syntax helper for ly:music-property

[Nicolas Sceaux]

Hello,

Manipulating music expressions makes me impatient and lazy (don't know
about hubris). Here is a little utility which can be used as a
shortcut for ly:music-property : 

(define (read-dotted-expression chr port)
  (define (gen-music-prop-expr music prop . rest)
    (if (null? rest)
        `(ly:music-property ,music ',prop)
        (apply gen-music-prop-expr `(ly:music-property ,music ',prop) rest)))
  (let ((tokens (map string->symbol (string-split (symbol->string (read port)) 
#\.))))
    (apply gen-music-prop-expr tokens)))

(read-hash-extend #\@ read-dotted-expression)

It has some limitations: the symbols (music variable and property
names) must not have dots. Example of use:

guile> (define toto (car (ly:music-property #{ \override TextScript #'padding = 
#4 #} 'elements)))
guile> (mus:display toto)
(make-music 'ContextSpeccedMusic
  'property-operations ()
  'context-type 'Bottom
  'element (make-music 'OverrideProperty
               'pop-first #t
               'grob-property 'padding
               'grob-value 4
               'symbol 'TextScript))
guile> (mus:display address@hidden)
(make-music 'OverrideProperty
  'pop-first #t
  'grob-property 'padding
  'grob-value 4
  'symbol 'TextScript)
guile> (set! address@hidden 'extra-offset)
guile> (set! address@hidden (cons 1 2))
guile> (mus:display toto)
(make-music 'ContextSpeccedMusic
  'property-operations ()
  'context-type 'Bottom
  'element (make-music 'OverrideProperty
               'pop-first #t
               'grob-property 'extra-offset
               'grob-value (1 . 2)
               'symbol 'TextScript))
guile> (let ((override-property address@hidden))
  (set! address@hidden (cons 2 3)))
guile> (mus:display toto)
(make-music 'ContextSpeccedMusic
  'property-operations ()
  'context-type 'Bottom
  'element (make-music 'OverrideProperty
               'pop-first #t
               'grob-property 'extra-offset
               'grob-value (2 . 3)
               'symbol 'TextScript))
guile> 

nicolas