Urs Liska <address@hidden> writes:
\version "2.19.80"
myFunc =
#(define-music-function (mus)(ly:music?)
(let*
((elts (ly:music-property mus 'elements))
(cnt (length elts)))
(ly:message "The music has ~a elements" cnt)
mus))
{
\myFunc { c' e' }
}
Create a music function with one ly:music? argument and extract some
information from the music expression (of course this is just an
example, in the real case it's a custom object attached to the music).
What I would like to have is what define-music-function does here but
with a pre-set argument list and essentially the let* bindings
transparently done so that something like this is possible:
userFunc =
#(define-my-custom-function
(ly:message "The music has ~a elements" cnt))
where one ly:music? argument is implicitly expected and the bindings
like 'cnt' have already been prepared.
#(define-macro (define-my-custom-function . body)
`(define-music-function (mus) (ly:music?)
(let*
((elts (ly:music-property mus 'elements))
(cnt (length elts)))
,@body
mus)))
That's what one would call a pretty unhygienic macro since it messes
with a number of symbols/identifiers not specified by the user.