Factorial in Lisp

Welcome to the Factorial in Lisp page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

(defun factorial (n)
  (if (= n 0)
      1
      (* n (factorial (- n 1))) ) )

(defun maybe-pos-int (input)
  (cond
    ((null input) nil)
    ((string= input "") nil)
    ((every #'digit-char-p input) (parse-integer input))
    (t nil)))

(defparameter num (maybe-pos-int (cadr *posix-argv*)))
(cond
  ((null num) (write-line "Usage: please input a non-negative integer"))
  (t (print (factorial num)))
)

Factorial in Lisp was written by:

• Parker Johansen
• Renato

If you see anything you'd like to change or update, please consider contributing.

Note: The solution shown above is the current solution in the Sample Programs repository as of Oct 11 2020 06:48:59. The solution was first committed on Oct 01 2020 17:40:32. As a result, documentation below may be outdated.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

No 'How to Run the Solution' section available. Please consider contributing.