%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Comment.sty   version 3.2, August 1997
% selectively in/exclude pieces of text: the user can define new
% comment versions, and each is controlled separately.
% Special comments can be defined where the user specifies the
% action that is to be taken with each comment line.
%
% This style can be used with plain TeX or LaTeX, and probably
% most other packages too.
%
% Author
%    Victor Eijkhout
%    Department of Mathematics
%    University of California
%    405 Hilgard Ave, MS 6363
%    Los Angeles, CA 90034
%    USA
%
%    eijkhout@math.ucla.edu
%
% Usage: all text included in between 
%    \comment ... \endcomment
% or \begin{comment} ... \end{comment}
% is discarded. 
% The opening and closing commands should appear on a line
% of their own. No starting spaces, nothing after it.
% This environment should work with arbitrary amounts
% of comment. 
%
% Other `comment' environments are defined by
% and are selected/deselected with
% \includecomment{versiona}
% \excludecoment{versionb}
%
% These environments are used as
% \versiona ... \endversiona
% or \begin{versiona} ... \end{versiona}
% with the opening and closing commands again on a line of 
% their own.
%
% LaTeX users note: for an included comment, the
% \begin and \end lines act as if they don't exist.
% In particular, assignments &c are not local.
%
% Special comments are defined as
% \specialcomment{name}{before commands}{after commands}
% where the second and third arguments are executed before
% and after each comment block.
% By defining a control sequence 
% \Thiscomment##1{...} in the before commands the user can
% specify what is to be done with each comment line.
% To keep definitions &c local, you can include \begingroup
% in the `before commands' and \endgroup in the `after commands'.
%
% Basic approach: 
% to comment something out, scoop up  every line in verbatim mode
% as macro argument, then throw it away.
% For inclusions, in LaTeX the block is written out to
% a file "comment.cut", which is then included.
% In plain TeX (and other formats) both the opening and 
% closing comands are defined as noop.
%
% Trick for short in/exclude macros (\maybe{this snippet}):
%\includeversion{cond}
%\newcommand{\maybe}[1]{}
%\begin{cond}
%\renewcommand{\maybe}[1]{#1}
%\end{cond}
%
% Changes in version 3.1
% - updated author's address
% - cleaned up some code
% - trailing contents on \begin{env} line is always discarded
%  even if you've done \includecomment{env}
% - comments no longer define grouping!! you can even
%   \includecomment{env}
%   \begin{env}
%   \begin{itemize}
%   \end{env}
%  Isn't that something ...
% - included comments are written to file and input again.
% Changes in 3.2
% - \specialcomment brought up to date (thanks to Ivo Welch).
%
\def\makeinnocent#1{\catcode`#1=12 }
\def\csarg#1#2{\expandafter#1\csname#2\endcsname}
\def\latexname{lplain}\def\latexename{LaTeX2e}
\newwrite\CommentStream

\def\ProcessComment#1{\begingroup
    \def\CurrentComment{#1}%
    \let\do\makeinnocent \dospecials 
    \makeinnocent\^^L% and whatever other special cases
    \endlinechar`\^^M \catcode`\^^M=12 \fxComment}
{\catcode`\^^M=12 \endlinechar=-1 %
 \gdef\fxComment#1^^M{\xComment}
 \gdef\xComment#1^^M{\def\test{#1}
      \csarg\ifx{End\CurrentComment Test}\test
          \edef\next{\noexpand\EndOfComment{\CurrentComment}}%
      \else \ThisComment{#1}\let\next\xComment
      \fi \next}
}

% 3.1 change: in LaTeX and LaTeX2e prevent grouping
\if 0%
\ifx\fmtname\latexename 
    0%
\else \ifx\fmtname\latexname 
          0%
      \else 
          1%
\fi   \fi
%%%%
%%%% definitions for LaTeX
%%%%
\edef\restoreat{\catcode\noexpand`\noexpand\@=\the\catcode`\@\relax}
\makeatletter
\def\AfterIncludedComment
   {\immediate\closeout\CommentStream
    \input comment.cut
    }%
\def\WriteCommentLine#1{\immediate\write\CommentStream{#1}}
\def\BeforeIncludedComment{\immediate\openout\CommentStream=comment.cut
    \let\ThisComment\WriteCommentLine}
\def\includecomment
 #1{\message{Include comment '#1'}%
    \csarg\let{After#1Comment}\AfterIncludedComment
    \csarg\def{#1}{\BeforeIncludedComment
        \ProcessComment{#1}}%
    \CommentEndDef{#1}}
\long\def\specialcomment
 #1#2#3{\message{Special comment '#1'}%
    \csarg\def{After#1Comment}{#2\AfterIncludedComment#3}%
    \csarg\def{#1}{\BeforeIncludedComment
          \ProcessComment{#1}}%
    \CommentEndDef{#1}}
\restoreat
\else 
%%%%
%%%%plain TeX and other formats
%%%%
\def\includecomment
 #1{\message{Including comment '#1'}%
    \csarg\def{#1}{}%
    \csarg\def{end#1}{}}
\long\def\specialcomment
 #1#2#3{\message{Special comment '#1'}%
    \csarg\def{#1}{\def\ThisComment{}\def\AfterComment{#3}#2%
           \ProcessComment{#1}}%
    \CommentEndDef{#1}}
\fi

%%%%
%%%% general definition of skipped comment
%%%%
\def\excludecomment
 #1{\message{Excluding comment '#1'}%
    \csarg\def{#1}{\let\AfterComment\relax
           \def\ThisComment####1{}\ProcessComment{#1}}%
    \CommentEndDef{#1}}

\if 0%
\ifx\fmtname\latexename 
    0%
\else \ifx\fmtname\latexname 
          0%
      \else 
          1%
\fi   \fi
% latex & latex2e:
\def\EndOfComment#1{\endgroup\end{#1}%
    \csname After#1Comment\endcsname}
\def\CommentEndDef#1{{\escapechar=-1\relax
    \csarg\xdef{End#1Test}{\string\\end\string\{#1\string\}}%
    }}
\else
% plain & other
\def\EndOfComment#1{\endgroup\AfterComment}
\def\CommentEndDef#1{{\escapechar=-1\relax
    \csarg\xdef{End#1Test}{\string\\end#1}%
    }}
\fi

\excludecomment{comment}

\endinput