Hi Urs,
define-macro is the method you are looking for:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.19.80"
% define macro
#(define-macro (define-my-custom-function code)
; all wrapping code is (semi)quoted
`(define-music-function
(mus)(ly:music?)
(let*
((elts (ly:music-property mus 'elements))
(cnt (length elts)))
,code ; insert (unquoted) user generated code
mus)))
% use macro
myFunc =
#(define-my-custom-function
(ly:message "The music has ~a elements" cnt))
% use function
{
\myFunc { c' e' }
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
HTH
Jan-Peter
Am 20.06.2018 um 11:18 schrieb Urs Liska:
I'm providing users with the option to configure some behaviour by
providing custom styling functions. These functions must have a certain
interface and will typically retrieve the same information from their
arguments. I would like to simplify this task by providing a "function
template". I think this may be achieved by macros or some other
syntactic extension mechansim, but I have no idea about how to go
forward with that.
This is what currently a user would have to do:
\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.
Is this possible? I would assume so, and I'd also would assume it's
quite easy - once you know what to look for.
Thanks
Urs
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