Introducing colour ta a separator

Question

I am having difficulty constructing the function \celest_separ:n that can handle colour because code level functions do not have optional arguments. Quite unfortunate. How may I get out of such problem ?

What is the advantage of using - versus \textemdash ?

\documentclass[a4paper,12pt]{article}
\usepackage{xcolor}
\ExplSyntaxOn
\definecolor{dblue}{RGB}{0,0,139}
\colorlet{celestk}{dblue}
\cs_set_eq:NN \wvAstr \textasteriskcentered
\cs_set_eq:NN \wvDash \textemdash
\cs_new_protected:Nn \celest_separ:n
  {
    \IfNoValueTF {#2}
        { \color[#1] }
      { \color[#1]{#2} }
\begin{center}
  \wvDash \wvDash \wvDash
  \ \wvAstr \, \wvAstr \, \wvAstr
  \ \wvDash \wvDash \wvDash
\end{center}

}
\NewDocumentCommand \separ {O{celestk}o}
  {
    \IfNoValueTF {#2}
        { \celest_separ:n [#1] }
      { \celest_separ:n [#1] [#2] }
  }
\ExplSyntaxOff
\begin{document}
\separ
\end{document}

Please don't edit to add a new question after your original has been answered. - is a hyphen. \emdash is a rule which I guess originally, at least, was of length 1em. Em and en are printer's measures. In many cases, -- and --- are ligatures. — cfr, Oct 15 '23 at 23:47

score 2 · Accepted Answer · answered Oct 15 '23 at 22:34

You can't call

\celest_separ:n [#1]

nor

\celest_separ:n [#1][#2]

You need to absorb the arguments and call internal functions having the correct signature (and definition).

But here I can't see how expl3 can really help.

You seem to want to allow for calls such as

\separ
\separ[red!80]
\separ[rgb][0.1,0.2,0.3]

I don't think that the center environment is good for the job, actually. And don't overthink about expl3.

\documentclass[twocolumn]{article}
\usepackage{xcolor}
\usepackage{lipsum}
\definecolor{dblue}{RGB}{0,0,139}
\colorlet{celestk}{dblue}
\NewDocumentCommand{\separ}{O{celestk}o}{%
  \par\nopagebreak\vspace{0.5\baselineskip}
  \noindent\makebox[\columnwidth]{%
    \IfNoValueTF{#2}{\color{#1}}{\color[#1]{#2}}%
    ---!---!---\ %
    \textasteriskcentered,\textasteriskcentered,\textasteriskcentered
    \ ---!---!---%
  }\par\vspace{0.5\baselineskip}
}
\begin{document}
\lipsum[1][1-2]
\separ
\lipsum[1][1-2]
\separ[red!80]
\lipsum[1][1-2]
\separ[rgb][0.4,0.1,0.1]
\lipsum[1][1-2]
\end{document}

Here twocolumn is used just to get a smaller picture.

Introducing colour ta a separator

1 Answers1