%%% LaTeX2e package file to set EBNF in the style of the Haskell report
%%%
%%% Manuel M. T. Chakravarty <chak@cse.unsw.edu.au> [1997..2001]
%%%
%%% $Id: grammar.sty,v 1.6 2001/08/08 13:55:43 chak Exp $
%%%
%%% This file is free software; you can redistribute it and/or modify
%%% it under the terms of the GNU General Public License as published by
%%% the Free Software Foundation; either version 2 of the License, or
%%% (at your option) any later version.
%%%
%%% This file is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%%% GNU General Public License for more details.
%%%
%%% DOCU ======================================================================
%%%
%%% As a cheap (and ineffective) substitute for proper documentation, here an
%%% example using the macros:
%%%
%%%   \begin{grammar}
%%%     \grule{ftype}{%
%%%       \gnterm{frtype}}
%%%     \gor{%
%%%       \gnterm{fatype} -> \gnterm{ftype}}
%%%     \grule{frtype}{%
%%%       \gnterm{fatype}}
%%%     \gor{%
%%%       ()}
%%%     \grule[$k\geq0$]{fatype}{%
%%%       \gnterm{qtycon} \gnterm[1]{atype} \gellipse\ \gnterm[k]{atype}}
%%%   \end{grammar}
%%%
%%% TODO ======================================================================
%%%
%%% * flexible way of determining the column width is needed (should be the
%%%   same throughout a single grammar (or even the whole document)
%%%

\ProvidesPackage{grammar}[2001/04/17, v0.5a, <chak@cse.unsw.edu.au>]

\RequirePackage{ifthen}

% font configuration
%
% * these two commands can be redefined to change the default fonts for
%   terminals and non-terminals, respectively
%
\newcommand{\gtermfont}{\ttfamily}
\newcommand{\gntermfont}{\rmfamily\itshape}

% remembers whether we are in the star form of the grammar environment
% (internal) 
%
\newif\if@quoted

% grammar environment
%
% * typeset in paragraph mode within a tabular
% * there are four columns, containing the nonterminal, rule symbol (-> or |),
%   the rules rhs, and a comment, respectively
% * the star form of the command is not `quote'd
%
\newenvironment{grammar}{%
  \@quotedtrue
  \@grammar
  }{%
  \@endgrammar
  }
\newenvironment{grammar*}{%
  \@quotedfalse
  \@grammar
  }{%
  \@endgrammar
  }

% internal implementation of the grammar environment
%
\newcommand{\@grammar}{%
  \gtermfont                                    % for terminals
  \if@quoted\quote\fi
  \tabular{@{}lcl@{\quad}l@{}}
  }
\newcommand{\@endgrammar}{%
  \endtabular
  \if@quoted\endquote\fi
  \ignorespaces\global\@ignoretrue
  }

% a rule: optional comment, lhs, and rhs
%
\newcommand{\grule}[3][!*NEVER USED ARGUMENT*!]{%
  \ifthenelse{\equal{#1}{!*NEVER USED ARGUMENT*!}}{%
    \gnterm{#2} &$\rightarrow$& #3 \\
    }{%
    \gnterm{#2} &$\rightarrow$& #3 & \rmfamily(#1)\\
    }%
  }

% a rule alternative: optional comment and rhs
%
\newcommand{\gor}[2][!*NEVER USED ARGUMENT*!]{%
  \ifthenelse{\equal{#1}{!*NEVER USED ARGUMENT*!}}{%
    &$|$& #2\\
    }{%
    &$|$& #2 & \rmfamily(#1)\\
    }%
  }

% set a non-terminal with an optimal subscript
%
\newcommand{\gnterm}[2][!*NEVER USED ARGUMENT*!]{%
  \bgroup
  \gntermfont#2%
  \ifthenelse{\equal{#1}{!*NEVER USED ARGUMENT*!}}\relax{%
    \(_{#1}\)%
    }%
  \egroup
  }

\newcommand{\galt}{$|$}                         % inline alternatives
\newcommand{\gellipse}{\textrm{\ldots}}         % ellipses
\newcommand{\ggroup}[1]{\textrm(#1\textrm)}     % grouped expression
\newcommand{\gopt}[1]{\textrm[#1\textrm]}       % optinal term
\newcommand{\grepeat}[1]{\textrm\{#1\textrm\}}  % repeated term
\newcommand{\gminus}[1]{%                       % set difference
  \(_{\langle\mbox{\scriptsize #1}\rangle}\)}
\newcommand{\gverbal}[1]{{\rmfamily\textbf{#1}}}% informal description

% the following command is for terminals, but it is not necessary with the
% `grammar' environment, as terminals are the default; it is however useful in 
% the rest of the text
%
\newcommand{\gterm}[1]{{\normalfont\gtermfont#1}}

% some characters that are difficult to denote 
%
\newcommand{\gbackslash}{\char"5C}
\newcommand{\gtilde}{\char"7E}
\newcommand{\ghat}{\char"5E}