Re: Catch possible non-rhythmic-event music expressions

[Urs Liska]

Am 25.06.2018 um 14:30 schrieb Urs Liska:
> ..
>
> 1)
> Determining Staff.Clef is obviously not correct since there are other 
> music-wrapper-music types around. How can I reliably determine if a 
> music expression (which has already been determined not to be 
> sequential and not to be rhythmic) consists of a \clef assignment?

A clef assignment looks like this if inspected:

#(make-music
  'ContextSpeccedMusic
  'context-type
  'Staff
  'element
  (make-music
    'SequentialMusic
    'elements
    (list (make-music
            'PropertySet
            'value
            "clefs.F"
            'symbol
            'clefGlyph)
          (make-music
            'PropertySet
            'value
            6
            'symbol
            'middleCClefPosition)
          (make-music
            'PropertySet
            'value
            2
            'symbol
            'clefPosition)
          (make-music
            'PropertySet
            'value
            0
            'symbol
            'clefTransposition)
          (make-music
            'PropertySet
            'value
            'default
            'symbol
            'clefTranspositionStyle)
          (make-music
            'ApplyContext
            'procedure
            ly:set-middle-C!))))

Is the order of these inner music expressions guaranteed, i.e. can I 
test if the first of 'elements has 'symbol 'clefGlyph?
Would that be a sufficient check if a music expression is a clef 
assignement.