Re: [racket-users] [racket users] list question
> On Feb 25, 2021, at 10:12 AM, Norman Gray wrote: > > > I think this is called 'zip', or a convolution [1]. The variant you describe > is (effectively) with circular lists, but seems to be the same principle. > > ...and I see that, with that name in hand, SRFI/1 does indeed have a zip > procedure, which works with circular lists. Thanks, Norman! Looks like “zip” is the right name for the general process, and now that I can browse the docs for it there seems to be several flavors in various library modules, depending on creator intention. I’ve generalized mine a bit to fit intention and some of theirs. (define/contract (zip #:length (len max) . lsts) (->* () (#:length (or/c procedure? natural?)) #:rest (listof list?) (listof list?)) (define (loop cnt (acc empty)) (cond [(zero? cnt) acc] [else (define n (sub1 cnt)) (loop n (cons (map (λ (lst) (list-ref lst (modulo n (length lst lsts) acc))])) (loop (cond [(procedure? len) (apply len (map length lsts))] [else len]))) Kevin -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/650A2841-B8F8-4802-9116-7AB9876EA901%40gmail.com.
Re: [racket-users] [racket users] list question
Kevin, hello. On 25 Feb 2021, at 17:07, Kevin Forchione wrote: As you can see each element of the sublist corresponds to the list-ref of the modulo n (length sublist) as n proceeds from 0 to some maximum value. I’ve created a function that does exactly this, but … I’ve no idea what this process might be called. As they say, the naming of cats, and all that.Does this sort of mapping have a formal name? I think this is called 'zip', or a convolution [1]. The variant you describe is (effectively) with circular lists, but seems to be the same principle. ...and I see that, with that name in hand, SRFI/1 does indeed have a zip procedure, which works with circular lists. [1] https://en.wikipedia.org/wiki/Convolution_(computer_science) Best wishes, Norman -- Norman Gray : https://nxg.me.uk SUPA School of Physics and Astronomy, University of Glasgow, UK -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/7F1C9263-EA6A-4B5F-A0CF-15A5725E1EAE%40glasgow.ac.uk.
