16

I have the following code to print catcodes as subscripts. Can one improve it to work also for the backslash and the braces? And what about the space? (I'm not asking about the comment char and ignored characters but it would be interesting too). 

\documentclass{article}
\usepackage{expl3,xparse}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\ExplSyntaxOn

\NewDocumentCommand\showcatcodes { m }
 {
  \tl_map_inline:nn { #1 } 
   {
     \tl_to_str:n {##1} \textsubscript{\char_value_catcode:n{`##1}}
   }
 }  

\ExplSyntaxOff


\begin{document}
\showcatcodes{abcde123!$_ ^€\{\}} 
\end{document}

enter image description here

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3
  • Probably this can be done by varying the output of \tl_show_analysis:N
    – Joseph Wright ♦
    Mar 15, 2017 at 19:21
  • Something like \def\showcatcodes#1#2\relax{% \string#1% \ifcat ###1$_{6}$\else% \ifcat &#1$_{4}$\else% \ifcat A#1$_{11}$\else% \ifcat .#1$_{12}$\else% \ifcat $#1$_{3}$\else% \ifcat _#1$_{8}$\else% \ifcat ^#1$_{7}$\else% \ifcat \noexpand\relax\noexpand#1$_{0}$\else% \fi\fi\fi\fi\fi\fi\fi\fi% \ifx\relax#2\relax\else\showcatcodes#2\relax\fi% } will show \{ and \} and other macros as catcode 0, but it does not handle actual braces { and }. Note invocation as \showcatcodes abc&de#123!$_ ^€\{\}\relax
    – Steven B. Segletes
    Mar 15, 2017 at 19:38
  • @JosephWright: I liked the "probably" -- it means that I didn't overlook something obvious ;-). I checked \tl_show_analysis:N but it returns things like \abc as a single token so I'm not sure if it is suitable.
    – Ulrike Fischer
    Mar 16, 2017 at 8:58

2 Answers 2

Reset to default
7

You can use l3regex:

\documentclass{article}
\usepackage{expl3,xparse,l3regex}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\ExplSyntaxOn

\NewDocumentCommand\showcatcodes { v }
 {
  \regex_extract_all:nnN { . } { #1 } \l_tmpa_seq
  \seq_map_inline:Nn \l_tmpa_seq
   { \ulrike_value_catcode:x { \tl_to_str:n {##1} } }
 }
\cs_new_protected:Nn \ulrike_value_catcode:n
 {
  #1\textsubscript{\char_value_catcode:n { `#1 }}
 }
\cs_generate_variant:Nn \ulrike_value_catcode:n { x }
\ExplSyntaxOff


\begin{document}
\showcatcodes{abcde123!$_ ^€\{\}}
\end{document}

enter image description here

This is the output with XeLaTeX (after removing inputenc and fontenc):

enter image description here

Final variant with \textvisiblespace and monospaced fonts for the characters:

\documentclass{article}
\usepackage{expl3,xparse,l3regex}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\ExplSyntaxOn

\NewDocumentCommand\showcatcodes { v }
 {
  \group_begin:
  \ttfamily
  \regex_extract_all:nnN { . } { #1 } \l_tmpa_seq
  \seq_map_inline:Nn \l_tmpa_seq
   { \ulrike_value_catcode:x { \tl_to_str:n {##1} } }
  \group_end:
 }
\cs_new_protected:Nn \ulrike_value_catcode:n
 {
  \tl_if_blank:nTF { #1 } { \textvisiblespace } { #1 }
  \textsubscript{\normalfont\char_value_catcode:n { `#1 }}
 }
\cs_generate_variant:Nn \ulrike_value_catcode:n { x }
\ExplSyntaxOff


\begin{document}
\showcatcodes{abcde123!$_ ^€\{\}}
\end{document}

enter image description here

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2
  • That works fine. I added a test \tl_if_blank:nTF to print the space as \textvisiblespace. But what does \tl_set:Nn \l_tmpa_tl { #1 } do? It is a rest from some older code?
    – Ulrike Fischer
    Mar 16, 2017 at 8:54
  • @UlrikeFischer Yes, it should have been removed.
    – egreg
    Mar 16, 2017 at 11:38
10

Apart from spaces you could do

enter image description here

\documentclass{article}
\usepackage{expl3,xparse}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\ExplSyntaxOn

\NewDocumentCommand\showcatcodes { m }
 {
   \expandafter\tl_map_inline:nn\expandafter{ \detokenize{#1} }
   {
     \tl_to_str:n {##1} \textsubscript{\char_value_catcode:n{`##1}}
   }
 }

\ExplSyntaxOff


\begin{document}

\showcatcodes{a bcde123!$_ ^€\{\} {} } 
\end{document}

spaces you ought to be able to do by using \scantokens to change the catcode of space after making everything else safe with `\detokenize but scantokens is a dangerous beast and it's biting back at present.

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6
  • 1
    That's good. But I think you should use \cs_generate_variant:Nn \tl_map_inline:nn { on } and \tl_map_inline:on { \tl_to_str:n {#1} } ;-)
    – Ulrike Fischer
    Mar 15, 2017 at 20:51
  • I was expecting egreg to reprimand me on poor l3 style not you:-) I did actually try \tl_map_inline:on and ;xn but as they didn't exist I reverted to form and used \expandafter :-)
    – David Carlisle
    Mar 15, 2017 at 21:03
  • Actually I don't understand why it works. Isn't after \detokenize the argument a list of chars with catcode 12? So why are the subscripts "correct" ?
    – Ulrike Fischer
    Mar 15, 2017 at 21:20
  • @UlrikeFischer you are not looking up the catcodes of the tokens passed in, you are looking up the current catcode values. If you want to inspect the catcodes of the tokens then you need \ifcat a #1 11 \else \ifcat^#1 7 \else....
    – David Carlisle
    Mar 15, 2017 at 21:26
  • I'm not sure if we have a standard function in L3 to return the catcode of a token as a number...
    – David Carlisle
    Mar 15, 2017 at 21:27

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