+(defpackage #:cl-nl.random
+ (:use :common-lisp)
+ (:export :set-seed :next-int :next-double))
+
+(in-package #:cl-nl.random)
+
+; This is a wrapper around the very nice mersenne twister mt19937 to match
+; NetLogo's implementation that tries to match how java.util.Random works
+
+(defun set-seed (n)
+ (setf mt19937:*random-state* (mt19937::make-random-object :state (mt19937:init-random-state n))))
+
+(defun next-int (n)
+ (rem (ash (mt19937:random-chunk mt19937:*random-state*) -1) n))
+
+(defun next-double (&optional (n 1d0))
+ (let
+ ((y (mt19937:random-chunk mt19937:*random-state*))
+ (z (mt19937:random-chunk mt19937:*random-state*)))
+ (*
+ (/
+ (+ (ash (ash y -6) 27) (ash z -5))
+ (coerce (ash 1 53) 'double-float))
+ n)))