ©R© is an \Index{rvalue} of type ©T &©$_1\cdots$ ©&©$_r$, where $r \ge 1$ references (©&© symbols), than ©&R© has type ©T ©\R{©*©}©&©\R{$_2$}$\cdots$ ©&©\R{$_r$}, \ie ©T© pointer with $r-1$ references (©&© symbols). 1936 1937 \item 1938 if ©L© is an \Index{lvalue} of type ©T &©$_1\cdots$ ©&©$_l$, where $l \ge 0$ references (©&© symbols), than ©&L© has type ©T ©\R{©*©}©&©\R{$_1$}$\cdots$ ©&©\R{$_l$}, \ie ©T© pointer with $l$ references (©&© symbols). 1952 1939 \end{itemize} 1953 1940 The following example shows the first rule applied to different \Index{rvalue} contexts: … … 1955 1942 int x, * px, ** ppx, *** pppx, **** ppppx; 1956 1943 int & rx = x, && rrx = rx, &&& rrrx = rrx ; 1957 x = rrrx; §\C[2.0in]{// rrrx is an lvalue with type int \&\&\& (equivalent to x)}§1958 px = &rrrx; §\C{// starting from rrrx, \&rrrx is an rvalue with type int *\&\&\& (\&x)}§1959 ppx = &&rrrx; §\C{// starting from \&rrrx, \&\&rrrx is an rvalue with type int **\&\& (\&rx)}§1960 pppx = &&&rrrx; §\C{// starting from \&\&rrrx, \&\&\&rrrx is an rvalue with type int ***\& (\&rrx)}§1961 ppppx = &&&&rrrx; §\C{// starting from \&\&\&rrrx, \&\&\&\&rrrx is an rvalue with type int **** (\&rrrx)}§1944 x = rrrx; $\C[2.0in]{// rrrx is an lvalue with type int \&\&\& (equivalent to x)}$ 1945 px = &rrrx; $\C{// starting from rrrx, \&rrrx is an rvalue with type int *\&\&\& (\&x)}$ 1946 ppx = &&rrrx; $\C{// starting from \&rrrx, \&\&rrrx is an rvalue with type int **\&\& (\&rx)}$ 1947 pppx = &&&rrrx; $\C{// starting from \&\&rrrx, \&\&\&rrrx is an rvalue with type int ***\& (\&rrx)}$ 1948 ppppx = &&&&rrrx; $\C{// starting from \&\&\&rrrx, \&\&\&\&rrrx is an rvalue with type int **** (\&rrrx)}$ 1962 1949 \end{cfa} 1963 1950 The following example shows the second rule applied to different \Index{lvalue} contexts: … … 1965 1952 int x, * px, ** ppx, *** pppx; 1966 1953 int & rx = x, && rrx = rx, &&& rrrx = rrx ; 1967 rrrx = 2; §\C{// rrrx is an lvalue with type int \&\&\& (equivalent to x)}§1968 &rrrx = px; §\C{// starting from rrrx, \&rrrx is an rvalue with type int *\&\&\& (rx)}§1969 &&rrrx = ppx; §\C{// starting from \&rrrx, \&\&rrrx is an rvalue with type int **\&\& (rrx)}§1970 &&&rrrx = pppx; §\C{// starting from \&\&rrrx, \&\&\&rrrx is an rvalue with type int ***\& (rrrx)}\CRT§1954 rrrx = 2; $\C{// rrrx is an lvalue with type int \&\&\& (equivalent to x)}$ 1955 &rrrx = px; $\C{// starting from rrrx, \&rrrx is an rvalue with type int *\&\&\& (rx)}$ 1956 &&rrrx = ppx; $\C{// starting from \&rrrx, \&\&rrrx is an rvalue with type int **\&\& (rrx)}$ 1957 &&&rrrx = pppx; $\C{// starting from \&\&rrrx, \&\&\&rrrx is an rvalue with type int ***\& (rrrx)}\CRT$ 1971 1958 \end{cfa} 1972 1959 … … 1981 1968 \begin{cfa} 1982 1969 int x; 1983 x + 1; §\C[2.0in]{// lvalue variable (int) converts to rvalue for expression}§1970 x + 1; $\C[2.0in]{// lvalue variable (int) converts to rvalue for expression}$ 1984 1971 \end{cfa} 1985 1972 An rvalue has no type qualifiers (©cv©), so the lvalue qualifiers are dropped. … … 1991 1978 \begin{cfa} 1992 1979 int x, &r = x, f( int p ); 1993 x = ®r® + f( ®r® ); §\C{// lvalue reference converts to rvalue}§1980 x = @r@ + f( @r@ ); $\C{// lvalue reference converts to rvalue}$ 1994 1981 \end{cfa} 1995 1982 An rvalue has no type qualifiers (©cv©), so the reference qualifiers are dropped. … … 1998 1985 lvalue to reference conversion: \lstinline[deletekeywords=lvalue]@lvalue-type cv1 T@ converts to ©cv2 T &©, which allows implicitly converting variables to references. 1999 1986 \begin{cfa} 2000 int x, &r = ®x®, f( int & p ); §\C{// lvalue variable (int) convert to reference (int \&)}§2001 f( ®x® ); §\C{// lvalue variable (int) convert to reference (int \&)}§1987 int x, &r = @x@, f( int & p ); $\C{// lvalue variable (int) convert to reference (int \&)}$ 1988 f( @x@ ); $\C{// lvalue variable (int) convert to reference (int \&)}$ 2002 1989 \end{cfa} 2003 1990 Conversion can restrict a type, where ©cv1© $\le$ ©cv2©, \eg passing an ©int© to a ©const volatile int &©, which has low cost. … … 2009 1996 \begin{cfa} 2010 1997 int x, & f( int & p ); 2011 f( ®x + 3® ); §\C[1.5in]{// rvalue parameter (int) implicitly converts to lvalue temporary reference (int \&)}§2012 ®&f®(...) = &x; §\C{// rvalue result (int \&) implicitly converts to lvalue temporary reference (int \&)}\CRT§ 1998 f( @x + 3@ ); $\C[1.5in]{// rvalue parameter (int) implicitly converts to lvalue temporary reference (int \&)}$ 1999 @&f@(...) = &x; $\C{// rvalue result (int \&) implicitly converts to lvalue temporary reference (int \&)}\CRT$ 2013 2000 \end{cfa} 2014 2001 In both case, modifications to the temporary are inaccessible (\Index{warning}). … … 2182 2169 The point of the new syntax is to allow returning multiple values from a routine~\cite{Galletly96,CLU}, \eg: 2183 2170 \begin{cfa} 2184 ®[ int o1, int o2, char o3 ]®f( int i1, char i2, char i3 ) {2185 §\emph{routine body}§2171 @[ int o1, int o2, char o3 ]@ f( int i1, char i2, char i3 ) { 2172 $\emph{routine body}$ 2186 2173 } 2187 2174 \end{cfa} … … 2194 2181 Declaration qualifiers can only appear at the start of a routine definition, \eg: 2195 2182 \begin{cfa} 2196 ®extern® [ int x ] g( int y ) {§\,§}2183 @extern@ [ int x ] g( int y ) {$\,$} 2197 2184 \end{cfa} 2198 2185 Lastly, if there are no output parameters or input parameters, the brackets and/or parentheses must still be specified; 2199 2186 in both cases the type is assumed to be void as opposed to old style C defaults of int return type and unknown parameter types, respectively, as in: 2200 2187 \begin{cfa} 2201 [ §\,§] g(); §\C{// no input or output parameters}§2202 [ void ] g( void ); §\C{// no input or output parameters}§2188 [$\,$] g(); $\C{// no input or output parameters}$ 2189 [ void ] g( void ); $\C{// no input or output parameters}$ 2203 2190 \end{cfa} 2204 2191 … … 2218 2205 \begin{cfa} 2219 2206 typedef int foo; 2220 int f( int (* foo) ); §\C{// foo is redefined as a parameter name}§2207 int f( int (* foo) ); $\C{// foo is redefined as a parameter name}$ 2221 2208 \end{cfa} 2222 2209 The string ``©int (* foo)©'' declares a C-style named-parameter of type pointer to an integer (the parenthesis are superfluous), while the same string declares a \CFA style unnamed parameter of type routine returning integer with unnamed parameter of type pointer to foo. … … 2226 2213 C-style declarations can be used to declare parameters for \CFA style routine definitions, \eg: 2227 2214 \begin{cfa} 2228 [ int ] f( * int, int * ); §\C{// returns an integer, accepts 2 pointers to integers}§2229 [ * int, int * ] f( int ); §\C{// returns 2 pointers to integers, accepts an integer}§2215 [ int ] f( * int, int * ); $\C{// returns an integer, accepts 2 pointers to integers}$ 2216 [ * int, int * ] f( int ); $\C{// returns 2 pointers to integers, accepts an integer}$ 2230 2217 \end{cfa} 2231 2218 The reason for allowing both declaration styles in the new context is for backwards compatibility with existing preprocessor macros that generate C-style declaration-syntax, as in: 2232 2219 \begin{cfa} 2233 2220 #define ptoa( n, d ) int (*n)[ d ] 2234 int f( ptoa( p, 5 ) ) ... §\C{// expands to int f( int (*p)[ 5 ] )}§2235 [ int ] f( ptoa( p, 5 ) ) ... §\C{// expands to [ int ] f( int (*p)[ 5 ] )}§2221 int f( ptoa( p, 5 ) ) ... $\C{// expands to int f( int (*p)[ 5 ] )}$ 2222 [ int ] f( ptoa( p, 5 ) ) ... $\C{// expands to [ int ] f( int (*p)[ 5 ] )}$ 2236 2223 \end{cfa} 2237 2224 Again, programmers are highly encouraged to use one declaration form or the other, rather than mixing the forms. … … 2252 2239 \begin{minipage}{\linewidth} 2253 2240 \begin{cfa} 2254 ®[ int x, int y ]®f() {2241 @[ int x, int y ]@ f() { 2255 2242 int z; 2256 2243 ... x = 0; ... y = z; ... 2257 ®return;® §\C{// implicitly return x, y}§2244 @return;@ $\C{// implicitly return x, y}$ 2258 2245 } 2259 2246 \end{cfa} … … 2265 2252 [ int x, int y ] f() { 2266 2253 ... 2267 } §\C{// implicitly return x, y}§2254 } $\C{// implicitly return x, y}$ 2268 2255 \end{cfa} 2269 2256 In this case, the current values of ©x© and ©y© are returned to the calling routine just as if a ©return© had been encountered. … … 2274 2261 [ int x, int y ] f( int, x, int y ) { 2275 2262 ... 2276 } §\C{// implicitly return x, y}§2263 } $\C{// implicitly return x, y}$ 2277 2264 \end{cfa} 2278 2265 This notation allows the compiler to eliminate temporary variables in nested routine calls. 2279 2266 \begin{cfa} 2280 [ int x, int y ] f( int, x, int y ); §\C{// prototype declaration}§2267 [ int x, int y ] f( int, x, int y ); $\C{// prototype declaration}$ 2281 2268 int a, b; 2282 2269 [a, b] = f( f( f( a, b ) ) ); … … 2292 2279 as well, parameter names are optional, \eg: 2293 2280 \begin{cfa} 2294 [ int x ] f (); §\C{// returning int with no parameters}§2295 [ * int ] g (int y); §\C{// returning pointer to int with int parameter}§2296 [ ] h ( int, char ); §\C{// returning no result with int and char parameters}§2297 [ * int, int ] j ( int ); §\C{// returning pointer to int and int, with int parameter}§2281 [ int x ] f (); $\C{// returning int with no parameters}$ 2282 [ * int ] g (int y); $\C{// returning pointer to int with int parameter}$ 2283 [ ] h ( int, char ); $\C{// returning no result with int and char parameters}$ 2284 [ * int, int ] j ( int ); $\C{// returning pointer to int and int, with int parameter}$ 2298 2285 \end{cfa} 2299 2286 This syntax allows a prototype declaration to be created by cutting and pasting source text from the routine definition header (or vice versa). 2300 Like C, it is possible to declare multiple routine-prototypes in a single declaration, where the return type is distributed across \emph{all} routine names in the declaration list (see~\VRef{s:AlternativeDeclarations}), \eg:2287 Like C, it is possible to declare multiple routine-prototypes in a single declaration, where the return type is distributed across \emph{all} routine names in the declaration list \see{\VRef{s:AlternativeDeclarations}}, \eg: 2301 2288 \begin{cfa} 2302 2289 C : const double bar1(), bar2( int ), bar3( double ); 2303 §\CFA§: [const double] foo(), foo( int ), foo( double ) { return 3.0; }2290 $\CFA$: [const double] foo(), foo( int ), foo( double ) { return 3.0; } 2304 2291 \end{cfa} 2305 2292 \CFA allows the last routine in the list to define its body. … … 2316 2303 The syntax for pointers to \CFA routines specifies the pointer name on the right, \eg: 2317 2304 \begin{cfa} 2318 * [ int x ] () fp; §\C{// pointer to routine returning int with no parameters}§2319 * [ * int ] (int y) gp; §\C{// pointer to routine returning pointer to int with int parameter}§2320 * [ ] (int,char) hp; §\C{// pointer to routine returning no result with int and char parameters}§2321 * [ * int,int ] ( int ) jp; §\C{// pointer to routine returning pointer to int and int, with int parameter}§2305 * [ int x ] () fp; $\C[2.25in]{// pointer to routine returning int with no parameters}$ 2306 * [ * int ] (int y) gp; $\C{// pointer to routine returning pointer to int with int parameter}$ 2307 * [ ] (int,char) hp; $\C{// pointer to routine returning no result with int and char parameters}$ 2308 * [ * int,int ] ( int ) jp; $\C{// pointer to routine returning pointer to int and int, with int parameter}\CRT$ 2322 2309 \end{cfa} 2323 2310 While parameter names are optional, \emph{a routine name cannot be specified}; 2324 2311 for example, the following is incorrect: 2325 2312 \begin{cfa} 2326 * [ int x ] f () fp; §\C{// routine name "f" is not allowed}§2313 * [ int x ] f () fp; $\C{// routine name "f" is not allowed}$ 2327 2314 \end{cfa} 2328 2315 … … 2347 2334 whereas a named (keyword) call may be: 2348 2335 \begin{cfa} 2349 p( z : 3, x : 4, y : 7 ); §\C{// rewrite $\Rightarrow$ p( 4, 7, 3 )}§2336 p( z : 3, x : 4, y : 7 ); $\C{// rewrite \(\Rightarrow\) p( 4, 7, 3 )}$ 2350 2337 \end{cfa} 2351 2338 Here the order of the arguments is unimportant, and the names of the parameters are used to associate argument values with the corresponding parameters. … … 2364 2351 For example, the following routine prototypes and definition are all valid. 2365 2352 \begin{cfa} 2366 void p( int, int, int ); §\C{// equivalent prototypes}§2353 void p( int, int, int ); $\C{// equivalent prototypes}$ 2367 2354 void p( int x, int y, int z ); 2368 2355 void p( int y, int x, int z ); 2369 2356 void p( int z, int y, int x ); 2370 void p( int q, int r, int s ) {} §\C{// match with this definition}§2357 void p( int q, int r, int s ) {} $\C{// match with this definition}$ 2371 2358 \end{cfa} 2372 2359 Forcing matching parameter names in routine prototypes with corresponding routine definitions is possible, but goes against a strong tradition in C programming. … … 2380 2367 int f( int x, double y ); 2381 2368 2382 f( j : 3, i : 4 ); §\C{// 1st f}§2383 f( x : 7, y : 8.1 ); §\C{// 2nd f}§2384 f( 4, 5 ); §\C{// ambiguous call}§2369 f( j : 3, i : 4 ); $\C{// 1st f}$ 2370 f( x : 7, y : 8.1 ); $\C{// 2nd f}$ 2371 f( 4, 5 ); $\C{// ambiguous call}$ 2385 2372 \end{cfa} 2386 2373 However, named arguments compound routine resolution in conjunction with conversions: 2387 2374 \begin{cfa} 2388 f( i : 3, 5.7 ); §\C{// ambiguous call ?}§2375 f( i : 3, 5.7 ); $\C{// ambiguous call ?}$ 2389 2376 \end{cfa} 2390 2377 Depending on the cost associated with named arguments, this call could be resolvable or ambiguous. … … 2400 2387 the allowable positional calls are: 2401 2388 \begin{cfa} 2402 p(); §\C{// rewrite $\Rightarrow$ p( 1, 2, 3 )}§2403 p( 4 ); §\C{// rewrite $\Rightarrow$ p( 4, 2, 3 )}§2404 p( 4, 4 ); §\C{// rewrite $\Rightarrow$ p( 4, 4, 3 )}§2405 p( 4, 4, 4 ); §\C{// rewrite $\Rightarrow$ p( 4, 4, 4 )}§2389 p(); $\C{// rewrite \(\Rightarrow\) p( 1, 2, 3 )}$ 2390 p( 4 ); $\C{// rewrite \(\Rightarrow\) p( 4, 2, 3 )}$ 2391 p( 4, 4 ); $\C{// rewrite \(\Rightarrow\) p( 4, 4, 3 )}$ 2392 p( 4, 4, 4 ); $\C{// rewrite \(\Rightarrow\) p( 4, 4, 4 )}$ 2406 2393 // empty arguments 2407 p( , 4, 4 ); §\C{// rewrite $\Rightarrow$ p( 1, 4, 4 )}§2408 p( 4, , 4 ); §\C{// rewrite $\Rightarrow$ p( 4, 2, 4 )}§2409 p( 4, 4, ); §\C{// rewrite $\Rightarrow$ p( 4, 4, 3 )}§2410 p( 4, , ); §\C{// rewrite $\Rightarrow$ p( 4, 2, 3 )}§2411 p( , 4, ); §\C{// rewrite $\Rightarrow$ p( 1, 4, 3 )}§2412 p( , , 4 ); §\C{// rewrite $\Rightarrow$ p( 1, 2, 4 )}§2413 p( , , ); §\C{// rewrite $\Rightarrow$ p( 1, 2, 3 )}§2394 p( , 4, 4 ); $\C{// rewrite \(\Rightarrow\) p( 1, 4, 4 )}$ 2395 p( 4, , 4 ); $\C{// rewrite \(\Rightarrow\) p( 4, 2, 4 )}$ 2396 p( 4, 4, ); $\C{// rewrite \(\Rightarrow\) p( 4, 4, 3 )}$ 2397 p( 4, , ); $\C{// rewrite \(\Rightarrow\) p( 4, 2, 3 )}$ 2398 p( , 4, ); $\C{// rewrite \(\Rightarrow\) p( 1, 4, 3 )}$ 2399 p( , , 4 ); $\C{// rewrite \(\Rightarrow\) p( 1, 2, 4 )}$ 2400 p( , , ); $\C{// rewrite \(\Rightarrow\) p( 1, 2, 3 )}$ 2414 2401 \end{cfa} 2415 2402 Here the missing arguments are inserted from the default values in the parameter list. … … 2435 2422 Default values may only appear in a prototype versus definition context: 2436 2423 \begin{cfa} 2437 void p( int x, int y = 2, int z = 3 ); §\C{// prototype: allowed}§2438 void p( int, int = 2, int = 3 ); §\C{// prototype: allowed}§2439 void p( int x, int y = 2, int z = 3 ) {} §\C{// definition: not allowed}§2424 void p( int x, int y = 2, int z = 3 ); $\C{// prototype: allowed}$ 2425 void p( int, int = 2, int = 3 ); $\C{// prototype: allowed}$ 2426 void p( int x, int y = 2, int z = 3 ) {} $\C{// definition: not allowed}$ 2440 2427 \end{cfa} 2441 2428 The reason for this restriction is to allow separate compilation. … … 2452 2439 \begin{cfa} 2453 2440 p( int x, int y, int z, ... ); 2454 p( 1, 4, 5, 6, z : 3, y : 2 ); §\C{// assume p( /* positional */, ... , /* named */ );}§2455 p( 1, z : 3, y : 2, 4, 5, 6 ); §\C{// assume p( /* positional */, /* named */, ... );}§2441 p( 1, 4, 5, 6, z : 3, y : 2 ); $\C{// assume p( /* positional */, ... , /* named */ );}$ 2442 p( 1, z : 3, y : 2, 4, 5, 6 ); $\C{// assume p( /* positional */, /* named */, ... );}$ 2456 2443 \end{cfa} 2457 2444 In the first call, it is necessary for the programmer to conceptually rewrite the call, changing named arguments into positional, before knowing where the ellipse arguments begin. … … 2462 2449 \begin{cfa} 2463 2450 void p( int x, int y = 2, int z = 3... ); 2464 p( 1, 4, 5, 6, z : 3 ); §\C{// assume p( /* positional */, ... , /* named */ );}§2465 p( 1, z : 3, 4, 5, 6 ); §\C{// assume p( /* positional */, /* named */, ... );}§2451 p( 1, 4, 5, 6, z : 3 ); $\C{// assume p( /* positional */, ... , /* named */ );}$ 2452 p( 1, z : 3, 4, 5, 6 ); $\C{// assume p( /* positional */, /* named */, ... );}$ 2466 2453 \end{cfa} 2467 2454 The first call is an error because arguments 4 and 5 are actually positional not ellipse arguments; … … 2469 2456 In the second call, the default value for y is implicitly inserted after argument 1 and the named arguments separate the positional and ellipse arguments, making it trivial to read the call. 2470 2457 For these reasons, \CFA requires named arguments before ellipse arguments. 2471 Finally, while ellipse arguments are needed for a small set of existing C routines, like printf, the extended \CFA type system largely eliminates the need for ellipse arguments (see Section 24), making much of this discussion moot.2472 2473 Default arguments and overloading (see Section 24)are complementary.2458 Finally, while ellipse arguments are needed for a small set of existing C routines, like ©printf©, the extended \CFA type system largely eliminates the need for ellipse arguments \see{\VRef{s:Overloading}}, making much of this discussion moot. 2459 2460 Default arguments and overloading \see{\VRef{s:Overloading}} are complementary. 2474 2461 While in theory default arguments can be simulated with overloading, as in: 2475 2462 \begin{cquote} … … 2493 2480 Furthermore, overloading cannot handle accessing default arguments in the middle of a positional list, via a missing argument, such as: 2494 2481 \begin{cfa} 2495 p( 1, /* default */, 5 ); §\C{// rewrite $\Rightarrow$ p( 1, 2, 5 )}§2482 p( 1, /* default */, 5 ); $\C{// rewrite \(\Rightarrow\) p( 1, 2, 5 )}$ 2496 2483 \end{cfa} 2497 2484 … … 2506 2493 \begin{cfa} 2507 2494 struct { 2508 int f1; §\C{// named field}§2509 int f2 : 4; §\C{// named field with bit field size}§2510 int : 3; §\C{// unnamed field for basic type with bit field size}§2511 int ; §\C{// disallowed, unnamed field}§2512 int *; §\C{// disallowed, unnamed field}§2513 int (*)( int ); §\C{// disallowed, unnamed field}§2495 int f1; $\C{// named field}$ 2496 int f2 : 4; $\C{// named field with bit field size}$ 2497 int : 3; $\C{// unnamed field for basic type with bit field size}$ 2498 int ; $\C{// disallowed, unnamed field}$ 2499 int *; $\C{// disallowed, unnamed field}$ 2500 int (*)( int ); $\C{// disallowed, unnamed field}$ 2514 2501 }; 2515 2502 \end{cfa} … … 2519 2506 \begin{cfa} 2520 2507 struct { 2521 int , , ; §\C{// 3 unnamed fields}§2508 int , , ; $\C{// 3 unnamed fields}$ 2522 2509 } 2523 2510 \end{cfa} … … 2531 2518 \subsection{Type Nesting} 2532 2519 2533 \CFA allows \Index{type nesting}, and type qualification of the nested types (see \VRef[Figure]{f:TypeNestingQualification}), where as C hoists\index{type hoisting} (refactors) nested types into the enclosing scope and has no type qualification.2520 \CFA allows \Index{type nesting}, and type qualification of the nested types \see{\VRef[Figure]{f:TypeNestingQualification}}, where as C hoists\index{type hoisting} (refactors) nested types into the enclosing scope and has no type qualification. 2534 2521 \begin{figure} 2535 2522 \centering … … 2587 2574 2588 2575 int fred() { 2589 s.t.c = ®S.®R; // type qualification2590 struct ®S.®T t = { ®S.®R, 1, 2 };2591 enum ®S.®C c;2592 union ®S.T.®U u;2576 s.t.c = @S.@R; // type qualification 2577 struct @S.@T t = { @S.@R, 1, 2 }; 2578 enum @S.@C c; 2579 union @S.T.@U u; 2593 2580 } 2594 2581 \end{cfa} … … 2613 2600 const unsigned int size = 5; 2614 2601 int ia[size]; 2615 ... §\C{// assign values to array ia}§2616 qsort( ia, size ); §\C{// sort ascending order using builtin ?<?}§2602 ... $\C{// assign values to array ia}$ 2603 qsort( ia, size ); $\C{// sort ascending order using builtin ?<?}$ 2617 2604 { 2618 ®int ?<?( int x, int y ) { return x > y; }® §\C{// nested routine}§2619 qsort( ia, size ); §\C{// sort descending order by local redefinition}§2605 @int ?<?( int x, int y ) { return x > y; }@ $\C{// nested routine}$ 2606 qsort( ia, size ); $\C{// sort descending order by local redefinition}$ 2620 2607 } 2621 2608 \end{cfa} … … 2625 2612 The following program in undefined in \CFA (and Indexc{gcc}) 2626 2613 \begin{cfa} 2627 [* [int]( int )] foo() { §\C{// int (* foo())( int )}§2628 int ®i®= 7;2614 [* [int]( int )] foo() { $\C{// int (* foo())( int )}$ 2615 int @i@ = 7; 2629 2616 int bar( int p ) { 2630 ®i® += 1; §\C{// dependent on local variable}§2631 sout | ®i®;2617 @i@ += 1; $\C{// dependent on local variable}$ 2618 sout | @i@; 2632 2619 } 2633 return bar; §\C{// undefined because of local dependence}§2620 return bar; $\C{// undefined because of local dependence}$ 2634 2621 } 2635 2622 int main() { 2636 * [int]( int ) fp = foo(); §\C{// int (* fp)( int )}§2623 * [int]( int ) fp = foo(); $\C{// int (* fp)( int )}$ 2637 2624 sout | fp( 3 ); 2638 2625 } … … 2647 2634 In C and \CFA, lists of elements appear in several contexts, such as the parameter list of a routine call. 2648 2635 \begin{cfa} 2649 f( ®2, x, 3 + i® ); §\C{// element list}§2636 f( @2, x, 3 + i@ ); $\C{// element list}$ 2650 2637 \end{cfa} 2651 2638 A list of elements is called a \newterm{tuple}, and is different from a \Index{comma expression}. … … 2656 2643 2657 2644 In C and most programming languages, functions return at most one value; 2658 however, many operations have multiple outcomes, some exceptional (see~\VRef{s:ExceptionHandling}).2645 however, many operations have multiple outcomes, some exceptional \see{\VRef{s:ExceptionHandling}}. 2659 2646 To emulate functions with multiple return values, \emph{\Index{aggregation}} and/or \emph{\Index{aliasing}} is used. 2660 2647 … … 2662 2649 For example, consider C's \Indexc{div} function, which returns the quotient and remainder for a division of an integer value. 2663 2650 \begin{cfa} 2664 typedef struct { int quot, rem; } div_t; §\C[7cm]{// from include stdlib.h}§2651 typedef struct { int quot, rem; } div_t; $\C[7cm]{// from include stdlib.h}$ 2665 2652 div_t div( int num, int den ); 2666 div_t qr = div( 13, 5 ); §\C{// return quotient/remainder aggregate}§2667 printf( "%d %d\n", qr.quot, qr.rem ); §\C{// print quotient/remainder}§2653 div_t qr = div( 13, 5 ); $\C{// return quotient/remainder aggregate}$ 2654 printf( "%d %d\n", qr.quot, qr.rem ); $\C{// print quotient/remainder}$ 2668 2655 \end{cfa} 2669 2656 This approach requires a name for the return type and fields, where \Index{naming} is a common programming-language issue. … … 2675 2662 For example, consider C's \Indexc{modf} function, which returns the integral and fractional part of a floating value. 2676 2663 \begin{cfa} 2677 double modf( double x, double * i ); §\C{// from include math.h}§2678 double intp, frac = modf( 13.5, &intp ); §\C{// return integral and fractional components}§2679 printf( "%g %g\n", intp, frac ); §\C{// print integral/fractional components}§2664 double modf( double x, double * i ); $\C{// from include math.h}$ 2665 double intp, frac = modf( 13.5, &intp ); $\C{// return integral and fractional components}$ 2666 printf( "%g %g\n", intp, frac ); $\C{// print integral/fractional components}$ 2680 2667 \end{cfa} 2681 2668 This approach requires allocating storage for the return values, which complicates the call site with a sequence of variable declarations leading to the call. … … 2704 2691 When a function call is passed as an argument to another call, the best match of actual arguments to formal parameters is evaluated given all possible expression interpretations in the current scope. 2705 2692 \begin{cfa} 2706 void g( int, int ); §\C{// 1}§2707 void g( double, double ); §\C{// 2}§2708 g( div( 13, 5 ) ); §\C{// select 1}§2709 g( modf( 13.5 ) ); §\C{// select 2}§2693 void g( int, int ); $\C{// 1}$ 2694 void g( double, double ); $\C{// 2}$ 2695 g( div( 13, 5 ) ); $\C{// select 1}$ 2696 g( modf( 13.5 ) ); $\C{// select 2}$ 2710 2697 \end{cfa} 2711 2698 In this case, there are two overloaded ©g© routines. … … 2716 2703 The previous examples can be rewritten passing the multiple returned-values directly to the ©printf© function call. 2717 2704 \begin{cfa} 2718 [ int, int ] div( int x, int y ); §\C{// from include stdlib}§2719 printf( "%d %d\n", div( 13, 5 ) ); §\C{// print quotient/remainder}§2720 2721 [ double, double ] modf( double x ); §\C{// from include math}§2722 printf( "%g %g\n", modf( 13.5 ) ); §\C{// print integral/fractional components}§2705 [ int, int ] div( int x, int y ); $\C{// from include stdlib}$ 2706 printf( "%d %d\n", div( 13, 5 ) ); $\C{// print quotient/remainder}$ 2707 2708 [ double, double ] modf( double x ); $\C{// from include math}$ 2709 printf( "%g %g\n", modf( 13.5 ) ); $\C{// print integral/fractional components}$ 2723 2710 \end{cfa} 2724 2711 This approach provides the benefits of compile-time checking for appropriate return statements as in aggregation, but without the required verbosity of declaring a new named type. … … 2730 2717 \begin{cfa} 2731 2718 int quot, rem; 2732 [ quot, rem ] = div( 13, 5 ); §\C{// assign multiple variables}§2733 printf( "%d %d\n", quot, rem ); §\C{// print quotient/remainder}\CRT§2719 [ quot, rem ] = div( 13, 5 ); $\C{// assign multiple variables}$ 2720 printf( "%d %d\n", quot, rem ); $\C{// print quotient/remainder}\CRT$ 2734 2721 \end{cfa} 2735 2722 Here, the multiple return-values are matched in much the same way as passing multiple return-values to multiple parameters in a call. … … 2760 2747 In \CFA, it is possible to overcome this restriction by declaring a \newterm{tuple variable}. 2761 2748 \begin{cfa} 2762 [int, int] ®qr® = div( 13, 5 ); §\C{// initialize tuple variable}§2763 printf( "%d %d\n", ®qr® ); §\C{// print quotient/remainder}§2749 [int, int] @qr@ = div( 13, 5 ); $\C{// initialize tuple variable}$ 2750 printf( "%d %d\n", @qr@ ); $\C{// print quotient/remainder}$ 2764 2751 \end{cfa} 2765 2752 It is now possible to match the multiple return-values to a single variable, in much the same way as \Index{aggregation}. … … 2767 2754 One way to access the individual components of a tuple variable is with assignment. 2768 2755 \begin{cfa} 2769 [ quot, rem ] = qr; §\C{// assign multiple variables}§2756 [ quot, rem ] = qr; $\C{// assign multiple variables}$ 2770 2757 \end{cfa} 2771 2758 … … 2790 2777 [int, double] * p; 2791 2778 2792 int y = x.0; §\C{// access int component of x}§2793 y = f().1; §\C{// access int component of f}§2794 p->0 = 5; §\C{// access int component of tuple pointed-to by p}§2795 g( x.1, x.0 ); §\C{// rearrange x to pass to g}§2796 double z = [ x, f() ].0.1; §\C{// access second component of first component of tuple expression}§2779 int y = x.0; $\C{// access int component of x}$ 2780 y = f().1; $\C{// access int component of f}$ 2781 p->0 = 5; $\C{// access int component of tuple pointed-to by p}$ 2782 g( x.1, x.0 ); $\C{// rearrange x to pass to g}$ 2783 double z = [ x, f() ].0.1; $\C{// access second component of first component of tuple expression}$ 2797 2784 \end{cfa} 2798 2785 Tuple-index expressions can occur on any tuple-typed expression, including tuple-returning functions, square-bracketed tuple expressions, and other tuple-index expressions, provided the retrieved component is also a tuple. … … 2801 2788 2802 2789 \subsection{Flattening and Structuring} 2790 \label{s:FlatteningStructuring} 2803 2791 2804 2792 As evident in previous examples, tuples in \CFA do not have a rigid structure. … … 2861 2849 double y; 2862 2850 [int, double] z; 2863 [y, x] = 3.14; §\C{// mass assignment}§2864 [x, y] = z; §\C{// multiple assignment}§2865 z = 10; §\C{// mass assignment}§2866 z = [x, y]; §\C{// multiple assignment}§2851 [y, x] = 3.14; $\C{// mass assignment}$ 2852 [x, y] = z; $\C{// multiple assignment}$ 2853 z = 10; $\C{// mass assignment}$ 2854 z = [x, y]; $\C{// multiple assignment}$ 2867 2855 \end{cfa} 2868 2856 Let $L_i$ for $i$ in $[0, n)$ represent each component of the flattened left side, $R_i$ represent each component of the flattened right side of a multiple assignment, and $R$ represent the right side of a mass assignment. … … 2872 2860 \begin{cfa} 2873 2861 [ int, int ] x, y, z; 2874 [ x, y ] = z; §\C{// multiple assignment, invalid 4 != 2}§2862 [ x, y ] = z; $\C{// multiple assignment, invalid 4 != 2}$ 2875 2863 \end{cfa} 2876 2864 Multiple assignment assigns $R_i$ to $L_i$ for each $i$. … … 2908 2896 double c, d; 2909 2897 [ void ] f( [ int, int ] ); 2910 f( [ c, a ] = [ b, d ] = 1.5 ); §\C{// assignments in parameter list}§2898 f( [ c, a ] = [ b, d ] = 1.5 ); $\C{// assignments in parameter list}$ 2911 2899 \end{cfa} 2912 2900 The tuple expression begins with a mass assignment of ©1.5© into ©[b, d]©, which assigns ©1.5© into ©b©, which is truncated to ©1©, and ©1.5© into ©d©, producing the tuple ©[1, 1.5]© as a result. … … 2921 2909 \begin{cfa} 2922 2910 struct S; 2923 void ?{}(S *); §\C{// (1)}§2924 void ?{}(S *, int); §\C{// (2)}§2925 void ?{}(S * double); §\C{// (3)}§2926 void ?{}(S *, S); §\C{// (4)}§2927 2928 [S, S] x = [3, 6.28]; §\C{// uses (2), (3), specialized constructors}§2929 [S, S] y; §\C{// uses (1), (1), default constructor}§2930 [S, S] z = x.0; §\C{// uses (4), (4), copy constructor}§2911 void ?{}(S *); $\C{// (1)}$ 2912 void ?{}(S *, int); $\C{// (2)}$ 2913 void ?{}(S * double); $\C{// (3)}$ 2914 void ?{}(S *, S); $\C{// (4)}$ 2915 2916 [S, S] x = [3, 6.28]; $\C{// uses (2), (3), specialized constructors}$ 2917 [S, S] y; $\C{// uses (1), (1), default constructor}$ 2918 [S, S] z = x.0; $\C{// uses (4), (4), copy constructor}$ 2931 2919 \end{cfa} 2932 2920 In this example, ©x© is initialized by the multiple constructor calls ©?{}(&x.0, 3)© and ©?{}(&x.1, 6.28)©, while ©y© is initialized by two default constructor calls ©?{}(&y.0)© and ©?{}(&y.1)©. … … 2969 2957 A member-access tuple may be used anywhere a tuple can be used, \eg: 2970 2958 \begin{cfa} 2971 s.[ y, z, x ] = [ 3, 3.2, 'x' ]; §\C{// equivalent to s.x = 'x', s.y = 3, s.z = 3.2}§2972 f( s.[ y, z ] ); §\C{// equivalent to f( s.y, s.z )}§2959 s.[ y, z, x ] = [ 3, 3.2, 'x' ]; $\C{// equivalent to s.x = 'x', s.y = 3, s.z = 3.2}$ 2960 f( s.[ y, z ] ); $\C{// equivalent to f( s.y, s.z )}$ 2973 2961 \end{cfa} 2974 2962 Note, the fields appearing in a record-field tuple may be specified in any order; … … 2980 2968 void f( double, long ); 2981 2969 2982 f( x.[ 0, 3 ] ); §\C{// f( x.0, x.3 )}§2983 x.[ 0, 1 ] = x.[ 1, 0 ]; §\C{// [ x.0, x.1 ] = [ x.1, x.0 ]}§2970 f( x.[ 0, 3 ] ); $\C{// f( x.0, x.3 )}$ 2971 x.[ 0, 1 ] = x.[ 1, 0 ]; $\C{// [ x.0, x.1 ] = [ x.1, x.0 ]}$ 2984 2972 [ long, int, long ] y = x.[ 2, 0, 2 ]; 2985 2973 \end{cfa} … … 2998 2986 \begin{cfa} 2999 2987 [ int, float, double ] f(); 3000 [ double, float ] x = f().[ 2, 1 ]; §\C{// f() called once}§2988 [ double, float ] x = f().[ 2, 1 ]; $\C{// f() called once}$ 3001 2989 \end{cfa} 3002 2990 … … 3011 2999 That is, a cast can be used to select the type of an expression when it is ambiguous, as in the call to an overloaded function. 3012 3000 \begin{cfa} 3013 int f(); §\C{// (1)}§3014 double f(); §\C{// (2)}§3015 3016 f(); §\C{// ambiguous - (1),(2) both equally viable}§3017 (int)f(); §\C{// choose (2)}§3001 int f(); $\C{// (1)}$ 3002 double f(); $\C{// (2)}$ 3003 3004 f(); $\C{// ambiguous - (1),(2) both equally viable}$ 3005 (int)f(); $\C{// choose (2)}$ 3018 3006 \end{cfa} 3019 3007 Since casting is a fundamental operation in \CFA, casts need to be given a meaningful interpretation in the context of tuples. … … 3023 3011 void g(); 3024 3012 3025 (void)f(); §\C{// valid, ignore results}§3026 (int)g(); §\C{// invalid, void cannot be converted to int}§3013 (void)f(); $\C{// valid, ignore results}$ 3014 (int)g(); $\C{// invalid, void cannot be converted to int}$ 3027 3015 3028 3016 struct A { int x; }; 3029 (struct A)f(); §\C{// invalid, int cannot be converted to A}§3017 (struct A)f(); $\C{// invalid, int cannot be converted to A}$ 3030 3018 \end{cfa} 3031 3019 In C, line 4 is a valid cast, which calls ©f© and discards its result. … … 3043 3031 [int, [int, int], int] g(); 3044 3032 3045 ([int, double])f(); §\C{// (1) valid}§3046 ([int, int, int])g(); §\C{// (2) valid}§3047 ([void, [int, int]])g(); §\C{// (3) valid}§3048 ([int, int, int, int])g(); §\C{// (4) invalid}§3049 ([int, [int, int, int]])g(); §\C{// (5) invalid}§3033 ([int, double])f(); $\C{// (1) valid}$ 3034 ([int, int, int])g(); $\C{// (2) valid}$ 3035 ([void, [int, int]])g(); $\C{// (3) valid}$ 3036 ([int, int, int, int])g(); $\C{// (4) invalid}$ 3037 ([int, [int, int, int]])g(); $\C{// (5) invalid}$ 3050 3038 \end{cfa} 3051 3039 … … 3107 3095 void f([int, int], int, int); 3108 3096 3109 f([0, 0], 0, 0); §\C{// no cost}§3110 f(0, 0, 0, 0); §\C{// cost for structuring}§3111 f([0, 0,], [0, 0]); §\C{// cost for flattening}§3112 f([0, 0, 0], 0); §\C{// cost for flattening and structuring}§3097 f([0, 0], 0, 0); $\C{// no cost}$ 3098 f(0, 0, 0, 0); $\C{// cost for structuring}$ 3099 f([0, 0,], [0, 0]); $\C{// cost for flattening}$ 3100 f([0, 0, 0], 0); $\C{// cost for flattening and structuring}$ 3113 3101 \end{cfa} 3114 3102 … … 3146 3134 The general syntax of a lexical list is: 3147 3135 \begin{cfa} 3148 [ §\emph{exprlist}§]3136 [ $\emph{exprlist}$ ] 3149 3137 \end{cfa} 3150 3138 where ©$\emph{exprlist}$© is a list of one or more expressions separated by commas. … … 3158 3146 Tuples are permitted to contain sub-tuples (\ie nesting), such as ©[ [ 14, 21 ], 9 ]©, which is a 2-element tuple whose first element is itself a tuple. 3159 3147 Note, a tuple is not a record (structure); 3160 a record denotes a single value with substructure, whereas a tuple is multiple values with no substructure (see flattening coercion in Section 12.1).3148 a record denotes a single value with substructure, whereas a tuple is multiple values with no substructure \see{flattening coercion in \VRef{s:FlatteningStructuring}}. 3161 3149 In essence, tuples are largely a compile time phenomenon, having little or no runtime presence. 3162 3150 … … 3166 3154 The general syntax of a tuple type is: 3167 3155 \begin{cfa} 3168 [ §\emph{typelist}§]3156 [ $\emph{typelist}$ ] 3169 3157 \end{cfa} 3170 3158 where ©$\emph{typelist}$© is a list of one or more legal \CFA or C type specifications separated by commas, which may include other tuple type specifications. … … 3173 3161 [ unsigned int, char ] 3174 3162 [ double, double, double ] 3175 [ * int, int * ] §\C{// mix of CFA and ANSI}§3163 [ * int, int * ] $\C{// mix of CFA and ANSI}$ 3176 3164 [ * [ 5 ] int, * * char, * [ [ int, int ] ] (int, int) ] 3177 3165 \end{cfa} … … 3180 3168 Examples of declarations using tuple types are: 3181 3169 \begin{cfa} 3182 [ int, int ] x; §\C{// 2 element tuple, each element of type int}§3183 * [ char, char ] y; §\C{// pointer to a 2 element tuple}§3170 [ int, int ] x; $\C{// 2 element tuple, each element of type int}$ 3171 * [ char, char ] y; $\C{// pointer to a 2 element tuple}$ 3184 3172 [ [ int, int ] ] z ([ int, int ]); 3185 3173 \end{cfa} … … 3198 3186 [ int, int ] w1; 3199 3187 [ int, int, int ] w2; 3200 [ void ] f (int, int, int); §\C{// three input parameters of type int}§3201 [ void ] g ([ int, int, int ]); §\C{3 element tuple as input}§3188 [ void ] f (int, int, int); $\C{// three input parameters of type int}$ 3189 [ void ] g ([ int, int, int ]); $\C{3 element tuple as input}$ 3202 3190 f( [ 1, 2, 3 ] ); 3203 3191 f( w1, 3 ); … … 3279 3267 [ int, int, int, int ] w = [ 1, 2, 3, 4 ]; 3280 3268 int x = 5; 3281 [ x, w ] = [ w, x ]; §\C{// all four tuple coercions}§3269 [ x, w ] = [ w, x ]; $\C{// all four tuple coercions}$ 3282 3270 \end{cfa} 3283 3271 Starting on the right-hand tuple in the last assignment statement, w is opened, producing a tuple of four values; … … 3285 3273 This tuple is then flattened, yielding ©[ 1, 2, 3, 4, 5 ]©, which is structured into ©[ 1, [ 2, 3, 4, 5 ] ]© to match the tuple type of the left-hand side. 3286 3274 The tuple ©[ 2, 3, 4, 5 ]© is then closed to create a tuple value. 3287 Finally, ©x© is assigned ©1© and ©w© is assigned the tuple value using multiple assignment (see Section 14).3275 Finally, ©x© is assigned ©1© and ©w© is assigned the tuple value using \Index{multiple assignment} \see{\VRef{s:TupleAssignment}}. 3288 3276 \begin{rationale} 3289 3277 A possible additional language extension is to use the structuring coercion for tuples to initialize a complex record with a tuple. … … 3296 3284 Mass assignment has the following form: 3297 3285 \begin{cfa} 3298 [ §\emph{lvalue}§, ... , §\emph{lvalue}§ ] = §\emph{expr}§;3286 [ $\emph{lvalue}$, ... , $\emph{lvalue}$ ] = $\emph{expr}$; 3299 3287 \end{cfa} 3300 3288 \index{lvalue} … … 3336 3324 Multiple assignment has the following form: 3337 3325 \begin{cfa} 3338 [ §\emph{lvalue}§, ... , §\emph{lvalue}§ ] = [ §\emph{expr}§, ... , §\emph{expr}§];3326 [ $\emph{lvalue}$, ... , $\emph{lvalue}$ ] = [ $\emph{expr}$, ... , $\emph{expr}$ ]; 3339 3327 \end{cfa} 3340 3328 \index{lvalue} … … 3367 3355 both these examples produce indeterminate results: 3368 3356 \begin{cfa} 3369 f( x++, x++ ); §\C{// C routine call with side effects in arguments}§3370 [ v1, v2 ] = [ x++, x++ ]; §\C{// side effects in righthand side of multiple assignment}§3357 f( x++, x++ ); $\C{// C routine call with side effects in arguments}$ 3358 [ v1, v2 ] = [ x++, x++ ]; $\C{// side effects in right-hand side of multiple assignment}$ 3371 3359 \end{cfa} 3372 3360 … … 3377 3365 Cascade assignment has the following form: 3378 3366 \begin{cfa} 3379 §\emph{tuple}§ = §\emph{tuple}§ = ... = §\emph{tuple}§;3367 $\emph{tuple}$ = $\emph{tuple}$ = ... = $\emph{tuple}$; 3380 3368 \end{cfa} 3381 3369 and it has the same parallel semantics as for mass and multiple assignment. … … 3424 3412 \begin{cfa} 3425 3413 int x = 1, y = 2, z = 3; 3426 sout | x ®|® y ®|®z;3414 sout | x @|@ y @|@ z; 3427 3415 \end{cfa} 3428 3416 & 3429 3417 \begin{cfa} 3430 3418 3431 cout << x ®<< " "® << y ®<< " "®<< z << endl;3419 cout << x @<< " "@ << y @<< " "@ << z << endl; 3432 3420 \end{cfa} 3433 3421 & … … 3438 3426 \\ 3439 3427 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3440 1 ® ®2® ®33428 1@ @2@ @3 3441 3429 \end{cfa} 3442 3430 & 3443 3431 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3444 1 ® ®2® ®33432 1@ @2@ @3 3445 3433 \end{cfa} 3446 3434 & 3447 3435 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3448 1 ® ®2® ®33436 1@ @2@ @3 3449 3437 \end{cfa} 3450 3438 \end{tabular} … … 3454 3442 \begin{cfa} 3455 3443 [int, [ int, int ] ] t1 = [ 1, [ 2, 3 ] ], t2 = [ 4, [ 5, 6 ] ]; 3456 sout | t1 | t2; §\C{// print tuples}§3444 sout | t1 | t2; $\C{// print tuples}$ 3457 3445 \end{cfa} 3458 3446 \begin{cfa}[showspaces=true,aboveskip=0pt] 3459 1 ®, ®2®, ®3 4®, ®5®, ®63447 1@, @2@, @3 4@, @5@, @6 3460 3448 \end{cfa} 3461 3449 Finally, \CFA uses the logical-or operator for I/O as it is the lowest-priority \emph{overloadable} operator, other than assignment. … … 3466 3454 & 3467 3455 \begin{cfa} 3468 sout | x * 3 | y + 1 | z << 2 | x == y | ®(®x | y®)® | ®(®x || y®)® | ®(®x > z ? 1 : 2®)®;3456 sout | x * 3 | y + 1 | z << 2 | x == y | @(@x | y@)@ | @(@x || y@)@ | @(@x > z ? 1 : 2@)@; 3469 3457 \end{cfa} 3470 3458 \\ … … 3472 3460 & 3473 3461 \begin{cfa} 3474 cout << x * 3 << y + 1 << ®(®z << 2®)® << ®(®x == y®)® << ®(®x | y®)® << ®(®x || y®)® << ®(®x > z ? 1 : 2®)®<< endl;3462 cout << x * 3 << y + 1 << @(@z << 2@)@ << @(@x == y@)@ << @(@x | y@)@ << @(@x || y@)@ << @(@x > z ? 1 : 2@)@ << endl; 3475 3463 \end{cfa} 3476 3464 \\ … … 3507 3495 \\ 3508 3496 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3509 ®1® ®2.5® ®A® 3497 @1@ @2.5@ @A@ 3510 3498 3511 3499 … … 3513 3501 & 3514 3502 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3515 ®1® ®2.5® ®A® 3503 @1@ @2.5@ @A@ 3516 3504 3517 3505 … … 3519 3507 & 3520 3508 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3521 ®1® 3522 ®2.5® 3523 ®A® 3509 @1@ 3510 @2.5@ 3511 @A@ 3524 3512 \end{cfa} 3525 3513 \end{tabular} … … 3557 3545 3558 3546 \item 3559 {\lstset{language=CFA,deletedelim=**[is][]{¢}{¢}} 3560 A separator does not appear before a C string starting with the (extended) \Index*{ASCII}\index{ASCII!extended} characters: \lstinline[basicstyle=\tt]@,.;!?)]}%¢»@, where \lstinline[basicstyle=\tt]@»@ is a closing citation mark. 3561 \begin{cfa}[belowskip=0pt] 3547 A separator does not appear before a C string starting with the (extended) \Index*{ASCII}\index{ASCII!extended} characters: \LstStringStyle{,.;!?)]\}\%\textcent\guillemotright}, where \LstStringStyle{\guillemotright} a closing citation mark. 3548 \begin{cfa} 3562 3549 sout | 1 | ", x" | 2 | ". x" | 3 | "; x" | 4 | "! x" | 5 | "? x" | 6 | "% x" 3563 | 7 | "¢ x" | 8 | "»x" | 9 | ") x" | 10 | "] x" | 11 | "} x";3564 \end{cfa} 3565 \begin{cfa}[ basicstyle=\tt,showspaces=true,aboveskip=0pt,belowskip=0pt]3566 1 ®,® x 2®.® x 3®;® x 4®!® x 5®?® x 6®%® x 7§\color{red}\textcent§ x 8®»® x 9®)® x 10®]® x 11®}®x3567 \end{cfa} }%3568 3569 \item 3570 A separator does not appear after a C string ending with the (extended) \Index*{ASCII}\index{ASCII!extended} characters: \ lstinline[mathescape=off,basicstyle=\tt]@([{=$£¥¡¿«@, where \lstinline[basicstyle=\tt]@¡¿@ are inverted opening exclamation and question marks, and \lstinline[basicstyle=\tt]@«@is an opening citation mark.3550 | 7 | "$\LstStringStyle{\textcent}$ x" | 8 | "$\LstStringStyle{\guillemotright}$ x" | 9 | ") x" | 10 | "] x" | 11 | "} x"; 3551 \end{cfa} 3552 \begin{cfa}[showspaces=true] 3553 1@,@ x 2@.@ x 3@;@ x 4@!@ x 5@?@ x 6@%@ x 7$\R{\LstStringStyle{\textcent}}$ x 8$\R{\LstStringStyle{\guillemotright}}$ x 9@)@ x 10@]@ x 11@}@ x 3554 \end{cfa} 3555 3556 \item 3557 A separator does not appear after a C string ending with the (extended) \Index*{ASCII}\index{ASCII!extended} characters: \LstStringStyle{([\{=\$\textsterling\textyen\textexclamdown\textquestiondown\guillemotleft}, where \LstStringStyle{\textexclamdown\textquestiondown} are inverted opening exclamation and question marks, and \LstStringStyle{\guillemotleft} is an opening citation mark. 3571 3558 %$ 3572 \begin{cfa} [mathescape=off]3573 sout | "x (" | 1 | "x [" | 2 | "x {" | 3 | "x =" | 4 | "x $" | 5 | "x £" | 6 | "x ¥"3574 | 7 | "x ¡" | 8 | "x ¿" | 9 | "x «" | 10;3559 \begin{cfa} 3560 sout | "x (" | 1 | "x [" | 2 | "x {" | 3 | "x =" | 4 | "x $" | 5 | "x $\LstStringStyle{\textsterling}$" | 6 | "x $\LstStringStyle{\textyen}$" 3561 | 7 | "x $\LstStringStyle{\textexclamdown}$" | 8 | "x $\LstStringStyle{\textquestiondown}$" | 9 | "x $\LstStringStyle{\guillemotleft}$" | 10; 3575 3562 \end{cfa} 3576 3563 %$ 3577 \begin{cfa}[ mathescape=off,basicstyle=\tt,showspaces=true,aboveskip=0pt,belowskip=0pt]3578 x ®(®1 x ®[®2 x ®{®3 x ®=®4 x ®$®5 x ®£®6 x ®¥®7 x ®¡®8 x ®¿®9 x ®«®103564 \begin{cfa}[showspaces=true] 3565 x @(@1 x @[@2 x @{@3 x @=@4 x $\LstStringStyle{\textdollar}$5 x $\R{\LstStringStyle{\textsterling}}$6 x $\R{\LstStringStyle{\textyen}}$7 x $\R{\LstStringStyle{\textexclamdown}}$8 x $\R{\LstStringStyle{\textquestiondown}}$9 x $\R{\LstStringStyle{\guillemotleft}}$10 3579 3566 \end{cfa} 3580 3567 %$ 3581 3568 3582 3569 \item 3583 A seperator does not appear before/after a C string starting/ending with the \Index*{ASCII} quote or whitespace characters: \lstinline[basicstyle=\tt,showspaces=true] @`'": \t\v\f\r\n@3584 \begin{cfa} [belowskip=0pt]3570 A seperator does not appear before/after a C string starting/ending with the \Index*{ASCII} quote or whitespace characters: \lstinline[basicstyle=\tt,showspaces=true]{`'": \t\v\f\r\n} 3571 \begin{cfa} 3585 3572 sout | "x`" | 1 | "`x'" | 2 | "'x\"" | 3 | "\"x:" | 4 | ":x " | 5 | " x\t" | 6 | "\tx"; 3586 3573 \end{cfa} 3587 \begin{cfa}[ basicstyle=\tt,showspaces=true,showtabs=true,aboveskip=0pt,belowskip=0pt]3588 x ®`®1®`®x§\color{red}\texttt{'}§2§\color{red}\texttt{'}§x§\color{red}\texttt{"}§3§\color{red}\texttt{"}§x®:®4®:®x® ®5® ®x® ®6® ®x3574 \begin{cfa}[showspaces=true,showtabs=true] 3575 x@`@1@`@x$\R{\texttt{'}}$2$\R{\texttt{'}}$x$\R{\texttt{"}}$3$\R{\texttt{"}}$x@:@4@:@x@ @5@ @x@ @6@ @x 3589 3576 \end{cfa} 3590 3577 3591 3578 \item 3592 3579 If a space is desired before or after one of the special string start/end characters, simply insert a space. 3593 \begin{cfa} [belowskip=0pt]3594 sout | "x ( §\color{red}\texttt{\textvisiblespace}§" | 1 | "§\color{red}\texttt{\textvisiblespace}§) x" | 2 | "§\color{red}\texttt{\textvisiblespace}§, x" | 3 | "§\color{red}\texttt{\textvisiblespace}§:x:§\color{red}\texttt{\textvisiblespace}§" | 4;3595 \end{cfa} 3596 \begin{cfa}[ basicstyle=\tt,showspaces=true,showtabs=true,aboveskip=0pt,belowskip=0pt]3597 x ( ® ®1® ®) x 2® ®, x 3® ®:x:® ®43580 \begin{cfa} 3581 sout | "x ($\R{\texttt{\textvisiblespace}}$" | 1 | "$\R{\texttt{\textvisiblespace}}$) x" | 2 | "$\R{\texttt{\textvisiblespace}}$, x" | 3 | "$\R{\texttt{\textvisiblespace}}$:x:$\R{\texttt{\textvisiblespace}}$" | 4; 3582 \end{cfa} 3583 \begin{cfa}[showspaces=true,showtabs=true] 3584 x (@ @1@ @) x 2@ @, x 3@ @:x:@ @4 3598 3585 \end{cfa} 3599 3586 \end{enumerate} … … 3608 3595 \Indexc{sepSet}\index{manipulator!sepSet@©sepSet©} and \Indexc{sep}\index{manipulator!sep@©sep©}/\Indexc{sepGet}\index{manipulator!sepGet@©sepGet©} set and get the separator string. 3609 3596 The separator string can be at most 16 characters including the ©'\0'© string terminator (15 printable characters). 3610 \begin{cfa}[ mathescape=off,belowskip=0pt]3611 sepSet( sout, ", $" ); §\C{// set separator from " " to ", \$"}§3612 sout | 1 | 2 | 3 | " \"" | ®sep®| "\"";3597 \begin{cfa}[escapechar=off,belowskip=0pt] 3598 sepSet( sout, ", $" ); $\C{// set separator from " " to ", \$"}$ 3599 sout | 1 | 2 | 3 | " \"" | @sep@ | "\""; 3613 3600 \end{cfa} 3614 3601 %$ 3615 3602 \begin{cfa}[mathescape=off,showspaces=true,aboveskip=0pt] 3616 1 ®, $®2®, $®3 ®", $"®3603 1@, $@2@, $@3 @", $"@ 3617 3604 \end{cfa} 3618 3605 %$ 3619 3606 \begin{cfa}[belowskip=0pt] 3620 sepSet( sout, " " ); §\C{// reset separator to " "}§3621 sout | 1 | 2 | 3 | " \"" | ®sepGet( sout )®| "\"";3607 sepSet( sout, " " ); $\C{// reset separator to " "}$ 3608 sout | 1 | 2 | 3 | " \"" | @sepGet( sout )@ | "\""; 3622 3609 \end{cfa} 3623 3610 \begin{cfa}[showspaces=true,aboveskip=0pt] 3624 1 ® ®2® ®3 ®" "®3611 1@ @2@ @3 @" "@ 3625 3612 \end{cfa} 3626 3613 ©sepGet© can be used to store a separator and then restore it: 3627 3614 \begin{cfa}[belowskip=0pt] 3628 char store[ ®sepSize®]; §\C{// sepSize is the maximum separator size}§3629 strcpy( store, sepGet( sout ) ); §\C{// copy current separator}§3630 sepSet( sout, "_" ); §\C{// change separator to underscore}§3615 char store[@sepSize@]; $\C{// sepSize is the maximum separator size}$ 3616 strcpy( store, sepGet( sout ) ); $\C{// copy current separator}$ 3617 sepSet( sout, "_" ); $\C{// change separator to underscore}$ 3631 3618 sout | 1 | 2 | 3; 3632 3619 \end{cfa} 3633 3620 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3634 1 ®_®2®_®33621 1@_@2@_@3 3635 3622 \end{cfa} 3636 3623 \begin{cfa}[belowskip=0pt] 3637 sepSet( sout, store ); §\C{// change separator back to original}§3624 sepSet( sout, store ); $\C{// change separator back to original}$ 3638 3625 sout | 1 | 2 | 3; 3639 3626 \end{cfa} 3640 3627 \begin{cfa}[showspaces=true,aboveskip=0pt] 3641 1 ® ®2® ®33628 1@ @2@ @3 3642 3629 \end{cfa} 3643 3630 … … 3646 3633 The tuple separator-string can be at most 16 characters including the ©'\0'© string terminator (15 printable characters). 3647 3634 \begin{cfa}[belowskip=0pt] 3648 sepSetTuple( sout, " " ); §\C{// set tuple separator from ", " to " "}§3649 sout | t1 | t2 | " \"" | ®sepTuple®| "\"";3635 sepSetTuple( sout, " " ); $\C{// set tuple separator from ", " to " "}$ 3636 sout | t1 | t2 | " \"" | @sepTuple@ | "\""; 3650 3637 \end{cfa} 3651 3638 \begin{cfa}[showspaces=true,aboveskip=0pt] 3652 1 2 3 4 5 6 ®" "®3639 1 2 3 4 5 6 @" "@ 3653 3640 \end{cfa} 3654 3641 \begin{cfa}[belowskip=0pt] 3655 sepSetTuple( sout, ", " ); §\C{// reset tuple separator to ", "}§3656 sout | t1 | t2 | " \"" | ®sepGetTuple( sout )®| "\"";3642 sepSetTuple( sout, ", " ); $\C{// reset tuple separator to ", "}$ 3643 sout | t1 | t2 | " \"" | @sepGetTuple( sout )@ | "\""; 3657 3644 \end{cfa} 3658 3645 \begin{cfa}[showspaces=true,aboveskip=0pt] 3659 1, 2, 3 4, 5, 6 ®", "®3646 1, 2, 3 4, 5, 6 @", "@ 3660 3647 \end{cfa} 3661 3648 As for ©sepGet©, ©sepGetTuple© can be use to store a tuple separator and then restore it. … … 3664 3651 \Indexc{sepDisable}\index{manipulator!sepDisable@©sepDisable©} and \Indexc{sepEnable}\index{manipulator!sepEnable@©sepEnable©} toggle printing the separator. 3665 3652 \begin{cfa}[belowskip=0pt] 3666 sout | sepDisable | 1 | 2 | 3; §\C{// turn off implicit separator}§3653 sout | sepDisable | 1 | 2 | 3; $\C{// turn off implicit separator}$ 3667 3654 \end{cfa} 3668 3655 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3670 3657 \end{cfa} 3671 3658 \begin{cfa}[belowskip=0pt] 3672 sout | sepEnable | 1 | 2 | 3; §\C{// turn on implicit separator}§3659 sout | sepEnable | 1 | 2 | 3; $\C{// turn on implicit separator}$ 3673 3660 \end{cfa} 3674 3661 \begin{cfa}[mathescape=off,showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3679 3666 \Indexc{sepOn}\index{manipulator!sepOn@©sepOn©} and \Indexc{sepOff}\index{manipulator!sepOff@©sepOff©} toggle printing the separator with respect to the next printed item, and then return to the global seperator setting. 3680 3667 \begin{cfa}[belowskip=0pt] 3681 sout | 1 | sepOff | 2 | 3; §\C{// turn off implicit separator for the next item}§3668 sout | 1 | sepOff | 2 | 3; $\C{// turn off implicit separator for the next item}$ 3682 3669 \end{cfa} 3683 3670 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3685 3672 \end{cfa} 3686 3673 \begin{cfa}[belowskip=0pt] 3687 sout | sepDisable | 1 | sepOn | 2 | 3; §\C{// turn on implicit separator for the next item}§3674 sout | sepDisable | 1 | sepOn | 2 | 3; $\C{// turn on implicit separator for the next item}$ 3688 3675 \end{cfa} 3689 3676 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3692 3679 The tuple separator also responses to being turned on and off. 3693 3680 \begin{cfa}[belowskip=0pt] 3694 sout | t1 | sepOff | t2; §\C{// turn off implicit separator for the next item}§3681 sout | t1 | sepOff | t2; $\C{// turn off implicit separator for the next item}$ 3695 3682 \end{cfa} 3696 3683 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3700 3687 use ©sep© to accomplish this functionality. 3701 3688 \begin{cfa}[belowskip=0pt] 3702 sout | sepOn | 1 | 2 | 3 | sepOn; §\C{// sepOn does nothing at start/end of line}§3689 sout | sepOn | 1 | 2 | 3 | sepOn; $\C{// sepOn does nothing at start/end of line}$ 3703 3690 \end{cfa} 3704 3691 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] … … 3706 3693 \end{cfa} 3707 3694 \begin{cfa}[belowskip=0pt] 3708 sout | sep | 1 | 2 | 3 | sep ; §\C{// use sep to print separator at start/end of line}§3695 sout | sep | 1 | 2 | 3 | sep ; $\C{// use sep to print separator at start/end of line}$ 3709 3696 \end{cfa} 3710 3697 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3711 ® ®1 2 3® ® 3698 @ @1 2 3@ @ 3712 3699 \end{cfa} 3713 3700 \end{enumerate} … … 3721 3708 \begin{enumerate}[parsep=0pt] 3722 3709 \item 3723 \Indexc{nl}\index{manipulator!nl@©nl©} scans characters until the next newline character, i.e.,ignore the remaining characters in the line.3710 \Indexc{nl}\index{manipulator!nl@©nl©} scans characters until the next newline character, \ie ignore the remaining characters in the line. 3724 3711 \item 3725 3712 \Indexc{nlOn}\index{manipulator!nlOn@©nlOn©} reads the newline character, when reading single characters. … … 3729 3716 For example, in: 3730 3717 \begin{cfa} 3731 sin | i | ®nl®| j;3732 1 ®2®3718 sin | i | @nl@ | j; 3719 1 @2@ 3733 3720 3 3734 3721 \end{cfa} … … 3740 3727 \Indexc{nl}\index{manipulator!nl@©nl©} inserts a newline. 3741 3728 \begin{cfa} 3742 sout | nl; §\C{// only print newline}§3743 sout | 2; §\C{// implicit newline}§3744 sout | 3 | nl | 4 | nl; §\C{// terminating nl merged with implicit newline}§3745 sout | 5 | nl | nl; §\C{// again terminating nl merged with implicit newline}§3746 sout | 6; §\C{// implicit newline}§3729 sout | nl; $\C{// only print newline}$ 3730 sout | 2; $\C{// implicit newline}$ 3731 sout | 3 | nl | 4 | nl; $\C{// terminating nl merged with implicit newline}$ 3732 sout | 5 | nl | nl; $\C{// again terminating nl merged with implicit newline}$ 3733 sout | 6; $\C{// implicit newline}$ 3747 3734 3748 3735 2 … … 3771 3758 0b0 0b11011 0b11011 0b11011 0b11011 3772 3759 sout | bin( -27HH ) | bin( -27H ) | bin( -27 ) | bin( -27L ); 3773 0b11100101 0b1111111111100101 0b11111111111111111111111111100101 0b ®(58 1s)®1001013760 0b11100101 0b1111111111100101 0b11111111111111111111111111100101 0b@(58 1s)@100101 3774 3761 \end{cfa} 3775 3762 … … 3810 3797 \begin{cfa}[belowskip=0pt] 3811 3798 sout | upcase( bin( 27 ) ) | upcase( hex( 27 ) ) | upcase( 27.5e-10 ) | upcase( hex( 27.5 ) ); 3812 0 ®B®11011 0®X®1®B® 2.75®E®-09 0®X®1.®B®8®P®+43799 0@B@11011 0@X@1@B@ 2.75@E@-09 0@X@1.@B@8@P@+4 3813 3800 \end{cfa} 3814 3801 … … 3826 3813 \begin{cfa}[belowskip=0pt] 3827 3814 sout | 0. | nodp( 0. ) | 27.0 | nodp( 27.0 ) | nodp( 27.5 ); 3828 0.0 ®0® 27.0 ®27®27.53815 0.0 @0@ 27.0 @27@ 27.5 3829 3816 \end{cfa} 3830 3817 … … 3833 3820 \begin{cfa}[belowskip=0pt] 3834 3821 sout | sign( 27 ) | sign( -27 ) | sign( 27. ) | sign( -27. ) | sign( 27.5 ) | sign( -27.5 ); 3835 ®+®27 -27 ®+®27.0 -27.0 ®+®27.5 -27.53822 @+@27 -27 @+@27.0 -27.0 @+@27.5 -27.5 3836 3823 \end{cfa} 3837 3824 … … 3846 3833 \end{cfa} 3847 3834 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3848 ® ®34 ® ®34 343849 ® ®4.000000 ® ®4.000000 4.0000003850 ® ®ab ® ®ab ab3835 @ @34 @ @34 34 3836 @ @4.000000 @ @4.000000 4.000000 3837 @ @ab @ @ab ab 3851 3838 \end{cfa} 3852 3839 If the value is larger, it is printed without truncation, ignoring the ©minimum©. … … 3857 3844 \end{cfa} 3858 3845 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3859 3456 ®7® 345®67® 34®567®3860 3456 ®.® 345®6.® 34®56.®3861 abcd ®e® abc®de® ab®cde®3846 3456@7@ 345@67@ 34@567@ 3847 3456@.@ 345@6.@ 34@56.@ 3848 abcd@e@ abc@de@ ab@cde@ 3862 3849 \end{cfa} 3863 3850 … … 3868 3855 \end{cfa} 3869 3856 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3870 ®0®34 ®00®34 ®00000000®343857 @0@34 @00@34 @00000000@34 3871 3858 \end{cfa} 3872 3859 If the value is larger, it is printed without truncation, ignoring the ©precision©. … … 3883 3870 \end{cfa} 3884 3871 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3885 ® ® ®00000000®343872 @ @ @00000000@34 3886 3873 \end{cfa} 3887 3874 For floating-point types, ©precision© is the minimum number of digits after the decimal point. … … 3890 3877 \end{cfa} 3891 3878 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3892 27. ®500® 27.®5® 28. 27.®50000000®3893 \end{cfa} 3894 For the C-string type, ©precision© is the maximum number of printed characters, so the string is trunca red if it exceeds the maximum.3879 27.@500@ 27.@5@ 28. 27.@50000000@ 3880 \end{cfa} 3881 For the C-string type, ©precision© is the maximum number of printed characters, so the string is truncated if it exceeds the maximum. 3895 3882 \begin{cfa}[belowskip=0pt] 3896 3883 sout | wd( 6,8, "abcd" ) | wd( 6,8, "abcdefghijk" ) | wd( 6,3, "abcd" ); … … 3908 3895 \end{cfa} 3909 3896 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3910 234.567 234.5 ®7® 234.®6® 23®5®3897 234.567 234.5@7@ 234.@6@ 23@5@ 3911 3898 \end{cfa} 3912 3899 If a value's magnitude is greater than ©significant©, the value is printed in scientific notation with the specified number of significant digits. … … 3915 3902 \end{cfa} 3916 3903 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3917 234567. 2.3457 ®e+05® 2.346®e+05® 2.35®e+05®3904 234567. 2.3457@e+05@ 2.346@e+05@ 2.35@e+05@ 3918 3905 \end{cfa} 3919 3906 If ©significant© is greater than ©minimum©, it defines the number of printed characters. … … 3931 3918 \end{cfa} 3932 3919 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 3933 27 ® ® 27.000000 27.500000 027 27.500® ®3920 27@ @ 27.000000 27.500000 027 27.500@ @ 3934 3921 \end{cfa} 3935 3922 … … 3938 3925 \begin{cfa}[belowskip=0pt] 3939 3926 sout | pad0( wd( 4, 27 ) ) | pad0( wd( 4,3, 27 ) ) | pad0( wd( 8,3, 27.5 ) ); 3940 ®00®27 ®0®27 ®00®27.5003927 @00@27 @0@27 @00@27.500 3941 3928 \end{cfa} 3942 3929 \end{enumerate} … … 4034 4021 \end{cfa} 4035 4022 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 4036 ®abc ® 4037 ®abc ® 4038 ®xx® 4023 @abc @ 4024 @abc @ 4025 @xx@ 4039 4026 \end{cfa} 4040 4027 … … 4047 4034 \end{cfa} 4048 4035 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 4049 ®abcd1233.456E+2® 4036 @abcd1233.456E+2@ 4050 4037 \end{cfa} 4051 4038 Note, input ©wdi© cannot be overloaded with output ©wd© because both have the same parameters but return different types. … … 4060 4047 \end{cfa} 4061 4048 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 4062 ® -75.35e-4®254049 @ -75.35e-4@ 25 4063 4050 \end{cfa} 4064 4051 … … 4072 4059 \end{cfa} 4073 4060 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 4074 ®bca®xyz4061 @bca@xyz 4075 4062 \end{cfa} 4076 4063 … … 4084 4071 \end{cfa} 4085 4072 \begin{cfa}[showspaces=true,aboveskip=0pt,belowskip=0pt] 4086 ®xyz®bca4073 @xyz@bca 4087 4074 \end{cfa} 4088 4075 \end{enumerate} … … 4101 4088 4102 4089 A type definition is different from a typedef in C because a typedef just creates an alias for a type, while Do.s type definition creates a distinct type. 4103 This means that users can define distinct function overloads for the new type (see Overloading for more information).4090 This means that users can define distinct function overloads for the new type \see{\VRef{s:Overloading} for more information}. 4104 4091 For example: 4105 4092 … … 4207 4194 \CFA supports C initialization of structures, but it also adds constructors for more advanced initialization. 4208 4195 Additionally, \CFA adds destructors that are called when a variable is deallocated (variable goes out of scope or object is deleted). 4209 These functions take a reference to the structure as a parameter (see References for more information).4196 These functions take a reference to the structure as a parameter \see{\VRef{s:PointerReference} for more information}. 4210 4197 4211 4198 \begin{figure} … … 4258 4245 4259 4246 \section{Overloading} 4247 \label{s:Overloading} 4260 4248 4261 4249 Overloading refers to the capability of a programmer to define and use multiple objects in a program with the same name. … … 4290 4278 4291 4279 4292 \subsection{ OverloadedConstant}4280 \subsection{Constant} 4293 4281 4294 4282 The constants 0 and 1 have special meaning. … … 4329 4317 4330 4318 4331 \subsection{Variable Overloading} 4319 \subsection{Variable} 4320 \label{s:VariableOverload} 4332 4321 4333 4322 The overload rules of \CFA allow a programmer to define multiple variables with the same name, but different types. … … 4372 4361 4373 4362 4374 \subsection{Operator Overloading}4363 \subsection{Operator} 4375 4364 4376 4365 \CFA also allows operators to be overloaded, to simplify the use of user-defined types. … … 4468 4457 For example, given 4469 4458 \begin{cfa} 4470 auto j = ®...®4459 auto j = @...@ 4471 4460 \end{cfa} 4472 4461 and the need to write a routine to compute using ©j© 4473 4462 \begin{cfa} 4474 void rtn( ®...®parm );4463 void rtn( @...@ parm ); 4475 4464 rtn( j ); 4476 4465 \end{cfa} … … 4713 4702 4714 4703 coroutine Fibonacci { 4715 int fn; §\C{// used for communication}§4704 int fn; $\C{// used for communication}$ 4716 4705 }; 4717 4706 void ?{}( Fibonacci * this ) { … … 4719 4708 } 4720 4709 void main( Fibonacci * this ) { 4721 int fn1, fn2; §\C{// retained between resumes}§4722 this->fn = 0; §\C{// case 0}§4710 int fn1, fn2; $\C{// retained between resumes}$ 4711 this->fn = 0; $\C{// case 0}$ 4723 4712 fn1 = this->fn; 4724 suspend(); §\C{// return to last resume}§4725 4726 this->fn = 1; §\C{// case 1}§4713 suspend(); $\C{// return to last resume}$ 4714 4715 this->fn = 1; $\C{// case 1}$ 4727 4716 fn2 = fn1; 4728 4717 fn1 = this->fn; 4729 suspend(); §\C{// return to last resume}§4730 4731 for ( ;; ) { §\C{// general case}§4718 suspend(); $\C{// return to last resume}$ 4719 4720 for ( ;; ) { $\C{// general case}$ 4732 4721 this->fn = fn1 + fn2; 4733 4722 fn2 = fn1; 4734 4723 fn1 = this->fn; 4735 suspend(); §\C{// return to last resume}§4724 suspend(); $\C{// return to last resume}$ 4736 4725 } // for 4737 4726 } 4738 4727 int next( Fibonacci * this ) { 4739 resume( this ); §\C{// transfer to last suspend}§4728 resume( this ); $\C{// transfer to last suspend}$ 4740 4729 return this->fn; 4741 4730 } … … 4964 4953 When building a \CFA module which needs to be callable from C code, users can use the tools to generate a header file suitable for including in these C files with all of the needed declarations. 4965 4954 4966 In order to interoperate with existing C code, \CFA files can still include header files, the contents of which will be enclosed in a C linkage section to indicate C calling conventions (see Interoperability for more information).4955 In order to interoperate with existing C code, \CFA files can still include header files, the contents of which will be enclosed in a C linkage section to indicate C calling conventions \see{\VRef{s:Interoperability} for more information}. 4967 4956 4968 4957 … … 5630 5619 \end{cfa} 5631 5620 & 5632 \begin{ lstlisting}[language=C++]5621 \begin{C++} 5633 5622 class Line { 5634 5623 float lnth; … … 5657 5646 Line line1; 5658 5647 Line line2( 3.4 ); 5659 \end{ lstlisting}5648 \end{C++} 5660 5649 & 5661 5650 \begin{lstlisting}[language=Golang] … … 6282 6271 In \CFA, there are ambiguous cases with dereference and operator identifiers, \eg ©int *?*?()©, where the string ©*?*?© can be interpreted as: 6283 6272 \begin{cfa} 6284 *? §\color{red}\textvisiblespace§*? §\C{// dereference operator, dereference operator}§6285 * §\color{red}\textvisiblespace§?*? §\C{// dereference, multiplication operator}§6273 *?$\R{\textvisiblespace}$*? $\C{// dereference operator, dereference operator}$ 6274 *$\R{\textvisiblespace}$?*? $\C{// dereference, multiplication operator}$ 6286 6275 \end{cfa} 6287 6276 By default, the first interpretation is selected, which does not yield a meaningful parse. … … 6292 6281 The ambiguity occurs when the deference operator has no parameters: 6293 6282 \begin{cfa} 6294 *?() §\color{red}\textvisiblespace...§;6295 *?() §\color{red}\textvisiblespace...§(...) ;6283 *?()$\R{\textvisiblespace...}$ ; 6284 *?()$\R{\textvisiblespace...}$(...) ; 6296 6285 \end{cfa} 6297 6286 requiring arbitrary whitespace look-ahead for the routine-call parameter-list to disambiguate. … … 6301 6290 The remaining cases are with the increment/decrement operators and conditional expression, \eg: 6302 6291 \begin{cfa} 6303 i++? §\color{red}\textvisiblespace...§(...);6304 i?++ §\color{red}\textvisiblespace...§(...);6292 i++?$\R{\textvisiblespace...}$(...); 6293 i?++$\R{\textvisiblespace...}$(...); 6305 6294 \end{cfa} 6306 6295 requiring arbitrary whitespace look-ahead for the operator parameter-list, even though that interpretation is an incorrect expression (juxtaposed identifiers). 6307 6296 Therefore, it is necessary to disambiguate these cases with a space: 6308 6297 \begin{cfa} 6309 i++ §\color{red}\textvisiblespace§? i : 0;6310 i? §\color{red}\textvisiblespace§++i : 0;6298 i++$\R{\textvisiblespace}$? i : 0; 6299 i?$\R{\textvisiblespace}$++i : 0; 6311 6300 \end{cfa} 6312 6301 … … 6321 6310 \begin{description} 6322 6311 \item[Change:] add new keywords \\ 6323 New keywords are added to \CFA (see~\VRef{s:CFAKeywords}).6312 New keywords are added to \CFA \see{\VRef{s:CFAKeywords}}. 6324 6313 \item[Rationale:] keywords added to implement new semantics of \CFA. 6325 6314 \item[Effect on original feature:] change to semantics of well-defined feature. \\ 6326 6315 Any \Celeven programs using these keywords as identifiers are invalid \CFA programs. 6327 \item[Difficulty of converting:] keyword clashes are accommodated by syntactic transformations using the \CFA backquote escape-mechanism (see~\VRef{s:BackquoteIdentifiers}).6316 \item[Difficulty of converting:] keyword clashes are accommodated by syntactic transformations using the \CFA backquote escape-mechanism \see{\VRef{s:BackquoteIdentifiers}}. 6328 6317 \item[How widely used:] clashes among new \CFA keywords and existing identifiers are rare. 6329 6318 \end{description} … … 6335 6324 \eg: 6336 6325 \begin{cfa} 6337 x; §\C{// int x}§6338 *y; §\C{// int *y}§6339 f( p1, p2 ); §\C{// int f( int p1, int p2 );}§6340 g( p1, p2 ) int p1, p2; §\C{// int g( int p1, int p2 );}§6326 x; $\C{// int x}$ 6327 *y; $\C{// int *y}$ 6328 f( p1, p2 ); $\C{// int f( int p1, int p2 );}$ 6329 g( p1, p2 ) int p1, p2; $\C{// int g( int p1, int p2 );}$ 6341 6330 \end{cfa} 6342 6331 \CFA continues to support K\&R routine definitions: 6343 6332 \begin{cfa} 6344 f( a, b, c ) §\C{// default int return}§6345 int a, b; char c §\C{// K\&R parameter declarations}§6333 f( a, b, c ) $\C{// default int return}$ 6334 int a, b; char c $\C{// K\&R parameter declarations}$ 6346 6335 { 6347 6336 ... … … 6362 6351 int rtn( int i ); 6363 6352 int rtn( char c ); 6364 rtn( 'x' ); §\C{// programmer expects 2nd rtn to be called}§6353 rtn( 'x' ); $\C{// programmer expects 2nd rtn to be called}$ 6365 6354 \end{cfa} 6366 6355 \item[Rationale:] it is more intuitive for the call to ©rtn© to match the second version of definition of ©rtn© rather than the first. … … 6384 6373 \item[Change:] make string literals ©const©: 6385 6374 \begin{cfa} 6386 char * p = "abc"; §\C{// valid in C, deprecated in \CFA}§6387 char * q = expr ? "abc" : "de"; §\C{// valid in C, invalid in \CFA}§6375 char * p = "abc"; $\C{// valid in C, deprecated in \CFA}$ 6376 char * q = expr ? "abc" : "de"; $\C{// valid in C, invalid in \CFA}$ 6388 6377 \end{cfa} 6389 6378 The type of a string literal is changed from ©[] char© to ©const [] char©. … … 6392 6381 \begin{cfa} 6393 6382 char * p = "abc"; 6394 p[0] = 'w'; §\C{// segment fault or change constant literal}§6383 p[0] = 'w'; $\C{// segment fault or change constant literal}$ 6395 6384 \end{cfa} 6396 6385 The same problem occurs when passing a string literal to a routine that changes its argument. … … 6404 6393 \item[Change:] remove \newterm{tentative definitions}, which only occurs at file scope: 6405 6394 \begin{cfa} 6406 int i; §\C{// forward definition}§6407 int *j = ®&i®; §\C{// forward reference, valid in C, invalid in \CFA}§6408 int i = 0; §\C{// definition}§6395 int i; $\C{// forward definition}$ 6396 int *j = @&i@; $\C{// forward reference, valid in C, invalid in \CFA}$ 6397 int i = 0; $\C{// definition}$ 6409 6398 \end{cfa} 6410 6399 is valid in C, and invalid in \CFA because duplicate overloaded object definitions at the same scope level are disallowed. … … 6412 6401 \begin{cfa} 6413 6402 struct X { int i; struct X *next; }; 6414 static struct X a; §\C{// forward definition}§6415 static struct X b = { 0, ®&a® };§\C{// forward reference, valid in C, invalid in \CFA}§6416 static struct X a = { 1, &b }; §\C{// definition}§6403 static struct X a; $\C{// forward definition}$ 6404 static struct X b = { 0, @&a@ };$\C{// forward reference, valid in C, invalid in \CFA}$ 6405 static struct X a = { 1, &b }; $\C{// definition}$ 6417 6406 \end{cfa} 6418 6407 \item[Rationale:] avoids having different initialization rules for builtin types and user-defined types. … … 6426 6415 \item[Change:] have ©struct© introduce a scope for nested types: 6427 6416 \begin{cfa} 6428 enum ®Colour®{ R, G, B, Y, C, M };6417 enum @Colour@ { R, G, B, Y, C, M }; 6429 6418 struct Person { 6430 enum ®Colour® { R, G, B }; §\C[7cm]{// nested type}§6431 struct Face { §\C{// nested type}§6432 ®Colour® Eyes, Hair; §\C{// type defined outside (1 level)}§6419 enum @Colour@ { R, G, B }; $\C[7cm]{// nested type}$ 6420 struct Face { $\C{// nested type}$ 6421 @Colour@ Eyes, Hair; $\C{// type defined outside (1 level)}$ 6433 6422 }; 6434 ®.Colour® shirt; §\C{// type defined outside (top level)}§6435 ®Colour® pants; §\C{// type defined same level}§6436 Face looks[10]; §\C{// type defined same level}§6423 @.Colour@ shirt; $\C{// type defined outside (top level)}$ 6424 @Colour@ pants; $\C{// type defined same level}$ 6425 Face looks[10]; $\C{// type defined same level}$ 6437 6426 }; 6438 ®Colour® c = R; §\C{// type/enum defined same level}§ 6439 Person ®.Colour® pc = Person®.®R;§\C{// type/enum defined inside}§6440 Person ®.®Face pretty; §\C{// type defined inside}\CRT§6427 @Colour@ c = R; $\C{// type/enum defined same level}$ 6428 Person@.Colour@ pc = Person@.@R;$\C{// type/enum defined inside}$ 6429 Person@.@Face pretty; $\C{// type defined inside}\CRT$ 6441 6430 \end{cfa} 6442 6431 In C, the name of the nested types belongs to the same scope as the name of the outermost enclosing structure, \ie the nested types are hoisted to the scope of the outer-most type, which is not useful and confusing. … … 6455 6444 \item[Difficulty of converting:] Semantic transformation. To make the struct type name visible in the scope of the enclosing struct, the struct tag could be declared in the scope of the enclosing struct, before the enclosing struct is defined. Example: 6456 6445 \begin{cfa} 6457 struct Y; §\C{// struct Y and struct X are at the same scope}§6446 struct Y; $\C{// struct Y and struct X are at the same scope}$ 6458 6447 struct X { 6459 6448 struct Y { /* ... */ } y; … … 6470 6459 \begin{cfa} 6471 6460 void foo() { 6472 int * b = malloc( sizeof(int) ); §\C{// implicitly convert void * to int *}§6473 char * c = b; §\C{// implicitly convert int * to void *, and then void * to char *}§6461 int * b = malloc( sizeof(int) ); $\C{// implicitly convert void * to int *}$ 6462 char * c = b; $\C{// implicitly convert int * to void *, and then void * to char *}$ 6474 6463 } 6475 6464 \end{cfa} 6476 6465 \item[Rationale:] increase type safety 6477 6466 \item[Effect on original feature:] deletion of semantically well-defined feature. 6478 \item[Difficulty of converting:] requires adding a cast (see \VRef{s:StorageManagement} for better alternatives):6467 \item[Difficulty of converting:] requires adding a cast \see{\VRef{s:StorageManagement} for better alternatives}: 6479 6468 \begin{cfa} 6480 6469 int * b = (int *)malloc( sizeof(int) ); … … 6586 6575 \end{cquote} 6587 6576 For the prescribed head-files, \CFA uses header interposition to wraps these includes in an ©extern "C"©; 6588 hence, names in these include files are not mangled\index{mangling!name} (see~\VRef{s:Interoperability}).6577 hence, names in these include files are not mangled\index{mangling!name} \see{\VRef{s:Interoperability}}. 6589 6578 All other C header files must be explicitly wrapped in ©extern "C"© to prevent name mangling. 6590 6579 This approach is different from \Index*[C++]{\CC{}} where the name-mangling issue is handled internally in C header-files through checks for preprocessor variable ©__cplusplus©, which adds appropriate ©extern "C"© qualifiers. … … 6649 6638 Type-safe allocation is provided for all C allocation routines and new \CFA allocation routines, \eg in 6650 6639 \begin{cfa} 6651 int * ip = (int *)malloc( sizeof(int) ); §\C{// C}§6652 int * ip = malloc(); §\C{// \CFA type-safe version of C malloc}§6653 int * ip = alloc(); §\C{// \CFA type-safe uniform alloc}§6640 int * ip = (int *)malloc( sizeof(int) ); $\C{// C}$ 6641 int * ip = malloc(); $\C{// \CFA type-safe version of C malloc}$ 6642 int * ip = alloc(); $\C{// \CFA type-safe uniform alloc}$ 6654 6643 \end{cfa} 6655 6644 the latter two allocations determine the allocation size from the type of ©p© (©int©) and cast the pointer to the allocated storage to ©int *©. … … 6658 6647 \begin{cfa} 6659 6648 struct S { int i; } __attribute__(( aligned( 128 ) )); // cache-line alignment 6660 S * sp = malloc(); §\C{// honour type alignment}§6649 S * sp = malloc(); $\C{// honour type alignment}$ 6661 6650 \end{cfa} 6662 6651 the storage allocation is implicitly aligned to 128 rather than the default 16. … … 6673 6662 \CFA memory management extends allocation to support constructors for initialization of allocated storage, \eg in 6674 6663 \begin{cfa} 6675 struct S { int i; }; §\C{// cache-line aglinment}§6664 struct S { int i; }; $\C{// cache-line alignment}$ 6676 6665 void ?{}( S & s, int i ) { s.i = i; } 6677 6666 // assume ?|? operator for printing an S 6678 6667 6679 S & sp = * ®new®( 3 ); §\C{// call constructor after allocation}§6668 S & sp = *@new@( 3 ); $\C{// call constructor after allocation}$ 6680 6669 sout | sp.i; 6681 ®delete®( &sp );6682 6683 S * spa = ®anew®( 10, 5 ); §\C{// allocate array and initialize each array element}§6670 @delete@( &sp ); 6671 6672 S * spa = @anew@( 10, 5 ); $\C{// allocate array and initialize each array element}$ 6684 6673 for ( i; 10 ) sout | spa[i] | nonl; 6685 6674 sout | nl; 6686 ®adelete®( 10, spa );6675 @adelete@( 10, spa ); 6687 6676 \end{cfa} 6688 6677 Allocation routines ©new©/©anew© allocate a variable/array and initialize storage using the allocated type's constructor. … … 6693 6682 extern "C" { 6694 6683 // C unsafe allocation 6695 void * malloc( size_t size ); §\indexc{malloc}§6696 void * calloc( size_t dim, size_t size ); §\indexc{calloc}§6697 void * realloc( void * ptr, size_t size ); §\indexc{realloc}§6698 void * memalign( size_t align, size_t size ); §\indexc{memalign}§6699 void * aligned_alloc( size_t align, size_t size ); §\indexc{aligned_alloc}§6700 int posix_memalign( void ** ptr, size_t align, size_t size ); §\indexc{posix_memalign}§6701 void * cmemalign( size_t alignment, size_t noOfElems, size_t elemSize ); §\indexc{cmemalign}§// CFA6684 void * malloc( size_t size );$\indexc{malloc}$ 6685 void * calloc( size_t dim, size_t size );$\indexc{calloc}$ 6686 void * realloc( void * ptr, size_t size );$\indexc{realloc}$ 6687 void * memalign( size_t align, size_t size );$\indexc{memalign}$ 6688 void * aligned_alloc( size_t align, size_t size );$\indexc{aligned_alloc}$ 6689 int posix_memalign( void ** ptr, size_t align, size_t size );$\indexc{posix_memalign}$ 6690 void * cmemalign( size_t alignment, size_t noOfElems, size_t elemSize );$\indexc{cmemalign}$ // CFA 6702 6691 6703 6692 // C unsafe initialization/copy 6704 void * memset( void * dest, int c, size_t size ); §\indexc{memset}§6705 void * memcpy( void * dest, const void * src, size_t size ); §\indexc{memcpy}§6693 void * memset( void * dest, int c, size_t size );$\indexc{memset}$ 6694 void * memcpy( void * dest, const void * src, size_t size );$\indexc{memcpy}$ 6706 6695 } 6707 6696 … … 6709 6698 6710 6699 forall( dtype T | sized(T) ) { 6711 // §\CFA§safe equivalents, i.e., implicit size specification6700 // $\CFA$ safe equivalents, i.e., implicit size specification 6712 6701 T * malloc( void ); 6713 6702 T * calloc( size_t dim ); … … 6718 6707 int posix_memalign( T ** ptr, size_t align ); 6719 6708 6720 // §\CFA§safe general allocation, fill, resize, alignment, array6721 T * alloc( void ); §\indexc{alloc}§ §\C[3.5in]{// variable, T size}§6722 T * alloc( size_t dim ); §\C{// array[dim], T size elements}§6723 T * alloc( T ptr[], size_t dim ); §\C{// realloc array[dim], T size elements}§6724 6725 T * alloc_set( char fill ); §\indexc{alloc_set}§ §\C{// variable, T size, fill bytes with value}§6726 T * alloc_set( T fill ); §\C{// variable, T size, fill with value}§6727 T * alloc_set( size_t dim, char fill ); §\C{// array[dim], T size elements, fill bytes with value}§6728 T * alloc_set( size_t dim, T fill ); §\C{// array[dim], T size elements, fill elements with value}§6729 T * alloc_set( size_t dim, const T fill[] ); §\C{// array[dim], T size elements, fill elements with array}§6730 T * alloc_set( T ptr[], size_t dim, char fill ); §\C{// realloc array[dim], T size elements, fill bytes with value}§6731 6732 T * alloc_align( size_t align ); §\C{// aligned variable, T size}§6733 T * alloc_align( size_t align, size_t dim ); §\C{// aligned array[dim], T size elements}§6734 T * alloc_align( T ptr[], size_t align ); §\C{// realloc new aligned array}§6735 T * alloc_align( T ptr[], size_t align, size_t dim ); §\C{// realloc new aligned array[dim]}§6736 6737 T * alloc_align_set( size_t align, char fill ); §\C{// aligned variable, T size, fill bytes with value}§6738 T * alloc_align_set( size_t align, T fill ); §\C{// aligned variable, T size, fill with value}§6739 T * alloc_align_set( size_t align, size_t dim, char fill ); §\C{// aligned array[dim], T size elements, fill bytes with value}§6740 T * alloc_align_set( size_t align, size_t dim, T fill ); §\C{// aligned array[dim], T size elements, fill elements with value}§6741 T * alloc_align_set( size_t align, size_t dim, const T fill[] ); §\C{// aligned array[dim], T size elements, fill elements with array}§6742 T * alloc_align_set( T ptr[], size_t align, size_t dim, char fill ); §\C{// realloc new aligned array[dim], fill new bytes with value}§6743 6744 // §\CFA§safe initialization/copy, i.e., implicit size specification6745 T * memset( T * dest, char fill ); §\indexc{memset}§6746 T * memcpy( T * dest, const T * src ); §\indexc{memcpy}§6747 6748 // §\CFA§safe initialization/copy, i.e., implicit size specification, array types6709 // $\CFA$ safe general allocation, fill, resize, alignment, array 6710 T * alloc( void );$\indexc{alloc}$ $\C[3.5in]{// variable, T size}$ 6711 T * alloc( size_t dim ); $\C{// array[dim], T size elements}$ 6712 T * alloc( T ptr[], size_t dim ); $\C{// realloc array[dim], T size elements}$ 6713 6714 T * alloc_set( char fill );$\indexc{alloc_set}$ $\C{// variable, T size, fill bytes with value}$ 6715 T * alloc_set( T fill ); $\C{// variable, T size, fill with value}$ 6716 T * alloc_set( size_t dim, char fill ); $\C{// array[dim], T size elements, fill bytes with value}$ 6717 T * alloc_set( size_t dim, T fill ); $\C{// array[dim], T size elements, fill elements with value}$ 6718 T * alloc_set( size_t dim, const T fill[] ); $\C{// array[dim], T size elements, fill elements with array}$ 6719 T * alloc_set( T ptr[], size_t dim, char fill ); $\C{// realloc array[dim], T size elements, fill bytes with value}$ 6720 6721 T * alloc_align( size_t align ); $\C{// aligned variable, T size}$ 6722 T * alloc_align( size_t align, size_t dim ); $\C{// aligned array[dim], T size elements}$ 6723 T * alloc_align( T ptr[], size_t align ); $\C{// realloc new aligned array}$ 6724 T * alloc_align( T ptr[], size_t align, size_t dim ); $\C{// realloc new aligned array[dim]}$ 6725 6726 T * alloc_align_set( size_t align, char fill ); $\C{// aligned variable, T size, fill bytes with value}$ 6727 T * alloc_align_set( size_t align, T fill ); $\C{// aligned variable, T size, fill with value}$ 6728 T * alloc_align_set( size_t align, size_t dim, char fill ); $\C{// aligned array[dim], T size elements, fill bytes with value}$ 6729 T * alloc_align_set( size_t align, size_t dim, T fill ); $\C{// aligned array[dim], T size elements, fill elements with value}$ 6730 T * alloc_align_set( size_t align, size_t dim, const T fill[] ); $\C{// aligned array[dim], T size elements, fill elements with array}$ 6731 T * alloc_align_set( T ptr[], size_t align, size_t dim, char fill ); $\C{// realloc new aligned array[dim], fill new bytes with value}$ 6732 6733 // $\CFA$ safe initialization/copy, i.e., implicit size specification 6734 T * memset( T * dest, char fill );$\indexc{memset}$ 6735 T * memcpy( T * dest, const T * src );$\indexc{memcpy}$ 6736 6737 // $\CFA$ safe initialization/copy, i.e., implicit size specification, array types 6749 6738 T * amemset( T dest[], char fill, size_t dim ); 6750 6739 T * amemcpy( T dest[], const T src[], size_t dim ); 6751 6740 } 6752 6741 6753 // §\CFA§allocation/deallocation and constructor/destructor, non-array types6754 forall( dtype T | sized(T), ttype Params | { void ?{}( T &, Params ); } ) T * new( Params p ); §\indexc{new}§6755 forall( dtype T | sized(T) | { void ^?{}( T & ); } ) void delete( T * ptr ); §\indexc{delete}§6742 // $\CFA$ allocation/deallocation and constructor/destructor, non-array types 6743 forall( dtype T | sized(T), ttype Params | { void ?{}( T &, Params ); } ) T * new( Params p );$\indexc{new}$ 6744 forall( dtype T | sized(T) | { void ^?{}( T & ); } ) void delete( T * ptr );$\indexc{delete}$ 6756 6745 forall( dtype T, ttype Params | sized(T) | { void ^?{}( T & ); void delete( Params ); } ) 6757 6746 void delete( T * ptr, Params rest ); 6758 6747 6759 // §\CFA§allocation/deallocation and constructor/destructor, array types6760 forall( dtype T | sized(T), ttype Params | { void ?{}( T &, Params ); } ) T * anew( size_t dim, Params p ); §\indexc{anew}§6761 forall( dtype T | sized(T) | { void ^?{}( T & ); } ) void adelete( size_t dim, T arr[] ); §\indexc{adelete}§6748 // $\CFA$ allocation/deallocation and constructor/destructor, array types 6749 forall( dtype T | sized(T), ttype Params | { void ?{}( T &, Params ); } ) T * anew( size_t dim, Params p );$\indexc{anew}$ 6750 forall( dtype T | sized(T) | { void ^?{}( T & ); } ) void adelete( size_t dim, T arr[] );$\indexc{adelete}$ 6762 6751 forall( dtype T | sized(T) | { void ^?{}( T & ); }, ttype Params | { void adelete( Params ); } ) 6763 6752 void adelete( size_t dim, T arr[], Params rest ); … … 6769 6758 \leavevmode 6770 6759 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6771 int ato( const char * ptr ); §\indexc{ato}§6760 int ato( const char * ptr );$\indexc{ato}$ 6772 6761 unsigned int ato( const char * ptr ); 6773 6762 long int ato( const char * ptr ); … … 6801 6790 \leavevmode 6802 6791 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6803 forall( otype T | { int ?<?( T, T ); } ) §\C{// location}§6804 T * bsearch( T key, const T * arr, size_t dim ); §\indexc{bsearch}§6805 6806 forall( otype T | { int ?<?( T, T ); } ) §\C{// position}§6792 forall( otype T | { int ?<?( T, T ); } ) $\C{// location}$ 6793 T * bsearch( T key, const T * arr, size_t dim );$\indexc{bsearch}$ 6794 6795 forall( otype T | { int ?<?( T, T ); } ) $\C{// position}$ 6807 6796 unsigned int bsearch( T key, const T * arr, size_t dim ); 6808 6797 6809 6798 forall( otype T | { int ?<?( T, T ); } ) 6810 void qsort( const T * arr, size_t dim ); §\indexc{qsort}§6799 void qsort( const T * arr, size_t dim );$\indexc{qsort}$ 6811 6800 6812 6801 forall( otype E | { int ?<?( E, E ); } ) { 6813 E * bsearch( E key, const E * vals, size_t dim ); §\indexc{bsearch}§ §\C{// location}§6814 size_t bsearch( E key, const E * vals, size_t dim ); §\C{// position}§6815 E * bsearchl( E key, const E * vals, size_t dim ); §\indexc{bsearchl}§6802 E * bsearch( E key, const E * vals, size_t dim );$\indexc{bsearch}$ $\C{// location}$ 6803 size_t bsearch( E key, const E * vals, size_t dim );$\C{// position}$ 6804 E * bsearchl( E key, const E * vals, size_t dim );$\indexc{bsearchl}$ 6816 6805 size_t bsearchl( E key, const E * vals, size_t dim ); 6817 E * bsearchu( E key, const E * vals, size_t dim ); §\indexc{bsearchu}§6806 E * bsearchu( E key, const E * vals, size_t dim );$\indexc{bsearchu}$ 6818 6807 size_t bsearchu( E key, const E * vals, size_t dim ); 6819 6808 } … … 6829 6818 6830 6819 forall( otype E | { int ?<?( E, E ); } ) { 6831 void qsort( E * vals, size_t dim ); §\indexc{qsort}§6820 void qsort( E * vals, size_t dim );$\indexc{qsort}$ 6832 6821 } 6833 6822 \end{cfa} … … 6838 6827 \leavevmode 6839 6828 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6840 unsigned char abs( signed char ); §\indexc{abs}§6829 unsigned char abs( signed char );$\indexc{abs}$ 6841 6830 int abs( int ); 6842 6831 unsigned long int abs( long int ); … … 6857 6846 \leavevmode 6858 6847 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6859 void srandom( unsigned int seed ); §\indexc{srandom}§6860 char random( void ); §\indexc{random}§6861 char random( char u ); §\C{// [0,u)}§6862 char random( char l, char u ); §\C{// [l,u)}§6848 void srandom( unsigned int seed );$\indexc{srandom}$ 6849 char random( void );$\indexc{random}$ 6850 char random( char u ); $\C{// [0,u)}$ 6851 char random( char l, char u ); $\C{// [l,u)}$ 6863 6852 int random( void ); 6864 int random( int u ); §\C{// [0,u)}§6865 int random( int l, int u ); §\C{// [l,u)}§6853 int random( int u ); $\C{// [0,u)}$ 6854 int random( int l, int u ); $\C{// [l,u)}$ 6866 6855 unsigned int random( void ); 6867 unsigned int random( unsigned int u ); §\C{// [0,u)}§6868 unsigned int random( unsigned int l, unsigned int u ); §\C{// [l,u)}§6856 unsigned int random( unsigned int u ); $\C{// [0,u)}$ 6857 unsigned int random( unsigned int l, unsigned int u ); $\C{// [l,u)}$ 6869 6858 long int random( void ); 6870 long int random( long int u ); §\C{// [0,u)}§6871 long int random( long int l, long int u ); §\C{// [l,u)}§6859 long int random( long int u ); $\C{// [0,u)}$ 6860 long int random( long int l, long int u ); $\C{// [l,u)}$ 6872 6861 unsigned long int random( void ); 6873 unsigned long int random( unsigned long int u ); §\C{// [0,u)}§6874 unsigned long int random( unsigned long int l, unsigned long int u ); §\C{// [l,u)}§6875 float random( void ); §\C{// [0.0, 1.0)}§6876 double random( void ); §\C{// [0.0, 1.0)}§6877 float _Complex random( void ); §\C{// [0.0, 1.0)+[0.0, 1.0)i}§6878 double _Complex random( void ); §\C{// [0.0, 1.0)+[0.0, 1.0)i}§6879 long double _Complex random( void ); §\C{// [0.0, 1.0)+[0.0, 1.0)i}§6862 unsigned long int random( unsigned long int u ); $\C{// [0,u)}$ 6863 unsigned long int random( unsigned long int l, unsigned long int u ); $\C{// [l,u)}$ 6864 float random( void ); $\C{// [0.0, 1.0)}$ 6865 double random( void ); $\C{// [0.0, 1.0)}$ 6866 float _Complex random( void ); $\C{// [0.0, 1.0)+[0.0, 1.0)i}$ 6867 double _Complex random( void ); $\C{// [0.0, 1.0)+[0.0, 1.0)i}$ 6868 long double _Complex random( void ); $\C{// [0.0, 1.0)+[0.0, 1.0)i}$ 6880 6869 \end{cfa} 6881 6870 … … 6885 6874 \leavevmode 6886 6875 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6887 forall( otype T | { int ?<?( T, T ); } ) T min( T t1, T t2 ); §\indexc{min}§6888 forall( otype T | { int ?>?( T, T ); } ) T max( T t1, T t2 ); §\indexc{max}§6889 forall( otype T | { T min( T, T ); T max( T, T ); } ) T clamp( T value, T min_val, T max_val ); §\indexc{clamp}§6890 forall( otype T ) void swap( T * t1, T * t2 ); §\indexc{swap}§6876 forall( otype T | { int ?<?( T, T ); } ) T min( T t1, T t2 );$\indexc{min}$ 6877 forall( otype T | { int ?>?( T, T ); } ) T max( T t1, T t2 );$\indexc{max}$ 6878 forall( otype T | { T min( T, T ); T max( T, T ); } ) T clamp( T value, T min_val, T max_val );$\indexc{clamp}$ 6879 forall( otype T ) void swap( T * t1, T * t2 );$\indexc{swap}$ 6891 6880 \end{cfa} 6892 6881 … … 6902 6891 \leavevmode 6903 6892 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6904 float ?%?( float, float ); §\indexc{fmod}§6893 float ?%?( float, float );$\indexc{fmod}$ 6905 6894 float fmod( float, float ); 6906 6895 double ?%?( double, double ); … … 6909 6898 long double fmod( long double, long double ); 6910 6899 6911 float remainder( float, float ); §\indexc{remainder}§6900 float remainder( float, float );$\indexc{remainder}$ 6912 6901 double remainder( double, double ); 6913 6902 long double remainder( long double, long double ); 6914 6903 6915 float remquo( float, float, int * ); §\indexc{remquo}§6904 float remquo( float, float, int * );$\indexc{remquo}$ 6916 6905 double remquo( double, double, int * ); 6917 6906 long double remquo( long double, long double, int * ); … … 6920 6909 [ int, long double ] remquo( long double, long double ); 6921 6910 6922 float div( float, float, int * ); §\indexc{div}§ §\C{// alternative name for remquo}§6911 float div( float, float, int * );$\indexc{div}$ $\C{// alternative name for remquo}$ 6923 6912 double div( double, double, int * ); 6924 6913 long double div( long double, long double, int * ); … … 6927 6916 [ int, long double ] div( long double, long double ); 6928 6917 6929 float fma( float, float, float ); §\indexc{fma}§6918 float fma( float, float, float );$\indexc{fma}$ 6930 6919 double fma( double, double, double ); 6931 6920 long double fma( long double, long double, long double ); 6932 6921 6933 float fdim( float, float ); §\indexc{fdim}§6922 float fdim( float, float );$\indexc{fdim}$ 6934 6923 double fdim( double, double ); 6935 6924 long double fdim( long double, long double ); 6936 6925 6937 float nan( const char * ); §\indexc{nan}§6926 float nan( const char * );$\indexc{nan}$ 6938 6927 double nan( const char * ); 6939 6928 long double nan( const char * ); … … 6945 6934 \leavevmode 6946 6935 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6947 float exp( float ); §\indexc{exp}§6936 float exp( float );$\indexc{exp}$ 6948 6937 double exp( double ); 6949 6938 long double exp( long double ); … … 6952 6941 long double _Complex exp( long double _Complex ); 6953 6942 6954 float exp2( float ); §\indexc{exp2}§6943 float exp2( float );$\indexc{exp2}$ 6955 6944 double exp2( double ); 6956 6945 long double exp2( long double ); … … 6959 6948 // long double _Complex exp2( long double _Complex ); 6960 6949 6961 float expm1( float ); §\indexc{expm1}§6950 float expm1( float );$\indexc{expm1}$ 6962 6951 double expm1( double ); 6963 6952 long double expm1( long double ); 6964 6953 6965 float pow( float, float ); §\indexc{pow}§6954 float pow( float, float );$\indexc{pow}$ 6966 6955 double pow( double, double ); 6967 6956 long double pow( long double, long double ); … … 6976 6965 \leavevmode 6977 6966 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 6978 float log( float ); §\indexc{log}§6967 float log( float );$\indexc{log}$ 6979 6968 double log( double ); 6980 6969 long double log( long double ); … … 6983 6972 long double _Complex log( long double _Complex ); 6984 6973 6985 float log2( float ); §\indexc{log2}§6974 float log2( float );$\indexc{log2}$ 6986 6975 double log2( double ); 6987 6976 long double log2( long double ); … … 6990 6979 // long double _Complex log2( long double _Complex ); 6991 6980 6992 float log10( float ); §\indexc{log10}§6981 float log10( float );$\indexc{log10}$ 6993 6982 double log10( double ); 6994 6983 long double log10( long double ); … … 6997 6986 // long double _Complex log10( long double _Complex ); 6998 6987 6999 float log1p( float ); §\indexc{log1p}§6988 float log1p( float );$\indexc{log1p}$ 7000 6989 double log1p( double ); 7001 6990 long double log1p( long double ); 7002 6991 7003 int ilogb( float ); §\indexc{ilogb}§6992 int ilogb( float );$\indexc{ilogb}$ 7004 6993 int ilogb( double ); 7005 6994 int ilogb( long double ); 7006 6995 7007 float logb( float ); §\indexc{logb}§6996 float logb( float );$\indexc{logb}$ 7008 6997 double logb( double ); 7009 6998 long double logb( long double ); 7010 6999 7011 float sqrt( float ); §\indexc{sqrt}§7000 float sqrt( float );$\indexc{sqrt}$ 7012 7001 double sqrt( double ); 7013 7002 long double sqrt( long double ); … … 7016 7005 long double _Complex sqrt( long double _Complex ); 7017 7006 7018 float cbrt( float ); §\indexc{cbrt}§7007 float cbrt( float );$\indexc{cbrt}$ 7019 7008 double cbrt( double ); 7020 7009 long double cbrt( long double ); 7021 7010 7022 float hypot( float, float ); §\indexc{hypot}§7011 float hypot( float, float );$\indexc{hypot}$ 7023 7012 double hypot( double, double ); 7024 7013 long double hypot( long double, long double ); … … 7030 7019 \leavevmode 7031 7020 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7032 float sin( float ); §\indexc{sin}§7021 float sin( float );$\indexc{sin}$ 7033 7022 double sin( double ); 7034 7023 long double sin( long double ); … … 7037 7026 long double _Complex sin( long double _Complex ); 7038 7027 7039 float cos( float ); §\indexc{cos}§7028 float cos( float );$\indexc{cos}$ 7040 7029 double cos( double ); 7041 7030 long double cos( long double ); … … 7044 7033 long double _Complex cos( long double _Complex ); 7045 7034 7046 float tan( float ); §\indexc{tan}§7035 float tan( float );$\indexc{tan}$ 7047 7036 double tan( double ); 7048 7037 long double tan( long double ); … … 7051 7040 long double _Complex tan( long double _Complex ); 7052 7041 7053 float asin( float ); §\indexc{asin}§7042 float asin( float );$\indexc{asin}$ 7054 7043 double asin( double ); 7055 7044 long double asin( long double ); … … 7058 7047 long double _Complex asin( long double _Complex ); 7059 7048 7060 float acos( float ); §\indexc{acos}§7049 float acos( float );$\indexc{acos}$ 7061 7050 double acos( double ); 7062 7051 long double acos( long double ); … … 7065 7054 long double _Complex acos( long double _Complex ); 7066 7055 7067 float atan( float ); §\indexc{atan}§7056 float atan( float );$\indexc{atan}$ 7068 7057 double atan( double ); 7069 7058 long double atan( long double ); … … 7072 7061 long double _Complex atan( long double _Complex ); 7073 7062 7074 float atan2( float, float ); §\indexc{atan2}§7063 float atan2( float, float );$\indexc{atan2}$ 7075 7064 double atan2( double, double ); 7076 7065 long double atan2( long double, long double ); 7077 7066 7078 float atan( float, float ); §\C{// alternative name for atan2}§7079 double atan( double, double ); §\indexc{atan}§7067 float atan( float, float ); $\C{// alternative name for atan2}$ 7068 double atan( double, double );$\indexc{atan}$ 7080 7069 long double atan( long double, long double ); 7081 7070 \end{cfa} … … 7086 7075 \leavevmode 7087 7076 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7088 float sinh( float ); §\indexc{sinh}§7077 float sinh( float );$\indexc{sinh}$ 7089 7078 double sinh( double ); 7090 7079 long double sinh( long double ); … … 7093 7082 long double _Complex sinh( long double _Complex ); 7094 7083 7095 float cosh( float ); §\indexc{cosh}§7084 float cosh( float );$\indexc{cosh}$ 7096 7085 double cosh( double ); 7097 7086 long double cosh( long double ); … … 7100 7089 long double _Complex cosh( long double _Complex ); 7101 7090 7102 float tanh( float ); §\indexc{tanh}§7091 float tanh( float );$\indexc{tanh}$ 7103 7092 double tanh( double ); 7104 7093 long double tanh( long double ); … … 7107 7096 long double _Complex tanh( long double _Complex ); 7108 7097 7109 float asinh( float ); §\indexc{asinh}§7098 float asinh( float );$\indexc{asinh}$ 7110 7099 double asinh( double ); 7111 7100 long double asinh( long double ); … … 7114 7103 long double _Complex asinh( long double _Complex ); 7115 7104 7116 float acosh( float ); §\indexc{acosh}§7105 float acosh( float );$\indexc{acosh}$ 7117 7106 double acosh( double ); 7118 7107 long double acosh( long double ); … … 7121 7110 long double _Complex acosh( long double _Complex ); 7122 7111 7123 float atanh( float ); §\indexc{atanh}§7112 float atanh( float );$\indexc{atanh}$ 7124 7113 double atanh( double ); 7125 7114 long double atanh( long double ); … … 7134 7123 \leavevmode 7135 7124 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7136 float erf( float ); §\indexc{erf}§7125 float erf( float );$\indexc{erf}$ 7137 7126 double erf( double ); 7138 7127 long double erf( long double ); … … 7141 7130 long double _Complex erf( long double _Complex ); 7142 7131 7143 float erfc( float ); §\indexc{erfc}§7132 float erfc( float );$\indexc{erfc}$ 7144 7133 double erfc( double ); 7145 7134 long double erfc( long double ); … … 7148 7137 long double _Complex erfc( long double _Complex ); 7149 7138 7150 float lgamma( float ); §\indexc{lgamma}§7139 float lgamma( float );$\indexc{lgamma}$ 7151 7140 double lgamma( double ); 7152 7141 long double lgamma( long double ); … … 7155 7144 long double lgamma( long double, int * ); 7156 7145 7157 float tgamma( float ); §\indexc{tgamma}§7146 float tgamma( float );$\indexc{tgamma}$ 7158 7147 double tgamma( double ); 7159 7148 long double tgamma( long double ); … … 7165 7154 \leavevmode 7166 7155 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7167 float floor( float ); §\indexc{floor}§7156 float floor( float );$\indexc{floor}$ 7168 7157 double floor( double ); 7169 7158 long double floor( long double ); 7170 7159 7171 float ceil( float ); §\indexc{ceil}§7160 float ceil( float );$\indexc{ceil}$ 7172 7161 double ceil( double ); 7173 7162 long double ceil( long double ); 7174 7163 7175 float trunc( float ); §\indexc{trunc}§7164 float trunc( float );$\indexc{trunc}$ 7176 7165 double trunc( double ); 7177 7166 long double trunc( long double ); 7178 7167 7179 float rint( float ); §\indexc{rint}§7168 float rint( float );$\indexc{rint}$ 7180 7169 long double rint( long double ); 7181 7170 long int rint( float ); … … 7186 7175 long long int rint( long double ); 7187 7176 7188 long int lrint( float ); §\indexc{lrint}§7177 long int lrint( float );$\indexc{lrint}$ 7189 7178 long int lrint( double ); 7190 7179 long int lrint( long double ); … … 7193 7182 long long int llrint( long double ); 7194 7183 7195 float nearbyint( float ); §\indexc{nearbyint}§7184 float nearbyint( float );$\indexc{nearbyint}$ 7196 7185 double nearbyint( double ); 7197 7186 long double nearbyint( long double ); 7198 7187 7199 float round( float ); §\indexc{round}§7188 float round( float );$\indexc{round}$ 7200 7189 long double round( long double ); 7201 7190 long int round( float ); … … 7206 7195 long long int round( long double ); 7207 7196 7208 long int lround( float ); §\indexc{lround}§7197 long int lround( float );$\indexc{lround}$ 7209 7198 long int lround( double ); 7210 7199 long int lround( long double ); … … 7219 7208 \leavevmode 7220 7209 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7221 float copysign( float, float ); §\indexc{copysign}§7210 float copysign( float, float );$\indexc{copysign}$ 7222 7211 double copysign( double, double ); 7223 7212 long double copysign( long double, long double ); 7224 7213 7225 float frexp( float, int * ); §\indexc{frexp}§7214 float frexp( float, int * );$\indexc{frexp}$ 7226 7215 double frexp( double, int * ); 7227 7216 long double frexp( long double, int * ); 7228 7217 7229 float ldexp( float, int ); §\indexc{ldexp}§7218 float ldexp( float, int );$\indexc{ldexp}$ 7230 7219 double ldexp( double, int ); 7231 7220 long double ldexp( long double, int ); 7232 7221 7233 [ float, float ] modf( float ); §\indexc{modf}§7222 [ float, float ] modf( float );$\indexc{modf}$ 7234 7223 float modf( float, float * ); 7235 7224 [ double, double ] modf( double ); … … 7238 7227 long double modf( long double, long double * ); 7239 7228 7240 float nextafter( float, float ); §\indexc{nextafter}§7229 float nextafter( float, float );$\indexc{nextafter}$ 7241 7230 double nextafter( double, double ); 7242 7231 long double nextafter( long double, long double ); 7243 7232 7244 float nexttoward( float, long double ); §\indexc{nexttoward}§7233 float nexttoward( float, long double );$\indexc{nexttoward}$ 7245 7234 double nexttoward( double, long double ); 7246 7235 long double nexttoward( long double, long double ); 7247 7236 7248 float scalbn( float, int ); §\indexc{scalbn}§7237 float scalbn( float, int );$\indexc{scalbn}$ 7249 7238 double scalbn( double, int ); 7250 7239 long double scalbn( long double, int ); 7251 7240 7252 float scalbln( float, long int ); §\indexc{scalbln}§7241 float scalbln( float, long int );$\indexc{scalbln}$ 7253 7242 double scalbln( double, long int ); 7254 7243 long double scalbln( long double, long int ); … … 7267 7256 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7268 7257 struct Duration { 7269 int64_t tv; §\C{// nanoseconds}§7258 int64_t tv; $\C{// nanoseconds}$ 7270 7259 }; 7271 7260 … … 7397 7386 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7398 7387 struct Time { 7399 uint64_t tv; §\C{// nanoseconds since UNIX epoch}§7388 uint64_t tv; $\C{// nanoseconds since UNIX epoch}$ 7400 7389 }; 7401 7390 … … 7468 7457 \begin{cfa}[aboveskip=0pt,belowskip=0pt] 7469 7458 struct Clock { 7470 Duration offset; §\C{// for virtual clock: contains offset from real-time}§7471 int clocktype; §\C{// implementation only -1 (virtual), CLOCK\_REALTIME}§7459 Duration offset; $\C{// for virtual clock: contains offset from real-time}$ 7460 int clocktype; $\C{// implementation only -1 (virtual), CLOCK\_REALTIME}$ 7472 7461 }; 7473 7462 … … 7477 7466 void ?{}( Clock & clk, Duration adj ); 7478 7467 7479 Duration getResNsec(); §\C{// with nanoseconds}§7480 Duration getRes(); §\C{// without nanoseconds}§7481 7482 Time getTimeNsec(); §\C{// with nanoseconds}§7483 Time getTime(); §\C{// without nanoseconds}§7468 Duration getResNsec(); $\C{// with nanoseconds}$ 7469 Duration getRes(); $\C{// without nanoseconds}$ 7470 7471 Time getTimeNsec(); $\C{// with nanoseconds}$ 7472 Time getTime(); $\C{// without nanoseconds}$ 7484 7473 Time getTime( Clock & clk ); 7485 7474 Time ?()( Clock & clk ); … … 7497 7486 7498 7487 \begin{cfa} 7499 void ?{}( Int * this ); §\C{// constructor/destructor}§7488 void ?{}( Int * this ); $\C{// constructor/destructor}$ 7500 7489 void ?{}( Int * this, Int init ); 7501 7490 void ?{}( Int * this, zero_t ); … … 7506 7495 void ^?{}( Int * this ); 7507 7496 7508 Int ?=?( Int * lhs, Int rhs ); §\C{// assignment}§7497 Int ?=?( Int * lhs, Int rhs ); $\C{// assignment}$ 7509 7498 Int ?=?( Int * lhs, long int rhs ); 7510 7499 Int ?=?( Int * lhs, unsigned long int rhs ); … … 7523 7512 unsigned long int narrow( Int val ); 7524 7513 7525 int ?==?( Int oper1, Int oper2 ); §\C{// comparison}§7514 int ?==?( Int oper1, Int oper2 ); $\C{// comparison}$ 7526 7515 int ?==?( Int oper1, long int oper2 ); 7527 7516 int ?==?( long int oper2, Int oper1 ); … … 7559 7548 int ?>=?( unsigned long int oper1, Int oper2 ); 7560 7549 7561 Int +?( Int oper ); §\C{// arithmetic}§7550 Int +?( Int oper ); $\C{// arithmetic}$ 7562 7551 Int -?( Int oper ); 7563 7552 Int ~?( Int oper ); … … 7641 7630 Int ?>>=?( Int * lhs, mp_bitcnt_t shift ); 7642 7631 7643 Int abs( Int oper ); §\C{// number functions}§7632 Int abs( Int oper ); $\C{// number functions}$ 7644 7633 Int fact( unsigned long int N ); 7645 7634 Int gcd( Int oper1, Int oper2 ); … … 7653 7642 Int sqrt( Int oper ); 7654 7643 7655 forall( dtype istype | istream( istype ) ) istype * ?|?( istype * is, Int * mp ); §\C{// I/O}§7644 forall( dtype istype | istream( istype ) ) istype * ?|?( istype * is, Int * mp ); $\C{// I/O}$ 7656 7645 forall( dtype ostype | ostream( ostype ) ) ostype * ?|?( ostype * os, Int mp ); 7657 7646 \end{cfa} … … 7664 7653 \hline 7665 7654 \begin{cfa} 7666 #include <gmp> §\indexc{gmp}§7655 #include <gmp>$\indexc{gmp}$ 7667 7656 int main( void ) { 7668 7657 sout | "Factorial Numbers"; … … 7678 7667 & 7679 7668 \begin{cfa} 7680 #include <gmp.h> §\indexc{gmp.h}§7669 #include <gmp.h>$\indexc{gmp.h}$ 7681 7670 int main( void ) { 7682 ®gmp_printf®( "Factorial Numbers\n" );7683 ®mpz_t®fact;7684 ®mpz_init_set_ui®( fact, 1 );7685 ®gmp_printf®( "%d %Zd\n", 0, fact );7671 @gmp_printf@( "Factorial Numbers\n" ); 7672 @mpz_t@ fact; 7673 @mpz_init_set_ui@( fact, 1 ); 7674 @gmp_printf@( "%d %Zd\n", 0, fact ); 7686 7675 for ( unsigned int i = 1; i <= 40; i += 1 ) { 7687 ®mpz_mul_ui®( fact, fact, i );7688 ®gmp_printf®( "%d %Zd\n", i, fact );7676 @mpz_mul_ui@( fact, fact, i ); 7677 @gmp_printf@( "%d %Zd\n", i, fact ); 7689 7678 } 7690 7679 } … … 7751 7740 \begin{cfa}[belowskip=0pt] 7752 7741 // implementation 7753 struct Rational { §\indexc{Rational}§7754 long int numerator, denominator; §\C{// invariant: denominator > 0}§7742 struct Rational {$\indexc{Rational}$ 7743 long int numerator, denominator; $\C{// invariant: denominator > 0}$ 7755 7744 }; // Rational 7756 7745 7757 Rational rational(); §\C{// constructors}§7746 Rational rational(); $\C{// constructors}$ 7758 7747 Rational rational( long int n ); 7759 7748 Rational rational( long int n, long int d ); … … 7761 7750 void ?{}( Rational * r, one_t ); 7762 7751 7763 long int numerator( Rational r ); §\C{// numerator/denominator getter/setter}§7752 long int numerator( Rational r ); $\C{// numerator/denominator getter/setter}$ 7764 7753 long int numerator( Rational r, long int n ); 7765 7754 long int denominator( Rational r ); 7766 7755 long int denominator( Rational r, long int d ); 7767 7756 7768 int ?==?( Rational l, Rational r ); §\C{// comparison}§7757 int ?==?( Rational l, Rational r ); $\C{// comparison}$ 7769 7758 int ?!=?( Rational l, Rational r ); 7770 7759 int ?<?( Rational l, Rational r ); … … 7773 7762 int ?>=?( Rational l, Rational r ); 7774 7763 7775 Rational -?( Rational r ); §\C{// arithmetic}§7764 Rational -?( Rational r ); $\C{// arithmetic}$ 7776 7765 Rational ?+?( Rational l, Rational r ); 7777 7766 Rational ?-?( Rational l, Rational r ); … … 7779 7768 Rational ?/?( Rational l, Rational r ); 7780 7769 7781 double widen( Rational r ); §\C{// conversion}§7770 double widen( Rational r ); $\C{// conversion}$ 7782 7771 Rational narrow( double f, long int md ); 7783 7772
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