Re: Two optional arguments

[Urs Liska]

Hi Aaron,

Am Mittwoch, den 15.07.2020, 07:09 -0700 schrieb 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?

Thank you, this was a terrific idea which seems to get me over the goal
line.

> 
> %%%%
> \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'
> 
> %%%%

The actual implementation will be totally different, given what I
already have and that all this happens inside a macro, but I could
translate the idea without problems.

> 
> 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.

Yes, this is not my original syntax, but that doesn't matter.
My wish was to spare the user to write a \with block for just that
symbol. But when the user has to write that anyway it's no hassle to
provide that symbol as a regular property within the \with block.

So this solution allows me to work around the fact that I can't use the
two optional arguments.

Best
Urs

> 
> 
> -- Aaron Hill