Re: simple scheme function #{ $note #}

[David Kastrup]

Aaron Hill <address@hidden> writes:

> On 2018-05-11 08:46, David Kastrup wrote:
>> Aaron Hill <address@hidden> writes:
>>
>>> On 2018-05-11 06:53, Gianmaria Lari wrote:
>>>> Sorry to bother with a simple question. Why this does not work?
>>>>
>>>> \version "2.19.81"
>>>> pit = #(define-music-function
>>>>         (p) (ly:pitch?)
>>>>         #{ $p #}
>>>>         )
>>>> { \pit c' }
>>>
>>> The result is "error: music function cannot return c'".  It appears
>>> that a simple pitch by itself is not enough to qualify as music.
>>
>> It's desirable to be able to enter pitches as #{ c' #} and similar.
>> Add
>> a duration to get a music expression.
>
> But can you return an incomplete music expression?

There is no "incomplete music expression".  #{ ... #} is used for
converting a whole slew of different expression types from LilyPond
syntax to Scheme: pitches, durations, markups, music, numbers with
dimension and other stuff.  A pitch is not an "incomplete music
expression".  It's a type of its own.

-- 
David Kastrup