Changeset 7d9a805b

Timestamp:

Mar 21, 2024, 9:34:28 PM (9 months ago)

Author:

Peter A. Buhr <pabuhr@…>

Branches:

master

Children:

6394ac6

Parents:

0139351

Message:

more proofreading for enumerations

Location:

doc/theses/jiada_liang_MMath

Files:

• CFAenum.tex (modified) (10 diffs)
• background.tex (modified) (2 diffs)
• implementation.tex (modified) (1 diff)
• intro.tex (modified) (3 diffs)
• relatedwork.tex (modified) (23 diffs)

doc/theses/jiada_liang_MMath/CFAenum.tex

@@ -1 @@
-\chapter{\CFA-Style Enum}
-
-
-\CFA supports C-Style enumeration using the same syntax and semantics for backwards compatibility.
+\chapter{\CFA Enumeration}
+
+
+\CFA supports C enumeration using the same syntax and semantics for backwards compatibility.
 \CFA also extends C-Style enumeration by adding a number of new features that bring enumerations inline with other modern programming languages.
 
@@ -16 +16 @@
 Finally, qualification is provided to disambiguate any ambiguous situations.
 \begin{cfa}
-enum C1 { First, Second, Third, Fourth };
-enum C2 { @Fourth@, @Third@, @Second@, @First@ };
-C1 p() { return Third; }                                $\C{// correctly resolved duplicate names}$
-C2 p() { return Fourth; }
+enum E1 { First, Second, Third, Fourth };
+enum E2 { @Fourth@, @Third@, @Second@, @First@ };
+E1 p() { return Third; }                                $\C{// correctly resolved duplicate names}$
+E2 p() { return Fourth; }
 void foo() {
-        C1 e1 = First;   C2 e2 = First;
+        E1 e1 = First;   E2 e2 = First;
         e1 = Second;   e2 = Second;
         e1 = p();   e2 = p();                           $\C{// correctly resolved function call}$
-        int i = @C1.@First + @C2.@First;        $\C{// ambiguous without qualification}$
-}
-\end{cfa}
-\CFA overloading allows programmers to use the most meaningful names without fear of unresolvable clashes from included files, which are correctable with qualification.
+        int i = @E1.@First + @E2.@First;        $\C{// disambiguate with qualification}$
+        int j = @(E1)@First + @(E2)@First;      $\C{// disambiguate with cast}$
+}
+\end{cfa}
+\CFA overloading allows programmers to use the most meaningful names without fear of name clashes from include files.
+Either the type system implicitly disambiguates or the programmer explicitly disambiguates using qualification or casting.
 
 
@@ -34 +36 @@
 An enumeration can be scoped, so the enumerator constants are not projected into the enclosing scope, using @'!'@.
 \begin{cfa}
-enum Weekday @!@ { /* as above */ };
-enum( char * ) Names @!@ { /* as above */ };
+enum Weekday @!@ { Mon, Tue, Wed, Thu = 10, Fri, Sat, Sun };
+enum RGB @!@ { Red, Green, Blue };
 \end{cfa}
 Now the enumerators \emph{must} be qualified with the associated enumeration.
 \begin{cfa}
-Weekday weekday = @Weekday@.Monday;
-Names names = @Names.@Fred;
-names = @Names.@Jane;
+Weekday weekday = @Weekday@.Mon;
+weekday = @Weekday@.Sat;
+RGB rgb = RGB.Red;
+rgb = RGB.Blue;
 \end{cfa}
 It is possible to toggle back to unscoping using the \CFA @with@ clause/statement (see also \CC \lstinline[language=c++]{using enum} in Section~\ref{s:C++RelatedWork}).
 \begin{cfa}
-Weekday weekday;
-with ( @Weekday@, @Names@ ) {                   $\C{// type names}$
-         Names names = @Fred@;
-         names = @Jane@;
-         weekday = Saturday;
-}
-\end{cfa}
-As in Section~\ref{s:EnumeratorNameResolution}, opening multiple unscoped enumerations can result in duplicate enumeration names, but \CFA type resolution and falling back to explicit qualification handles name resolution.
+with ( @Weekday@, @RGB@ ) {                     $\C{// type names}$
+         weekday = @Sun@;                               $\C{// no qualification}$
+         rgb = @Green@;
+}
+\end{cfa}
+As in Section~\ref{s:EnumeratorNameResolution}, opening multiple unscoped enumerations can result in duplicate enumeration names, but \CFA implicit type resolution and explicit qualification/casting handles name resolution.
 
 \section{Enumerator Typing}
@@ -80 +81 @@
 \begin{cfa}
 // integral
-        enum( @char@ ) Currency { Dollar = '$\textdollar$', Euro = '$\texteuro$', Pound = '$\textsterling$'  };
+        enum( @char@ ) Currency { Dollar = '$\textdollar$', Cent = '$\textcent$', Yen = '$\textyen$', Pound = '$\textsterling$', Euro = 'E' };
         enum( @signed char@ ) srgb { Red = -1, Green = 0, Blue = 1 };
         enum( @long long int@ ) BigNum { X = 123_456_789_012_345,  Y = 345_012_789_456_123 };
@@ -87 +88 @@
         enum( @_Complex@ ) Plane { X = 1.5+3.4i, Y = 7+3i, Z = 0+0.5i };
 // pointer
-        enum( @char *@ ) Names { Fred = "FRED", Mary = "MARY", Jane = "JANE" };
+        enum( @const char *@ ) Name { Fred = "FRED", Mary = "MARY", Jane = "JANE" };
         int i, j, k;
         enum( @int *@ ) ptr { I = &i,  J = &j,  K = &k };
@@ -98 +99 @@
 // aggregate
         struct Person { char * name; int age, height; };
-@***@enum( @Person@ ) friends { @Liz@ = { "ELIZABETH", 22, 170 }, @Beth@ = Liz, Jon = { "JONATHAN", 35, 190 } };
+@***@enum( @Person@ ) friends { @Liz@ = { "ELIZABETH", 22, 170 }, @Beth@ = Liz,
+                                                                                        Jon = { "JONATHAN", 35, 190 } };
 \end{cfa}
 \caption{Enumerator Typing}
@@ -140 +142 @@
 \begin{cfa}
 enum() Mode { O_RDONLY, O_WRONLY, O_CREAT, O_TRUNC, O_APPEND };
-@***@Mode iomode = O_RDONLY;
-bool b = iomode == O_RDONLY || iomode < O_APPEND;
-int i = iomode;                                                 $\C{\color{red}// disallowed}$
+Mode iomode = O_RDONLY;
+bool b = iomode == O_RDONLY || iomode < O_APPEND; $\C{// ordering}$
+@***@@int i = iomode;@                                                  $\C{// disallow conversion to int}$
 \end{cfa}
 
@@ -149 +151 @@
 If follows from enumerator typing that the enumerator type can be another enumerator.
 \begin{cfa}
-enum( @char@ ) Currency { Dollar = '$\textdollar$', Euro = '$\texteuro$', Pound = '$\textsterling$'  };
-enum( @Currency@ ) Europe { Euro = Currency.Euro, Pound = Currency.Pound }; // intersection
+enum( @char@ ) Currency { Dollar = '$\textdollar$', Cent = '$\textcent$', Yen = '$\textyen$', Pound = '$\textsterling$', Euro = 'E' };
+enum( Currency ) Europe { Euro = Currency.Euro, Pound = Currency.Pound };
 enum( char ) Letter { A = 'A',  B = 'B', C = 'C', ..., Z = 'Z' };
 enum( @Letter@ ) Greek { Alph = A, Beta = B, ..., Zeta = Z }; // intersection
@@ -158 +160 @@
 \begin{cfa}
 Letter letter = A;
-@***@Greak greek = Beta;
-letter = Beta;                                                  $\C{// allowed, letter == B}$
-greek = A;                                                              $\C{\color{red}// disallowed}$
+Greak greek = Beta;
+letter = Beta;                                                  $\C{// allowed, greek == B}$
+@greek = A;@                                                    $\C{// disallowed}$
 \end{cfa}
 
@@ -277 +279 @@
 p(variable_d); // 3
 \end{cfa}
+
+
+\section{Planet Example}
+
+\VRef[Figure]{f:PlanetExample} shows an archetypal enumeration example illustrating all of the \CFA enumeration features.
+Enumeration @Planet@ is a typed enumeration of type @MR@.
+Each of the planet enumerators is initialized to a specific mass/radius, @MR@, value.
+The unnamed enumeration projects the gravitational-constant enumerator @G@.
+The program main iterates through the planets computing the weight on each planet for a given earth weight.
+
+\begin{figure}
+\begin{cfa}
+struct MR { double mass, radius; };
+enum( MR ) Planet {
+        //                           mass          radius
+        MERCURY = { 3.303_E23, 2.4397_E6 },
+        VENUS       = { 4.869_E24, 6.0518_E6 },
+        EARTH       = { 5.976_E24, 6.3781_E6 },
+        MARS         = { 6.421_E23, 3.3972_E6 },
+        JUPITER    = { 1.898_E27, 7.1492_E7 },
+        SATURN     = { 5.688_E26, 6.0268_E7 },
+        URANUS    = { 8.686_E25, 2.5559_E7 },
+        NEPTUNE  = { 1.024_E26, 2.4746_E7 },
+};
+enum( double ) { G = 6.6743E-11 }; // universal gravitational constant (m3 kg-1 s-2)
+
+static double surfaceGravity( Planet p ) with( p ) {
+        return G * mass / ( radius * radius );
+}
+static double surfaceWeight( Planet p, double otherMass ) {
+        return otherMass * surfaceGravity( p );
+}
+int main( int argc, char * argv[] ) {
+        if ( argc != 2 ) exit | "Usage: " | argv[0] | "earth-weight";
+        double earthWeight = convert( argv[1] );
+        double mass = earthWeight / surfaceGravity( EARTH );
+        for ( p; Planet ) {
+                sout | "Your weight on" | labelE(p) | "is" | surfaceWeight( p, mass );
+        }
+}
+\end{cfa}
+\caption{Planet Example}
+\label{f:PlanetExample}
+\end{figure}

doc/theses/jiada_liang_MMath/background.tex

@@ -1 +1 @@
 \chapter{Background}
+\lstnewenvironment{clang}[1][]{\lstset{language=[ANSI]C,escapechar=\$,moredelim=**[is][\color{red}]{@}{@},}\lstset{#1}}{}
+
+\CFA is a backwards-compatible extension of the C programming language.
+Therefore, it must support C-style enumerations and any enumeration extensions must be intuitive to C programmers both in syntax and semantics.
+
+It is common for C programmers to ``believe'' there are three equivalent forms of named constants.
+\begin{clang}
+#define Mon 0
+static const int Mon = 0;
+enum { Mon };
+\end{clang}
+\begin{enumerate}[leftmargin=*]
+\item
+For @#define@, the programmer has to explicitly manage the constant name and value.
+Furthermore, these C preprocessor macro names are outside of the C type-system, and hence cannot be overloaded, and can incorrectly change random text in a program.
+\item
+The same explicit management is true for the @const@ declaration, and the @const@ variable cannot appear in constant-expression locations, like @case@ labels, array dimensions,\footnote{
+C allows variable-length array-declarations (VLA), so this case does work, but it fails in \CC, which does not support VLAs, unless it is \lstinline{g++}.} immediate operands of assembler instructions, and occupy storage.
+\begin{clang}
+$\$$ nm test.o
+0000000000000018 r Mon
+\end{clang}
+\item
+Only the @enum@ form is managed by the compiler, is part of the language type-system, and works in all C constant-expression locations.
+\end{enumerate}
 
 
-\section{C-Style Enum}
+\section{C \lstinline{const}}
 
-The C-Style enumeration has the following syntax and semantics.
-\begin{cfa}
-enum Weekday { Monday, Tuesday, Wednesday, Thursday@ = 10@, Friday, Saturday, Sunday };
-\end{cfa}
+As noted, C has the equivalent of Pascal typed @const@ declarations \see{\VRef{s:Pascal}}, with static and dynamic initialization.
+\begin{clang}
+static const int one = 0 + 1;                   $\C{// static intialization}$
+static const void * NIL = NULL;
+static const double PI = 3.14159;
+static const char Plus = '+';
+static const char * Fred = "Fred";
+static const int Mon = 0, Tue = Mon + 1, Wed = Tue + 1, Thu = Wed + 1, Fri = Thu + 1,
+                                        Sat = Fri + 1, Sun = Sat + 1;
+void foo() {
+        const int r = random();                         $\C{// dynamic intialization}$
+        int sa[Sun];                                            $\C{// VLA, local scope only}$
+}
+\end{clang}
+Statically initialized identifiers may appear in any constant-expression context, \eg @case@.
+Dynamically initialized identifiers may appear as array dimensions in @g++@, which allows variable-sized arrays.
+
+
+\section{C Enumeration}
+
+The C enumeration has the following syntax and semantics.
+\begin{clang}
+enum Weekday { Mon, Tue, Wed, Thu@ = 10@, Fri, Sat, Sun, };
+\end{clang}
 Enumerators without an explicitly designated constant value are \Newterm{auto-initialized} by the compiler: from left to right, starting at zero or the next explicitly initialized constant, incrementing by @1@.
-For example, @Monday@ to @Wednesday@ are implicitly assigned with constants @0@--@2@, @Thursday@ is explicitly set to constant @10@, and @Friday@ to @Sunday@ are implicitly assigned with constants @11@--@13@.
+For example, @Mon@ to @Wed@ are implicitly assigned with constants @0@--@2@, @Thu@ is explicitly set to constant @10@, and @Fri@ to @Sun@ are implicitly assigned with constants @11@--@13@.
 Initialization may occur in any order.
-\begin{cfa}
-enum Weekday { Thursday@ = 10@, Friday, Saturday, Sunday, Monday@ = 0@, Tuesday, Wednesday };
-\end{cfa}
+\begin{clang}
+enum Weekday { Thu@ = 10@, Fri, Sat, Sun, Mon@ = 0@, Tue, Wed };
+\end{clang}
 Note, the comma in the enumerator list can be a terminator or a separator, allowing the list to end with a dangling comma.
-\begin{cfa}
+\begin{clang}
 enum Weekday {
-        Thursday = 10, Friday, Saturday, Sunday,
-        Monday = 0, Tuesday, Wednesday@,@ // terminating comma
+        Thu = 10, Fri, Sat, Sun,
+        Mon = 0, Tue, Wed@,@ // terminating comma
 };
-\end{cfa}
+\end{clang}
 This feature allow enumerator lines to be interchanged without moving a comma.\footnote{
 A terminating comma appears in other C syntax, \eg the initializer list.}
@@ -28 +73 @@
 In practice, since integral constants are used, which have type @int@ (unless qualified with a size suffix), C uses @int@ as the underlying type for enumeration variables.
 Finally, there is an implicit bidirectional conversion between an enumeration and its integral type.
-\begin{cfa}
+\begin{clang}
 {
         enum Weekday { /* as above */ };        $\C{// enumerators implicitly projected into local scope}$
-        Weekday weekday = Monday;                       $\C{// weekday == 0}$
-        weekday = Friday;                                       $\C{// weekday == 11}$
-        int i = Sunday;                                         $\C{// implicit conversion to int, i == 13}$
+        Weekday weekday = Mon;                          $\C{// weekday == 0}$
+        weekday = Fri;                                          $\C{// weekday == 11}$
+        int i = Sun;                                            $\C{// implicit conversion to int, i == 13}$
         weekday = 10000;                                        $\C{// UNDEFINED! implicit conversion to Weekday}$
 }
-int j = Wednesday;                                              $\C{// ERROR! Wednesday is not declared in this scope}$
-\end{cfa}
+int j = Wed;                                                    $\C{// ERROR! Wed is not declared in this scope}$
+\end{clang}
 The implicit conversion from @int@ to an enumeration type is an unnecessary source of error.
-
-It is common for C programmers to ``believe'' there are 3 equivalent forms of constant enumeration.
-\begin{cfa}
-#define Monday 0
-static const int Monday = 0;
-enum { Monday };
-\end{cfa}
-For @#define@, the programmer has to play compiler and explicitly manage the enumeration values;
-furthermore, these are independent constants outside of any language type mechanism.
-The same explicit management is true for @const@ declarations, and the @const@ variable cannot appear in constant-expression locations, like @case@ labels, array dimensions,\footnote{
-C allows variable-length array-declarations (VLA), so this case does work, but it fails in \CC, which does not support VLAs, unless it is \lstinline{g++}.} and immediate operands of assembler instructions.
-Only the @enum@ form is managed by the compiler, is part of the language type-system, and works in all C constant-expression locations.

doc/theses/jiada_liang_MMath/implementation.tex

@@ -548 +548 @@
 \begin{cfa}
 enum(int) Weekday {
-        Monday=10, Tuesday, ...
+        Mon = 10, Tue, ...
 };
 

doc/theses/jiada_liang_MMath/intro.tex

@@ -4 +4 @@
 Naming is also commonly used to represent many other numerical phenomenon, such as days of the week, months of a year, floors of a building (basement), specific times (noon, New Years).
 Many programming languages capture this important software engineering capability through a mechanism called an \Newterm{enumeration}.
-An enumeration is similar to other programming-language types by providing a set of constrained values, but adds the ability to name \emph{all} the values in its set.
+An enumeration is similar to other programming-language types by providing a set of constrained values, but adds the ability to name \emph{all} the values in the set.
 Note, all enumeration names must be unique but different names can represent the same value (eight note, quaver), which are synonyms.
 
@@ -11 +11 @@
 
 Fundamentally, all enumeration systems have an \Newterm{enumeration} type with an associated set of \Newterm{enumerator} names.
-An enumeration has three universal attributes, \Newterm{position}, \Newterm{label}, and \Newterm{value}, as shown by this representative enumeration, where position and value can be different.
+An enumeration has three universal attributes, \Newterm{label}, \Newterm{position}, and \Newterm{value}, as shown by this representative enumeration, where position and value can be different.
 \begin{cquote}
 \small\sf\setlength{\tabcolsep}{3pt}
@@ -17 +17 @@
 \it\color{red}enumeration & \multicolumn{7}{c}{\it\color{red}enumerators}       \\
 $\downarrow$\hspace*{25pt} & \multicolumn{7}{c}{$\downarrow$}                           \\
-@enum@ Weekday \{                               & Monday,       & Tuesday,      & Wednesday,    & Thursday,& Friday,    & Saturday,     & Sunday \}; \\
-\it\color{red}position                  & 0                     & 1                     & 2                             & 3                             & 4                     & 5                     & 6                     \\
-\it\color{red}label                             & Monday        & Tuesday       & Wednesday             & Thursday              & Friday        & Saturday      & Sunday        \\
-\it\color{red}value                             & 0                     & 1                     & 2                             & 3                             & 4                     & 5             & 6
+@enum@ Weekday \{                               & Mon,  & Tue,  & Wed,  & Thu,  & Fri,  & Sat,  & Sun \};       \\
+\it\color{red}label                             & Mon   & Tue   & Wed   & Thu   & Fri   & Sat   & Sun           \\
+\it\color{red}position                  & 0             & 1             & 2             & 3             & 4             & 5             & 6                     \\
+\it\color{red}value                             & 0             & 1             & 2             & 3             & 4             & 5             & 6
 \end{tabular}
 \end{cquote}
-Here, the \Newterm{enumeration} @Weekday@ defines the ordered \Newterm{enumerator}s @Monday@, @Tuesday@, @Wednesday@, @Thursday@, @Friday@, @Saturday@ and @Sunday@.
-By convention, the successor of @Tuesday@ is @Monday@ and the predecessor of @Tuesday@ is @Wednesday@, independent of the associated enumerator constant values.
-Because an enumerator is a constant, it cannot appear in a mutable context, \eg @Mon = Sun@ is meaningless, and an enumerator has no address, it is an \Newterm{rvalue}\footnote{
-The term rvalue defines an expression that can only appear on the right-hand side of an assignment.}.
+Here, the \Newterm{enumeration} @Weekday@ defines the ordered \Newterm{enumerator}s @Mon@, @Tue@, @Wed@, @Thu@, @Fri@, @Sat@ and @Sun@.
+By convention, the successor of @Tue@ is @Mon@ and the predecessor of @Tue@ is @Wed@, independent of the associated enumerator constant values, implying an ordering among the enumerators.
+As well, the value can be explicitly set so it is different from the position.
+Because an enumerator is a constant, it cannot appear in a mutable context, \eg @Mon = Sun@ is meaningless, and an enumerator has no address, \ie it is an \Newterm{rvalue}\footnote{
+The term rvalue defines an expression that can only appear on the right-hand side of an assignment expression.}.
+
+On the surface, enumerations seem like a simple type.
+However, when extended with features available in other language types, enumerations become a complex.
+
+The goal of this work is to to extend the simple and unsafe enumeration type in the C programming-language into a sophisticated and safe type in the \CFA programming-language, while maintain backwards compatibility with C.
 
 \section{Contributions}
+

doc/theses/jiada_liang_MMath/relatedwork.tex

@@ -2 +2 @@
 \label{s:RelatedWork}
 
+\begin{comment}
 An algebraic data type (ADT) can be viewed as a recursive sum of product types.
 A sum type lists values as members.
@@ -15 +16 @@
 Enumerated types are a special case of product/sum types with non-mutable fields, \ie initialized (constructed) once at the type's declaration, possible restricted to compile-time initialization.
 Values of algebraic types are access by subscripting, field qualification, or type (pattern) matching.
+\end{comment}
 
 Enumeration types exist in many popular programming languages, both past and present, \eg Pascal~\cite{Pascal}, Ada~\cite{Ada}, \Csharp~\cite{Csharp}, OCaml~\cite{OCaml} \CC, Go~\cite{Go}, Java~\cite{Java}, Modula-3~\cite{Modula-3}, Rust~\cite{Rust}, Swift~\cite{Swift}, Python~\cite{Python}.
@@ -20 +22 @@
 
 \section{Pascal}
+\label{s:Pascal}
 \lstnewenvironment{pascal}[1][]{\lstset{language=pascal,escapechar=\$,moredelim=**[is][\color{red}]{@}{@},}\lstset{#1}}{}
 
@@ -27 +30 @@
                  PI = 3.14159;   Plus = '+';   Fred = 'Fred';
 \end{pascal}
-Here, there is no enumeration because there is no specific type (pseudo enumeration).
+This mechanism is not an enumeration because there is no specific type (pseudo enumeration).
 Hence, there is no notion of a (possibly ordered) set, modulo the \lstinline[language=pascal]{set of} type.
 The type of each constant name (enumerator) is inferred from the constant-expression type.
@@ -81 +84 @@
 with Ada.Text_IO; use Ada.Text_IO;
 procedure test is
-   type RGB is ( @Red@, Green, Blue );
-   type Traffic_Light is ( @Red@, Yellow, Green );         -- overload
-   procedure @Red@( Colour : RGB ) is begin            -- overload
-       Put_Line( "Colour is " & RGB'Image( Colour ) );
-   end Red;
-   procedure @Red@( TL : Traffic_Light ) is begin       -- overload
-       Put_Line( "Light is " & Traffic_Light'Image( TL ) );
-   end Red;
+        type RGB is ( @Red@, Green, Blue );
+        type Traffic_Light is ( @Red@, Yellow, Green );         -- overload
+        procedure @Red@( Colour : RGB ) is begin            -- overload
+                Put_Line( "Colour is " & RGB'Image( Colour ) );
+        end Red;
+        procedure @Red@( TL : Traffic_Light ) is begin       -- overload
+                Put_Line( "Light is " & Traffic_Light'Image( TL ) );
+        end Red;
 begin
-    @Red@( Blue );                               -- RGB
-    @Red@( Yellow );                            -- Traffic_Light
-    @Red@( @RGB'(Red)@ );               -- ambiguous without cast
+        @Red@( Blue );                           -- RGB
+        @Red@( Yellow );                                -- Traffic_Light
+        @Red@( @RGB'(Red)@ );           -- ambiguous without cast
 end test;
 \end{ada}
@@ -224 +227 @@
 \lstnewenvironment{c++}[1][]{\lstset{language=[GNU]C++,escapechar=\$,moredelim=**[is][\color{red}]{@}{@},}\lstset{#1}}{}
 
-\CC is largely backwards compatible with C, so it inherited C's enumerations.
-However, the following non-backwards compatible changes have been made.
+\CC has the equivalent of Pascal typed @const@ declarations \see{\VRef{s:Pascal}}, with static and dynamic initialization.
+\begin{c++}
+const auto one = 0 + 1;                                 $\C{// static intialization}$
+const auto NULL = nullptr;
+const auto PI = 3.14159;
+const auto Plus = '+';
+const auto Fred = "Fred";
+const auto Mon = 0, Tue = Mon + 1, Wed = Tue + 1, Thu = Wed + 1, Fri = Thu + 1,
+                                Sat = Fri + 1, Sun = Sat + 1;
+int sa[Sun];
+const auto r = random();                                $\C{// dynamic intialization}$
+int da[r];                                                              $\C{// VLA}$
+\end{c++}
+Statically initialized identifiers may appear in any constant-expression context, \eg @case@.
+Dynamically intialized identifiers may appear as array dimensions in @g++@, which allows variable-sized arrays.
+Interestingly, global \CC @const@ declarations are implicitly marked @static@ (@r@ rather than @R@).
+\begin{c++}
+$\$$ nm test.o
+0000000000000018 @r@ Mon
+\end{c++}
+
+\CC enumeration is largely backwards compatible with C, so it inherited C's enumerations.
+However, the following non-backwards compatible changes are made.
 
 \begin{cquote}
@@ -423 +447 @@
 \begin{Go}
 const ( Mon = iota; Tue; Wed; // 0, 1, 2
-         @Thu = 10@; Fri; Sat; Sun ) // 10, 10, 10, 10
+        @Thu = 10@; Fri; Sat; Sun ) // 10, 10, 10, 10
 \end{Go}
 Auto-incrementing can be restarted with an expression containing \emph{one} \lstinline[language=Go]{iota}.
@@ -429 +453 @@
 const ( V1 = iota; V2; @V3 = 7;@ V4 = @iota@; V5 ) // 0 1 7 3 4
 const ( Mon = iota; Tue; Wed; // 0, 1, 2
-         @Thu = 10;@ Fri = @iota - Wed + Thu - 1@; Sat; Sun ) // 10, 11, 12, 13
+        @Thu = 10;@ Fri = @iota - Wed + Thu - 1@; Sat; Sun ) // 10, 11, 12, 13
 \end{Go}
 Note, \lstinline[language=Go]{iota} is advanced for an explicitly initialized enumerator, like the underscore @_@ identifier.
@@ -1200 +1224 @@
 \lstnewenvironment{python}[1][]{\lstset{language=Python,escapechar=\$,moredelim=**[is][\color{red}]{@}{@},}\lstset{#1}}{}
 
-An @Enum@ is a set of symbolic names bound to unique values.
-They are similar to global variables, but they offer a more useful @repr()@, grouping, type-safety, and a few other features.
-
-They are most useful when you have a variable that can take one of a limited selection of values. For example, the days of the week:
-\begin{python}
->>> from enum import Enum
->>> class Weekday(Enum):
-...    MONDAY = 1
-...    TUESDAY = 2
-...    WEDNESDAY = 3
-...    THURSDAY = 4
-...    FRIDAY = 5
-...    SATURDAY = 6
-...    SUNDAY = 7
-\end{python}
-Or perhaps the RGB primary colors:
-\begin{python}
->>> from enum import Enum
->>> class Color(Enum):
-...    RED = 1
-...    GREEN = 2
-...    BLUE = 3
-\end{python}
-As you can see, creating an @Enum@ is as simple as writing a class that inherits from @Enum@ itself.
-
-Note: Case of Enum Members
-
-Because Enums are used to represent constants, and to help avoid issues with name clashes between mixin-class methods/attributes and enum names, we strongly recommend using @UPPER_CASE@ names for members, and will be using that style in our examples.
+A Python enumeration is a set of symbolic names bound to \emph{unique} values.
+They are similar to global variables, but offer a more useful @repr()@, grouping, type-safety, and additional features.
+Enumerations inherits from the @Enum@ class, \eg:
+\begin{python}
+class Weekday(@Enum@): Mon = 1; Tue = 2; Wed = 3; Thu = 4; Fri = 5; Sat = 6; Sun = 7
+class RGB(@Enum@): Red = 1; Green = 2; Blue = 3
+\end{python}
 
 Depending on the nature of the enum a member's value may or may not be important, but either way that value can be used to get the corresponding member:
 \begin{python}
->>> Weekday(3)
-<Weekday.WEDNESDAY: 3>
+print( repr( Weekday( 3 ) ) )
+<Weekday.Wed: 3>
 \end{python}
 As you can see, the @repr()@ of a member shows the enum name, the member name, and the value.
 The @str()@ of a member shows only the enum name and member name:
 \begin{python}
-print(Weekday.THURSDAY)
-Weekday.THURSDAY
+print( str( Weekday.Thu ), Weekday.Thu )
+Weekday.Thu Weekday.Thu
 \end{python}
 The type of an enumeration member is the enum it belongs to:
 \begin{python}
->>> type(Weekday.MONDAY)
+print( type( Weekday.Thu ) )
 <enum 'Weekday'>
-isinstance(Weekday.FRIDAY, Weekday)
+print( isinstance(Weekday.Fri, Weekday) )
 True
 \end{python}
 Enum members have an attribute that contains just their name:
 \begin{python}
->>> print(Weekday.TUESDAY.name)
+print(Weekday.TUESDAY.name)
 TUESDAY
 \end{python}
 Likewise, they have an attribute for their value:
 \begin{python}
->>> Weekday.WEDNESDAY.value
+Weekday.WEDNESDAY.value
 3
 \end{python}
+
 Unlike many languages that treat enumerations solely as name/value pairs, Python @Enum@s can have behavior added.
 For example, @datetime.date@ has two methods for returning the weekday: @weekday()@ and @isoweekday()@.
@@ -1262 +1266 @@
 Rather than keep track of that ourselves we can add a method to the @Weekday@ enum to extract the day from the date instance and return the matching enum member:
 \begin{python}
+class Weekday(Enum): Mon = 1; Tue = 2; Wed = 3; Thu = 10; Fri = 15; Sat = 16; Sun = 17
 $@$classmethod
 def from_date(cls, date):
-    return cls(date.isoweekday())
-\end{python}
-The complete Weekday enum now looks like this:
-\begin{python}
->>> class Weekday(Enum):
-...    MONDAY = 1
-...    TUESDAY = 2
-...    WEDNESDAY = 3
-...    THURSDAY = 4
-...    FRIDAY = 5
-...    SATURDAY = 6
-...    SUNDAY = 7
-...    #
-...    $@$classmethod
-...    def from_date(cls, date):
-...        return cls(date.isoweekday())
+        return cls(date.isoweekday())
 \end{python}
 Now we can find out what today is! Observe:
@@ -1291 +1281 @@
 This Weekday enum is great if our variable only needs one day, but what if we need several? Maybe we're writing a function to plot chores during a week, and don't want to use a @list@ -- we could use a different type of @Enum@:
 \begin{python}
->>> from enum import Flag
->>> class Weekday(Flag):
-...    MONDAY = 1
-...    TUESDAY = 2
-...    WEDNESDAY = 4
-...    THURSDAY = 8
-...    FRIDAY = 16
-...    SATURDAY = 32
-...    SUNDAY = 64
+from enum import Flag
+class WeekdayF(@Flag@): Mon = @1@; Tue = @2@; Wed = @4@; Thu = @8@; Fri = @16@; Sat = @32@; Sun = @64@
 \end{python}
 We've changed two things: we're inherited from @Flag@, and the values are all powers of 2.
 
-Just like the original @Weekday@ enum above, we can have a single selection:
-\begin{python}
->>> first_week_day = Weekday.MONDAY
->>> first_week_day
-<Weekday.MONDAY: 1>
-\end{python}
-But @Flag@ also allows us to combine several members into a single variable:
-\begin{python}
->>> weekend = Weekday.SATURDAY | Weekday.SUNDAY
->>> weekend
-<Weekday.SATURDAY|SUNDAY: 96>
+@Flag@ allows combining several members into a single variable:
+\begin{python}
+print( repr(WeekdayF.Sat | WeekdayF.Sun) )
+<WeekdayF.Sun|Sat: 96>
 \end{python}
 You can even iterate over a @Flag@ variable:
 \begin{python}
->>> for day in weekend:
-...    print(day)
+for day in weekend:
+        print(day)
 Weekday.SATURDAY
 Weekday.SUNDAY
@@ -1382 +1358 @@
 \subsection{Duplicating enum members and values}
 
-Having two enum members with the same name is invalid:
-\begin{python}
->>> class Shape(Enum):
-...    SQUARE = 2
-...    SQUARE = 3
-...
-Traceback (most recent call last):
-...
-TypeError: 'SQUARE' already defined as 2
-\end{python}
-However, an enum member can have other names associated with it.
+An enum member can have other names associated with it.
 Given two entries @A@ and @B@ with the same value (and @A@ defined first), @B@ is an alias for the member @A@.
 By-value lookup of the value of @A@ will return the member @A@.
@@ -1398 +1364 @@
 By-name lookup of @B@ will also return the member @A@:
 \begin{python}
->>> class Shape(Enum):
-...    SQUARE = 2
-...    DIAMOND = 1
-...    CIRCLE = 3
-...    ALIAS_FOR_SQUARE = 2
-...
+class Shape(Enum): SQUARE = 2; DIAMOND = 1; CIRCLE = 3; ALIAS_FOR_SQUARE = 2
 >>> Shape.SQUARE
 <Shape.SQUARE: 2>
@@ -1419 +1380 @@
 When this behavior isn't desired, you can use the @unique()@ decorator:
 \begin{python}
->>> from enum import Enum, unique
->>> $@$unique
-... class Mistake(Enum):
-...     ONE = 1
-...     TWO = 2
-...     THREE = 3
-...     FOUR = 3
-... 
-Traceback (most recent call last):
-...
+from enum import Enum, unique
+$@$unique
+class DupVal(Enum): ONE = 1; TWO = 2; THREE = 3; FOUR = 3
 ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE
 \end{python}
@@ -1436 +1390 @@
 If the exact value is unimportant you can use @auto@:
 \begin{python}
->>> from enum import Enum, auto
->>> class Color(Enum):
-...     RED = auto()
-...     BLUE = auto()
-...     GREEN = auto()
-... 
->>> [member.value for member in Color]
-[1, 2, 3]
-\end{python}
-The values are chosen by \_generate\_next\_value\_(), which can be overridden:
+from enum import Enum, auto
+class RGBa(Enum): RED = auto(); BLUE = auto(); GREEN = auto()
+\end{python}
+(Like Golang @iota@.)
+The values are chosen by @_generate_next_value_()@, which can be overridden:
 \begin{python}
 >>> class AutoName(Enum):
@@ -1582 +1531 @@
 \begin{python}
 class EnumName([mix-in, ...,] [data-type,] base-enum):
-    pass
+        pass
 \end{python}
 Also, subclassing an enumeration is allowed only if the enumeration does not define any members.
@@ -1699 +1648 @@
 \begin{python}
 Enum(
-    value='NewEnumName',
-    names=<...>,
-    *,
-    module='...',
-    qualname='...',
-    type=<mixed-in class>,
-    start=1,
-    )
+        value='NewEnumName',
+        names=<...>,
+        *,
+        module='...',
+        qualname='...',
+        type=<mixed-in class>,
+        start=1,
+        )
 \end{python}
 \begin{itemize}
@@ -1935 +1884 @@
 \begin{python}
 class IntEnum(int, Enum):
-    pass
+        pass
 \end{python}
 This demonstrates how similar derived enumerations can be defined;
@@ -2070 +2019 @@
 \begin{python}
 def __bool__(self):
-    return bool(self.value)
+        return bool(self.value)
 \end{python}
 Plain @Enum@ classes always evaluate as @True@.
@@ -2414 +2363 @@
 
 If @__new__()@ or @__init__()@ is defined, the value of the enum member will be passed to those methods:
-\begin{python}
->>> class Planet(Enum):
-...     MERCURY = (3.303e+23, 2.4397e6)
-...     VENUS   = (4.869e+24, 6.0518e6)
-...     EARTH   = (5.976e+24, 6.37814e6)
-...     MARS    = (6.421e+23, 3.3972e6)
-...     JUPITER = (1.9e+27,   7.1492e7)
-...     SATURN  = (5.688e+26, 6.0268e7)
-...     URANUS  = (8.686e+25, 2.5559e7)
-...     NEPTUNE = (1.024e+26, 2.4746e7)
-...     def __init__(self, mass, radius):
-...         self.mass = mass       # in kilograms
-...         self.radius = radius   # in meters
-...     $\@$property
-...     def surface_gravity(self):
-...         # universal gravitational constant  (m3 kg-1 s-2)
-...         G = 6.67300E-11
-...         return G * self.mass / (self.radius * self.radius)
-... 
->>> Planet.EARTH.value
-(5.976e+24, 6378140.0)
->>> Planet.EARTH.surface_gravity
-9.802652743337129
-\end{python}
+\begin{figure}
+\begin{python}
+from enum import Enum
+class Planet(Enum):
+        MERCURY = ( 3.303E23, 2.4397E6 )
+        VENUS       = ( 4.869E24, 6.0518E6 )
+        EARTH       = (5.976E24, 6.37814E6)
+        MARS         = (6.421E23, 3.3972E6)
+        JUPITER    = (1.9E27,   7.1492E7)
+        SATURN     = (5.688E26, 6.0268E7)
+        URANUS    = (8.686E25, 2.5559E7)
+        NEPTUNE  = (1.024E26, 2.4746E7)
+        def __init__( self, mass, radius ):
+                self.mass = mass                # in kilograms
+                self.radius = radius    # in meters
+        def surface_gravity( self ):
+                # universal gravitational constant  (m3 kg-1 s-2)
+                G = 6.67300E-11
+                return G * self.mass / (self.radius * self.radius)
+for p in Planet:
+        print( f"{p.name}: {p.value}" )
+
+MERCURY: (3.303e+23, 2439700.0)
+VENUS: (4.869e+24, 6051800.0)
+EARTH: (5.976e+24, 6378140.0)
+MARS: (6.421e+23, 3397200.0)
+JUPITER: (1.9e+27, 71492000.0)
+SATURN: (5.688e+26, 60268000.0)
+URANUS: (8.686e+25, 25559000.0)
+NEPTUNE: (1.024e+26, 24746000.0)
+\end{python}
+\caption{Python Planet Example}
+\label{f:PythonPlanetExample}
+\end{figure}
+
 
 \subsection{TimePeriod}
@@ -2464 +2424 @@
 \section{OCaml}
 \lstnewenvironment{ocaml}[1][]{\lstset{language=OCaml,escapechar=\$,moredelim=**[is][\color{red}]{@}{@},}\lstset{#1}}{}
+
+% https://ocaml.org/docs/basic-data-types#enumerated-data-types
 
 OCaml provides a variant (union) type, where multiple heterogeneously-typed objects share the same storage.
@@ -2553 +2515 @@
 With valediction,
   - Gregor Richards
+
+
+Date: Thu, 14 Mar 2024 21:45:52 -0400
+Subject: Re: OCaml "enums" do come with ordering
+To: "Peter A. Buhr" <pabuhr@uwaterloo.ca>
+From: Gregor Richards <gregor.richards@uwaterloo.ca>
+
+On 3/14/24 21:30, Peter A. Buhr wrote:
+> I've marked 3 places with your name to shows places with enum ordering.
+>
+> type weekday = Mon | Tue | Wed | Thu | Fri | Sat | Sun
+> let day : weekday = Mon
+> let take_class( d : weekday ) =
+>       if d <= Fri then                                (* Gregor *)
+>               Printf.printf "weekday\n"
+>       else if d >= Sat then                   (* Gregor *)
+>               Printf.printf "weekend\n";
+>       match d with
+>               Mon | Wed -> Printf.printf "CS442\n" |
+>               Tue | Thu -> Printf.printf "CS343\n" |
+>               Fri -> Printf.printf "Tutorial\n" |
+>               _ -> Printf.printf "Take a break\n"
+>
+> let _ = take_class( Mon ); take_class( Sat );
+>
+> type colour = Red | Green of string | Blue of int * float
+> let c = Red
+> let _ = match c with Red -> Printf.printf "Red, "
+> let c = Green( "abc" )
+> let _ = match c with Green g -> Printf.printf "%s, " g
+> let c = Blue( 1, 1.5 )
+> let _ = match c with Blue( i, f ) -> Printf.printf "%d %g\n" i f
+>
+> let check_colour(c: colour): string =
+>       if c < Green( "xyz" ) then              (* Gregor *)
+>               Printf.printf "green\n";
+>       match c with
+>               Red -> "Red" |
+>               Green g -> g |
+>               Blue(i, f) -> string_of_int i ^ string_of_float f
+> let _ = check_colour( Red ); check_colour( Green( "xyz" ) );
+>
+> type stringList = Empty | Pair of string * stringList
+> let rec len_of_string_list(l: stringList): int =
+>       match l with
+>               Empty -> 0 |
+>               Pair(_ , r) -> 1 + len_of_string_list r
+>
+> let _ = for i = 1 to 10 do
+>       Printf.printf "%d, " i
+> done
+>
+> (* Local Variables: *)
+> (* tab-width: 4 *)
+> (* compile-command: "ocaml test.ml" *)
+> (* End: *)
+
+My functional-language familiarity is far more with Haskell than OCaml.  I
+mostly view OCaml through a lens of "it's Haskell but with cheating".  Haskell
+"enums" (ADTs) aren't ordered unless you specifically and manually put them in
+the Ord typeclass by defining the comparators.  Apparently, OCaml has some
+other rule, which I would guess is something like "sort by tag then by order of
+parameter". Having a default behavior for comparators is *bizarre*; my guess
+would be that it gained this behavior in its flirtation with object
+orientation, but that's just a guess (and irrelevant).
+
+This gives a total order, but not enumerability (which would still be
+effectively impossible or even meaningless since enums are just a special case
+of ADTs).
+
+With valediction,
+  - Gregor Richards
 \end{comment}
 
@@ -2558 +2592 @@
 \section{Comparison}
 
-\begin{tabular}{r|ccccccccc}
-feat. / lang. & Pascal  & Ada   & \Csharp       & OCaml & Java  & Modula-3      & Rust  & Swift & Python        \\
+\VRef[Table]{t:FeatureLanguageComparison} shows a comparison of enumeration features and programming languages.
+The features are high level and may not capture nuances within a particular language
+The @const@ feature is simple macros substitution and not a typed enumeration.
+
+\begin{table}
+\caption{Enumeration Feature / Language Comparison}
+\label{t:FeatureLanguageComparison}
+\small
+\setlength{\tabcolsep}{3pt}
+\newcommand{\CM}{\checkmark}
+\begin{tabular}{r|c|c|c|c|c|c|c|c|c|c|c|c|c}
+                                &Pascal & Ada   &\Csharp& OCaml & Java  &Modula-3&Golang& Rust  & Swift & Python& C             & \CC   & \CFA  \\
 \hline
-pure            &                       &               &                       &               &               &                       &               &               &                       \\
-ordered         &                       &               &                       &               &               &                       &               &               &                       \\
-setable         &                       &               &                       &               &               &                       &               &               &                       \\
-auto-init       &                       &               &                       &               &               &                       &               &               &                       \\
-scoped          &                       &               &                       &               &               &                       &               &               &                       \\
-typed           &                       &               &                       &               &               &                       &               &               &                       \\
-switch          &                       &               &                       &               &               &                       &               &               &                       \\
-loop            &                       &               &                       &               &               &                       &               &               &                       \\
-array           &                       &               &                       &               &               &                       &               &               &                       \\
+@const@                 & \CM   &               &               &               &               &               & \CM   &               &               &               &               & \CM   &               \\
+\hline
+\hline
+pure                    &               &               &               &               &               &               &               &               &               &               &               &               & \CM   \\
+\hline
+typed                   &               &               &               &               &               &               &               &               &               &               & @int@ & integral      & @T@   \\
+\hline
+safe                    &               &               &               &               &               &               &               &               &               &               &               & \CM   & \CM   \\
+\hline
+ordered                 &               &               &               &               &               &               &               &               &               &               & \CM   & \CM   & \CM   \\
+\hline
+dup. values             &               &               &               &               &               &               &               &               &               & alias & \CM   & \CM   & \CM   \\
+\hline
+setable                 &               &               &               &               &               &               &               &               &               &               & \CM   & \CM   & \CM   \\
+\hline
+auto-init               &               &               &               &               &               &               &               &               &               &               & \CM   & \CM   & \CM   \\
+\hline
+(un)scoped              &               &               &               &               &               &               &               &               &               &               & U             & U/S   & U/S   \\
+\hline
+overload                &               & \CM   &               &               &               &               &               &               &               &               &               & \CM   & \CM   \\
+\hline
+switch                  &               &               &               &               &               &               &               &               &               &               & \CM   & \CM   & \CM   \\
+\hline
+loop                    &               &               &               &               &               &               &               &               &               &               &               &               & \CM   \\
+\hline
+array                   &               &               &               &               &               &               &               &               &               &               & \CM   &               & \CM   \\
+\hline
+subtype                 &               &               &               &               &               &               &               &               &               &               &               &               & \CM   \\
+\hline
+inheritance             &               &               &               &               &               &               &               &               &               &               &               &               & \CM   \\
 \end{tabular}
+\end{table}