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Subject:      environ.sty
Date: Wed, 22 Aug 1990 10:39:12 +0100
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%          ****************************************
%          *            ENVIRONMENTS              *
%          ****************************************
%
%
%  \begin{foo} and \end{foo} are used to delimit environment foo.
%  \begin{foo} starts a group and calls \foo if it is defined, otherwise
%  it does nothing.  \end{foo} checks to see that it matches the
%  corresponding \begin and if so, it calls \endfoo and does an
%  \endgroup.  Otherwise, \end{foo} tries the following recovery:
%
%  1) if \end{foo} is unknown we assume that the user misspelled the
%     name and recover by replacing \end{foo} with \end{<currenvir>}
%
%  2) if \end{foo} is a legitime end command we check whether there
%     exists any unresolved \begin{foo}.
%
%     a) if so, the currently open environment (\end{<currenvir>} is
%        closed. Afterwards \end{foo} is tried again.
%        This mechanism will close all open enviroments until the
%        correct one is found.
%
%     b) if there is no open \begin{foo} we simply ignore the \end tag.
%
%
%  If \end{foo} needs to ignore blanks after it, then \endfoo should
%  globally set the @ignore switch true with \global\@ignoretrue.
%
%
%% \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        \=3D     Greater than  \>     Question mark \?
%%   Commercial at \@     Left bracket  \[     Backslash     \\
%%   Right bracket \]     Circumflex    \^     Underscore    \_
%%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%%   Right brace   \}     Tilde         \~}


% First some stuff which is necessary if the macros are used as a
% substitute for LaTeX's environments part in latex.tex.

% \addto@hook\everyjob{\typeout{environ: new error recovery for
%                               missplaced \string\end.}}

\catcode`\_=3D11
\catcode`\0=3D11
\makeatletter % to allow using \input in test files


\def\inner_begin#1{%
  \ifx#1\relax
    \@latexerr{Environment \expandafter\@gobble\string#1 undefined}\@eha
  \else
    \begingroup
     \@endpefalse
     \@aligningfalse  % not in \halign by default
     \expandafter
     \xdef\csname l_\the\env_level\endcsname
      {\expandafter\@gobble\string#1,%
       \csname l_\the\env_level\endcsname}%
     \expandafter #1\fi   % put \fi out of the way in case the env has =
args.
}


% \begin is supposed to get all attributes and then calls \inner_begin
% at the moment it only calls it.

\def\begin#1{%
 \expandafter\inner_begin\csname #1\endcsname
}

\def\@gobblefour#1#2#3#4{}


\newcount\env_level

\def\l_0{GROUND}

\def\separate_stack{%
   \global\advance\env_level\@ne
   \expandafter\gdef
     \csname l_\the\env_level\endcsname
     {}%
}


\def\combine_stack#1{%
  \count@\env_level
  \global\advance\env_level\m@ne
  \expandafter
  \xdef\csname l_\the\env_level\endcsname
    {\expandafter\@gobble\string#1,%
     \csname l_\the\count@\endcsname
     \expandafter\expandafter\expandafter
     \gobble_to_comma                       %remove old top entry from =
begin
     \csname l_\the\env_level\endcsname}%
%  \expandafter\show\csname l_\the\env_level\endcsname
}

\def\gobble_to_comma#1,{}


\def\end#1{\expandafter\inner_end
           \csname end#1\endcsname}


\def\hidden_crcr{\crcr\noalign\bgroup
            \let\test_undefined\undefined}
% hide \crcr in skipped conditional text. To make the next macro faster
% we also put some other stuff into it.

\def\inner_end#1{%
%
% The next lines place everything which is not expandable inside a
% \noalign group if we are ending an \halign environment. Of course such
% environments have to set the switch.
%
    \if@aligning \hidden_crcr\fi
      \edef\@tempa{\expandafter\@gobblefour\string#1}%
      \expandafter\expandafter\expandafter
         \pop_stack\csname l_\the\env_level\endcsname\@nil
%    \typeout{\showmeaning\@tempa}%
%    \typeout{\showmeaning\cur_envir}%
    \ifx  \@tempa\cur_envir
      \global\let\end_env_game\normal_game
    \else
      \expandafter
      \xdef\csname l_\the\env_level\endcsname
        {\cur_envir,\csname l_\the\env_level\endcsname}%
      \ifx#1\test_undefined
         \@latexerr{\string\begin{\cur_envir} ended by
                     \string\end{\@tempa} which is undefined}%
                    {Your command was replaced by
                     \string\end{\cur_envir}.}%
         \gdef\end_env_game{\end\cur_envir\@gobble}\else
         \if_on_stack\@tempa
             {\err_warn{\string\begin{\cur_envir} ended by
                        \ifx#1\dummy a right brace\else
                          \string\end{\@tempa}\fi}%
                    {An \string\end{\cur_envir} tag was
                     added.}%
              \gdef\end_env_game{\end\cur_envir
                            \inner_end}}%
             {\@latexerr{\string\begin{\cur_envir} ended by
                     \string\end{\@tempa} which was never opened}%
                    {The offending \string\end{\@tempa} tag was =
ignored.}%
              \global\let\end_env_game\@gobble}%
       \fi
    \fi
    \if@aligning \egroup \fi
    \end_env_game#1}

\let\test_undefined\relax % during if@aligning this has to be =
*undefined*



% At the moment only a warning
%
\def\err_warn#1#2{\typeout{Warning: #1!^^J\@spaces\@spaces\space#2}}

\def\omitendtags{\let\err_warn\@gobbletwo}


% Using \newif will alway define three control sequences even if we need
% only two of them, so we better define them directly. This would save
% a lot of macro names in \LaTeX{}, we can also omit the equal sign
% in the definition of \..true:

\let\if@aligning\iffalse \def\@aligningtrue{\let\if@aligning\iftrue}
\def\@aligningfalse{\let\if@aligning\iffalse}

% Another point worth considering is to define \newglobalif to omit the
% \global\..true etc. in many places of \LaTeX{}.

\long\def\normal_game#1{#1%
      \if@endpe\aftergroup\@doendpe\fi
    \endgroup
    \if@ignore \global\@ignorefalse
                      \ignorespaces\fi}


% Here the test macros for looking at the stack, the \in@ macro
% is coming from the AMS-TeX implementation. We have to use \@tempb
% \@tempa is already used above
%

\def\pop_stack#1,#2\@nil{\gdef\cur_envir{#1}%
      \expandafter
      \gdef\csname l_\the\env_level\endcsname{#2}}

\def\if_on_stack#1#2#3{%
  \edef\@tempb{\noexpand\in@{#1,}{\l_0,}}%
  \@tempb \ifin@ #2\else #3\fi}%


\def\in@#1#2{%
  \def\in@@##1#1##2##3\in@@{%
    \ifx\in@##2\in@false\else\in@true\fi}%
  \in@@#2#1\in@\in@@}

\newif\ifin@

\def\showstack{\show\l_0}

\catcode`\0=3D12


\def\newenvironment#1{\@ifnextchar
     [{\@newenv{#1}}{\@newenv{#1}[0]}}

\long\def\@newenv#1[#2]#3#4{\expandafter\newcommand
     \csname #1\endcsname[#2]{\separate_stack#3%
       \expandafter\combine_stack\csname#1\endcsname}%
     \long\expandafter\def\csname end#1\endcsname{#4}}

% this is a very simple test for checking the catcodes of a list of =
characters
% containing no braces maybe somebody can spend some thoughts on writing
% a complete test using  some sort of \futurelet mechanism.

\def\showmeaning#1{\expandafter\show@meaning#1\@nil}
\def\show@meaning#1{\ifx\@nil#1\else
  \string#1
    (\ifnum\the\catcode\expandafter`\csname\string#1\endcsname<10 0\fi
    \the\catcode\expandafter`\csname\string#1\endcsname)
  \expandafter\show@meaning\fi}

%%%%%%%%%%%%%%%%%%%%



\def\@tabarray{\@aligningtrue\@ifnextchar[{\@array}{\@array[c]}}

%the math envs have to be handled similar

\def\eqnarray{\stepcounter{equation}\let\@currentlabel=3D\theequation
\global\@eqnswtrue
\@aligningtrue
\global\@eqcnt\z@\tabskip\@centering\let\\=3D\@eqncr
$$\halign to \displaywidth\bgroup\@eqnsel\hskip\@centering
  $\displaystyle\tabskip\z@{##}$&\global\@eqcnt\@ne
  \hskip 2\arraycolsep \hfil${##}$\hfil
  &\global\@eqcnt\tw@ \hskip 2\arraycolsep =
$\displaystyle\tabskip\z@{##}$\hfil
   \tabskip\@centering&\llap{##}\tabskip\z@\cr}

% We also have to restore if@aligning inside parboxes etc.



\catcode`\_=3D8

\endinput


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<TITLE>     environ.sty</TITLE>
</HEAD>
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<!-- Converted from text/plain format -->

<P><FONT =
SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
****************************************</FONT>

<BR><FONT =
SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
ENVIRONMENTS&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp; *</FONT>

<BR><FONT =
SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
****************************************</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp; \begin{foo} and \end{foo} are used to delimit =
environment foo.</FONT>

<BR><FONT SIZE=3D2>%&nbsp; \begin{foo} starts a group and calls \foo if =
it is defined, otherwise</FONT>

<BR><FONT SIZE=3D2>%&nbsp; it does nothing.&nbsp; \end{foo} checks to =
see that it matches the</FONT>

<BR><FONT SIZE=3D2>%&nbsp; corresponding \begin and if so, it calls =
\endfoo and does an</FONT>

<BR><FONT SIZE=3D2>%&nbsp; \endgroup.&nbsp; Otherwise, \end{foo} tries =
the following recovery:</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp; 1) if \end{foo} is unknown we assume that the =
user misspelled the</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp; name and recover by =
replacing \end{foo} with \end{&lt;currenvir&gt;}</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp; 2) if \end{foo} is a legitime end command we =
check whether there</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp; exists any unresolved =
\begin{foo}.</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp; a) if so, the currently =
open environment (\end{&lt;currenvir&gt;} is</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; closed. =
Afterwards \end{foo} is tried again.</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; This =
mechanism will close all open enviroments until the</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; correct =
one is found.</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp; b) if there is no open =
\begin{foo} we simply ignore the \end tag.</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%&nbsp; If \end{foo} needs to ignore blanks after it, =
then \endfoo should</FONT>

<BR><FONT SIZE=3D2>%&nbsp; globally set the @ignore switch true with =
\global\@ignoretrue.</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>%% \CharacterTable</FONT>

<BR><FONT SIZE=3D2>%%&nbsp; {Upper-case&nbsp;&nbsp;&nbsp; =
\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</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Lower-case&nbsp;&nbsp;&nbsp; =
\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</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; =
Digits&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\0\1\2\3\4\5\6\7\8\9</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Exclamation&nbsp;&nbsp; =
\!&nbsp;&nbsp;&nbsp;&nbsp; Double quote&nbsp; =
\&quot;&nbsp;&nbsp;&nbsp;&nbsp; Hash (number) \#</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; =
Dollar&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\$&nbsp;&nbsp;&nbsp;&nbsp; Percent&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\%&nbsp;&nbsp;&nbsp;&nbsp; Ampersand&nbsp;&nbsp;&nbsp;&nbsp; =
\&amp;</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Acute accent&nbsp; =
\'&nbsp;&nbsp;&nbsp;&nbsp; Left paren&nbsp;&nbsp;&nbsp; =
\(&nbsp;&nbsp;&nbsp;&nbsp; Right paren&nbsp;&nbsp; \)</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Asterisk&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\*&nbsp;&nbsp;&nbsp;&nbsp; =
Plus&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\+&nbsp;&nbsp;&nbsp;&nbsp; =
Comma&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \,</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; =
Minus&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\-&nbsp;&nbsp;&nbsp;&nbsp; =
Point&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\.&nbsp;&nbsp;&nbsp;&nbsp; Solidus&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\/</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; =
Colon&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\:&nbsp;&nbsp;&nbsp;&nbsp; Semicolon&nbsp;&nbsp;&nbsp;&nbsp; =
\;&nbsp;&nbsp;&nbsp;&nbsp; Less than&nbsp;&nbsp;&nbsp;&nbsp; =
\&lt;</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; =
Equals&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\=3D&nbsp;&nbsp;&nbsp;&nbsp; Greater than&nbsp; =
\&gt;&nbsp;&nbsp;&nbsp;&nbsp; Question mark \?</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Commercial at =
\@&nbsp;&nbsp;&nbsp;&nbsp; Left bracket&nbsp; \[&nbsp;&nbsp;&nbsp;&nbsp; =
Backslash&nbsp;&nbsp;&nbsp;&nbsp; \\</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Right bracket =
\]&nbsp;&nbsp;&nbsp;&nbsp; Circumflex&nbsp;&nbsp;&nbsp; =
\^&nbsp;&nbsp;&nbsp;&nbsp; Underscore&nbsp;&nbsp;&nbsp; \_</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Grave accent&nbsp; =
\`&nbsp;&nbsp;&nbsp;&nbsp; Left brace&nbsp;&nbsp;&nbsp; =
\{&nbsp;&nbsp;&nbsp;&nbsp; Vertical bar&nbsp; \|</FONT>

<BR><FONT SIZE=3D2>%%&nbsp;&nbsp; Right brace&nbsp;&nbsp; =
\}&nbsp;&nbsp;&nbsp;&nbsp; =
Tilde&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \~}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>% First some stuff which is necessary if the macros =
are used as a</FONT>

<BR><FONT SIZE=3D2>% substitute for LaTeX's environments part in =
latex.tex.</FONT>
</P>

<P><FONT SIZE=3D2>% \addto@hook\everyjob{\typeout{environ: new error =
recovery for</FONT>

<BR><FONT =
SIZE=3D2>%&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nb=
sp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; missplaced =
\string\end.}}</FONT>
</P>

<P><FONT SIZE=3D2>\catcode`\_=3D11</FONT>

<BR><FONT SIZE=3D2>\catcode`\0=3D11</FONT>

<BR><FONT SIZE=3D2>\makeatletter % to allow using \input in test =
files</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\inner_begin#1{%</FONT>

<BR><FONT SIZE=3D2>&nbsp; \ifx#1\relax</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \@latexerr{Environment =
\expandafter\@gobble\string#1 undefined}\@eha</FONT>

<BR><FONT SIZE=3D2>&nbsp; \else</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \begingroup</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \@endpefalse</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \@aligningfalse&nbsp; % not =
in \halign by default</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \xdef\csname =
l_\the\env_level\endcsname</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
{\expandafter\@gobble\string#1,%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \csname =
l_\the\env_level\endcsname}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \expandafter =
#1\fi&nbsp;&nbsp; % put \fi out of the way in case the env has =
args.</FONT>

<BR><FONT SIZE=3D2>}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>% \begin is supposed to get all attributes and then =
calls \inner_begin</FONT>

<BR><FONT SIZE=3D2>% at the moment it only calls it.</FONT>
</P>

<P><FONT SIZE=3D2>\def\begin#1{%</FONT>

<BR><FONT SIZE=3D2>&nbsp;\expandafter\inner_begin\csname =
#1\endcsname</FONT>

<BR><FONT SIZE=3D2>}</FONT>
</P>

<P><FONT SIZE=3D2>\def\@gobblefour#1#2#3#4{}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\newcount\env_level</FONT>
</P>

<P><FONT SIZE=3D2>\def\l_0{GROUND}</FONT>
</P>

<P><FONT SIZE=3D2>\def\separate_stack{%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp; \global\advance\env_level\@ne</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp; \expandafter\gdef</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \csname =
l_\the\env_level\endcsname</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; {}%</FONT>

<BR><FONT SIZE=3D2>}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\combine_stack#1{%</FONT>

<BR><FONT SIZE=3D2>&nbsp; \count@\env_level</FONT>

<BR><FONT SIZE=3D2>&nbsp; \global\advance\env_level\m@ne</FONT>

<BR><FONT SIZE=3D2>&nbsp; \expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp; \xdef\csname l_\the\env_level\endcsname</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; =
{\expandafter\@gobble\string#1,%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \csname =
l_\the\count@\endcsname</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; =
\expandafter\expandafter\expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; =
\gobble_to_comma&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nb=
sp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p; %remove old top entry from begin</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \csname =
l_\the\env_level\endcsname}%</FONT>

<BR><FONT SIZE=3D2>%&nbsp; \expandafter\show\csname =
l_\the\env_level\endcsname</FONT>

<BR><FONT SIZE=3D2>}</FONT>
</P>

<P><FONT SIZE=3D2>\def\gobble_to_comma#1,{}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\end#1{\expandafter\inner_end</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\csname end#1\endcsname}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\hidden_crcr{\crcr\noalign\bgroup</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p; \let\test_undefined\undefined}</FONT>

<BR><FONT SIZE=3D2>% hide \crcr in skipped conditional text. To make the =
next macro faster</FONT>

<BR><FONT SIZE=3D2>% we also put some other stuff into it.</FONT>
</P>

<P><FONT SIZE=3D2>\def\inner_end#1{%</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>% The next lines place everything which is not =
expandable inside a</FONT>

<BR><FONT SIZE=3D2>% \noalign group if we are ending an \halign =
environment. Of course such</FONT>

<BR><FONT SIZE=3D2>% environments have to set the switch.</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \if@aligning =
\hidden_crcr\fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\edef\@tempa{\expandafter\@gobblefour\string#1}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\expandafter\expandafter\expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\pop_stack\csname l_\the\env_level\endcsname\@nil</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp; =
\typeout{\showmeaning\@tempa}%</FONT>

<BR><FONT SIZE=3D2>%&nbsp;&nbsp;&nbsp; =
\typeout{\showmeaning\cur_envir}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \ifx&nbsp; =
\@tempa\cur_envir</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\global\let\end_env_game\normal_game</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \else</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \xdef\csname =
l_\the\env_level\endcsname</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
{\cur_envir,\csname l_\the\env_level\endcsname}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\ifx#1\test_undefined</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\@latexerr{\string\begin{\cur_envir} ended by</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\string\end{\@tempa} which is undefined}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {Your command was =
replaced by</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\string\end{\cur_envir}.}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\gdef\end_env_game{\end\cur_envir\@gobble}\else</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\if_on_stack\@tempa</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp; {\err_warn{\string\begin{\cur_envir} ended by</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
; \ifx#1\dummy a right brace\else</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
;&nbsp;&nbsp; \string\end{\@tempa}\fi}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {An =
\string\end{\cur_envir} tag was</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; added.}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp; \gdef\end_env_game{\end\cur_envir</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp=
;&nbsp;&nbsp;&nbsp;&nbsp; \inner_end}}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp; {\@latexerr{\string\begin{\cur_envir} ended by</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\string\end{\@tempa} which was never opened}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {The offending =
\string\end{\@tempa} tag was ignored.}%</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp; \global\let\end_env_game\@gobble}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \if@aligning \egroup \fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \end_env_game#1}</FONT>
</P>

<P><FONT SIZE=3D2>\let\test_undefined\relax % during if@aligning this =
has to be *undefined*</FONT>
</P>
<BR>
<BR>

<P><FONT SIZE=3D2>% At the moment only a warning</FONT>

<BR><FONT SIZE=3D2>%</FONT>

<BR><FONT SIZE=3D2>\def\err_warn#1#2{\typeout{Warning: =
#1!^^J\@spaces\@spaces\space#2}}</FONT>
</P>

<P><FONT SIZE=3D2>\def\omitendtags{\let\err_warn\@gobbletwo}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>% Using \newif will alway define three control =
sequences even if we need</FONT>

<BR><FONT SIZE=3D2>% only two of them, so we better define them =
directly. This would save</FONT>

<BR><FONT SIZE=3D2>% a lot of macro names in \LaTeX{}, we can also omit =
the equal sign</FONT>

<BR><FONT SIZE=3D2>% in the definition of \..true:</FONT>
</P>

<P><FONT SIZE=3D2>\let\if@aligning\iffalse =
\def\@aligningtrue{\let\if@aligning\iftrue}</FONT>

<BR><FONT SIZE=3D2>\def\@aligningfalse{\let\if@aligning\iffalse}</FONT>
</P>

<P><FONT SIZE=3D2>% Another point worth considering is to define =
\newglobalif to omit the</FONT>

<BR><FONT SIZE=3D2>% \global\..true etc. in many places of =
\LaTeX{}.</FONT>
</P>

<P><FONT SIZE=3D2>\long\def\normal_game#1{#1%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\if@endpe\aftergroup\@doendpe\fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \endgroup</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; \if@ignore =
\global\@ignorefalse</FONT>

<BR><FONT =
SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\ignorespaces\fi}</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>% Here the test macros for looking at the stack, the =
\in@ macro</FONT>

<BR><FONT SIZE=3D2>% is coming from the AMS-TeX implementation. We have =
to use \@tempb</FONT>

<BR><FONT SIZE=3D2>% \@tempa is already used above</FONT>

<BR><FONT SIZE=3D2>%</FONT>
</P>

<P><FONT SIZE=3D2>\def\pop_stack#1,#2\@nil{\gdef\cur_envir{#1}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \expandafter</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \gdef\csname =
l_\the\env_level\endcsname{#2}}</FONT>
</P>

<P><FONT SIZE=3D2>\def\if_on_stack#1#2#3{%</FONT>

<BR><FONT SIZE=3D2>&nbsp; =
\edef\@tempb{\noexpand\in@{#1,}{\l_0,}}%</FONT>

<BR><FONT SIZE=3D2>&nbsp; \@tempb \ifin@ #2\else #3\fi}%</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\in@#1#2{%</FONT>

<BR><FONT SIZE=3D2>&nbsp; \def\in@@##1#1##2##3\in@@{%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; =
\ifx\in@##2\in@false\else\in@true\fi}%</FONT>

<BR><FONT SIZE=3D2>&nbsp; \in@@#2#1\in@\in@@}</FONT>
</P>

<P><FONT SIZE=3D2>\newif\ifin@</FONT>
</P>

<P><FONT SIZE=3D2>\def\showstack{\show\l_0}</FONT>
</P>

<P><FONT SIZE=3D2>\catcode`\0=3D12</FONT>
</P>
<BR>

<P><FONT SIZE=3D2>\def\newenvironment#1{\@ifnextchar</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; =
[{\@newenv{#1}}{\@newenv{#1}[0]}}</FONT>
</P>

<P><FONT =
SIZE=3D2>\long\def\@newenv#1[#2]#3#4{\expandafter\newcommand</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \csname =
#1\endcsname[#2]{\separate_stack#3%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =
\expandafter\combine_stack\csname#1\endcsname}%</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp;&nbsp; \long\expandafter\def\csname =
end#1\endcsname{#4}}</FONT>
</P>

<P><FONT SIZE=3D2>% this is a very simple test for checking the catcodes =
of a list of characters</FONT>

<BR><FONT SIZE=3D2>% containing no braces maybe somebody can spend some =
thoughts on writing</FONT>

<BR><FONT SIZE=3D2>% a complete test using&nbsp; some sort of \futurelet =
mechanism.</FONT>
</P>

<P><FONT =
SIZE=3D2>\def\showmeaning#1{\expandafter\show@meaning#1\@nil}</FONT>

<BR><FONT SIZE=3D2>\def\show@meaning#1{\ifx\@nil#1\else</FONT>

<BR><FONT SIZE=3D2>&nbsp; \string#1</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; =
(\ifnum\the\catcode\expandafter`\csname\string#1\endcsname&lt;10 =
0\fi</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp;&nbsp; =
\the\catcode\expandafter`\csname\string#1\endcsname)</FONT>

<BR><FONT SIZE=3D2>&nbsp; \expandafter\show@meaning\fi}</FONT>
</P>

<P><FONT SIZE=3D2>%%%%%%%%%%%%%%%%%%%%</FONT>
</P>
<BR>
<BR>

<P><FONT =
SIZE=3D2>\def\@tabarray{\@aligningtrue\@ifnextchar[{\@array}{\@array[c]}}=
</FONT>
</P>

<P><FONT SIZE=3D2>%the math envs have to be handled similar</FONT>
</P>

<P><FONT =
SIZE=3D2>\def\eqnarray{\stepcounter{equation}\let\@currentlabel=3D\theequ=
ation</FONT>

<BR><FONT SIZE=3D2>\global\@eqnswtrue</FONT>

<BR><FONT SIZE=3D2>\@aligningtrue</FONT>

<BR><FONT =
SIZE=3D2>\global\@eqcnt\z@\tabskip\@centering\let\\=3D\@eqncr</FONT>

<BR><FONT SIZE=3D2>$$\halign to =
\displaywidth\bgroup\@eqnsel\hskip\@centering</FONT>

<BR><FONT SIZE=3D2>&nbsp; =
$\displaystyle\tabskip\z@{##}$&amp;\global\@eqcnt\@ne</FONT>

<BR><FONT SIZE=3D2>&nbsp; \hskip 2\arraycolsep \hfil${##}$\hfil</FONT>

<BR><FONT SIZE=3D2>&nbsp; &amp;\global\@eqcnt\tw@ \hskip 2\arraycolsep =
$\displaystyle\tabskip\z@{##}$\hfil</FONT>

<BR><FONT SIZE=3D2>&nbsp;&nbsp; =
\tabskip\@centering&amp;\llap{##}\tabskip\z@\cr}</FONT>
</P>

<P><FONT SIZE=3D2>% We also have to restore if@aligning inside parboxes =
etc.</FONT>
</P>
<BR>
<BR>

<P><FONT SIZE=3D2>\catcode`\_=3D8</FONT>
</P>

<P><FONT SIZE=3D2>\endinput</FONT>
</P>

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