#ifndef CA_UWATERLOO_ALUMNI_DWHARDER_CENTRAL_LIMIT_THEOREM
#define CA_UWATERLOO_ALUMNI_DWHARDER_CENTRAL_LIMIT_THEOREM

// Author:  Douglas Wilhelm Harder
// Copyright (c) 2012 by Douglas Wilhelm Harder.  All rights reserved.

// On successive calls to randn_clt(), this function returns
// a random standard normal value (a mean of zero and standard deviation of one).
//
// It generates twelve uniformly distributed values on the interval [0, 1], adds them, and subtracts
// six giving a reasonably close approximation to a standard normal.

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

double randn_clt() {
	double u = 0.0;

	int i;

	for ( i = 0; i < 12; ++i ) {
		u += drand48();
	}

	return u - 6.0;
}

#endif