Park-Miller Minimum Standard Random Number Generator in Common Lisp

randomgen.lisp

(defun get-msrn-naive (x n)
	(let ((a 16807) (m 2147483647))
	(mod (* 
		  a
		 ;Multiply either by x or recursive call
		  (if (eq n 1)
		   x
		   (get-msrn-naive x (- n 1))))
	 m)))

(defun get-next-msrn (x)
	(let (
			(a 16807) 
			(m 2147483647)
			(q 127773)
			(r 2836)			
		 )
		(let
			(
				(result 
						(-
							(* a (mod x q))
							(* r (floor (/ x q)))
						)
				)
			)
			(if 
				(<= result 0)
				(+ result m)
				result
			 )
		)
	)
)
			
(defun get-msrn-schrage (x n)
	(if (eq n 1)
	 (get-next-msrn x)
	 (get-msrn-schrage (get-next-msrn x) (- n 1)))