[2010-01] some project euler stuff in sbcl

euler003.lisp

#!/usr/bin/env sbclx
; I actually might want to use a function? Goodie!

(defun isPrime (n) ; a crude brute-force prime check
	(do
		(
			(limit (ceiling (sqrt n))) ; maximum requred to determine if it is prime
			(i 2 (1+ i))
		)
		
		((> i limit))
		
		(if
			(=
				0
				(mod n i)
			)
			
			(return-from isPrime nil)
		)
	)
	
	(return-from isPrime T)
)

(let
	(
		(n 600851475143) ; the number we're factoring -  for real
	)
	
	(do
		(
			(factor 1 (1+ factor))
			(limit (ceiling (/ n 2)))
		)
		
		((> factor limit))
		
		(if
			(and
				(= 0 (mod n factor)) ; it's a factor
				(isPrime (/ n factor))
			)
			
			(progn
				(print (/ n factor))
				(return)
			)
		)
	)
)