;;; $Id: make-all-positive.scm,v 1.1 2004/01/29 04:53:50 leavens Exp $
;;; AUTHOR: Dalei Li and Gary T. Leavens

(deftype make-all-positive (-> ((list-of number)) (list-of number)))
(define make-all-positive
  (lambda (lon)
    ;; ENSURES: Result is like lon but with all its negative elements
    ;; changed to their absolute value.
    (if (null? lon)
	'()
	(cons (abs (car lon)) (make-all-positive (cdr lon))))))