How to get groups from a LaTex regex match?

Question

\documentclass{article}

\usepackage{hyperref}
\usepackage{expl3}


\hypersetup{
    colorlinks=true,
    linkcolor=blue,
    filecolor=magenta,      
    urlcolor=cyan,
    pdftitle={Overleaf Example},
    pdfpagemode=FullScreen,
}

\ExplSyntaxOn
\NewDocumentCommand{\curl}{m}{
    \tl_set:Nn \l_tmpa_tl {#1}
    \regex_extract_once:nnN  {\/([a-z0-9]{10})}  {#1} \l_uiy_result_seq
    \seq_map_inline:Nn \l_uiy_result_seq {\href{#1}{##1}}
}
\ExplSyntaxOff


\begin{document} 

\curl{https://www.facebook.com/reel/1a1c6e99h60a3169h86816}

\end{document}

Using this code I'm getting match & match group one after one.

Example

\curl{https://www.facebook.com/reel/1a1c6e99h60a3169h86816}

Output is

Where First /1a1c6e99h6 is match & second half is match group 1a1c6e99h6

How can I only map match group 1a1c6e99h6

Have you tried to pop the first element via \seq_pop_left before iterating on the sequence? The doc says : "If it exists, the match is stored as the first item of the ⟨seq var⟩, and further items are the contents of capturing groups, in the order of their opening parenthesis. " — projetmbc, Feb 15 '23 at 08:32
That's the only code I'm using. Also \seq_pop_left is not working — d4rkshad0w, Feb 15 '23 at 08:47
Gives us a code with \begin{document}... etc. This will allow us to copy and paste your code in https://texlive.net/run to quickly try something... — projetmbc, Feb 15 '23 at 08:48

score 5 · Accepted Answer · answered Feb 15 '23 at 09:02

Here is how to pop left the sequence such as to obtain 1a1c6e99h6.

\documentclass{article}
\usepackage{hyperref}
\usepackage{expl3}
\hypersetup{
    colorlinks=true,
    linkcolor=blue,
    filecolor=magenta,

    urlcolor=cyan,
    pdftitle={Overleaf Example},
    pdfpagemode=FullScreen,
}
\ExplSyntaxOn
\NewDocumentCommand{\curl}{m}{
    \regex_extract_once:nnN  {/([a-z0-9]{10})}  {#1} \l_uiy_result_seq
% One good example of use of l_tmpa_tl.
\seq_pop_left:NNTF \l_uiy_result_seq \l_tmpa_tl {
    \seq_map_inline:Nn \l_uiy_result_seq {\href{#1}{##1}}
}{
    No ~ match!
}

}
\ExplSyntaxOff
\begin{document}
\curl{https://www.facebook.com/reel/1a1c6e99h60a3169h86816}
\curl{PB}
\end{document}

score 3 · Answer 2 · answered Feb 15 '23 at 10:32

I think you don't want extraction, but just replacement:

\documentclass{article}
\usepackage{hyperref}
\usepackage{expl3}
\hypersetup{
    colorlinks=true,
    linkcolor=blue,
    filecolor=magenta,

    urlcolor=cyan,
    pdftitle={Overleaf Example},
    pdfpagemode=FullScreen,
}
\ExplSyntaxOn
\NewDocumentCommand{\curl}{m}
  {
    \tl_set:Nn \l_tmpa_tl {#1}
    \regex_replace_once:nnN  {./([a-z0-9]{10}).} {\1} \l_tmpa_tl
    \href{#1}{\l_tmpa_tl}
  }
\ExplSyntaxOff
\begin{document}
\curl{https://www.facebook.com/reel/1a1c6e99h60a3169h86816}
\end{document}

How to get groups from a LaTex regex match?

2 Answers2