Re: Help with music-function generating music

[Urs Liska]

Am 26.03.2014 22:53, schrieb Paul Morris:
> Hi Urs,
>
> I had a chance to work on the iteration part.  This one accepts a note as an
> argument which is a better approach, following the examples here:
>
> http://lilypond.org/doc/v2.18/Documentation/extending/doubling-a-note-with-slurs-_0028example_0029
> http://lilypond.org/doc/v2.18/Documentation/extending/adding-articulation-to-notes-_0028example_0029
>
> The iteration is done with a "named let" (which is just one option) see
> these docs for Guile and Scheme:
>
> https://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/Iteration.html
> https://www.gnu.org/software/guile/manual/guile.html#while-do
>
> Cheers,
> -Paul

Thank you very much. Such concrete examples are incredibly helpful.
I had already started to fiddle around with yesterday's example and was 
trying to achieve something similar to your new example.  But I didn't 
come to an end (Scheme gives you soo many opportunities to do something 
wrong ...), so I can now investigate your example with some pre-knowledge.

I hope (but honestly doubt) to find the time to pour these experiences 
in a tutorial (series), as I think that this step is a hard one for many 
people, and the respective documentation is really hard to grasp.

Urs

> \version "2.18.0"
>
> myNotes =
> #(define-music-function (parser location note num)
>     (ly:music? number?)
>     "Returns a series of notes. @var{note} is repeated @var{num} times.
>     @var{note} is supposed to be a single note."
>     ;; iteration by named let
>     (let loop
>       ;; two variables/arguments,
>       ;; i is the iteration count
>       ;; nts is the list of notes we're building
>       ((i 0)
>        (nts '()))
>
>       ;; conditional
>       (cond
>        ((< i num)
>         ;; call the loop again with modified values for i and nts
>         (loop
>          (+ i 1)
>          (append nts (list (ly:music-deep-copy note)))))
>
>        (else
>         ;; when done, return the music
>         (make-music 'SequentialMusic 'elements nts)))))
>
> {
>    \myNotes g'16 #8
> }
>
>
>
> --
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> http://lilypond.1069038.n5.nabble.com/Help-with-music-function-generating-music-tp160833p160867.html
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