/* --------------------------------------------------------------------------  
// Figure 7.29: Generating random numbers. 
// -------------------------------------------------------------------------- 
//      Generate and print a series of pseudo-random numbers.  Count and print 
//      the number of trials that were equal to 0.  Also print the number that 
//      was expected, based on probability        
*/
#include "tools.h"  

#define HOW_MANY 500    /* Generate HOW_MANY random numbers */
#define NCOL 10         /* Number of columns in which to print the output. */
#define MAX 100         /* Upper limit on size of random numbers generated. */

void main( void )                                                                                                              
{  
    long num;       /* a randomly-generated integer   */  
    short select;   /* input: the divisor to test     */  
    short n;        /* # of random numbers generated  */ 
    int count;      /* # of zeros generated.     */

    banner();
    srand( (unsigned) time( NULL ) );   /* seed random number generator */

    printf( " Generate and print %i random numbers in the range 0..n-1.\n"
            " Please choose an n, between 2 and %i: ", HOW_MANY, MAX );
    scanf( "%hi", &select );
    if (select < 2 || select > MAX ) fatal( " Number is out of range." );

    /* Generate random numbers and test for zeros. --------------------- */
    count = 0;                      /* Count zeros generated.            */
    for (n = 0; n < HOW_MANY;){     /* Generate HOW_MANY random numbers. */
        num = rand();               /* Generate a random long integer.   */
        num %= select;              /* Scale to range 0..select-1.       */
        
        ++n;                        /* Count the trials and ...          */
        printf( "%5li", num);       /* print all numbers generated and.. */
        if (n % NCOL == 0) puts( "" );   /* end line every NCOL outputs. */

        if (num == 0) ++count;              /* Count the zeros.          */
    }

    if (n % NCOL != 0) printf( "\n" );      /* End last line of output.  */

    printf( "\n %5i   zeros were generated.", count );
    printf( "\n %7.1f are expected on average.\n", HOW_MANY/(float)select );
    bye();            
}