Re: \omit multiple/list

[David Kastrup]

Kieren MacMillan <kieren@kierenmacmillan.info> writes:

> Hi Damian,
>
>> how would I reduce e.g.
>> 
>> \once \omit TupletBracket 
>> \once \omit TupletNumber 
>> \once \omit Stem
>> 
>> to a structure conceptually like:
>> 
>> \once \omit (TupletBracket, TupletNumber, Stem)
>> 
>> i.e. put the grobs in a list
>
> Maybe something like this (but something that actually works LOL):
>
> %%%  SNIPPET BEGINS
> \version "2.25.11"
>
> omitt =
>   #(define-scheme-function (groblist) (grob-list?)
>       (for-each
>         (lambda (gr)
>           #{ \omit gr #})
>          groblist))
>
> \omitt #'(TimeSignature NoteHead)
> %%%  SNIPPET ENDS

How about

omitt =
#(define-music-function (groblist) (symbol-list?)
  #{ #@(map omit (map list groblist)) #})

\void \displayLilyMusic \omitt TimeSignature,NoteHead

I'll admit that the need for the "map list" surprised me.  You can of
course write the non-surprising

omitt =
#(define-music-function (groblist) (symbol-list?)
  #{ #@(map (lambda (gr) #{ \omit $gr #}) groblist) #})

\void \displayLilyMusic \omitt TimeSignature,NoteHead

> This snippet “works”, in that it iterates through the list and correctly 
> outputs the grob name:
>
> %%%  SNIPPET BEGINS
> omitt =
>   #(define-scheme-function (groblist) (list?)
>       (for-each
>         (lambda (gr)
>           (ly:message
>            (format #f "~y" gr)))
>          groblist))
>
> \omitt #'(TimeSignature NoteHead)
> %%%  SNIPPET ENDS
>
> I’m just not sure the precise incantation to make the first snippet Do
> The Right Thing™.

You need to return music (instead of pretending that calling omit will
achieve anything by side-effect).

And of course you need a music function.

-- 
David Kastrup