X-VM-v5-Data: ([nil nil nil nil nil nil nil t nil]
	[nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil])
Date:         Thu, 17 May 90 11:45:59 CET
Reply-To: LaTeX-L Mailing list <LATEX-L%DHDURZ1@unido.bitnet>
From: PZF5HZ@RUIPC1E.bitnet
To: Rainer Schoepf <BK4@DHDURZ1.uucp>
Status: R
X-Status: 
X-Keywords:                  
X-UID: 102

To bring some life into the discussion about attributes
I implemented a version with a simple syntax. The code
below is not meant to be good, correct or something
else. It is simply  a playground for you a possible
syntax but perhaps not a good one.

I also changed the end tag to  detect wrong and or
missing nested environments. See comments in the code.
Again this part was only hack to provide the
functionality

To give a possible application I redefined the
\newtheorem command to provide the attributes
`nonumber' , `number=....' and `name=...' Examples are
given in the short test file. I used my theorem.sty as
a basis but it will work (with a few error messages)
with the standard theorem stuff. The example .tex file
also shows certain error cases with typos missing end's
etc.  I used \Start and \Stop instead of \begin \end
for testing reasons.

I would be interested in comments about this approach
especially about the syntax. There are numerous other
possibilties, for example, allowing spaces (with no
effect) or using spaces as delimiters and double quotes
for strings (that's similar to IBM DCF) and and and

Okay, below is the code in three parts: test.tex,
environ.ltx and theorem.tst.

Greetings Frank Mittelbach


%%%%%%%%

\documentstyle[theorem]{article}

\errorcontextlines-200
\scrollmode

\theoremstyle{plain}
\newtheorem{lem}{Lemma}


\makeatletter
\input environ.ltx
\input theorem.tst

\Start{document|paper=A4|twocolumn}

This is some starting bla  bla

\Start{lem}
  \label{first}
  A normal lemma.
\Stop{lem}

But now:
\Start{lem|name=Zorn'sches Lemma|nonumber}
   Well, this is something which shouldn't be called lemma at all.
\Stop{lem}

And finally:
\Start{lem|number=\ref{first}'}
  Here we have a sub lemma to the first one.
\Stop{lem}

\Start{lem}
  Another normal lemma. But unfortunatly, the number is off by two
  (see remarks in theorem.tst).
\Stop{lem}



\Start{itemize|form=compact}
\item more bla bla
\Stop{itemi}


\Start{small}
some small text

\Start{quote|compact}
  this is a quote

\Stop{document}




%%%%%%%% environ.ltx %%%%%%%%%%%%



%          ****************************************
%          *            ENVIRONMENTS              *
%          ****************************************
%
%  \Start{foo} and \Stop{foo} are used to delimit environment foo.
%  \Start{foo} starts a group and calls \foo if it is defined, otherwise
%  it does nothing.  \Stop{foo} checks to see that it matches the
%  corresponding \Start and if so, it calls \endfoo and does an
%  \endgroup.  Otherwise, \Stop{foo} tries the following recovery:
%
%  1) if \Stop{foo} is unknown we assume that the user misspelled the
%     name and recover by replacing \Stop{foo} with \Stop{<currenvir>}
%
%  2) if \Stop{foo} is a legitime end command we check whether there
%     exists any unresolved \Start{foo}.
%
%     a) if so, the currently open environment (\Stop{<currenvir>} is
%        closed. Afterwards \Stop{foo} is tried again.
%        This mechanism will close all open enviroments until the
%        correct one is found.
%
%     b) if there is no open \Start{foo} we simply ignore the \Stop tag.
%
%  To make this error recovery work correctly one has to define things
%  like \endsmall to be different from \relax. (i.e. \@empty) Otherwise
%  the end tag is mistaken as undefined in case of errors.
%
%  If \Stop{foo} needs to ignore blanks after it, then \endfoo should
%  globally set the @ignore switch true with \global\@ignoretrue.
%
%


% 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.}}



\def\@preamblecmds{\do\document \do\documentstyle \do\@documentstyle
   \do\@options \do\@preamblecmds \do\@optionlist \do\@optionfiles
   \do\nofiles \do\includeonly \do\makeindex \do\makeglossary}

\newif\if@ignore

\def\@testdef #1#2#3{\def\@tempa{#3}\expandafter \ifx \csname #1@#2\endcsname
 \@tempa  \else \@tempswatrue \fi}

\long\def\@writefile#1#2{\@ifundefined{tf@#1}{}{\expandafter
   \immediate\write\csname tf@#1\endcsname{#2}}}
 % \long added 8 Feb 90

\def\stop{\clearpage\deadcycles\z@\let\par\@@par\@@end}

\everypar{\@nodocument} %% To get an error if text appears before the
\nullfont               %% \begin{document}


% cmds removed: They are still needed in other places of LaTeX
%               at the moment!
%
% \def\@checkend#1{}
% \def\@badend#1{}


\def\@checkend#1{\def\@tempa{#1}\ifx
      \@tempa\@currenvir \else\@badend{#1}\fi}



%%% Here the new stuff

% The next two commands are added to allow simple tests with special
% prefixes for the internal environment commands.

\def\end@prefix{end}
\def\begin@prefix{}



\expandafter\def
\csname \end@prefix document\endcsname{\clearpage\begingroup
\if@filesw \immediate\closeout\@mainaux
\def\global\@namedef##1##2{}\def\newlabel{\@testdef r}%
\def\bibcite{\@testdef b}\@tempswafalse \makeatletter\input \jobname.aux
\if@tempswa \@warning{Label(s) may have changed.  Rerun to get
cross-references right}\fi\fi\endgroup\deadcycles\z@\@@end}

\expandafter\let
\csname\begin@prefix document\endcsname\document

\def\@currenvir{document}


% we save the enviroment names on a simple stack. \edef can be used
% because env names will contain no expandable stuff.

\def\env@stack{document}

\def\push@currenvir{\edef\env@stack{\@currenvir,\env@stack}}





\def\Start#1{%
%
%   First we grab the attributes and extract the real env name.
%
 \get@attrib#1|\@nil
 \typeout{EnvName: \env@name.}%
 \typeout{Attribs: \meaning\env@attribs.}%
 \with@attribs\env@attribs\do
      {\typeout{Attrib: \attrib\space with \meaning\value.}}
 \begingroup  \@endpefalse
%
%   Here we push the name onto the stack.
  \push@currenvir
  \let\@currenvir\env@name
%
%   The rest is executing the env macros if defined.
%   If an env macro is undefined the name is nevertheless
%   placed onto the stack so that the end tag doesn't produce
%   a second error (if both are the same).
  \expandafter
  \ifx\csname \begin@prefix\@currenvir \endcsname\relax
    \@latexerr{Environment \@currenvir\space undefined}\@eha
  \else
    \csname \begin@prefix\@currenvir \expandafter\endcsname
  \fi}


% The way it works at the moment \env@name isn't really necessary
% (the local \@currenvir would do if we move \get@attrib after the
% \begingroup. But I also wrote a version where spaces etc where allowed.
%

\def\get@attrib#1|#2\@nil{%
  \gdef\env@name{#1}%
  \gdef\env@attribs{|#2}}


% \Stop will implement the recoveries above. Of course, a version
% prducing only warnings or nothing in case of omitted end tags could
% be defined  similar.


\def\Stop#1{%
    \let\end@game\normal@game
    \def\@tempa{#1}%
    \ifx  \@tempa\@currenvir
    \else
      \@ifundefined{\end@prefix #1}%
         {\@latexerr{\string\Start{\@currenvir} ended by
                     \string\Stop{#1} which is undefined}%
                    {Your command was replaced by
                     \string\Stop{\@currenvir}.}}%
         {\ifonstack{#1}%
             {\@latexerr{\string\Start{\@currenvir} ended by
                     \string\Stop{#1}}%
                    {A \string\Stop{\@currenvir} tag was
                     added.}%
% The next lines are necessary to put the \Stop macro after the
% \endgroup inside \end@game. (\@gtempa would do, too, I suppose).
                \gdef\retry@Stop{\Stop{#1}}%
                \aftergroup\retry@Stop}%
             {\@latexerr{\string\Start{\@currenvir} ended by
                     \string\Stop{#1} which was never opened}%
                    {The offending \string\Stop{#1} tag was ignored.}%
              \let\end@game\@empty}}%
    \fi
    \end@game}

\def\normal@game{\csname \end@prefix \@currenvir\endcsname
    \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.

\def\ifonstack#1#2#3{%
  \edef\@tempa{\noexpand\in@{#1,}{\env@stack,}}%
  \@tempa \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@


% The \with@attribs macros runs through the attrib list (given)
% and executes a list of commands for every attribute.
% The attributes are stored in \attrib and \value during looping.

% \with@attribs can't be used recurive since it has a global variable
% i.e., \do@attr. This is done for speed but it is only faster
% if a suitable number of attributs are to be processed.

\def\with@attribs#1\do#2{\expandafter\def\expandafter
                                         \@tempa\expandafter{#1}%
   \def\@tempb{|}%
   \ifx\@tempa\@tempb
     \typeout{Empty Attrib list}%
   \else
     \def\do@attr{#2}%
     \expandafter\attr@for#1\@nil\fi}

\def\attr@for|#1|#2\@nil{%
   \get@value#1=\@nil
   \def\@tempa{#2}%
   \ifx\@tempa\@empty \let\next\do@attr
   \else
      \def\next{\do@attr\attr@for|#2\@nil}\fi
   \next}


% then ext one will fail for format= without a right side value.
% so it's not very stable

\def\get@value#1=#2\@nil{%
  \def\attrib{#1}%
  \def\value{#2}%
   \ifx\value\@empty
    \else \correct@value#2\fi}

\def\correct@value#1={\def\value{#1}}



\endinput

% The next lines show a dirty trick where we get \verb+\Stop<foo>+
% to be undefined instead of \verb+\relax+ if it was undefined before.
      {\aftergroup\ifx
       \expandafter\aftergroup\csname\end@prefix #1\endcsname}%
       \undefined



%%% theorem.tst %%%%%%%%%%%%%%

\gdef\@thm#1#2{%
   \trivlist
%   \tracingall
   \@topsep \theorempreskipamount               % used by first \item
   \@topsepadd \theorempostskipamount           % used by \@endparenv
%
% Default is to update and use the counter.
% If number or nonumber attribute is used this
% command will be overwritten.
% We also have to disable updating the counter
% and should generate a new \@currentlabel, but this is left
% out at the moment.
   \refstepcounter{#1}%
   \def\avth@number{\csname the#1\endcsname}%
%
% Default is to use the supplied name. This will be overwritten
% by the name attribute.
   \def\avth@name{#2}%
   \use@attribs{th}%
   \@ifnextchar [%
      \@ythm{\@begintheorem\avth@name\avth@number\ignorespaces}}

\def\@ythm[#1]{\@opargbegintheorem\avth@name\avth@number{#1}\ignorespaces}


% the use@attribs command will look whether \a#1<attrib> is defined and
% if so will execute it using \value as an argument. Otherwise it will
% store the \value in \av#1<attrib> for later use.
% Whether such a scheme is useful depends on the number of occasions
% where an attributes value has to be filed away.

\def\use@attribs#1{\with@attribs\env@attribs\do
   {\expandafter\ifx\csname a#1@\attrib\endcsname\relax
    \expandafter\let\csname av#1@\attrib\endcsname\value
    \else \csname a#1@\attrib\expandafter\endcsname\expandafter{\value}%
    \fi}}


\def\ath@nonumber{\let\avth@number\@empty}

%%%% finish