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I am trying to create a command \projlib_langauge_define_multilingual_text:Nn for creating multilingual text macros. Given a macro name \<name>, and a key-value configuration of texts (english = ..., french = ...), it should create sub-macros \<name>_projlib_language_text_<languagename>, and define the main macro \<name> to refer to them accordingly.

Below is my current attempt, which produces a few errors of Undefined control sequence.

Where does it go wrong?

\documentclass{article} \ExplSyntaxOn \cs_new:Nn \projlib_langauge_define_multilingual_text:Nn % #1 = command name % #2 = key-value name configuration { \keyval_parse:nnn {} { \__projlib_langauge_define_multilingual_text_do:nnn { \cs_to_str:N #1 } } { #2 } \tl_new:c { #1 } \tl_set:cn { #1 } { \tl_use:c { #1 _projlib_language_text_ \languagename } } } \cs_generate_variant:Nn \projlib_langauge_define_multilingual_text:Nn { cn } \cs_new:Nn \__projlib_langauge_define_multilingual_text_do:nnn % #1 = command name % #2 = language name % #3 = the text { \exp_args:Nx \tl_new:c { #1 _projlib_language_text_ \projlib_language_str_to_languagename:n { #2 } } \exp_args:Nx \tl_set:cn { #1 _projlib_language_text_ \projlib_language_str_to_languagename:n { #2 } } { #3 } } \cs_new:Nn \projlib_language_str_to_languagename:n { \str_case_e:nn { \str_foldcase:n { #1 } } { {en} {english} {english} {english} {fr} {french} {french} {french} } } \ExplSyntaxOff \usepackage[french,english]{babel} \begin{document} \ExplSyntaxOn \projlib_langauge_define_multilingual_text:Nn \test_text { EN = Some english text, FR = Quelques textes en français, } % Should produce \test_text_projlib_language_text_english and \test_text_projlib_language_text_french, and define \test_text to call them accordingly \selectlanguage{french} % Should be >> Quelques textes en français \test_text \selectlanguage{english} % Should be >> Some english text \test_text \ExplSyntaxOff \end{document}

ADD: The accepted answer (alongside with his comments under the question) of David Carlisle kindly reminded the most dangerous syntax errors. The code above remains a few minor logical errors, for which the corrected version is posted below as an answer for your reference.

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  • \tl_new:N or \tl_new:c just take the command name to be declared, not a n argument with the value, did you intende \tl_const:cn ? or \tl_new followed by tl_set ? Commented Feb 6, 2022 at 15:48
  • more generally if a comand is not documented in textdoc interface3 then it is not defined by default. Commented Feb 6, 2022 at 15:50
  • @DavidCarlisle Thank you, I confused with \cs_new:cn. But even if I change them to \tl_new followed by \tl_set, it still have several errors. Commented Feb 6, 2022 at 15:53
  • If I make that change I get ! Undefined control sequence. l.60 \seleclanguage as you have not defined that. Is this a typo for selecTlanguage? Commented Feb 6, 2022 at 15:55
  • then ! Package babel Error: You haven't defined the language 'language' yet. What did you expect \selectlanguage{language} to do? Commented Feb 6, 2022 at 15:57

2 Answers 2

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The expl3 error is that (as the error message says) there is no tl_new:cn you need to separate thedeclaration with \tl_new and setting with \tl_set, then the remaining errors were typos in the \selectlanguage use.

\documentclass{article} \ExplSyntaxOn \cs_new:Nn \projlib_langauge_define_multilingual_text:Nn % #1 = command name % #2 = key-value name configuration { \keyval_parse:nnn {} { \__projlib_langauge_define_multilingual_text_do:nnn { \cs_to_str:N #1 } } { #2 } \tl_set:cn { #1 } { \tl_use:c { #1 _projlib_language_text_ \languagename } } } \cs_generate_variant:Nn \projlib_langauge_define_multilingual_text:Nn { cn } \cs_new:Nn \__projlib_langauge_define_multilingual_text_do:nnn % #1 = command name % #2 = language name % #3 = the text { \exp_args:Nx \tl_set:cn { #1 _projlib_language_text_ \projlib_language_str_to_languagename:n { #2 } } { #3 } } \cs_new:Nn \projlib_language_str_to_languagename:n { \str_case_e:nn { \str_foldcase:n { #1 } } { {en} {english} {english} {english} {fr} {french} {french} {french} } } \ExplSyntaxOff \usepackage[french,english]{babel} \begin{document} \ExplSyntaxOn \tl_new:N\test_text \projlib_langauge_define_multilingual_text:Nn \test_text { EN = Some english text, FR = Quelques textes en français, } % Should produce \test_text_projlib_language_text_english and \test_text_projlib_language_text_french, and define \test_text to call them accordingly \selectlanguage{french} % Should be >> Quelques textes en français \test_text \selectlanguage{english} % Should be >> Some english text \test_text \ExplSyntaxOff \end{document}
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  • Thank you, but there should exist some other mistakes, as the edited code still can't compile. I'm getting error messages Undefined control sequence. \test_text. Commented Feb 6, 2022 at 16:02
  • @Jinwen you do not get that error with the code as above. that is why it has \tl_new:N\test_text The code posted runs without error. Commented Feb 6, 2022 at 16:07
  • Ah, the error is actually Latexmk: Log file says no output from latex, so there is no LaTeX error, but there are logical errors as \test_text shouldn't be empty. Commented Feb 6, 2022 at 16:12
  • @Jinwen ah.there is that! I get no error but no output either, but I don't really know what the code's doing I just fixed the syntax errors, I'll let you debug for a bit, ask a new question if it's not clear Commented Feb 6, 2022 at 16:16
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There are several places in the original code that confuse c and N type argument. The correct version should be:

\documentclass{article} \ExplSyntaxOn \cs_new:Nn \projlib_langauge_define_multilingual_text:Nn % #1 = command name % #2 = key-value name configuration { \keyval_parse:nnn {} { \__projlib_langauge_define_multilingual_text_do:nnn { \cs_to_str:N #1 } } { #2 } \tl_set:Nn #1 { \tl_use:c { \cs_to_str:N #1 _projlib_language_text_ \languagename } } } \cs_generate_variant:Nn \projlib_langauge_define_multilingual_text:Nn { cn } \cs_new:Nn \__projlib_langauge_define_multilingual_text_do:nnn % #1 = command name % #2 = language name % #3 = the text { \exp_args:Nx \tl_set:cn { #1 _projlib_language_text_ \projlib_language_str_to_languagename:n { #2 } } { #3 } } \cs_new:Nn \projlib_language_str_to_languagename:n { \str_case_e:nn { \str_foldcase:n { #1 } } { {en} {english} {english} {english} {fr} {french} {french} {french} } } \ExplSyntaxOff \usepackage[french,english]{babel} \begin{document} \ExplSyntaxOn \tl_new:N\test_text \projlib_langauge_define_multilingual_text:Nn \test_text { EN = Some\ english\ text, FR = Quelques\ textes\ en\ français, } % Should produce \test_text_projlib_language_text_english and \test_text_projlib_language_text_french, and define \test_text to call them accordingly \selectlanguage{french} % Should be >> Quelques textes en français \test_text\\ \selectlanguage{english} % Should be >> Some english text \test_text\\ % \cs_meaning:N \test_text\\ % \test_text_projlib_language_text_english\\ % \test_text_projlib_language_text_french\\ -- \ExplSyntaxOff \end{document}
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  • it would probably be less confusing for future readers if you accepted this one (I can manage without the 15 points:-) Commented Feb 6, 2022 at 16:24
  • @DavidCarlisle I understand but surely your answer is more useful. I'm just posting the final version for future reference. Maybe it will be more helpful if I mention it under the question. Commented Feb 6, 2022 at 16:28

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