Replace instances of \cite that have a specific argument

Question

In LaTeX, is there a way to define a macro (or something) to replace every instance of

\cite{a_literal_string}

with

\ref{appendix:a_different_literal_string}

without touching instances of \cite with arguments that aren't a_literal_string? I would like to do this for several different possible replacements.

The idea here is that I'm including some modular documents in a larger project, and I want to use some of them as appendices. I don't want to just find/replace, because the sub-documents need to be able to refer to each other when they aren't being used in the larger project.

Answer 1

Here's an implementation with expl3 and xparse:

\begin{filecontents*}{\jobname.bib}
@article{cite:a,
 author={A. Uthor},
 title={Title a},
 journal={J. A},
 year={2014},
}
@article{cite:b,
 author={B. Athor},
 title={Title b},
 journal={J. B},
 year={2014},
}
@article{cite:c,
 author={C. Ethor},
 title={Title c},
 journal={J. C},
 year={2014},
}
\end{filecontents*}

\documentclass{article}
\usepackage{xparse,letltxmacro}
\LetLtxMacro{\latexcite}{\cite}

\ExplSyntaxOn
\RenewDocumentCommand{\cite}{om}
 {
  \IfNoValueTF{#1}
   { \daniel_cite_or_ref:n { #2 } }
   { \latexcite[#1]{#2} }
 }
\NewDocumentCommand{\addsubstitution}{mm}
 {
  \tl_gput_right:Nn \g_daniel_changes_tl { {#1}{\ref{#2}} }
 }

\tl_new:N \g_daniel_changes_tl

\cs_new_protected:Npn \daniel_cite_or_ref:n #1
 {
  \str_case:nVTF { #1 } \g_daniel_changes_tl
  {
   % \nocite{#1} %%%% <---- uncomment this line if you want \nocite
  }
  {
   \latexcite{#1}
  }
 }

\cs_generate_variant:Nn \str_case:nnTF { nV }
\ExplSyntaxOff

\addsubstitution{cite:a}{ref:a}
\addsubstitution{cite:b}{ref:b}

\begin{document}

\section{Something}\label{sec:some}

Here we do the citations: \cite{cite:a}, \cite{cite:b}, 
\cite{cite:c} and \cite[p.~42]{cite:c}

\appendix

\section{First appendix}\label{ref:a}

Text

\section{Second appendix}\label{ref:b}

Text

\bibliographystyle{plain}
\bibliography{\jobname}

\end{document}

You're supposed to use just one item in a \cite command; taking into account multiple citations with substitutions is possible, but it requires a decision about the final format.

With the \addsubstitution command you add the substitutions you want to do: the first argument is the citation key, the second argument is the label.

In the references only the actually cited items are inserted; if you want to add also the items that you substitute, it's sufficient to uncomment \nocite in the macros above.

Note on the implementation

The expl3 function \str_case:nnTF takes four arguments:

1. the string to check;
2. a set of pairs {<string>}{<action>};
3. what to do if a match is found;
4. what to do if no match is found.

With the variant \str_case:nVTF, the second argument is a token list variable that contains the set of pairs.

The new \cite command will use the original \cite if the optional argument is given; otherwise it passes control to \daniel_cite_or_ref:n that checks the argument against the set of pairs stored in \g_daniel_changes_tl; this variable is populated by any number of \addsubstitution commands.

It would be easy, albeit not straightforward, to add other features, for instance accepting multiple keys in the argument of \cite and deciding what to do when a key needs the substitution.

Answer 2

If you're willing to use LuaLaTeX, your objective can be achieved using Lua's powerful string.gsub function. In the example below, the Lua-side code is stored in a file called string_replacements.lua. (For anything but the most trivial cases, it's usually easiest to store the Lua code in a separate file and to call it with a \directlua{ require("string_replacements.lua")} directive.) The function replace_string can perform multiple string replacements. Is is assigned to the process_input_buffer callback, which does its job before any processing by LaTeX takes place; the contents of the input file are not modified.

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{luatexbase}
\directlua{require("string_replacements.lua")}

\begin{document}
\section{Hello}
Here's a cross-reference to Appendix \cite{a_literal_string}. 
And here's a cross-reference to abcdefuvwxyz.

\appendix
\section{Good-bye} \label{appendix:a_different_literal_string}
\begin{equation} \label{eq:pyth}
a^2+b^2=c^2
\end{equation}
\end{document}

The contents of string_replacements.lua are:

-- string_replacements.lua
   local function replace_string ( line )
       line = string.gsub ( line, 
           "\\cite{a_literal_string}" , 
           "\\ref{appendix:a_different_literal_string}" )
       line = string.gsub ( line,
           "abcdefuvwxyz",
           "equation~(\\ref{eq:pyth})" )
       return line
   end
   luatexbase.add_to_callback( "process_input_buffer", 
       replace_string, "replace_string" )

Answer 3

Maybe you need something like this:

\def\speclabel#1#2{\expandafter\def\csname slab:#1\endcsname{#2}}
\let\citeOri=\cite
\def\cite#1{\expandafter\ifx\csname slab:#1\endcsname\relax\citeOri{#1}%
   \else \expandafter\expandafter\expandafter\ref
         \expandafter\expandafter\expandafter{\csname slab:#1\endcsname}\fi
}
\speclabel {a_literal_string}       {a_different_literal_string}
\speclabel {another_literal_strig}  {another_different_litral_string}

Now \cite{normal} behaves normal but \cite{a_literal_string} expands
to \ref{a_different_literal_string}.

You have to declare conversions by \speclabel macros and you can use normal \cite.