From Newsgroup: comp.lang.lisp

than version you've wrote in CL. i would write it like this:

(defun factorial (n)
(loop with p = 1
for i from 1 to n
do (setf p (* p i))
finally (return p)))

IMHO that's cleaner. or if i absolutely must use recursion:

It's shorter when one uses a Lispy language instead of CL.

(define (factorial n)
(do ((i n (- i 1))
(r 1 (* r i)))
((< i 1) r)))

(factorial 5)
===>
120

(factorial -2)
===>
1
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