# [NTG-context] Cross-reference expansion with ConTeXt and processing with LuaTeX

Oliver von Criegern oliver.v.criegern at badw-muenchen.de
Wed Sep 4 19:37:51 CEST 2019

Dear list members,

I want to process cross-references in ConTeXt/LuaTeX, that is, to do
some calculations in Lua with the page and line numbers returned by the
\at and \inlinerange commands.

But this does not work, as these commands are obviously not being
expanded before they are passed to Lua.

Here is a minimal example:

|\setupreferencing[state=start]||\definenumber[test]\setnumber[test][5]\startluacodefunction
TestVar(var)print('VARIABLE: ')print(var)tex.print(var)end
\stopluacode\def\TestLua#1{\ctxlua{TestVar([==[#1]==])}}% Cf.
https://www.contextgarden.net/Programming_in_LuaTeX\startbuffer[testtext]\dorecurse{100}{Words,
words, words. }\stopbuffer\starttext\startlinenumberingCounter:
\TestLua{\rawcountervalue[test]}\par% The counter is expanded before
being passed to Lua.Lineref: \TestLua{\inlinerange[1]}\par% The line
reference is not expanded before being passed to
Lua.\getbuffer[testtext]\someline[1]LABEL 1 \stoplinenumbering\stoptext|||

\TestLua just passes the argument to the Lua command TestVar, which
prints it to stdout and returns it to TeX. The pdf result looks good at
first glance, showing the correct values as expected, but in stdout we read:

|VARIABLE: 5 VARIABLE: \inlinerange[1] |||

The line reference obviously has not been expanded before but only after
having been passed to the Lua command. Accordingly, when trying to
perform mathematical calculations on it in Lua, there will be an error.

So how can I pass the value of my reference to Lua?

Best regards,
Oliver

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