Re: predicate pitch-or-music? - getting rid of ##{ #} ?

[Thomas Morley]

2012/10/19 David Kastrup <address@hidden>:
> Thomas Morley <address@hidden> writes:
>
>> Hi,
>>
>> I tried to create a function which should accept a pitch _or_ music.
>> So I defined a pitch-or-music? predicate:
>>
>> #(define (pitch-or-music? x)
>>   (or (ly:pitch? x) (ly:music? x)))
>>
>> Calling the function, I have to use ##{ ... #} for music _and_ for a
>> single pitch.
>
> For music it should work anyhow.  The problem with pitch is that at the
> current point of time, ly:pitch? and ly:duration? are specially detected
> and specially treated, so even if you do
>
> #(define (mypitch? x) (ly:pitch? x))
>
> it will not work.  However, the predicate does not make all that much
> sense since every pitch is also valid music.  If we fastforward a few
> months until pitch? is no longer special-cased, the parser will see the
> pitch, try passing it as a pitch to the predicate and, since the
> predicate accepts, will _stick_ with this choice.  You could pass music
> by starting with { or so.
>
>> Calling the function for a single pitch doesn't work, if ##{ #} are
>> omitted, but it'll work if the predicate would be ly:pitch?
>> I don't understand this behaviour.
>
> Welcome to the club.  In 2.14, _all_ predicates were special-cased, and
> people did not understand it.  Pitches and durations are hardest to
> normalize.  I am on it, but then frequent other projects got in between.
>
>> Is there any possibility to get rid of ##{ #}, when calling the
>> function with a single pitch, but to keep the possibility to call it
>> with some music?
>
> Well, I have the xxx.xxx.xxx project pending (and it will be quite a bit
> of work to document as well), waiting for the 2.16.1 release (also my
> responsibility) in order to get the translation branches switched over
> from 2.16 to 2.17.  Then I can get back to the pitch and duration
> problem.  Several weeks.
>
> --
> David Kastrup

Hi David,

thanks for your reply, I'll wait. :)

Let me take the opportunity to express my deepest gratefulness for all
your work, not only for developing LilyPond, but for all the time you
spend on the user-list, answering/solving all kind of
questions/problems.


Best,
  Harm