On Aug 4, 2016, at 3:10 PM, David Storrs <david.sto...@gmail.com> wrote:
> I'd like to be able to iterate over a list N elements at a time -- e.g., grab
> elements 1 and 2, do something with them, grab 3 and 4, etc.
Your technique seems fine. You could use `split-at` if you wanted to save a
list operation, otherwise it's the standard recursion pattern:
#lang racket
(define data '(("foo") ("bar") ("baz") ("jaz") ("quux") ("glug")))
(define (step-by-n func xs [num 2])
(if (null? xs)
null
(let-values ([(head tail) (split-at xs num)])
(cons (func head) (step-by-n func tail num)))))
(step-by-n (λ (xx) (apply hash (map car xx))) data)
(step-by-n (λ (xxx) (hash (caar xxx) (map car (cdr xxx)))) data 3)
I wrote a utility function called `slice-at` to handle this problem. [1]
[1]
http://docs.racket-lang.org/sugar/#%28def._%28%28lib._sugar%2Flist..rkt%29._slice-at%29%29
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