On 2019-11-18 1:44 pm, Thomas Morley wrote:
why wrap it into a music-function?
Only advantage seems to avoid a toplevel-definiton. Is it really an
advantage?
It's an advantage for \popTempo as it means *location* is properly set
to the use of \popTempo and not its definition.
Mind you, \pushTempo need not be a function.
You omitted throwing the error about redefining existing ones...
Feels safer to have it, but that's just me.
Certainly, there should be safer handling. How's this:
%%%%
\version "2.19.83"
registerContextProperty = #(define-void-function
(symbol type? description)
(symbol? procedure? string?)
(if (not (equal? #f (object-property symbol 'translation-doc)))
(ly:error (_ "symbol ~S redefined") symbol))
(set-object-property! symbol 'translation-type? type?)
(set-object-property! symbol 'translation-doc description)
(set! all-translation-properties (cons symbol
all-translation-properties))
symbol)
#(define (false-or-moment? x) (or (equal? #f x) (ly:moment? x)))
#(define (false-or-moment-list? x) (and (list? x) (every
false-or-moment? x)))
\registerContextProperty tempoStack #false-or-moment-list?
"A stack to keep track of tempi."
pushTempo = { \context Score \applyContext #(lambda (ctx)
(let ((tempoStack (ly:context-property ctx 'tempoStack))
(tempo (ly:context-property ctx 'tempoWholesPerMinute #f)))
(ly:context-set-property! ctx 'tempoStack (cons tempo tempoStack))))
}
popTempo = #(define-music-function () ()
#{ \context Score \applyContext #(lambda (ctx)
(let ((tempoStack (ly:context-property ctx 'tempoStack)))
(if (null? tempoStack)
(ly:input-warning (*location*)
(_ "Tempo stack is empty. Did you forget to \\pushTempo?"))
(let ((tempo (car tempoStack)))
(ly:context-set-property! ctx 'tempoStack (cdr tempoStack))
(if (equal? #f tempo)
(ly:context-unset-property ctx 'tempoWholesPerMinute)
(ly:context-set-property! ctx 'tempoWholesPerMinute
tempo)))))) #})
\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 "|."
}
\layout {} \midi {}
}
%%%%
-- Aaron Hill
