How to split optional arguments

Question

With commands such as \usepackage, all options can be given within the same pair of square brackets, using only commas as delimiters.

I'd like to achieve the same thing, here for example with the \coolphase command, i.e. write \coolphase[-77,2]{nab}.

How do I do it ?

I tried this but it doesn't work :

\NewDocumentCommand{\coolphasesplit}{>{\SplitArgument{4}{,}}o}{\coolphase#1}

MWE

\documentclass{article}

\usepackage[linguistics]{forest}

\NewDocumentCommand{\coolphase}{
    O{-58}
    O{0}
    O{8}
    O{150}
    O{110}
    m}
{\draw[dotted,thick]([xshift=#1pt,yshift=#2pt]#6) arc[start angle=#4,end angle=#5,radius=#3cm];}


\begin{document}
    
\begin{forest}
    [ASP[\textit{subject}][Asp 
    [asp][POL
    [AdvP[\textit{non},roof]][Pol
    [pol, name=nab][aP
    [~][a′
    [a][root]]]]]]]
    \coolphase[-77][2]{nab}
\end{forest}
    
\end{document}

Answer 1

It might be possible to do it without \ExplSyntaxOn, but it would be really cumbersome.

With \SplitArgument{4}{,}, the missing values are replaced by the special -NoValue- string, that can be tested with \tl_if_novalue:nTF.

We need to expand the test before \__krebs_coolphase:nnnnnn sees the actual arguments.

\documentclass{article}

\usepackage[linguistics]{forest}

% this uses TikZ so it cannot go in \ExplSyntaxOn
\NewDocumentCommand{\coolphaseaux}{mmmmmm}{%
  \draw[dotted,thick]([xshift=#1pt,yshift=#2pt]#6) arc[start angle=#4,end angle=#5,radius=#3cm];
}

\ExplSyntaxOn
\NewDocumentCommand{\coolphase}{>{\SplitArgument{4}{,}}om}
 {
  \krebs_coolphase:nnnnnn #1{#2}
 }
\cs_new_protected:Nn \krebs_coolphase:nnnnnn
 {
  \__krebs_coolphase:eeeeen
   { \tl_if_novalue:nTF { #1 } { -58 } { #1 } }
   { \tl_if_novalue:nTF { #2 } {   0 } { #2 } }
   { \tl_if_novalue:nTF { #3 } {   8 } { #3 } }
   { \tl_if_novalue:nTF { #4 } { 150 } { #4 } }
   { \tl_if_novalue:nTF { #5 } { 110 } { #5 } }
   { #6 }
 }
% make an internal version of \coolphaseaux
\cs_set_eq:NN \__krebs_coolphase:nnnnnn \coolphaseaux
% generate the needed variant
\cs_generate_variant:Nn \__krebs_coolphase:nnnnnn { eeeee }
\ExplSyntaxOff

\begin{document}
    
\begin{forest}
    [ASP[\textit{subject}][Asp 
    [asp][POL
    [AdvP[\textit{non},roof]][Pol
    [pol, name=nab][aP
    [~][a'
    [a][root]]]]]]]
    \coolphase[-77,2]{nab}
\end{forest}
    
\end{document}

However, it is much better if you use a key-value system, so you need not remember the precise order of the options.

\documentclass{article}

\usepackage[linguistics]{forest}

% this uses TikZ so it cannot go in \ExplSyntaxOn
\NewDocumentCommand{\coolphaseaux}{mmmmmm}{%
  \draw[dotted,thick]([xshift=#1pt,yshift=#2pt]#6) arc[start angle=#4,end angle=#5,radius=#3cm];
}

\ExplSyntaxOn
\NewDocumentCommand{\coolphase}{O{}m}
 {
  \group_begin:
  \keys_set:nn { krebs/coolphase } { #1 }
  \krebs_coolphase:VVVVVn
   \l__krebs_coolphase_x_tl
   \l__krebs_coolphase_y_tl
   \l__krebs_coolphase_sa_tl
   \l__krebs_coolphase_ea_tl
   \l__krebs_coolphase_r_tl
   {#2}
   \group_end:
 }
\keys_define:nn { krebs/coolphase }
 {
  x  .tl_set:N = \l__krebs_coolphase_x_tl,
  y  .tl_set:N = \l__krebs_coolphase_y_tl,
  sa .tl_set:N = \l__krebs_coolphase_sa_tl,
  ea .tl_set:N = \l__krebs_coolphase_ea_tl,
  r  .tl_set:N = \l__krebs_coolphase_r_tl,
  x  .initial:n = -58,
  y  .initial:n = 0,
  sa .initial:n = 8,
  ea .initial:n = 150,
  r  .initial:n = 110,
 }
% make an internal version of \coolphaseaux
\cs_set_eq:NN \krebs_coolphase:nnnnnn \coolphaseaux
% generate the needed variant
\cs_generate_variant:Nn \krebs_coolphase:nnnnnn { VVVVV }
\ExplSyntaxOff

\begin{document}
    
\begin{forest}
    [ASP[\textit{subject}][Asp 
    [asp][POL
    [AdvP[\textit{non},roof]][Pol
    [pol, name=nab][aP
    [~][a'
    [a][root]]]]]]]
    \coolphase[x=-77,y=2]{nab}
\end{forest}
    
\end{document}

You could pass r=110,sa=150,x=-77,ea=110,y=2, say, without worrying about the right order.

Answer 2

I know it is possible using TeX. Something like this should work:

\def\coolphase(#1, #2){
    %function definition
}

Answer 3

Using PythonTeX:

%! TEX program = lualatex
\documentclass{article}
\usepackage{pythontex}

\usepackage[linguistics]{forest}

\begin{pycode}
def coolphase(opt_parts, arg2):
    opt_default=[-58, 0, 8, 150, 110]
    if len(opt_parts)>len(opt_default):
        raise ValueError("Too many arguments")
    opt_parts+=opt_default[len(opt_parts):]  # fill in default arguments.
    # Now opt_parts = [77, 2, 8, 150, 110]

    print(
            r"\draw[dotted,thick]([xshift={xshift}pt,yshift={yshift}pt]{extra}) arc[start angle={start_angle},end angle={end_angle},radius={radius}cm];"
            .format(
                xshift=opt_parts[0],
                yshift=opt_parts[1],
                radius=opt_parts[2],
                start_angle=opt_parts[3],
                end_angle=opt_parts[4],
                extra=arg2
                )
            )
\end{pycode}
\NewDocumentCommand\coolphase{om}{\pyc{coolphase([#1],r"""#2""")}}


\begin{document}
    
\begin{forest}
    [ASP[\textit{subject}][Asp 
    [asp][POL
    [AdvP[\textit{non},roof]][Pol
    [pol, name=nab][aP
    [~][a′
    [a][root]]]]]]]
    \coolphase[-77,2]{nab}
\end{forest}
    
\end{document}

Output is as you expect.