path: root/macros/latex/contrib/backnaur/backnaur.dtx

% \iffalse meta-comment
%
% backnaur.dtx
% 7 June 2019
%
%    Documented LaTeX file for the backnaur package.
%
%    Run LaTeX on backnaur.ins to make the package's
%    backnaur.sty file.
%
%    Run LaTeX on this file to produce the package 
%    documentation.
%
% Copyright (C) 2019 by Adrian P Robson
%     adrian.robson@nepsweb.co.uk
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either 
% version 1.3c of this license or (at your option) any later
% version. The latest version of this license is in
%    http://www.latex-project.org/lppl.txt
%
% This work has the LPPL maintenance status `maintained'.
% 
% The Current Maintainer of this work is Adrian Robson.
%
% This work consists of the files backnaur.dtx and 
%                                 backnaur.ins
% and the derived files           backnaur.sty and 
%                                 backnaur.pdf
% -----------------------------------------------------------
% \fi
%
% \iffalse
%<package>\NeedsTeXFormat{LaTeX2e}[2011/06/27]
%<package>\ProvidesPackage{backnaur}
%<package>[2019/06/18 3.1 Typesetting for Backus-Naur Form (BNF) definitions]
%<*driver>
\documentclass[10pt,a4paper]{ltxdoc}
\usepackage{backnaur}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{textcomp}
\usepackage{bigstrut}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\OnlyDescription       % comment out for code implementation
\begin{document}
\DocInput{backnaur.dtx}
\end{document}
%</driver>
% \fi
%
%^^A-------------------------------------------------------------------
%^^A Change log...
%^^A--------------
%^^A
%^^A 15 November 2012
%^^A The original was based on a non-packaged version that was used 
%^^A in 2008 for the LaTeX editions of the author's foggy times 
%^^A reports.
%    \changes{v1.0}{2012/11/15}
%            {Initial version of the package.}
%^^A
%^^A 3 December 2012
%^^A Add tstt option and generally rewrite documentation.
%    \changes{v1.1}{2012/12/12}
%            {Updated and improved documentation.}
%
%^^A
%^^A 7 June 2019
%^^A Remove tstt option, add line number management, add altpo option 
%^^A and updated and improve documentation.
%    \changes{v3.0}{2019/06/07}
%            {Updated and improved documentation.}
%
%^^A-------------------------------------------------------------------
% 
% \CheckSum{0} %^^A no checksum for development
%^^A \CheckSum{80}
%
% \CharacterTable
%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%   Digits        \0\1\2\3\4\5\6\7\8\9
%   Exclamation   \!     Double quote  \"     Hash (number) \#
%   Dollar        \$     Percent       \%     Ampersand     \&
%   Acute accent  \'     Left paren    \(     Right paren   \)
%   Asterisk      \*     Plus          \+     Comma         \,
%   Minus         \-     Point         \.     Solidus       \/
%   Colon         \:     Semicolon     \;     Less than     \<
%   Equals        \=     Greater than  \>     Question mark \?
%   Commercial at \@     Left bracket  \[     Backslash     \\
%   Right bracket \]     Circumflex    \^     Underscore    \_
%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%   Right brace   \}     Tilde         \~}
%
% \GetFileInfo{backnaur.sty}
%
% \title{The \texttt{backnaur} package}
% \author{Adrian P. Robson\thanks{\texttt{adrian.robson@nepsweb.co.uk}}}
% \date{Version 3.1\\[0.5ex]18 June 2019}
%
% \maketitle
%
%^^A-------------------------------------------------------------------
%^^A Start report body
%^^A-------------------------------------------------------------------
%
% \section{Introduction}
%
% The \texttt{backnaur} package typesets Backus-Naur Form (BNF) definitions. 
% It creates aligned lists of productions, with numbers if required.
% It can also print  in line BNF expressions using math mode. 
%
% Backus-Naur Form is a notation for defining context free grammars.
% It is used to describe such things as programming languages, communication protocols 
% and command syntaxes, but it can be useful whenever a rigorous definition of language is needed.
%
% \section{BNF Definitions}
%
% The following is a BNF definition of a semicolon separated list:
% \begin{bnf*}
% \bnfprod{list}
%         {\bnfpn{listitems}  \bnfor \bnfes}\\
% \bnfprod{listitems}
%         {\bnfpn{item}  \bnfor \bnfpn{item}  
%          \bnfsp  \bnfts{;}  \bnfsp \bnfpn{listitems}}\\
% \bnfprod{item}
%         { \bnftd{description of item}}
% \end{bnf*}
%
% \noindent
% Here, $\bnfpo$ signifies \emph{produces}, $\mid$ is an \emph{or} operator, $\langle$...$\rangle$
% are \emph{production names}, 
% and $\bnfes$ represents the \emph{empty string}.
% However, some BNF users prefer alternative terminologies, 
% where $\bnfpo$  stands for \emph{is defined as}, 
% $\langle$...$\rangle$ is a \emph{category name} or \emph{nonterminal}, 
% and $\bnfes$ is refered to as \emph{null} or \emph{empty}.
%
% The above definition was created with the following code:
%
%\begin{verbatim}
%\usepackage{backnaur}
%...
%\begin{bnf*}
%   \bnfprod{list}
%           {\bnfpn{listitems} \bnfor \bnfes}\\
%   \bnfprod{listitems}
%           {\bnfpn{item} \bnfor \bnfpn{item}  
%            \bnfsp \bnfts{;} \bnfsp \bnfpn{listitems}}\\
%   \bnfprod{item}
%           {\bnftd{description of item}}
%\end{bnf*}
%
%\end{verbatim}
%
% \noindent
% Each BNF production is defined by a |\bnfprod| command, which has two arguments 
% giving its left and right sides.
% The right hand side of each production is specified with the commands described in
% \S\ref{prodef} below.
% Terminal (|\bnfts{;}|) and nonterminal (|\bnfpn{item}|), elements are separated 
% by spaces (|\bnfsp|) and OR symbols (|\bnfor|).
% The |\bnfes| command gives the symbol for the empty string.
%
% \section{Package Commands}\label{commandDesc}
%
% \subsection{Loading and options}\label{packopts}
%
% The package is loaded with
%
% \medskip\noindent
% \hspace{2.5em}|\usepackage{backnaur}| \\
% or\\
% \hspace*{2.5em}|\usepackage[|<options>|]{backnaur}|
% \medskip
%
% \noindent
% Possible options are
%
% \vspace{-1.5ex}
% \begin{tabbing}
% xxxxxxxxx \=\kill
% |perp|   \>The empty string symbol is $\perp$\\
% |epsilon| \>  The empty string symbol is $\epsilon$\\
% |tsrm| \>  Terminal string typeface is roman\\
% |altpo| \> Production operator is $::=$
%^^A |tstt| \>  Terminal string typeface is typewriter (default)
% \end{tabbing}
% \vspace{-1ex}
%
% \noindent
% The defaults are: the empty string symbol is $\lambda$, 
% the production operator is $\models$,
% and the terminal string typeface is typewriter.
% 
% \subsection{Environments}
%
% \DescribeEnv{bnf} 
% BNF productions are defined in a |bnf| or |bnf*| environment, 
% which respectively  give numbered or unnumbered lists of productions.
% \DescribeEnv{bnf*}
% \begin{quote}
% \begin{minipage}{0.5\linewidth}
%   |\begin{bnf}|\\
%   \hspace*{1em}<list of productions>\\
%   |\end{bnf}|
% \end{minipage}
%   \begin{minipage}{0.45\linewidth}
%   |\begin{bnf*}|\\
%   \hspace*{1em}<list of productions>\\
%   |\end{bnf*}|
% \end{minipage}
% \end{quote}
%
% \subsection{Productions}
%
% \DescribeMacro{\bnfprod}
% \DescribeMacro{\bnfprod*}
% A production is defined by |\bnfprod| or |\bnfprod*|, 
% which respectively give a numbered or unnumbered line in the {\tt bnf} environment.
% They have identical unnumbered behaviour in the {\tt bnf*} enviromment.
% They take two arguments:
% \begin{quote}
%   |\bnfprod{|<production name>|}{|<production definition>|}|\\
%   |\bnfprod*{|<production name>|}{|<production definition>|}|
% \end{quote}	
%
% \DescribeMacro{\bnfmore}
% \DescribeMacro{\bnfmore*}
% A production can be continued on addition lines by |\bnfmore| or |\bnfmore*|, 
% which respectively give a numbered or unnumbered line in the {\tt bnf} environment.
% They are treated the same in the {\tt bnf*} environment.
% They take one arguments:
% \begin{quote}
%   |\bnfmore{|<production definition>|}|\\
%   |\bnfmore*{|<production definition>|}|
% \end{quote}	
%
% \subsection{Production definitions}\label{prodef}
%
% The following commands are used to compose the right hand side of a production.
% They are deployed in the second argument of the |\bnfprod| command.
%
% \DescribeMacro{\bnfpn}
% The |\bnfpn| command generates a production name.
% It takes a single argument that is the name. 
% It is used as follows:
% \begin{quote}
% \begin{minipage}{0.6\linewidth}
%   |\bnfpn{list item}|
% \end{minipage}
% \begin{minipage}{0.3\linewidth}
%   $\bnfpn{list item}$
% \end{minipage}
% \end{quote}
%
% There are three types of terminal item: a literal string, a descriptive phrase and an empty string.
% \DescribeMacro{\bnftm}
% A literal terminal string is specified by the |\bnftm| command, which takes a single argument.
% By default literal terminal strings are printed in typewriter font, but this can be changed as a package option  (see \S\ref{packopts}).
% \DescribeMacro{\bnftd}
% The |\bnftd| command generates a descriptive phrase, as an alternative to a literal string.  
% \DescribeMacro{\bnfes}
% The |\bnfes| command generates a token that represents the empty string. 
% This is normally $\bnfes$, but it can be changed to $\epsilon$ or $\perp$ as a package option 
% (see \S\ref{packopts}).
% \begin{quote}
% \begin{minipage}{0.6\linewidth}
%   |\bnfts{terminal}|\\
%   |\bnftd{description}|\\
%   |\bnfes|
% \end{minipage}
% \begin{minipage}{0.3\linewidth}
%   $\bnfts{terminal}$\\
%   $\bnftd{description}$\\
%   $\bnfes$
% \end{minipage}
% \end{quote}
%
% \DescribeMacro{\bnfsk}
% Some literal terminal strings can be abbreviated with the `skip' token,
% which is generated by the |\bnfsk| command.
% This substitutes for a sequence of terminal characters.
% It is used like this:
% \begin{quote}
%   \begin{minipage}{0.6\linewidth}
%   |\bnfts{A} \bnfsk \bnfts{Z}|
%   \end{minipage}
% \begin{minipage}{0.3\linewidth}
%   $\bnfts{A} \bnfsk \bnfts{Z}$
% \end{minipage}
% \end{quote}
%
% \DescribeMacro{\bnfor}
% All items should be separated by an OR or a space. 
% The |\bnfor| command generates the OR symbol, and the |\bnfsp| command introduces a space.
% \DescribeMacro{\bnfsp} 
% A space can be considered equivalent to an AND operator.
% \begin{quote}
% \begin{minipage}{0.6\linewidth}
%   |\bnfpn{abc} \bnfor \bnfts{xzy}|\\
%   |\bnfpn{abc} \bnfsp \bnfts{xzy}|
% \end{minipage}
% \begin{minipage}{0.3\linewidth}
%   $\bnfpn{abc} \bnfor \bnfts{xzy}$\\
%   $\bnfpn{abc} \bnfsp \bnfts{xzy}$
% \end{minipage}
% \end{quote}
%
% \subsection{Inline expressions}
% The |\bnfprod| and |\bnfmore| macros cannot be used inline, so the |\bnfpn| and |\bnfpo| macros
%   are provided to support typeseting productions  inline using maths mode.
% \DescribeMacro{\bnfpn}
% \DescribeMacro{\bnfpo}
% The production's name can be typeset with |\bnfpn{name}| and the production operator with
% |\bnfpo|.
% By default the production operator is $\bnfpo$, but it can be changed to $::=$ with 
% a package option (see \S\ref{packopts}).
% The right side of the production can be defined with the usual macros (see \S\ref{prodef}). 
% So |$\bnfpn{name} \bnfpo \bnftd{description}$| gives $\bnfpn{name} \bnfpo \bnftd{description}$.
%
% \subsection{Command summary}
%
% The commands that can be used to define a BNF production in a |bnf| or |bnf*| environment 
% are as follows:
%
% \begin{center}
% \begin{tabular}{lll}
% \hline
% Command         & Operator             & Outcome               \bigstrut \\
% \hline
% |\bnprod|   & production line       & <name> $\bnfpo$ {\it def}           \bigstrut[t]  \\
% |\bnmore|   & extra  line &  \hspace{38.8pt} $\bnfpo$ {\it def}              \\[1ex]
% |\bnfor|   & OR operator          & $\bnfor$              \\
% |\bnfsk|   & skip                 & $\bnfsk$              \\
% |\bnfsp|   & space/AND operator   & $\bnfsp$              \\
% |\bnfes|   & empty string         & $\bnfes$              \\
% |\bnfts{}| & terminal string      & $\bnfts{terminal}$    \\
% |\bnftd{}| & terminal description & $\bnftd{description}$ \\[1ex]
% |\bnfpn{}| & production name      & $\bnfpn{name}$        \\
% |\bnfpo|   & production operator  & $\bnfpo$              \bigstrut[b] \\
% \hline
% \end{tabular}
% \end{center}
%
% \section{Example}\label{example}
%
% A more significant example is the following definition of a $\bnfpn{sentence}$, 
% where $\bnfpn{cchar}$ are countable characters, and $\bnfpn{ichar}$ are characters 
% that should be ignored:
%
% \begin{samepage}
% \small
%\begin{verbatim}
%\begin{bnf*}
%   \bnfprod{sentence}
%      {\bnfpn{start} \bnfsp \bnfpn{rest} \bnfsp \bnfts{.}}\\
%   \bnfprod{start}  
%      {\bnfpn{space} \bnfor \bnfes}\\
%   \bnfprod{rest}   
%      {\bnfpn{word} \bnfsp \bnfpn{space} \bnfsp \bnfpn{rest} 
%       \bnfor \bnfpn{word} \bnfor \bnfes}\\
%   \bnfprod{word}  
%      {\bnfpn{wchar} \bnfsp \bnfpn{word} \bnfor \bnfpn{wchar}}\\
%   \bnfprod{space}  
%      {\bnfpn{schar} \bnfsp \bnfpn{space} \bnfor \bnfpn{schar}}\\
%   \bnfprod{wchar}
%      {\bnfpn{cchar}  \bnfor \bnfpn{ichar} }\\
%   \bnfprod{cchar}
%      {\bnfts{A} \bnfsk \bnfts{Z} \bnfor \bnfts{a} \bnfsk 
%       \bnfts{z} \bnfor \bnfts{0} \bnfsk \bnfts{9} \bnfor 
%       \bnfts{\textquotesingle}}\\
%   \bnfprod{ichar}  
%      {\bnfts{-}}
%   \bnfprod{schar}
%      {\bnfts{`\hspace{1em}'} \bnfor \bnfts{!} \bnfor \bnfts{"} 
%       \bnfor \bnfts{(}  \bnfor \bnfts{)} \bnfor \bnfts{\{} 
%       \bnfor \bnfts{\}} \bnfor }\\
%   \bnfmore{\bnfts{:} \bnfor \bnfts{;} \bnfor \bnfts{?} \bnfor
%            \bnfts{,} }
%\end{bnf*}
%\end{verbatim}
% \end{samepage}
%
% \noindent
% This creates the following BNF definition:
%\begin{bnf}
%   \bnfprod{sentence}
%      {\bnfpn{start} \bnfsp \bnfpn{rest} \bnfsp \bnfts{.}}\\
%   \bnfprod{start}  
%      {\bnfpn{space} \bnfor \bnfes}\\
%   \bnfprod{rest}   
%      {\bnfpn{word} \bnfsp \bnfpn{space} \bnfsp \bnfpn{rest} 
%       \bnfor \bnfpn{word} \bnfor \bnfes }\\
%   \bnfprod{word}  
%      {\bnfpn{wchar} \bnfsp \bnfpn{word} \bnfor \bnfpn{wchar}}\\
%   \bnfprod{space}  
%      {\bnfpn{schar} \bnfsp \bnfpn{space} \bnfor \bnfpn{schar}}\\
%   \bnfprod{wchar}
%      {\bnfpn{cchar}  \bnfor \bnfpn{ichar} }\\
%   \bnfprod{cchar}
%      {\bnfts{A} \bnfsk \bnfts{Z} \bnfor \bnfts{a} \bnfsk 
%       \bnfts{z} \bnfor \bnfts{0} \bnfsk \bnfts{9} \bnfor 
%      \bnfts{\textquotesingle} }\\
%   \bnfprod{ichar}  
%      {\bnfts{-}}\\
%   \bnfprod*{schar}
%      {\textrm{`\hspace{1em}'} \bnfor \bnfts{!} \bnfor \bnfts{"} 
%       \bnfor \bnfts{(}  \bnfor \bnfts{)} \bnfor \bnfts{\{} 
%       \bnfor \bnfts{\}} \bnfor }\\
%   \bnfmore{\bnfts{:} \bnfor \bnfts{;} \bnfor \bnfts{?} \bnfor
%            \bnfts{,} }
%\end{bnf}
%
% \noindent
%^^A Notice the kludge in production 9: \verb|\textrm{`\hspace{1em}'}|.
% Notice the kludge in production 9. 
% We use \verb|\textrm{`\hspace{1em}'}| to typeset a representation for a space 
% character.
% This is needed because we do not want to print in typewriter font, 
% which would imply the quotes were part of an actual terminal string.
% The \verb|\textrm| is needed because are in maths mode.
%
%^^AT \appendix
% \section{Terminal string characters}
%
% The characters used with \verb|\bnfts{}| (terminal string) are just standard
% LaTeX that is typeset in either a roman or typewriter font. 
% This means we might have to use some escape pairs and a few special characters.
% Apostrophes and speech marks can be confusing. There are some of the possibilities:
%
% \begin{tabbing}
% xxxxxxxx \= xxxxxxxxxxxxxxxxxxxxxxxxxx  \= xxxxxxxxxxxxxxxxx\=  \kill
% alpha \> \verb|\bnfts{abcdABCD}| \> $\texttt{abcdABCD}$ \> $\textrm{abcdABCD}$\\
% numeric \> \verb|\bnfts{01234}| \> $\texttt{01234}$ \> $\textrm{01234}$\\
%
% simple \> \verb|\bnfts{<>[]()*+-=}| \> $\texttt{<>[]()*+-=}$ \> $\textrm{<>[]()*+-=}$\\
% simple \> \verb|\bnfts{@!?/,.;:}| \> $\texttt{@!?/,.;:}$ \> $\textrm{@!?/,.;:}$\\
%
% escaped \> \verb|\bnfts{\{\}\$\%\&\_\#}| \> $\texttt{\{\}\$\%\&\_\#}$ 
%                                          \> $\textrm{\{\}\$\%\&\_\#}$\\
%
% quotes \> \verb|\bnfts{' ` " `` ''}| \> $\texttt{' ` " `` ''}$ 
%                                      \> $\textrm{' ` " `` ''}$\\
% quotes \> \verb|\bnfts{\textquotesingle}| \> $\texttt{\textquotesingle}$ 
%                                           \> $\textrm{\textquotesingle}$\\
%
% pound \> \verb|\bnfts{\pounds}| \> $\texttt{\pounds}$ \> $\textrm{\pounds}$\\
% hat \> \verb|\bnfts{\textasciicircum}| \> $\texttt{\textasciicircum}$ 
%                                        \> $\textrm{\textasciicircum}$\\
% backslash \> \verb|\bnfts{\textbackslash}| \> $\texttt{\textbackslash}$  
%                                            \> $\textrm{\textbackslash}$\\
% tilde \> \verb|\bnfts{\textasciitilde}| \> $\texttt{\textasciitilde}$ \> 
%             $\textrm{\textasciitilde}$
% \end{tabbing}
%
%
% \noindent
% The \verb|\textquotesingle| symbol needs the {\tt textcomp} package, which provides 
% lots of other interesting symbols. Consult the excellent \emph{The Comprehensive LATEX Symbol List} by Scott Pakin for more information.
%
%^^A-------------------------------------------------------------------
%^^A Start code implementation
%^^A-------------------------------------------------------------------
%
%^^A \StopEventually{}
% \StopEventually{\PrintChanges}
%^^A    -> Run pdfLaTeX backnaur.dtx
%^^A           makeindex -s gglo.ist -o backnaur.gls backnaur.glo
%^^A           pdfLaTeX backnaur.dtx
%^^A \StopEventually{\PrintIndex}
%^^A    -> Run pdfLaTeX backnaur.dtx
%^^A           makeindex -s gind.ist -o backnaur.ind backnaur.idx
%^^A           pdfLaTeX backnaur.dtx
%
% \newpage
% \section{Implementation}
%
% The implementation of |backnaur.sty| uses only \LaTeX{} commands. 
%
% \subsection{Environments}\label{environ}
%
% There are two environments defined:
%
% \begin{environment}{bnf}
%    A production list with numbers. It is simply implemented as an |eqnarray|.
%    Surplus space is removed with an |\ignorespacesafterend| and |%| characters.
%    \begin{macrocode}
\newenvironment{bnf}%
{\begin{eqnarray}}%
{\end{eqnarray}\ignorespacesafterend}
%    \end{macrocode}
% \end{environment}
%
% \begin{environment}{bnf*}
%    A lists without numbers. It is implemented with an |eqnarray*|, 
%    and extra space is removed as in the |bnf| environment above. 
%    \begin{macrocode}
\newenvironment{bnf*}%
{\begin{eqnarray*}}%
{\end{eqnarray*}\ignorespacesafterend}
%    \end{macrocode}
% \end{environment}
%
% \subsection{Definition Commands}
%
% All of these commands run in the math mode supplied by the 
% |bnf| and |bnf*| environments (see \S\ref{environ}). 
%
% \begin{macro}{\bnfpn}
%    Production name / nonterminal.
%    \changes{v3.1}{2019/06/18}{Fix font handling}
%    \begin{macrocode}
\newcommand{\bnfpn}[1]{\langle \textrm{#1} \rangle}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfor}
%    OR operator.
%    \begin{macrocode}
\newcommand{\bnfor}{\; \mid \;}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfsp}
%    Space or AND operator.
%    \begin{macrocode}
\newcommand{\bnfsp}{\;}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfes}
%    Empty string symbol. This is the default if no package options are given.
%    \begin{macrocode}
\newcommand{\bnfes}{\lambda}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfts}\label{codebnfts}
%    \changes{v1.1}{2012/12/12}{Support for {\tt tstt} option added}
%    \changes{v3.1}{2019/06/18}{Fix font handling}
% \begin{macro}{\bnf@tsfont}
%    Terminal string. The font is controlled by the |\bnf@tsfont| macro,
%    and this macro can be redefined by the |tsrm| option (see \S\ref{codeoptions}).
%    The default is typewriter font.
%    \begin{macrocode}
\newcommand{\bnf@tsfont}[1]{\texttt{#1}}
\newcommand{\bnfts}[1]{\bnf@tsfont{#1}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\bnfpo}
%    Terminal description.
%    \changes{v3.1}{2019/06/18}{Fix font handling}
%    \begin{macrocode}
\newcommand{\bnftd}[1]{\textit{#1}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfsk}
%    Skip symbol.
%    \begin{macrocode}
\newcommand{\bnfsk}{\dots}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\bnfpo}
%    Production operator.
%    \begin{macrocode}
\newcommand{\bnfpo}{\models}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Production Commands}
%
%^^A \newcommand{\bnfprod}{\@ifstar{\bnf@prodnn}{\bnf@prodyn}}
%^^A \newcommand{\bnf@prodyn}[2]{\bnfpn{#1} & \bnfpo & #2}
%^^A \newcommand{\bnf@prodnn}[2]{\nonumber \bnfpn{#1} & \bnfpo & #2}
%^^A \newcommand{\bnfmore}{\@ifstar{\bnf@morenn}{\bnf@moreyn}}
%^^A \newcommand{\bnf@moreyn}[1]{ &  & #1}
%^^A \newcommand{\bnf@morenn}[1]{\nonumber &  & #1}
%
% \begin{macro}{\bnfprod}
% \begin{macro}{\bnfprod*}
%    \changes{v3.0}{2019/06/07}{Added {\tt *} version of the macro.}
% \begin{macro}{\bnf@prodyn}
% \begin{macro}{\bnf@prodnn}
%    A Backus-Naur Form production. 
%    This command is designed to exploit the behaviour the |equarray| used in 
%    the |bnf| and |bnf*| environments. 
%    In particular, the |\bnfpo| character will be vertically aligned. 
%    The {\tt *} version suppresses the line number%    \begin{macrocode}
\newcommand{\bnfprod}{\@ifstar{\bnf@prodnn}{\bnf@prodyn}}
\newcommand{\bnf@prodyn}[2]{\bnfpn{#1} & \bnfpo & #2}
\newcommand{\bnf@prodnn}[2]{\nonumber \bnfpn{#1} & \bnfpo & #2}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\bnfmore}
%    \changes{v2.0}{2019/04/07}{Added macro.}
% \begin{macro}{\bnfmore*}
%    \changes{v3.0}{2019/06/07}{Added {\tt *} version of the macro.}
% \begin{macro}{\bnf@moreyn}
% \begin{macro}{\bnf@morenn}
%    A continuation of a Backus-Naur Form production. 
%    This command is designed to exploit the behaviour the |equarray| used in 
%    the |bnf| and |bnf*| environments to correctly align with preceding 
%    |\bnfprod| and |\bnfmore| macros. 
%    The {\tt *} version suppresses the line number.
%    \begin{macrocode}
\newcommand{\bnfmore}{\@ifstar{\bnf@morenn}{\bnf@moreyn}}
\newcommand{\bnf@moreyn}[1]{ &  & #1}
\newcommand{\bnf@morenn}[1]{\nonumber &  & #1}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Options}\label{codeoptions}
%
%\begin{macro}{tstt}
%    \changes{v1.1}{2012/12/12}{New option}
%    \changes{v2.0}{2019/04/14}{Changed to be default}
%    \changes{v3.0}{2019/06/07}{Option removed but still default}
%    The |tstt| option is depreciated and can no longer be used.
%    Nevertheless, typewriter font for terminal stings, which it selected,
%    is still the package's default.
%\end{macro}
%
% \begin{macro}{tsrm}
%    \changes{v2.0}{2019/04/14}{New option}
% \begin{macro}{\bnf@tsfont}
%    The |tsrm| option redefines |\bnf@tsfont| to change the 
%    terminal string font used in the |\bnfts| command (see \S\ref{codebnfts}) to roman font.
%    \begin{macrocode}
\DeclareOption{tsrm}{\renewcommand{\bnf@tsfont}[1]{\textrm{#1}}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{perp}
% \begin{macro}{epsilon}
% \begin{macro}{\bnfes}
%    The |perp| and |epsilon| options redefine |\bnfes|, 
%    which is the empty string command:
%    \begin{macrocode}
\DeclareOption{perp}{\renewcommand{\bnfes}{\perp}}
\DeclareOption{epsilon}{\renewcommand{\bnfes}{\epsilon}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{altpo}
%    \changes{v3.0}{2019/06/07}{New option}
% \begin{macro}{\bnfpo}
%    The |altpo| option redefines |\bnfpo|  
%    which prints the production operator:
%    \begin{macrocode}
\DeclareOption{altpo}{\renewcommand{\bnfpo}{::=}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%\noindent
% Finally, the options that have been selected are executed:
%    \begin{macrocode}
\ProcessOptions\relax
%    \end{macrocode}
%
% \Finale
\endinput