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%% PACKAGE: sets                                                            %%
%% FILE: sets.sty                                                           %%
%%                                                                          %%
%% AUTHOR: Jochen Wertenauer                                                %%
%% VERSION: 1.3                                                             %%
%%                                                                          %%
%% LICENSE: This program may be distributed and/or modified under the       %%
%% conditions of the LaTeX Project Public License, either version 1.2       %%
%% of this license or (at your option) any later version.                   %%
%% The latest version of this license is in                                 %%
%%   http://www.latex-project.org/lppl.txt                                  %%
%% and version 1.2 or later is part of all distributions of LaTeX           %%
%% version 1999/12/01 or later.                                             %%
%%                                                                          %%
%% This program consists of the file sets.sty (this file).                  %%
%%                                                                          %%
%%--------------------------------------------------------------------------%%
%% DESCRIPTION (see separate file for more information):                    %%
%%   This package allows basic usage of sets. A set has the structure:      %%
%%                   set    --> {contents}                                  %%
%%                 contents --> element(|element)*                          %%
%%                 contents --> \epsilon                                    %%
%%     A element can consist of strings and command tokens. Command tokens  %%
%%   will not be expanded before you call \listset.  Command tokens with    %%
%%   parameters (in {}) are not allowed, i.e. \textbf{Test} would result in %%
%%   lots of errors. Defining a macro \boldTest                             %%
%%              \newcommand{\boldTest}{\textbf{Test}}                       %%
%%   and using that macro would solve the problem.  Commands like like "A   %%
%%   work fine.  Of course an element cannot contain the character | (but   %%
%%   you can "hide" it in a command like \boldTest, too).                   %%
%%     Other forbidden elemente are the commands \endset and \empty.        %%
%%     In this package a set is normally sorted and contains no duplicates  %%
%%   unless you explicitly want it as it is by using \newsetsimple (but     %%
%%   several operations will return a sorted set without duplicates).       %%
%%     An empty set cannot be destinguished from a set that contains only   %%
%%   the an empty string, i.e. {} is an empty set.                          %%
%%                                                                          %%
%% INTERFACE:                                                               %%
%%   Constructors:                                                          %%
%%     \newset, \newsetsimple                                               %%
%%   Inspectors:                                                            %%
%%     \sizeofset, \listset, \iselementofset                                %%
%%   Modificators:                                                          %%
%%     \deleteduplicates, \sortset                                          %%
%%     \unionsets, \intersectsets, \minussets                               %%
%%   OTHER COMMANDS:                                                        %%
%%     \setseparator                                                        %%
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\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{sets}

%% Helper Methods ------------------------------------------------------------

\def \sets@xxpa{\expandafter\expandafter\expandafter}

\def \sets@empty{\empty}

%% Appends #1 to the definition of macro #2.
\def \sets@append #1\to#2{\expandafter \def \expandafter #2\expandafter{#2#1}}

%% Removes the first character of the content of #2 and stores the result in
%% #1. Note that \expandafter\expandafter\expandafter cannot be replaced by \sets@xxpa here!
\def \sets@gobblefirst #1#2{%
  \sets@xxpa \def \expandafter\expandafter\expandafter #1\expandafter\expandafter\expandafter {\expandafter\@gobble #2}}

%% Deletes everthing to the next occurance of > inludung the >.
\def \sets@erasetobrace #1>{}

%% A do-while construct based on the macro of Alois Kabelschacht.
%%
%% Syntax:
%% \loop
%%   ...
%%   \if ...
%% \repeat  
\def \sets@loop #1\repeat{%
  \def \iterate {#1\expandafter \iterate\fi}%
  \iterate \let\iterate\relax}

\long\def \sets@ReturnFi #1\fi{\fi #1}
\long\def \sets@ReturnII #1\fi\fi{\fi\fi #1}
\long\def \sets@ReturnIII #1\fi\fi\fi{\fi\fi\fi #1}

\long\def \sets@ReturnElseIII #1\else#2\fi\fi\fi{\fi\fi\fi #1}

\long\def \sets@Returntrue #1\fi{\fi \iftrue}
\long\def \sets@Returnfalse #1\fi{\fi \iffalse}

\newif \ifsets@less \newif \ifsets@greater

%% Compares to strings. Result will be in \ifgreater and \ifless.
%% #1 and #2 are compared as they are. There will be no expansion.
%% The comparison is based on the position of the symbols in the
%% ASCII table. Therefore the comparison is case sensitive (B<a).
%%
%% The macros are based on a sort algorithm by Klaus Lagally.
\def \sets@compStrings #1#2{%
  \def \sets@CSti{#1}%
  \edef\sets@ctempi{\expandafter\sets@erasetobrace\meaning \sets@CSti}%
  \def \sets@CStii{#2}%
  \edef\sets@ctempii{\expandafter\sets@erasetobrace\meaning \sets@CStii}%
  \sets@lessfalse\sets@greaterfalse
  \sets@xxpa\sets@compI \expandafter\sets@ctempi\expandafter|\expandafter\\\sets@ctempii|\relax
}


%% Recursive string comparison. Called by \sets@compStrings.
%% (1) Because of the position of | in the ASCII table, there must be a
%%     special test to get the right result.
\def \sets@compI #1#2\\#3#4\relax{%
  \ifnum `#1<`#3
    \ifx |#3 \sets@greatertrue \else \sets@lesstrue \fi%(1)
  \else
    \ifnum `#1>`#3
      \ifx |#1 \sets@lesstrue \else \sets@greatertrue \fi%(1)
    \else
      \ifx |#1\else
  	\sets@ReturnIII{\sets@compI#2\\#4\relax}%
      \fi
    \fi
  \fi
}
%-----------------------------------------------------------------------------



%% Create a new set ----------------------------------------------------------

%% Creates a new set. The set will be sorted and will contain no duplicate
%% elements.
%%
%% Example: \newset{\myset}{Alice|Bob|Charly}
\def \newset #1#2{%
  \def #1{#2}%
  \sortset{#1}{#1}%
  \deleteduplicates{#1}{#1}%
}

%% Simple constructor of a set. There is no sorting or duplicate detection
%% done by this macro.
%%
%% Example: \newsetsimple{\myset}{Alice|Bob|Charly}
\def \newsetsimple #1#2{\def #1{#2}}
%-----------------------------------------------------------------------------



%% Size determination --------------------------------------------------------

%% Stores the size of set #1 in the LaTeX counter #2. #2 has to be existing.
\def \sizeofset #1\is#2{%
  \setcounter{#2}{0}%
  \expandafter\sets@sizeofset #1|\endset{#2}%
}

% Helper method for \sizeofset. Recursively calls itself. Implemented straight
% forward.
\def \sets@sizeofset #1|#2\endset#3{%
  \def \sizetemps@t{#1}%
  \ifx \sizetemps@t\empty\relax\else
    \stepcounter{#3}%
    \def \sizetemps@t{#2}%
    \ifx\sizetemps@t\empty\else
      \sets@ReturnII{\sets@sizeofset #2\endset{#3}}%
    \fi
  \fi
}
%-----------------------------------------------------------------------------



%% Printing a set ------------------------------------------------------------

%% The content of this macro will be used to separate the elements of the set.
\def \setseparator{, } 

%% Prints the contents of set #1. Elements will be separated by \setseparator.
%\def \listset #1{\expandafter\sets@listset #1|\empty\endset}
\def \listset #1{\expandafter\sets@listset #1|\endset|}


%% Helper method for \listset.
%\def \sets@listset #1|#2\endset{%
%  #1%
%  \def\temps@t{#2}%
%  \ifx \temps@t\sets@empty{}\else
%    \setseparator
%    \sets@ReturnFi{\sets@listset #2\endset}%
%  \fi
%}

\def \sets@listset #1|#2|{%
  #1%
  \ifx\endset #2%
  \else
    \setseparator\sets@ReturnFi{\sets@listset#2|}%
  \fi
}
%-----------------------------------------------------------------------------



%% Testing for membership ----------------------------------------------------

%% This macro tests, if #1 is included in set #2.  Can be used in constructs
%% like \if \iselementofset{...}{...} ... \else ... \fi.  It has complexity
%% O(1), assuming that the pattern matching is done in O(1), too.
%%
\def \iselementofset #1#2{%
  00\fi
  \begingroup
  \def \lookup ##1|#1|##2\endset{%
    \def \temp{##2}%
    \ifx \temp\empty 
      \endgroup
      \sets@Returnfalse
    \else
      \endgroup
      \sets@Returntrue
    \fi}%
  \expandafter\lookup \expandafter |#2|#1|\endset%
}
%-----------------------------------------------------------------------------



%% Duplicate detection: ------------------------------------------------------

%% This macro finds alle duplicate elements in the SORTED set #1 and removes
%% them. The result set (still sorted) is stored in #2.
\def \deleteduplicates #1#2{\expandafter\sets@duplicates#1|\endset#2}

%% Helper method for \deleteduplicates. Does some preparations and catches the
%% special case of an set with size <= 1. Parameter #3 is the result set.
\def \sets@duplicates #1|#2\endset#3{%
  \def #3{}% Clear #3
  \def \temps@t{#2}%
  \ifx \temps@t\empty% Has the set more than one element?
    \def #3{#1}% Just one element!
  \else% More than one element
    \sets@ReturnFi{\sets@duplicatesI#1|#2\endset#3}%
  \fi
}


%% Called by \sets@duplicates, if the sorted set contains two or more elements. It
%% checks, if two elements, which are directly following each other are equal.
%% If yes, the first one will not be part of the result set, which is stored
%% in #4.
\def \sets@duplicatesI #1|#2|#3\endset#4{%
  \def\temps@ti{#1}%
  \def\temps@tii{#2}%
  \def\temps@tiii{#3}%
  \ifx \temps@tii\empty % Is #2 empty?
    \def #4{#1}% A set with one element has no duplicates
  \else % #2 not empty --> at least two elements (left)
    \ifx \temps@tiii\empty% Is #3 empty?
      % The set contains two elements, so work is nearly done.
      % An additional | was inserted at the beginning. It has to be gobbled
      % away.
      \ifx \temps@ti\temps@tii % #1=#2
	\sets@append{|#1}\to#4%
        \sets@gobblefirst{#4}{#4}%
      \else
 	\sets@append{|#1|#2}\to#4%
        \sets@gobblefirst{#4}{#4}%
      \fi
    \else % #3 not empty --> at least three elements (left)
      \ifx \temps@ti\temps@tii
        \sets@ReturnElseIII{\sets@duplicatesI #2|#3\endset#4}%
      \else
        \sets@append{|#1}\to#4%
        \sets@ReturnIII{\sets@duplicatesI #2|#3\endset#4}%
      \fi
    \fi
  \fi
}
%-----------------------------------------------------------------------------



%% Sorting a set -------------------------------------------------------------
\newcounter{s@tlength} % LaTeX-counter used by \sortset.

%% Takes an unsorted set #1, sorts it and stores the result in #2. If #1 has
%% less than two elements, sorting is unneccessary, otherwise \sets@sortset is
%% called.
%%
%% Syntax \sortset <set> <result set>
\def \sortset #1#2{%
  \sizeofset#1\is{s@tlength}%
  \ifnum 2>\value{s@tlength}\relax
    \let #2 #1%
  \else
    \sets@sortset #1#2%
  \fi
}

%% Called by \sortset. This macro represents the outer loop of the bubblesort
%% algorithm. Bubblesort has O(n^2) and is stable.
%%
\def \sets@sortset #1#2{%
  \let \sorttemps@t #1%
  \sets@loop
    \expandafter\sets@bubblesortRun \sorttemps@t|\endset\sorttemps@t
    \addtocounter{s@tlength}{-1}%
    \ifnum 1<\value{s@tlength}\relax
  \repeat
  \let #2 \sorttemps@t
}

%% Called by \sets@sortset. Does some preparation for \sets@bubblesortRunI and
%% removes the first character of the result. #4 is the result set.
\def \sets@bubblesortRun #1|#2|#3\endset#4{%
  \def\temps@t{}%
  \sets@bubblesortRunI #1|#2|#3\endset\temps@t%
  \sets@gobblefirst{#4}{\temps@t}%
}

%% Called by \sets@bubblesortRun and recursively by itself.
%% This recursive macro represents the inner loop of "normal" bubblesort.
%% #4 is the result set.
\def \sets@bubblesortRunI #1|#2|#3\endset#4{%
  \def\temps@tii{#2}%
  \def\temps@tiii{#3}%
  \ifx \temps@tii\empty 
    \sets@append{|#1}\to#4%
  \else
    \ifx \temps@tiii\empty
      \sets@compStrings{#2}{#1}%
      \ifsets@greater
        \sets@append{|#1|#2}\to#4%
      \else
        \sets@append{|#2|#1}\to#4%
      \fi
    \else
      \sets@compStrings{#2}{#1}%
      \ifsets@greater
	\sets@ReturnElseIII{%
          \sets@append{|#1}\to#4%
          \sets@bubblesortRunI#2|#3\endset#4}%
      \else
        \sets@ReturnIII{%
          \sets@append{|#2}\to#4%
          \sets@bubblesortRunI#1|#3\endset#4}%
      \fi
    \fi
  \fi
}
%-----------------------------------------------------------------------------



%% Set manipulation ----------------------------------------------------------

%% Takes two sets #1 and #2 and performs a union operation. #1 and #2 do not
%% have to be sorted and may contain duplicate elements.
%% The result is stored in #3. It contains the elements of #1 and #2 and is
%% sorted. Duplicates are removed.
\def \unionsets #1#2\to#3{%
  \let\uniont@mpi=#1%
  \let\uniont@mpii=#2%
  \ifx \uniont@mpi\empty
    \let \uniontemps@t=\uniont@mpii
  \else
    \let \uniontemps@t=\uniont@mpi
    \ifx \uniont@mpii\empty \else
      \expandafter\sets@append\expandafter{\expandafter|#2}\to\uniontemps@t
    \fi
  \fi
  \sortset{\uniontemps@t}{\uniontemps@t}%
  \deleteduplicates{\uniontemps@t}{#3}%
}
%-----------------------------------------------------------------------------


%% Takes two sets #1 and #2 and performs an intersect operation. The result is
%% stored in #3. #3 contains only elements that have been in both sets #1 and
%% #2. #1 and #2 don't have to be sorted, but if #1 is sorted, #3 will be
%% sorted, too. If #1 contains duplicates, #3 may also contain duplicates.
\def \intersectsets #1#2\to#3{%
  \def \tempinters@ct{}%
  \expandafter \sets@intersectsets #1|\endset#2\tempinters@ct
  \ifx \tempinters@ct\empty
    \def #3{}%
  \else
    \sets@gobblefirst{#3}{\tempinters@ct}%
  \fi
}

%% #1 and #2 are parts of set #1 of \intersectsets. #3 is #2 of \intersectsets
%% #4 is the result set
\def \sets@intersectsets #1|#2\endset#3#4{%
  \if \iselementofset{#1}{#3}%
    \sets@append{|#1}\to#4%
  \fi
  \def \tempinters@cti{#2}%
  \ifx \tempinters@cti\empty \else
    \sets@ReturnFi{\sets@intersectsets #2\endset#3#4}%
  \fi
}
%-----------------------------------------------------------------------------


%% Takes two sets #1 and #2 and performs a minus operation, i.e. all elements
%% of #1 that are in #2, too, are removed. The result is saved in #3. If #1 is
%% sorted, #3 will be sorted, too.
%%
%% This macro is implemented like \intersectsets. The only difference is, that
%% an element will only be part of #1 if it is NOT in #2. In \intersectsets it
%% will be part if it is in #2.
\def \minussets #1\minus#2\to#3{%
  \def \@tempminus{}%
  \expandafter \sets@minussets #1|\endset#2\@tempminus
  \ifx \@tempminus\empty
    \def #3{}%
  \else
    \sets@gobblefirst{#3}{\@tempminus}%
  \fi
}

%% Syntax like \sets@intersectsets, but of course different semantics.
\def \sets@minussets #1|#2\endset#3#4{%
  \if \iselementofset{#1}{#3}\else
    \sets@append{|#1}\to#4%
  \fi
  \def \temp@minus{#2}%
  \ifx \temp@minus\empty \else
    \sets@ReturnFi{\sets@minussets #2\endset#3#4}%
  \fi
}
%-----------------------------------------------------------------------------

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\endinput
