group

gistfile1.rkt

#lang racket

;; splits the list into groups of n or less
;; nat (listof x) -> (listof (listof x))
(define (group n lst)
  (let loop ([lst lst] [acc '()])
    (if (null? lst)
        (reverse acc)
        (loop (drop-up-to lst n)
              (cons (take-up-to lst n) acc)))))

;; take n if available, otherwise all
;; (listof x) nat -> (listof x)
(define (take-up-to lst n)
  (if (< (length lst) n)
      lst
      (take lst n)))

;; drop n if available, otherwise none
;; (listof x) nat -> (listof x)
(define (drop-up-to lst n)
  (if (< (length lst) n)
      null
      (drop lst n)))