/*--------------------------------------------------------------*/
/*   Program xrand (Chapter 11)                                 */
/*                                                              */
/*   This program is written to test the rand ()                */
/*   random number generator (See Chapter 11:Monte Carlo).      */
/*                                                              */

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

main()
{
  FILE *out;
  int i;
  double rand_float(double a, double b);
  double random, random_new;
  unsigned int seed=1;
  srand(seed);
  out=fopen("output_rand.dat","w");
  random=rand_float(0.0,1.0);

  for (i=1; i<=5000000000; i++)
    {
      random_new=rand_float(0.0,1.0);      
      if ((random <= 0.001) && (random_new <= 0.001)) {
	fprintf(out, "%e %e \n", random, random_new);
      }
      random=random_new;
    }
  fclose(out);
  /*                                                             */
  /* Now view the plot in output_rand.dat using Matlab.          */
  /*                                                             */
  return EXIT_SUCCESS;
}

/* this function generates a random double value between a and b */

double rand_float(double a, double b)
{
  return ((double) rand()/RAND_MAX)*(b-a)+a;
}
/*---------------------------------------------------------------*/