Function: GROUP

Documentation

groups every n elements together into new sublists. e.g. (group '(1 a 2 b) 2) -> ((1 a) (2 b))

Source

(defun group (source n)
  "groups every n elements together into new sublists.
   e.g. (group '(1 a 2 b) 2) -> ((1 a) (2 b))"
  (when (zerop n) (error "zero length"))
  (labels ((rec (source acc)
	     (let ((rest (nthcdr n source)))
	       (if (consp rest)
		   (rec rest (cons (subseq source 0 n) acc))
		   (nreverse (cons source acc))))))
    (if source
	(rec source nil)
	nil)))