path: root/Master/texmf-dist/source/latex/tools/xspace.dtx

% \iffalse meta-comment
%
% Copyright 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
% The LaTeX3 Project and any individual authors listed elsewhere
% in this file. 
% 
% This file is part of the Standard LaTeX `Tools Bundle'.
% -------------------------------------------------------
% 
% It 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
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% The list of all files belonging to the LaTeX `Tools Bundle' is
% given in the file `manifest.txt'.
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% \fi
% \iffalse
%% File: xspace.dtx Copyright (C) 1991-1997 David Carlisle
%% File: xspace.dtx Copyright (C) 2004-2006 David Carlisle,
%%                                          Morten H\o gholm
%
%<*dtx>
          \ProvidesFile{xspace.dtx}
%</dtx>
%<package>\NeedsTeXFormat{LaTeX2e}
%<package>\ProvidesPackage{xspace}
%<driver>\ProvidesFile{xspace.drv}
% \fi
%         \ProvidesFile{xspace.dtx}
          [2006/05/08 v1.12 Space after command names (DPC,MH)]
%
% \iffalse
%<*driver>
\documentclass{ltxdoc}
\makeatletter
\providecommand*\eTeX{{%
  \if b\expandafter\@car\f@series\@nil\boldmath\fi$\m@th
  \varepsilon$-\TeX}}
\makeatother
\usepackage{xspace}[2006/05/08]
\begin{document}
\DocInput{xspace.dtx}
\end{document}
%</driver>
% \fi
%
% \GetFileInfo{xspace.dtx}
% \title{The \textsf{xspace} package\thanks{This file
%        has version number \fileversion, last
%        revised \filedate.}}
% \author{David Carlisle \and Morten H\o gholm}
% \date{\filedate}
% \maketitle
%
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% \CheckSum{209}
%
% \changes{v1.00}{1991/08/30}{Initial version}
% \changes{v1.01}{1992/06/26}{Re-issue for the new doc and docstrip}
% \changes{v1.02}{1994/01/31}{Re-issue for LaTeX2e (no change to
%   code)} 
% \changes{v1.07}{2004/12/07}{Make extensible. tools/3712}
% \changes{v1.07}{2004/12/07}{Fix active characters. tools/3747}
% \changes{v1.07}{2004/12/07}{Update documentation}
% \changes{v1.08}{2005/05/07}{Better fix for active characters}
% \changes{v1.09}{2005/07/26}{Improve test by exiting if
%   \cs{@let@token} is a letter}
% \changes{v1.10}{2005/10/04}{Use higher level functions for
% conditional processing} 
% \changes{v1.10}{2005/10/04}{Improve expansion method}
%
% \begin{abstract}
% |\xspace| should be used at the end of a macro designed to
% be used mainly in text. It adds a space unless the macro is
% followed by certain punctuation characters.
% \end{abstract}
%
% \section{Introduction}
% \newcommand{\gb}{Great Britain\xspace}\DescribeMacro{\xspace}
% After defining |\newcommand{\gb}{Great Britain\xspace}|,
% the command |\gb| will determine when to insert a space
% after itself and when not. Thus the input
% \begin{quote}
% |\gb is a very nice place to live.\\| \\
% |\gb, a small island off the coast of France.\\|\\
% |\gb\footnote{The small island off the coast of France.}|\\
% |is a very nice place to live.|
% \end{quote}
% results in the output
% \begin{quote}
% \gb is a very nice place to live. \\
% \gb, a small island off the coast of France.\\
% \gb\footnote{The small island off the coast of France.}
% is a very nice place to live.
% \end{quote}
% |\xspace| saves the user from having to type \verb*+\ + or
% |{}| after most occurrences of a macro name in text.
% However if either of these constructions follows |\xspace|,
% a space is not added by |\xspace|. This means that it is
% safe to add |\xspace| to the end of an existing macro
% without making too many changes in your document. In particular,
% |\xspace| will always insert a space if the thing following it is
% a normal letter which is the usual case.
%
% Sometimes |\xspace| may make the wrong decision, and add a
% space when it is not required. There may be different
% reasons for this behavior but it can always be handled by
% following the macro with |{}|, as this has the effect of
% suppressing the space.
%
%
% \subsection{Adding new exceptions}
%
% One of the most common reasons for |\xspace| to add an
% unwanted space is when it is followed by a macro not on its
% list of exceptions.
% \DescribeMacro{\xspaceaddexceptions}%
% With |\xspaceaddexceptions| you can add new commands or
% characters to be recognized by |\xspace|'s scanning
% mechanism. Users of advanced footnote packages like
% \textsf{manyfoot} will often define new footnote macros
% that should not cause a command ``enhanced'' with |\xspace|
% to insert a space. If you define the additional footnote
% macros |\footnoteA| and |\footnoteB|, simply add the
% following line to your preamble:
% \begin{quote}
% |\xspaceaddexceptions{\footnoteA \footnoteB}|
% \end{quote}
%
%
% \subsection{Support for active characters}
%
%
% The other common instance of |\xspace| not working quite right
% happens with active characters. Generally this package must be
% loaded \emph{after} any language (or other) packages that make
% punctuation characters `active'. This makes it difficult for
% \textsf{xspace} to work flawlessly with the popular \textsf{babel}
% package especially since the punctuation characters can switch
% between being `active' and `other'. Starting at \textsf{xspace}
% version~1.08 there are two different ways to handle this depending
% on which engine your \LaTeX-format uses:
% \begin{description}
%   \item[\TeX] The punctuation characters are added to the
%   exception list in both their normal and active states thus
%   ensuring that they are always recognized.
%   \item[\eTeX] The characters are re-read when going through
%   the exception list which means the internal comparison will test
%   against the current state of the character. This works for
%   whatever category code tricks some packages may use.
% \end{description}
%
% At the time of writing all major \TeX\ distributions are using
% \eTeX\ as engine for \LaTeX\ so usually everything should work out
% of the box. If you find that you're running normal \TeX\ and
% |\xspace| seems to be making the wrong choice then either use |{}|
% as described above to fix it or add the character to the list but
% with the desired category code. See the implementation for an example
% of how to do that.
%
% \subsection{Still not satisfied?}
%
% Some people don't like the default list of exceptions so they can
% remove one item at a time with the command
% \DescribeMacro{\xspaceremoveexception}^^A
% \cs{xspaceremoveexception}\marg{token}.  Furthermore the command
% \DescribeMacro{\@xspace@hook}\cs{@xspace@hook} can be redefined to
% scan forward in the input stream in case you want to check more
% tokens. It is called after \cs{xspace} has determined if it needed
% to insert a space or if an exception was found (the default
% definition is for \cs{@xspace@hook} to be empty). Hence you can use
% \cs{unskip} to remove the space inserted if \cs{@let@token} matches
% something special. Below is an example of how one can make sure an
% endash gets a space inserted before it but a single dash not.
% \begin{verbatim} 
% \xspaceremoveexception{-} 
% \makeatletter
% \renewcommand*\@xspace@hook{%
%   \ifx\@let@token-% 
%     \expandafter\@xspace@dash@i  
%   \fi
% }
% \def\@xspace@dash@i-{\futurelet\@let@token\@xspace@dash@ii} 
% \def\@xspace@dash@ii{% 
%   \ifx\@let@token-% 
%   \else  
%     \unskip
%   \fi 
%   -% 
% } 
% \makeatother
% \end{verbatim}
%
%
% \StopEventually{}
%
% \section{The Macros}
%
% |\xspace| peeks ahead for the next token. If the token is in our
% exception list we break the loop and do nothing; else we try to
% expand the token once and start over again. If this leads us to an
% unexpandable token without finding one of the exceptions we insert a
% space.
%
%    \begin{macrocode}
%<*package>
%    \end{macrocode}
%
% \begin{macro}{\xspace}
% |\xspace| just looks ahead, and then calls |\@xspace|.
% \changes{v1.03}{1994/11/15}{Make robust}
%    \begin{macrocode}
\DeclareRobustCommand\xspace{\@xspace@firsttrue
  \futurelet\@let@token\@xspace}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\if@xspace@first}
% \changes{v1.11}{2006/02/12}{Added macro}
% \begin{macro}{\@xspace@simple}
% \changes{v1.11}{2006/02/12}{Added macro}
% Some helpers to avoid multiple calls of |\@xspace@eTeX@setup|.
%    \begin{macrocode}
\newif\if@xspace@first
\def\@xspace@simple{\futurelet\@let@token\@xspace}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\@xspace@exceptions@tlp}
% \changes{v1.07}{2004/12/07}{Added macro}
% The exception list. If the scanning mechanism finds one of
% these, it won't insert a space after the command. The
% \texttt{tlp} in the name means `token list pointer.'
%    \begin{macrocode}
\def\@xspace@exceptions@tlp{%
  ,.'/?;:!~-)\ \/\bgroup\egroup\@sptoken\space\@xobeysp
  \footnote\footnotemark
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\xspaceaddexceptions}
% \changes{v1.07}{2004/12/07}{Added macro}
% The user command, which just adds tokens to the list.
%    \begin{macrocode}
\newcommand*\xspaceaddexceptions{%
  \g@addto@macro\@xspace@exceptions@tlp
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\xspaceremoveexception}
% \changes{v1.10}{2005/10/04}{Use higher level functions for
% conditional processing} 
% This command removes an exception globally.
%    \begin{macrocode}
\newcommand*\xspaceremoveexception[1]{%
%    \end{macrocode}
% First check that it is in the list at all.
%    \begin{macrocode}
  \def\reserved@a##1#1##2##3\@@{%
    \@xspace@if@q@nil@NF##2{%
%    \end{macrocode}
% It's in the list, remove it.
%    \begin{macrocode}
      \def\reserved@a####1#1####2\@@{%
        \gdef\@xspace@exceptions@tlp{####1####2}}%
      \expandafter\reserved@a\@xspace@exceptions@tlp\@@
    }%
  }%
  \expandafter\reserved@a\@xspace@exceptions@tlp#1\@xspace@q@nil\@@
}
%    \end{macrocode}  
% \end{macro}
%
% \begin{macro}{\@xspace@break@loop}
% \changes{v1.08}{2005/04/28}{Added macro}
% \changes{v1.10}{2005/10/04}{Use quark instead}
% To stop the loop.
%    \begin{macrocode}
\def\@xspace@break@loop#1\@nil{}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@xspace@hook}
% \changes{v1.09}{2005/07/26}{Added macro}
% A hook for users with special needs.
%    \begin{macrocode}
\providecommand*\@xspace@hook{}
%    \end{macrocode}
% \end{macro}
%
% Now we check if we're running \eTeX. We can't use \cs{@ifundefined}
% as that will lock catcodes and we need to change some of those.
% As there is a small risk that someone already set \cs{eTeXversion}
% to \cs{relax} by accident we make sure we check for that case but
% without setting it to \cs{relax} if it wasn't already.
%    \begin{macrocode}
\begingroup\expandafter\expandafter\expandafter\endgroup
  \expandafter\ifx\csname eTeXversion\endcsname\relax
%    \end{macrocode}
% If we are running normal \TeX\ we add the most common cases of active
% punctuation characters. First we make them active.
%    \begin{macrocode}
  \begingroup
    \catcode`\;=\active  \catcode`\:=\active
    \catcode`\?=\active  \catcode`\!=\active
%    \end{macrocode}
%  The \texttt{alltt} environment also makes |,|, |'|, and |-| active
%  so we add them as well.
%    \begin{macrocode}
    \catcode`\,=\active  \catcode`\'=\active  \catcode`\-=\active
    \xspaceaddexceptions{;:?!,'-}
  \endgroup  
  \let\@xspace@eTeX@setup\relax
%    \end{macrocode}
% \begin{macro}{\@xspace@eTeX@setup} 
% \changes{v1.10}{2005/10/04}{Added macro}
% \changes{v1.12}{2006/05/08}{Bug fix for verbatim in output routine}
% When we're running \eTeX, we have the advantage of \cs{scantokens}
% which will rescan tokens with current catcodes. This little
% expansion trick makes sure that the exception list is redefined to
% itself but with the contents of it exposed to the current catcode
% regime. That is why we must make sure the catcode of space is 10,
% since we have a \verb*|\ | inside the list.
%    \begin{macrocode}
\else
  \def\@xspace@eTeX@setup{%
    \begingroup
      \everyeof{}%
      \endlinechar=-1\relax
      \catcode`\ =10\relax
      \makeatletter
%    \end{macrocode}
% We may also be so unfortunate that the re-reading of the list takes
% place when the catcodes of |\|, |{| and |}| are ``other,'' e.g., if
% it takes place in a header and the output routine was called in the
% middle of a \texttt{verbatim} environment.
%    \begin{macrocode}
      \catcode`\\\z@
      \catcode`\{\@ne
      \catcode`\}\tw@
      \scantokens\expandafter{\expandafter\gdef
        \expandafter\@xspace@exceptions@tlp
        \expandafter{\@xspace@exceptions@tlp}}%
    \endgroup
  }
\fi
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\@xspace}
% \changes{v1.03}{1994/11/15}{Add exclamation mark}
% \changes{v1.04}{1996/05/17}{Add slash}
% \changes{v1.05}{1996/12/06}{Add space for alltt etc. tools/2322}
% \changes{v1.06}{1997/10/13}{Add normal space. tools/2632}
% \changes{v1.07}{2004/12/07}{Now runs through a list of exceptions}
% \changes{v1.07}{2004/12/07}{Added \cs{footnote} and
% \cs{footnotemark}}
% \changes{v1.08}{2005/05/07}{Use recursive loop instead of \cs{@tfor}}
% \changes{v1.09}{2005/07/26}{Only check non-letters and add hook}
% \changes{v1.10}{2005/10/04}{Use higher level functions for
% conditional processing} 
% \changes{v1.10}{2005/10/04}{Improve expansion method}
% If the next token is one of a specified list of characters,
% do nothing, otherwise add a space. With version~1.07 the
% approach was altered dramatically to run through the
% exception list |\@xspace@exceptions@tlp| and check each
% token one at a time.
%    \begin{macrocode}
\def\@xspace{%
%    \end{macrocode}
% Before we start checking the exception list it makes sense to
% performe a quick check on the token in question. Most of the time
% \cs{xspace} is used in regular text so \cs{@let@token} is set equal
% to a letter. In that case there is no point in checking the list
% because it will definitely not contain any tokens with catcode~11.
%
% You may wonder why there are special functions here instead of
% simpler \cs{ifx} conditionals. The reason is that a)~this way we
% don't have to add many, many \cs{expandafter}s to get the nesting
% right and b)~we don't get into trouble when \cs{@let@token} has been
% let equal to \cs{if} etc.
%    \begin{macrocode}
  \@xspace@lettoken@if@letter@TF \space{%
%    \end{macrocode}
% Otherwise we start testing after setting up a few things. If running
% \eTeX{} we rescan the catcodes but only the first time around.
%    \begin{macrocode}
    \if@xspace@first
      \@xspace@firstfalse
      \let\@xspace@maybespace\space
      \@xspace@eTeX@setup
    \fi
    \expandafter\@xspace@check@token
      \@xspace@exceptions@tlp\@xspace@q@nil\@nil
%    \end{macrocode}
% If an exception was found \cs{@xspace@maybespace} is let to
% \cs{relax} and we do nothing.
%    \begin{macrocode}
    \@xspace@token@if@equal@NNT \space \@xspace@maybespace
%    \end{macrocode}
% Otherwise we check to see if we found something expandable and try
% again with that token one level expanded. If no expandable token is
% found we insert a space and then execute the hook.
%    \begin{macrocode}
    {%
      \@xspace@lettoken@if@expandable@TF
      {\expandafter\@xspace@simple}%
      {\@xspace@maybespace\@xspace@hook}%
    }%
  }%
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@xspace@check@token}
% \changes{v1.07}{2004/12/07}{Added macro}
% \changes{v1.08}{2005/05/07}{Made function recursive}
% \changes{v1.10}{2005/10/04}{Use higher level functions for
% conditional processing} 
% \changes{v1.11}{2006/02/12}{Modified so the \cs{@let@token} can be
%   \cs{outer}} 
% This macro just checks the current item in the exception list
% against the \cs{@let@token}. If they are equal we make sure that no
% space is inserted and break the loop.
%    \begin{macrocode}
\def\@xspace@check@token #1{%
  \ifx\@xspace@q@nil#1%
    \expandafter\@xspace@break@loop
  \fi
  \expandafter\ifx\csname @let@token\endcsname#1%
    \let\@xspace@maybespace\relax
    \expandafter\@xspace@break@loop
  \fi
  \@xspace@check@token
}
%    \end{macrocode}
% \end{macro}
%
% That's all, folks! That is, if we were running \LaTeX3. In that case
% we would have had nice functions for all the conditionals but here
% we must define them ourselves. We also optimize them here as
% \cs{@let@token} will always be the argument in some cases.
%
% \begin{macro}{\@xspace@if@lettoken@letter@TF}
% \begin{macro}{\@xspace@if@lettoken@expandable@TF}
% \begin{macro}{\@xspace@cs@if@equal@NNF}
% First a few comparisons.
%    \begin{macrocode}
\def\@xspace@lettoken@if@letter@TF{%
  \ifcat\noexpand\@let@token @% letter
    \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi}
\def\@xspace@lettoken@if@expandable@TF{%
  \expandafter\ifx\noexpand\@let@token\@let@token%
    \expandafter\@secondoftwo
  \else
    \expandafter\@firstoftwo
  \fi
}
\def\@xspace@token@if@equal@NNT#1#2{%
  \ifx#1#2%
    \expandafter\@firstofone
  \else
    \expandafter\@gobble
  \fi}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\@xspace@q@nil}
% \begin{macro}{\@xspace@if@q@nil@NF}
% Some macros dealing with quarks.
%    \begin{macrocode}
\def\@xspace@q@nil{\@xspace@q@nil}
\def\@xspace@if@q@nil@NF#1{%
  \ifx\@xspace@q@nil#1%
    \expandafter\@gobble
  \else
    \expandafter\@firstofone
  \fi}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \Finale