Re: Changing the car or cdr of a pair

[Malte Meyn]

Am 25.12.2017 um 19:01 schrieb David Kastrup:
> David Kastrup <address@hidden> writes:
> > \once \override Staff.LigatureBracket.edge-height =
> > #(grob-transformer 'edge-height
> >    (lambda (grob original)
> >     (cons 0.3 (cdr original))))
> >
> > For example.
>
> Malte's suggestion to use \offset does something similar internally and
> employs a nicer user interface.

If you want to add something to the original value(s), \offset is 
easier, yes. But if you want to use absolute values, using 
grob-transformer instead of before-line-breaking is easier so I would 
prefer your suggestion in that case:

My suggested solution

\once \override LigatureBracket.before-line-breaking =
  #(lambda (grob)
     (let* ((orig-height (ly:grob-property grob 'edge-height))
            (orig-left (car orig-height)))
       (ly:grob-set-property! grob 'edge-height (cons orig-left 3))))

has the same effect as this variant of your simpler solution:

\once \override LigatureBracket.edge-height =
  #(grob-transformer 'edge-height
     (lambda (grob original)
       (cons (car original) 3)))