On Sun, Jan 15, 2012 at 5:27 AM, Morten Jagd Christensen
<address@hidden> wrote:
here is a working lisp
function
(defun mylist (l1 l2 n1)
(cond ((null l1) l2)
( t (mylist (cdr l1)
(append l2 (list (append '(place-fret) (car
l1) (list (1+ (mod (list-length l2)n1))))))
n1)
)))
so if l1 is ((5 3) (5 2) (5 1) (4 1) (4 3) (4 5) (3 1) (3 3) (2 1)
(2 5))
(mylist l4 '() 7) becomes (the number is the number of tones in the
relevant scale)
((PLACE-FRET 5 3 1) (PLACE-FRET 5 2 2) (PLACE-FRET 5 1 3)
(PLACE-FRET 4 1 4)
(PLACE-FRET 4 3 5) (PLACE-FRET 4 5 6) (PLACE-FRET 3 1 7)
(PLACE-FRET 3 3 1)
(PLACE-FRET 2 1 2) (PLACE-FRET 2 5 3))
Which is exactly what I want.
However am not having success integrating this in your example
because #1 I
fail to translate my (defun) based example to a working lambda
representation
and #2 I need to pass more than one argument to the lambda function.
First of all, I should say that I'm an amateur at all of this, but I'll answer your questions as best as I can.
Scheme is a dialect of Lisp (and Guile is a dialect of Scheme), so you should definitely consult the sources mentioned here:
The Guile Reference Manual is _extremely_ helpful, as is examining the code in .ly and .scm files in the Lilypond distribution.
In making your example work, I had to make a number of changes to the names of procedures (for example, defun --> define, list-length --> length) because these aren't defined in Guile.
In the attached file, I've shown you how you can express your function in several very similar ways, and call it from the custom markup command. One of the variants of "mylist" uses lambda, the others one of the alternatives described here:
Do you think this is a useful approach?
Well, if you enjoy programming and learning Scheme, why not! As for practicality: if this will save you (and others) time, make creating a score less tedious, then it is certainly useful.
HTH,
David
morten01.ly