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

/**************************************************************
 * This program generates 100 random variables following
 * a Poisson distribution with a parameter LAMBDA (that is,
 * LAMBDA events per unit time).
 *
 * To approximate this, we use an exponential distribution
 * with parameter LAMBDA to simulate the time intervals
 * between events.  The first event is scheduled to start
 * at time t = 0.
 *
 * Remember to compile with the -lm option.
 **************************************************************/

#define LAMBDA 0.7
#define N      100 

int main() {
	double event[N];
	int i;

	// Seed the random number generator by using the current
	// time.  If you want to recreate the random sequence,
	// use a fixed number other than 0.
	srand48( time( NULL ) );

	event[0] = 0.0;

	for ( i = 1; i < N; ++i ) {
		double x;

		// drand48() returns a random variable x in [0, 1)
		// To avoid taking the logarithm of 0 (NaN), we
		// calculate 1 - x which gives a random variable
		// in (0, 1].

		x = drand48();
		event[i] = event[i - 1] - log( 1 - x )/LAMBDA;
	}

	// This prints the values in the format
	// a, b, c, d, ..., x, y, z

	printf( "%f", event[0] );

	for ( i = 1; i < N; ++i ) {
		printf( ", %f", event[i] );
	}

	printf( "\n" );

	return 0;
}