Re: how to define a boolean?

[Marc Hohl]

Mark Polesky schrieb:
> Marc Hohl wrote:
>
>   
> > Sorry if this is a stupid question, but here im totally stuck:
> >     
>
> Not a stupid question. This involves "parser variables" which are
> giving us developers troubles, too! If you're curious, you can
> follow this long thread:
> http://lists.gnu.org/archive/html/lilypond-devel/2009-07/msg00921.html
>
>   
I followed this thread on -devel, but at some point, it went over my 
head, so
I didn't read in detail.
> > I need to define a boolean which is to be changed within a music-function
> > and a stencil callback.
> >     
>
> For the music-function you can do this:
>
> % you can also do:
> % mybool = ##f
> #(define mybool #f)
>
> myfunc =
> #(define-music-function (parser location note) (ly:music?)
>   (ly:parser-define! parser 'mybool #t)
>   (let* ((mybool (ly:parser-lookup parser 'mybool))
>          (color  (if mybool red blue)))
>     #{
>       \override  NoteHead #'color = $color
>       $note
>     #}))
>   
Thank you! At least I can play with this ...
> The callback is a little trickier for me for the moment.
> I'll get back to you.
>   
Great. I am awaiting your response.

Marc
> - Mark
>
>
>
>       
>
>