% File:   citeref.sty
% Author: Bj"orn Briel, Uni Oldenburg
% Date:   27.05.1999
% 
% (Partially based on CITESIDX.STY by Frank Buchholz)
% (Contributions by Florian Werner Sauer)
% (Modifications by Bjoern Briel)
%
% Main purpose:
% 	Add reference-page-list to bibliography-items.
%
% Features:
%	- This is done WITHOUT using the index-facility.
% 	- Full transparency - no special \cite-replacement
% 	- Works with or without BibTeX
% 	- No extra LaTeX runs needed, neither external programs
% 	- Customizeable look of the back-references
%
% Caveats:
% 	- Does probably NOT work with other \cite-related style-options
% 	  which redefine the (internal) \@citex macro
%	- Citation tags may no longer contain a '=' char due to expansion
%	  issues.
%
% Usage:
% 	\usepackage{citeref}
% 	No Options declared
%
% 	Change Style of printed page references by redefining the macro
% 	'\bibitempages#1'. The parameter is a comma-separated list of 
% 	page references. The default macro puts it into brackets [...].
%
% 	Print comments in the bibliography: Use the macro
%	\bibintro{Blah...} before \thebibliography
%
% Revision History:
%	1999/01/05	Initial release
%	1999/27/05	Got sometimes wrong page numbers;
%	                Removed \immediate from \write of \citepageref-Macro
%	                in redefinition of \@citex to fix this
%	2018/04/07	LICENSE: BSD (https://ctan.org/license/bsd4)
%
\def\fileversion{v1.1}
\def\filedate{1999/27/05}

% comment out the next two lines if using latex 2.09
\NeedsTeXFormat{LaTeX2e}[1996/12/01]
\ProvidesPackage{citeref}[\filedate]

\typeout{Package citeref \fileversion\space <\filedate> (Bjoern Briel)}

\def\@cprwrite#1={\write\@auxout{\string\citepageref{#1}{\thepage}}}

% REDEFINITION OF \@citex[#1]#2 TO FACILITATE REFERENCE BACKPOINTERS
% see LATEX.LTX
\def\@citex[#1]#2{%
  \let\@citea\@empty
  \@cite{\@for\@citeb:=#2\do
    {\@citea\def\@citea{,\penalty\@m\ }%
     \edef\@citeb{\expandafter\@firstofone\@citeb}%
% begin change
     \if@filesw%
       \immediate\write\@auxout{\string\citation{\@citeb}}%
       \expandafter\@cprwrite\@citeb=%
     \fi%
% end change
     \@ifundefined{b@\@citeb}{\mbox{\reset@font\bfseries ?}%
       \G@refundefinedtrue
       \@fcwarning{Citation `\@citeb' on page \thepage \space undefined}}%
       {\hbox{\csname b@\@citeb\endcsname}}}}{#1}}


% Seiten der Zitatstellen aus dem aux-File einlesen
\def\@namexdef#1{\expandafter\xdef\csname #1\endcsname}
\def\citepageref#1#2{%
	\xdef\cpr@testa{\@nameuse{cpr@last@#1}}%letzte Zitatstelle
	\xdef\cpr@testb{#2}% Seite dieser Zitatstelle
	\ifx\cpr@testa\cpr@testb%
		\relax% Konsekutive identische Seitenangaben weglassen
	\else%
		\@namexdef{cpr@last@#1}{#2}%
		\@ifundefined{cpr@#1}%
			{\@namexdef{cpr@#1}{#2}}%
			{\@namexdef{cpr@#1}{\@nameuse{cpr@#1}, #2}}%
	\fi
	}


% WARNING MESSAGE
\def\@fcwarning#1{\typeout{CiteRef Warning: #1.}}

% bibitem umdefinieren, damit Zitatstellen angefuegt werden:
\def\bibitem{\@ifnextchar[{\@@lbibitem}{\@@bibitem}}%

% used by \bibitem
\def\@@lbibitem[#1]#2#3\par{\@lbibitem[#1]{#2}#3\bibitempages{\@citerefpages{#2}}}
\def\@@bibitem#1#2\par{\@bibitem{#1}#2\bibitempages{\@citerefpages{#1}}}

% used by \@@lbibitem, \@@bibitem
% liefert die Liste der Seitenreferenzen
\def\@citerefpages#1{\@ifundefined{cpr@#1}%
                   {{\bf -}\@fcwarning{Never cited from `\@nameuse{#1}'}}%
                   {\@nameuse{cpr@#1}}%
}
% used by \@@lbibitem, \@@bibitem
\def\bibitempages#1{\newblock [#1]}

% used by \bibitempages#1 
% see ARTICLE.STY, REPORT.STY, BOOK.STY
%\def\newblock{\hskip .11em plus .33em minus -.07em}%

% put some text in front of the bibliography
\def\bibintro#1{%
  \let\@origthebib=\thebibliography
  \let\@origlist=\list
  \def\thebibliography{\def\list{#1\par\bigskip\@origlist}\@origthebib}%
}

\endinput