%%
%% substr.sty
%%
%% This package provides commands to deal with substrings in strings:
%% Determine if a string contains a substring, count appearances of a
%% substring in a string.
%%
%%
%% Commands:
%%
%% \IfSubStringInString{substring}{string}{true part}{false part}
%% This command searches <substring> in <string> and executes the 
%% <true part> if it is and else the <else part>
%%
%% \IfCharInString{char}{string}{true part}{false part}
%% Actualy the same as \IfSubStringInString.
%%
%% \BehindSubString{substring}{string}
%% Returns the part of <string> that is on the behind
%% <substring>. Always the first appearance of <substring> is taken.
%%
%% \BeforeSubString{substring}{string}
%% Returns the part of <string> that is on the before
%% <substring>. Always the first appearance of <substring> is taken.
%%
%% \CountSubStrings{substring}{string}
%% Counts the number of appearances of <substring> in <string> and
%% returns it as text.
%%
%% \SubStringsToCounter}{counter}{substring}{string}
%% Counts the number of appearances of <substring> in <string> and
%% sets the counter <counter> to that value.
%%
%%
%% History of this package:
%%
%% The package arises from a posting of me in the newsgroup
%% de.comp.text.tex in which I asked how to find out if a substring
%% is included in a string. Heiko Oberdiek
%% <oberdiek@ruf.uni-freiburg.de> posted the commands
%% \IfSubStringInString and \IfCharInString and suggested to write a
%% command which counts the appearances in a string. So, I wrote the
%% commands \CountSubStrings and \SubStringsToCounter.
%% After I wrote this package I sent it to Heiko Oberdiek
%% who improved and rewrote many parts of it.
%%
%%
%% Copyright 2000 Harald Harders
%%
%% This program can be redistributed and/or modified under the terms
%% of the LaTeX Project Public License Distributed from CTAN
%% archives in directory macros/latex/base/lppl.txt; either
%% version 1 of the License, or any later version.
%%
%%
%% 2000-06-15
%% Harald Harders
%% h.harders@tu-bs.de
%%
\ProvidesPackage{substr}[2000/06/15]
%%
% expands the first and second argument with
% \protected@edef and calls #3 with them:
\newcommand{\su@ExpandTwoArgs}[3]{%
  \protected@edef\su@SubString{#1}%
  \protected@edef\su@String{#2}%
  \expandafter\expandafter\expandafter#3%
  \expandafter\expandafter\expandafter{%
    \expandafter\su@SubString\expandafter
  }\expandafter{\su@String}%
}
%%
%% tests if #1 in #2. If yes execute #3, else #4
\newcommand*{\IfSubStringInString}[2]{%
  \su@ExpandTwoArgs{#1}{#2}\su@IfSubStringInString
}
%%
\newcommand*{\su@IfSubStringInString}[2]{%
  \def\su@compare##1#1##2\@nil{%
    \def\su@param{##2}%
    \ifx\su@param\@empty
      \expandafter\@secondoftwo
    \else
      \expandafter\@firstoftwo
    \fi
  }%
  \su@compare#2#1\@nil
}
%%
%% tests if #1 in #2. If yes execute #3, else #4
\newcommand\IfCharInString{}
\let\IfCharInString\IfSubStringInString
%%
%% returns the part of the string behind the found substring
\newcommand*{\BehindSubString}[2]{%
  \su@ExpandTwoArgs{#1}{#2}\su@BehindSubString
}
\newcommand*{\su@BehindSubString}[2]{%
  \def\su@rest##1#1##2\@nil{##2}%
  \IfSubStringInString{#1}{#2}{\su@rest#2\@nil}{}%
}
%%
%% returns the part of the string before the found substring
\newcommand*{\BeforeSubString}[2]{%
  \su@ExpandTwoArgs{#1}{#2}\su@BeforeSubString
}
\newcommand*{\su@BeforeSubString}[2]{%
  \def\su@rest##1#1##2\@nil{##1}%
  \IfSubStringInString{#1}{#2}{\su@rest#2\@nil}{#2}%
}
%%
%% counter for counting appearances
\newcounter{su@anzahl}
%%
% #1: String
% #2: Substring
% #3: Counter
\newcommand*{\su@StringSubstringCounter}[3]{%
  \su@IfSubStringInString{#2}{#1}{%
    \stepcounter{#3}%
    \def\su@rest##1#2##2\@nil{##2}%
    \expandafter\su@StringSubstringCounter\expandafter
    {\su@rest#1\@nil}{#2}{#3}%
  }{}%
}
%%
\newcommand*{\CountSubStrings}[2]{%
  \su@ExpandTwoArgs{#1}{#2}\su@CountSubStrings
}
\newcommand*{\su@CountSubStrings}[2]{%
  \setcounter{su@anzahl}{0}%
  \su@StringSubstringCounter{#2}{#1}{su@anzahl}%
  \thesu@anzahl
}
% #1: counter
% #2: substring
% #3: string
\newcommand*{\SubStringsToCounter}[3]{%
  \su@ExpandTwoArgs{#2}{#3}\su@SubStringsToCounter{#1}%
}
% #1: substring
% #2: string
% #3: counter
\newcommand*{\su@SubStringsToCounter}[3]{%
  \setcounter{#3}{0}%
  \su@StringSubstringCounter{#2}{#1}{#3}%
}
%%
\endinput
%% EOF