Re: Apply event function *within* music-function

[Jan-Peter Voigt]

Hi Urs,

Am 02.05.2017 um 17:30 schrieb Urs Liska:
> Hi Jan-Peter
>
> ...
> > \version "2.19.57"
> >
> > test =
> > #(define-music-function (mus)(ly:music?)
> >    (let* ((elms (ly:music-property mus 'elements))
> >           ; first and last music-element ...
> >           (frst (first elms)) ; TODO test for list? and ly:music?
> >           (lst (last elms)) ; TODO test for list? and ly:music?
> >           (fartic (ly:music-property frst 'articulations '())) ; look
> > for eventchords ...
> >           (lartic (ly:music-property lst 'articulations '()))
> >           )
> >      (ly:music-set-property! frst 'articulations `(,@fartic
> > ,(make-music 'NoteGroupingEvent 'span-direction -1)))
> >      (ly:music-set-property! lst 'articulations `(,@lartic
> > ,(make-music 'NoteGroupingEvent 'span-direction 1)))
> >    #{
> >      #mus
> >    #}))
> >
> > \new Staff \with {
> >   \consists "Horizontal_bracket_engraver"
> > } {
> >   \test { c' d' e' f' } g' a' b' c''
> > }
> >
> >
> > HTH
>
> Yes, it does. I don't think there's an even more straightforward
> solution (like the <> for the first element) to this. I successfully
> integrated it into my code.
> But what would be the cases where the element is a list? instead of
> ly:music? And what does the "eventchords" comment refer to?
If you have an eventchord (e.g. <c e g>) there will be no articulations 
property in that element. That means, you have to add the 
NoteGroupingEvent to the elements list.
In other words: If you have something other than a simple note- or 
rest-event inside the mus argument, this solution might fail.
You probably need to transcend the music tree, until you find an event 
appropriate for add the NoteGroupingEvent. As long as you take care that 
the first and the last element is such an element it should be fine.

Cheers
Jan-Peter