Re: Add an arbitrary music property

[Urs Liska]

Am 09.06.2018 um 14:21 schrieb Thomas Morley:
2018-06-08 21:26 GMT+02:00 Urs Liska <li...@openlilylib.org>:
Hi,

is there anything wrong with adding an arbitrary property to a
SequentialMusic like that:

\version "2.19.80"

someNote = { c' d' }

#(set! (ly:music-property someNote 'foo) "bar")

\displayMusic \someNote

?

The following is a MWE of a new extension I plan for scholarLY, and it seems
to work. \sic and \corr add such an arbitrary property to the music while
\choice uses that to retrieve one element out of a list of music
expressions.

\version "2.19.80"

#(define selection 'sic)
%#(define selection 'corr)

choice =
#(define-music-function (mus) (ly:music?)
    (let*
     ((elts
       (map
        (lambda (expr)
          (cons (ly:music-property expr 'choiceType) expr))
        (ly:music-property mus 'elements)))
       (chosen (assq-ref elts selection)))
     (if chosen
         chosen
         (first (ly:music-property mus 'elements)))))

tagMusic =
#(define-void-function (mus tag)(ly:music? symbol?)
    (set! (ly:music-property mus 'choiceType) tag))

sic =
#(define-music-function (mus) (ly:music?)
    (tagMusic mus 'sic)
    mus)

corr =
#(define-music-function (mus) (ly:music?)
    (tagMusic mus 'corr)
    mus)

\relative {
   c' c g' g |
   \choice {
     \sic { g }
     \corr { a }
   }
   a g2
}

But before proceeding I'd like to know if I'm not doing anything stupid by
injecting two list items like so:

(make-music

'SequentialMusic

'choiceType

'sic

'elements

(list (make-music

'NoteEvent

'pitch

(ly:make-pitch -1 4)

'duration

(ly:make-duration 2))))


Urs

Hi Urs,

this looks more or less the same as with custom-grob-properties.
Probably a bit safer, if you register them in `all-music-properties'
calling `music-property-description'.

Look at
http://lsr.di.unimi.it/LSR/Item?id=977
for an example

Cheers,
   Harm

You mean I should use set-object-property! rather than set! 
(ly:music-property .... ?
Does that also work with whole music expressions (vs. single grobs)? I 
want to "tag" the whole (sequential) music expression.

Best
Urs

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