My implementation for factorial in Lisp. This is a response to a post found here.

Also, it is tail recursive.

(defun fact (n)
       (labels ((rec (n acc)
           (if (< n 2)
           acc
           (rec (1- n ) (* acc n)))))
         (rec n 1)))

ps: Factorial in Haskell seems easier though

fact 0 = 1
fact n = n * fact (n-1)

or

fact = product . enumFromTo 1

Edit: fixed the (< n 1) bug