group-into and take

[samebchase]

Please consider these utilities that stassats wrote for inclusion. If you'd like these included, I'll make a proper pull request

(defun group-into (n list)
  (loop while list collect
        (loop repeat n while list
              collect (pop list))))

(defun take (n list)
  (loop repeat n for elt in list
        collect elt))

[stylewarning]

@samebchase There are more generalized versions of group-into and take that work on any kind of sequence. They're called qtl:subdivide and qtl:take respectively. See

• subdivide: http://quickutil.org/list?q=subdivide

  CL-USER> (qtl:subdivide #(a b c d e f) 2) (#(A B) #(C D) #(E F)) CL-USER> (qtl:subdivide '(a b c d e f) 2) ((A B) (C D) (E F))

• take: http://quickutil.org/list?q=take

  CL-USER> (qtl:take 3 '(a b c d e f)) (A B C) CL-USER> (qtl:take 3 #(a b c d e f))

  (A B C)