Hi David, Am Sa., 20. Apr. 2019 um 03:52 Uhr schrieb David Pirotte <da...@altosw.be>: > > Hi again, > > Replying twice to myself in a row, how is that :) > A little tired I guess ... > > > > Note that the above will only work if the last 'blue item' has 3 > > > elements, you'd > > > need to adapt for other use case (which also 'speak' in favor of the > > > cleaner > > > approach. > > > Actually, I didn't like what I wrote, here is a slightly better code: > > And here is a corrected version: the code in the mail I'm answering now would > not > return proper (expected) results for any other operator then car ... this one > will > let you really walk :) > > (use-modules (ice-9 match)) > > (define blue > (cons '(a b c) (cons '(1 2 3) '(x y z)))) > > (define fox > (cons '(a b c) (cons '(1 2 3) (cons '(x y z) '()))))
Thanks pointing me to this possibility, in my use-case I then could do: (define (p) (cons '(1 2 3) '(4 5 6))) (define l1 '(a b c)) (define l2 '(x y z)) (cons* l1 l2 (car (p)) (cdr (p)) '()) => ((a b c) (x y z) (1 2 3) (4 5 6)) > > (define (blue-walk blue proc) > (let loop ((blue blue) > (result '())) > (match blue > ((a . rest) > (if (pair? a) > (loop rest > (cons (proc a) result)) > (reverse! (cons (proc (cons a rest)) > result)))) > (() > (reverse! result))))) > > scheme@(guile-user)> (load "blue.scm") > ;;; note: source file /usr/alto/projects/guile/blue.scm > ;;; ... > scheme@(guile-user)> (blue-walk blue car) > $2 = (a 1 x) > scheme@(guile-user)> (blue-walk fox car) > $3 = (a 1 x) > scheme@(guile-user)> (blue-walk blue cdr) > $4 = ((b c) (2 3) (y z)) > scheme@(guile-user)> (blue-walk fox cdr) > $5 = ((b c) (2 3) (y z)) My guile-knowledge is mostly limited to what LilyPond needs. As far as I can tell (ice-9 match) isn't used in our source. So I need to study your `blue-walk´ from scratch. Thanks a lot, Harm _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
