Am Mo., 18. Nov. 2019 um 16:55 Uhr schrieb Aaron Hill
<lilyp...@hillvisions.com>:
>
> On 2019-11-18 6:24 am, David Kastrup wrote:
> > Aaron Hill <lilyp...@hillvisions.com> writes:
> >> Not sure if this is really the right way to do things:
> >
> > It isn't. It maintains the "stack" in a global variable rather than
> > some context property, meaning that when several iterations interlock
> > (like with tempo being changed in several contexts or in polyrhythmic
> > situations), chaos will ensue.
>
> Ah... you're no fun. To misquote Willy Wonka, "A little [chaos] now and
> then is relished by the wisest men." (:
>
> But seriously, I was imagining only the simplest use case. So, here's
> yet again another take:
>
> %%%%
> \version "2.19.83"
>
> #(begin
> (set-object-property! 'tempoStack 'translation-type? list?)
> (set-object-property! 'tempoStack 'translation-doc
> "A stack to keep track of previous tempi.")
> (set! all-translation-properties
> (cons 'tempoStack all-translation-properties)))
>
> pushTempo = #(define-music-function () ()
Hi Aaron,
why wrap it into a music-function?
Only advantage seems to avoid a toplevel-definiton. Is it really an advantage?
Same for popTempo.
Cheers,
Harm
> (define (pushTempoHelper ctx)
> (let ((tempoStack (ly:context-property ctx 'tempoStack '()))
> (tempo (ly:context-property ctx 'tempoWholesPerMinute #f)))
> (set! tempoStack (cons tempo tempoStack))
> (ly:context-set-property! ctx 'tempoStack tempoStack)))
> #{ \context Score \applyContext $pushTempoHelper #})
> popTempo = #(define-music-function () ()
> (define (popTempoHelper ctx)
> (let ((tempoStack (ly:context-property ctx 'tempoStack '())))
> (if (null? tempoStack)
> (ly:input-warning (*location*)
> "Unable to pop a tempo. Did you forget to \\pushTempo?")
> (let ((tempo (car tempoStack)))
> (set! tempoStack (cdr tempoStack))
> (ly:context-set-property! ctx 'tempoStack tempoStack)
> (if tempo
> (ly:context-set-property! ctx 'tempoWholesPerMinute tempo)
> (ly:context-unset-property ctx 'tempoWholesPerMinute))))))
> #{ \context Score \applyContext $popTempoHelper #})
>
> \score {
> {
> \markLengthOn
> \tempo "I. Default"
> { b'4 4 4 4 } \bar "||"
> \pushTempo \tempo "II. Andante" 4=90
> { b'4 4 4 4 } \bar "||"
> \pushTempo \tempo "III. Allegro" 4=140
> { b'4 4 4 4 } \bar "||"
> \popTempo \tempo "Tempo II"
> { b'4 4 4 4 } \bar "||"
> \popTempo \tempo "Tempo I"
> { b'4 4 4 4 } \bar "||"
> \popTempo \tempo "Tempo 0?!"
> { b'4 4 4 4 } \bar "|."
> }
> \layout {} \midi {}
> }
> %%%%
>
> I tried to follow the pattern in define-context-properties.scm, but
> there is no documentation in LM, NR, Extending nor Internals on this
> topic. David, would you kindly let me know if I am overlooking
> something?
Well, I'm not David ;)
You omitted throwing the error about redefining existing ones...
Feels safer to have it, but that's just me.
Cheers,
Harm
