I have a command \persName{key} that expands to the Name of a person represented by a key-string.

I would like to create a command \eindex that can have this command as argument, expanding it fully to the name of the person and then using this as argument to \sindex (from the splitidx-pacakge).

    % Only an example. Is more complicated than that.
    John Doe (#1)%

\NewDocumentCommand{\eindex}{o m}{%

But this solution does not work as intended. If I use \eindex[names]{\persName{Marc}} it enters

\indexentry{\persName {Marc}}{1}

into the .idx file. While creating the index, this will get expanded to "John Doe (Marc)", but is ordered under "M" in the index, not "J".

I would like to have \eindex expand the mandatory argument prior to entering it in the .idx-file like this:

\indexentry{John Doe (Marc)}{1}

More complicated version of \persName:

I use LuaLaTeX and defined a Lua-function (in the external package "Persons") to gather the name of the person in question from an addressbook.

\NewDocumentCommand{\persName}{O{} m d() o}{%
            local _case
            \csname IfValueTF\endcsname{#3}{%
                _case = tostring( '\luatexluaescapestring{#3}' )
            local _form
            \csname IfValueTF\endcsname{#4}{%
                _form = tostring( '\luatexluaescapestring{#4}' )
            local _key = tostring( '\luatexluaescapestring{#2}' )
            local _instance = tonumber( '\luatexluaescapestring{\cT@instance}' )
            tex.sprint( Persons.name( _key, { form=_form, case=_case, instance=_instance, } ) )
  • 2
    When you do \edef\temp@a{\persName{Mark}} no expansion is actually performed, because \persName is protected against expansion in \edef. I'm afraid you need to show the “more complicated” working of \persName if you want more help. – egreg Mar 27 '18 at 23:01
  • 2
    That wouldn’t happen if you defined \persName with \DeclareExpandableDocumentCommand (or, for that matter, with \newcommand) instead of with \NewDocumentCommand; but this may have undesired side effects, so I wouldn’t recommend doing so unless you provide further context for your question. – GuM Mar 27 '18 at 23:11
  • I edited the question to add the "more complicated" version of \persName. Since the command has an optional argument at the end \DeclareExpandableDocumentCommand seems not to be the way to go. – leviathan Mar 28 '18 at 17:36

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