Re: procedures with setters: patches

[Nicolas Sceaux]

Sat, 28 Feb 2004 11:53:15 +0100, Han-Wen a dit : 

 > I'm ambivalent. The danger is that the number of functions to create
 > and manipulate data structures explodes, and becomes harder to
 > learn. We have to find a balance between having a small "interface"
 > and an interface that is ultra-ergonomic to use. For the above case, I
 > think make-music-by-name-and-props and is useful, althouh I oppose of
 > the name. Why not have

 >       make-music-by-name

 > take an optional alist or list  of init values?

Of course, once there is a music maker that can have properties as
arguments, former make-music-by-name has no use.

By the way, why not `make-music'? I cannot find another
make-music-by-something in the sources. It would look like
(make-instance 'class-name ...options...) ==> instance of class-name.
[that's the way an object is created in CLOS]

(define-public (make-music name . music-properties)
  "Create a music object of given name, and set its properties
according to `music-properties', a list of alterning property symbols
and values. E.g:
  (make-music 'OverrideProperty 
              'symbol 'Stem
              'grob-property 'thickness
              'grob-value (* 2 1.5))"
  (if (not (symbol? name))
      (error (format "Not a symbol: ~a" name)))
  (let ((props (hashq-ref music-name-to-property-table name '())))
    (if (not (pair? props))
        (error "Can not find music object" name))
    (let ((m (ly:make-bare-music (cdr (assoc 'internal-class-name props)) 
props)))
      (define (set-props mus-props)
        (if (and (not (null? mus-props))
                 (not (null? (cdr mus-props))))
            (begin
              (set! (ly:music-property m (car mus-props)) (cadr mus-props))
              (set-props (cddr mus-props)))))
      (set-props music-properties)
      m)))

(make-music 'OverrideProperty 
            'symbol 'Stem
            'grob-property 'thickness
            'grob-value (* 2 1.5)
            'pop-first #t))
==>
<OverrideProperty :pop-first #t
                  :grob-value 3.0
                  :grob-property thickness
                  :symbol Stem>

If that's OK, I may build some patches.

nicolas