Re: problems trying to write a conditional \transpose

[David Kastrup]

Mark Polesky <address@hidden> writes:

> I'm trying to write a conditional version of the \transpose
> function, that would work something like this:
>
> input = { 
>   c c 
>   \conditionalTransposition c c' { c c }
> }
>
> \input
> => { c c c c }
>
> \processConditionalTransposition \input
> => { c c c' c' }

conditionalTransposition =
#(define-music-function (parser location from to music)
  (ly:pitch? ly:pitch? ly:music?)
  (set! music #{ \transpose c' c' #music #})
  (set! (ly:music-property 'from-to music) (cons from to))
  music)

processConditionalTransposition =
#(define-music-function (parser location music) (ly:music?)
  (map-some-music
    (lambda (m)
      (and (music-is-of-type? m 'transposed-music)
           (pair? (ly:music-property m 'from-to music))
           #{ \transpose #(car (ly:music-property m 'from-to-music))
                         #(cdr (ly:music-property m 'from-to-music))
                         #(ly:music-property m 'element)
           #}))
     music))

This is assuming that you don't nest processConditionalTransposition, if
you do, you need to write
\processConditionalTransposition #(ly:music-property m 'element) at the
appropriate place.

Untested.

-- 
David Kastrup