Re: Two optional arguments

[Aaron Hill]

On 2020-07-15 3:07 am, Urs Liska wrote:
> It would be nice if the user could write each of these (all in the
> context of my other discussion about presets/configuration/subsets):
>
> \myFrame                                c'
> \myFrame analogy                        c'
> \myFrame         \with { color = #red } c'
> \myFrame analogy \with { color = #red } c'
>
> It seems I would have to put a mandatory argument between the symbol
> and the \with block here, which seems like a bad interface.
>
> The solution I'll probably have to take is pulling the symbol inside
> the \with block:
>
> \myFrame \with {
>   configuration = analogy
>   color = #red
> }
>
> This forces the user to write a \with block when all they want is to
> load a configuration. But that's not a *bad* interface, only
> inconvenient, so clearly the lesser evil.

What about using a compound type predicate with alteration?

%%%%
\version "2.20.0"

asdf =
#(begin
  (define (context-mod-assign-alist context-mod)
    (map
      (lambda (mod) (cons (cadr mod) (caddr mod)))
      (filter
        (lambda (mod) (eq? 'assign (car mod)))
        (ly:get-context-mods context-mod))))

  (define (symbol-or-context-mod? arg)
    (or (symbol? arg)
        (ly:context-mod? arg)))

  (define-scheme-function
    (opt-arg mus-arg)
    ((symbol-or-context-mod? #{ \with {} #})
     ly:music?)

    (if (symbol? opt-arg)
      (set! opt-arg
            #{ \with { symbol = $opt-arg } #}))
    #{
      \markup \column {
        \line { \bold \typewriter "\asdf" invoked: }
        $@(map
          (lambda (elem) #{ \markup {
            with \bold #(symbol->string (car elem)) =
            \typewriter #(format #f "~s" (cdr elem)) } #})
          (context-mod-assign-alist opt-arg))
        \line { \score { #mus-arg } }
      }
    #}))

hline =
\markup \column {
  \vspace #0.5
  \override #'(span-factor . 1/4) \draw-hline
  \vspace #0.5
}

\asdf                                  g' \hline
\asdf                  foo             g' \hline
\asdf \with {              baz = 2/3 } g' \hline
\asdf \with { symbol = foo baz = 2/3 } g'
%%%%

While not exactly your original syntax, this does permit a user to 
shorthand "\with { symbol = foo }" as simply "foo" providing they do not 
need to use the \with block.


-- Aaron Hill

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