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I'm inserting graphics from data in a csv-file and due to lazy input I have to get rid of leading and trailing spaces. It works fine with the trimspaces package.


\def\testA{example-image-a }
%\includegraphics{\testA} %error

\def\testB{ example-image-a}
%\includegraphics{\testB} %error




By curiosity I tried to get this with expl3 and \tl_trim_spaces:n but didn't find a sensible way to store the content of the commands without the spaces in a command. Does someone know how to do it?

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up vote 7 down vote accepted

Two ways. With the first method you use \trimspaces in front of the macro; with the second you can ‘normalize’ a macro to have leading and trailing spaces removed.


  \tl_trim_spaces:V #1
\cs_generate_variant:Nn \tl_trim_spaces:n { V }

  \tl_trim_spaces:N #1


\def\testA{example-image-a }
\def\testB{ example-image-a}







enter image description here

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Ah I see. I hadn't understand that \tl_trim_spaces:N does the same as \trim@spaces@in, I thought it would leave things in the input stream like \tl_trim_spaces:n. And I hadn't thought about V type, I only tried x. –  Ulrike Fischer Dec 19 '13 at 10:53
@UlrikeFischer The description of \tl_trim_spaces:N could be clearer. –  egreg Dec 19 '13 at 10:56
I can look to improve the docs for a release likely next week: @UlrikeFischer was there something specific that was missing? –  Joseph Wright Dec 19 '13 at 11:23
@JosephWright Maybe “Resets ⟨tl var⟩ by removing any leading and trailing explicit space characters (explicit tokens with character code 32 and category code 10) from its content.” –  egreg Dec 19 '13 at 11:26
@JosephWright: The main source of confusion was in my case the naming of the commands: Both \tl_trim_spaces:n and \tl_trim_spaces:N share the same command "body" \tl_trim_spaces and so I assumed that they are variants and do more or less the same only on different types of arguments and I transfered "leaves the result in the input stream" from the description of \tl_trim_spaces:n to the other command. –  Ulrike Fischer Dec 19 '13 at 15:30
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