gistfile1.lisp

(defun rmap-over-list (function list)
  (when list
    (cons (funcall function (first list))
	  (rmap-over-list function (cdr list)))))

(defun imap-over-list (function list)
  (loop for value in list collect (funcall function value)))

(defun add7 (number) (+ number 7))

(defun sub7 (number) (- number 7))

(rmap-over-list #'add7 '(1 2 3 4 5))
(rmap-over-list #'sub7 '(1 2 3 4 5))

(imap-over-list #'add7 '(1 2 3 4 5))
(imap-over-list #'sub7 '(1 2 3 4 5))

(mapcar #'add7 '(1 2 3 4 5))
(mapcar #'sub7 '(1 2 3 4 5))

;;CL-USER> (rmap-over-list #'add7 '(1 2 3 4 5))
;;(8 9 10 11 12)
;;CL-USER> (imap-over-list #'add7 '(1 2 3 4 5))
;;(8 9 10 11 12)
;;CL-USER> (mapcar #'add7 '(1 2 3 4 5))
;;(8 9 10 11 12)
;;CL-USER> (mapcar #'sub7 '(1 2 3 4 5))
;;(-6 -5 -4 -3 -2)
;;CL-USER> (imap-over-list #'sub7 '(1 2 3 4 5))
;;(-6 -5 -4 -3 -2)
;;CL-USER> (rmap-over-list #'sub7 '(1 2 3 4 5))
;;(-6 -5 -4 -3 -2)
;;CL-USER>