patchcmd.sty

%%
%% This is file `patchcmd.sty',
%% generated with the docstrip utility.
%%
%% The original source files were:
%%
%% patchcmd.dtx 
%% 
%%% ====================================================================
%%% @LaTeX-doc-source-file{
%%%   filename  = "patchcmd.dtx",
%%%   version   = "1.03",
%%%   date      = "2000/07/31",
%%%   time      = "08:40:39 EDT",
%%%   author    = "Michael J Downes",
%%%   email     = "mjd@ams.org",
%%%   abstract  = "Provides a way to add material at beginning or end of
%%%                a macro's existing definition.",
%%%   checksum  = "23183 222 932 7411",
%%%   docstring = "The checksum field, produced by Robert Solovay's
%%%                checksum utility, gives CRC-16 checksum, lines,
%%%                words, and characters.",
%%%  }
%%% ====================================================================
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{patchcmd}[2000/07/31 v1.03]
%% Copyright 2000 Michael John Downes
%% This file has no restrictions on its use, distribution, or sale.

%%\def\wrs{\immediate\write\sixt@@n}
\newcommand{\patchcommand}[1]{%
  \expandafter\patchcmd@a\meaning#1??->@\@nil#1%
}
\long\def\patchcmd@a#1#2#3->#4#5\@nil#6{%
%%  \wrs{\string#6: [#1] [#2] [#3]->[#4]}%
  \ifx @#4\relax \patchcmdError#6#1%
    \expandafter\@gobbletwo % discard the other two arguments
  \else
    \if l#2\toks@{\patchcmd@e{}#6}% l in this position means \long
    \else \toks@{\patchcmd@e*#6}%   not \long
    \fi
    \patchcmd@b #3@#4#5 ? ? ? \@nil#6%
    \expandafter\the\expandafter\toks@
  \fi
}
\def\patchcmd@b#1:#2@#3#4 #5#6 #7 #8\@nil#9{%
%%  \wrs{[#1] [#2] [#3] [#4] [#5] [#6] ARG7=[#7] [#8]}%
  \if \ifx @#7@\expandafter
      \ifx\csname #6\endcsname#9T\else F\fi\else F\fi T%
    \toks@\expandafter{\expandafter\patchcommand\csname #6 \endcsname}%
  \else
    \ifx @#2@% No arguments
      \toks@\expandafter{\the\toks@ 0}%
    \else
      \patchcmd@c 0#2{\string##}0%
    \fi
  \fi
}
\def\patchcmd@c#1#2#3{%
  \if\string###2%      % yes it's a # token
    \ifodd 0#31 % and it's followed by a number
      \if 0#3\patchcmd@d#1\fi % number=0? then we're done
    \else \patchcmd@d D% # not a number: must be a delimited arg
    \fi
  \else \patchcmd@d D% not a # token: must be a delmited arg
  \fi
  \patchcmd@c#3%
}
\def\patchcmd@d#1{%
  \if D#1%
    \PackageError{patchcmd}{Cannot change a macro that has
      delimited arguments}\@ehd
  \else
    \toks@\expandafter{\the\toks@ #1}%
  \fi
  \begingroup
  \aftergroup\@gobble
  \let\patchcmd@c\endgroup
}
\def\patchcmd@e#1#2#3#4#5{%
  \begingroup
  \edef\@##1{%
    \@temptokena\noexpand\expandafter{%
      \noexpand#2%
        \ifnum#3>0 {####1}\ifnum#3>1 {####2}\ifnum#3>2 {####3}%
        \ifnum#3>3 {####4}\ifnum#3>4 {####5}\ifnum#3>5 {####6}%
        \ifnum#3>6 {####7}\ifnum#3>7 {####8}\ifnum#3>8 {####9}%
        \fi\fi\fi\fi\fi\fi\fi\fi\fi
      ##1%
    }%
  }
  \@{#5}%
  \edef\@##1{\endgroup
    \noexpand\renewcommand#1\noexpand#2\ifcase#3 \else [#3]\fi
    {##1\the\@temptokena}}%
  \@{#4}%
%%  \show#2%
}
\long\def\patchcmdError#1#2{%
  \begingroup
  \toks@{Not redefinable}%
  \ifcat\relax\noexpand#1% Is it a control sequence?
    \begingroup
    \let#1=?\ifx ?\relax % Is it "\relax"?
      \endgroup % accept current value of \toks@
    \else \endgroup
      \if\ifx\relax#1u\else #2\fi u%
        \toks@{Not defined}%
      \fi
    \fi
  \fi
  \edef\@{\endgroup
    \noexpand\PackageError{patchcmd}{%
      \the\toks@: \string#1}\noexpand\@ehd}%
  \@
}
\endinput
%%
%% End of file `patchcmd.sty'.