Re: music function to be included somewhere in scm/*

[Alexander Kobel]

On 2016-12-16 15:20, Urs Liska wrote:
> Am 16. Dezember 2016 15:11:59 MEZ, schrieb David Nalesnik <address@hidden>:
> > On Fri, Dec 16, 2016 at 8:07 AM, Knut Petersen [...]
> > > (define-public (forceExtender)
> > >   (once (overrideProperty '(LyricExtender force-extender) #t)))
> > >
> > > into scm/music-functions.scm, lilypond does know \forceExtender ...
> > > but it complains about a "non-music expression" if it is used ...
>
> Ah, this one. You explicitly have to create a music function. Maybe
>
> https://scheme-book.ursliska.de/scheme/music-function-primer.html
>
> helps you?

Oh, that looks nice... I need to spend some time on that one.

> But you can say
>
> (define forceExtender (define-musi-function ...

(define forceExtender
 (define-music-function () ()
  (once (overrideProperty '(LyricExtender force-extender) #t))))

should work, yes. But I think David's suggestion is even easier and 
recommended. Note that
  fgrep define-music-function scm/*
gives a pretty short list of 4 hits, and 2 of which are in the 
definition of define-music-function itself. And
  fgrep define-music-function ly/* | wc -l
shows a count of 131...

> > If you are defining a music function, do it in
> > ly/music-functions-init.ly,

In a .ly file (which is processed with all the syntactic sugar that 
Lilypond has to offer) you can simply write
  forceExtender = \once \override LyricExtender.force-extender = ##t
and that's it.
By the way, for the sake of consistency with other commands (except, 
maybe, \hideNotes and \unHideNotes): My preferred choice of names would be
  forcedExtendersOn  = \override LyricExtender.force-extender = ##t
  forcedExtendersOff = \override LyricExtender.force-extender = ##f
and a user can prefix a \once if necessary. (Unless someone comes up 
with an apt antonym of "force" here - free, release, permit don't sound 
sound...)


Cheers,
Alexander