asb: head /dev/brain > /dev/www

My home, musings, and wanderings on the world wide web.

99 LISP problems: Problem #17

Solution to the 99 LISP Problems #17

I solved #18 first and am using the solution to that to do this.

1
2
3
4
5
6
7
8
9
10
11
12
13
14

(defun slice (alist from to)
  (let ((i 1))
    (mapcan
      (lambda (x)
        (let ((j i))
          (setf i (1+ i))
          (if (and (>= j from) (<= j to))
            (list x) nil)))
      alist)))

(defun split (alist n)
  (list
    (slice alist 1 n)
    (slice alist (1+ n) (length alist))))

Lisp dialect: Steel Bank Common Lisp