List Version of \str_if_eq

Question

I am using \str_if_eq:xxTF{\A}{\Target}{<true>}{<false} to execute the <true> or <false> code if \A=\Target.

What is the list version equivalent of this?

So I am looking for something such as

\str_if_in_list:xxTF{\A}{\TargetList}{<true>}{<false}

which executes the appropriate <true>/<false> if A is in the list (CSV) \TargetList?

I have to admit I have not tried for too long on this as I really can't read expl3 syntax yet, but a few of the macros presented at Using Expl3 token-list variables where token lists are called for looked interesting, but I was not able to get them to work.

So, in the MWE below, by changing \GetTexFilePath and \GetTexFilePathExpandable the last three lines should not have an xxx in the directory path. The current output is:

Notes:

• The \TargetList is always a macro that contains the list.
• The source of the comparison is usually a value declared with \newtoks as per the MWE below (not sure if that matters).

---

References:

Before people get the wrong idea and think that I actually understand some expl3 syntax, here is where that code originated from:

• Text being output when none should be
• How to expand values stored in a token defined by newtoks

Possible clue to solution:

• Using Expl3 token-list variables where token lists are called for

---

Code:

\documentclass{article}
\usepackage{xparse}
\newcommand{\NotSpecialDirectory}{foo}
%% These directories should never have an "xxx" in the path.
%% The values here do NOT change at run time.
%% https://tex.stackexchange.com/questions/46323/how-to-expand-values-stored-in-a-token-defined-by-newtoks
\protected\def\SpecialDirectory{AAA}
\protected\def\SpecialDirectoryB{BBB}
\protected\def\SpecialDirectoryC{CCC}
%% The list of members here do NOT change at run time.
\newcommand{\ListOfSpecialDirectories}{%
    \SpecialDirectory,%
    \SpecialDirectoryB,% 
    \SpecialDirectoryC,% <-- would prefer to be allowed extra comma here, but
                       %     can do without that if it adds too much complexity
}
\newtoks{\CurrentDirectory}
\ExplSyntaxOn%%% These work fine...
% Determine path: Always #1/xxx#2/#3 unless #1=\SpecialDirectory
\NewDocumentCommand{\GetTexFilePathOld}{m m m}{%
    \str_if_eq:xxTF{#1}{\SpecialDirectory}{#1/#2/#3}{#1/xxx#2/#3}%
}%
\DeclareExpandableDocumentCommand{\GetTexFilePathExpandableOld}{m m m}{%
    \str_if_eq:xxTF{#1}{\SpecialDirectory}{#1/#2/#3}{#1/xxx#2/#3}%
}%
%%% how do I define these ...
% Determine path: Always #1/xxx#2/#3 unless #1 is in \ListOfSpecialDirectories
% Don't work: % \tl_if_in:nnTF  \str_if_in:nnTF,  \str_if_in:xxTF
\NewDocumentCommand{\GetTexFilePath}{m m m}{%
    \str_if_eq:xxTF{#1}{\ListOfSpecialDirectories}{#1/#2/#3}{#1/xxx#2/#3}%
}%
\DeclareExpandableDocumentCommand{\GetTexFilePathExpandable}{m m m}{%
    \str_if_eq:xxTF{#1}{\ListOfSpecialDirectories}{#1/#2/#3}{#1/xxx#2/#3}%
}%
\ExplSyntaxOff
\begin{document}
\noindent\textbf{These work fine:}
\CurrentDirectory={\NotSpecialDirectory}
Should have xxx in path: 
    \GetTexFilePathOld{\the\CurrentDirectory}{2012}{01},
    \GetTexFilePathExpandableOld{\the\CurrentDirectory}{2012}{02}
\CurrentDirectory={\SpecialDirectory}
\medskip\par Should \emph{not} have xxx: 
    \GetTexFilePathOld{\the\CurrentDirectory}{2013}{03},
    \GetTexFilePathExpandableOld{\the\CurrentDirectory}{2013}{04}
\bigskip\hrule\bigskip
\noindent\textbf{Paths starting with AAA, BBB, or CCC should not have an xxxx in the path}
\medskip\par
\CurrentDirectory={\NotSpecialDirectory}
Should have xxx in path: 
    \GetTexFilePath{\the\CurrentDirectory}{2012}{05},
    \GetTexFilePathExpandable{\the\CurrentDirectory}{2012}{06}
\CurrentDirectory={\SpecialDirectory}
\medskip\par Should \emph{not} have xxx: 
    \GetTexFilePath{\the\CurrentDirectory}{2013}{07},
    \GetTexFilePathExpandable{\the\CurrentDirectory}{2013}{08}
\CurrentDirectory={\SpecialDirectory}
\medskip\par Should \emph{not} have xxx: 
    \GetTexFilePath{\the\CurrentDirectory}{2013}{09},
    \GetTexFilePathExpandable{\the\CurrentDirectory}{2013}{10}
\CurrentDirectory={\SpecialDirectoryB}
\medskip\par Should \emph{not} have xxx: 
    \GetTexFilePath{\the\CurrentDirectory}{2013}{01},
    \GetTexFilePathExpandable{\the\CurrentDirectory}{2013}{11}
\bigskip
\end{document}

Answer 1

I don't know if this really answers your needs, which I can't understand precisely.

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\GetTeXFilePath}{m m m}
 {
  \grill_str_if_eq_x_in:nVTF { #1 } \ListOfSpecialDirectories {#1/#2/#3} {#1/xxx#2/#3}
 }

\bool_new:N \l__grill_path_bool
\prg_new_protected_conditional:Npnn \grill_str_if_eq_x_in:nn #1 #2 { T,F,TF }
 {
  \bool_set_false:N \l__grill_path_bool
  \clist_map_inline:nn { #2 }
   {
    \str_if_eq_x:nnT { #1 } { ##1 }
     { \clist_map_break:n { \bool_set_true:N \l__grill_path_bool } }
   }
   \bool_if:NTF \l__grill_path_bool
    { \prg_return_true: }
    { \prg_return_false: }
 }
\cs_generate_variant:Nn \grill_str_if_eq_x_in:nnTF { nV }

\ExplSyntaxOff

\def\SpecialDirectory{AAA}
\def\SpecialDirectoryB{BBB}
\def\SpecialDirectoryC{CCC}
\newcommand{\ListOfSpecialDirectories}{\SpecialDirectory, \SpecialDirectoryB, \SpecialDirectoryC}

\begin{document}
\GetTeXFilePath{AAA}{2012}{05}

\GetTeXFilePath{\SpecialDirectoryB}{2012}{05}

\GetTeXFilePath{DDD}{2012}{05}
\end{document}

This will print

AAA/2012/05
BBB/2012/05
DDD/xxx2012/05

but of course this can't be used in an expandable context. However, if you want to use the result, just say

\NewDocumentCommand{\GetTeXFilePath}{m m m}
 {
  \grill_str_if_eq_x_in:nVTF { #1 } \ListOfSpecialDirectories
    { \tl_set:Nn \l_grill_result_tl {#1/#2/#3} }
    { \tl_set:Nn \l_grill_result_tl {#1/xxx#2/#3} }
 }

and use \l_grill_result_tl for passing it to some other macro.