Prime Number in Lisp

Welcome to the Prime Number 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 primep (n)
 (cond
  ((= 0    n)          nil)
  ((= 1    n)          nil)
  ((= 2    n)          T)
   (t
   (loop
     :with root     = (isqrt n)
     :with divisors = (cons 2 (loop :for i :from 3 :to root :by 2 :collect i))
     :for d = (pop divisors)
     :if (zerop (mod n d))
     :do (return nil)
     :else :do (setf divisors (delete-if (lambda (x) (zerop (mod x d))) divisors))
     :while divisors
     :finally (return t)))))

(defun print-bool (b)
  (if b
    (write-line "prime")
    (write-line "composite")))

(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-bool (primep num))))

Prime Number in Lisp was written by:

• Parker Johansen
• Renato

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

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.