#include <math.h>
#include <stdlib.h>
#include "genran.h"

double ran_normal()
{ 
	static int iset = 0; 
	static double gset; 
	double fac, rsq, v1, v2; 
	if (iset == 0) {
		do { 
			v1 = 2.0 * ran_uniform() - 1.0;
			v2 = 2.0 * ran_uniform() - 1.0; 
			rsq = v1 * v1 + v2 * v2;
		} while (rsq >= 1.0 || rsq == 0.0);
		fac = sqrt(-2.0 * log(rsq) / rsq); 
		gset = v1 * fac; 
		iset = 1;
		return v2 * fac;
	} else {
		iset = 0;
		return gset;
	}
}