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

int iran ( int a, int b, int *seed )

//
//  Purpose:
//
//    IRAN returns a scaled pseudorandom integer between A and B.
//
//  Parameters:
//
//    Input, int A, B, the limits of the interval.
//
//    Input/output, int *SEED, the "seed" value, which should NOT be 0.
//    On output, SEED has been updated.
//
//    Output, int IRAN, a number between A and B.
//
{
  int i4_huge = 2147483647;
  int k;
  float value;
//
//  Check SEED.
//
  if ( *seed == 0 )
  {
    printf ( "\n" );
    printf ( "IRAN - Fatal error!\n" );
    printf ( "  Input value of SEED = 0.\n" );
    exit ( 1 );
  }
//
//  Update SEED.
//
  k = *seed / 127773;

  *seed = 16807 * ( *seed - k * 127773 ) - k * 2836;

  if ( *seed < 0 )
  {
    *seed = *seed + i4_huge;
  }
//
//  Use the MOD function.
//
  if ( b < a )
  {
    value = b + ( *seed % ( a - b ) );
  }
  else if ( b == a )
  {
    value = a;
  }
  else
  {
    value = a + ( *seed % ( b - a ) );
  }

  return value;
}