// Include file:  random.h
// Date:  2 July 1995
// Programmer:  F. D. Lewis
//
// Generate random numbers by the linear congruential method
//
// NOTE:  to use these routines, you must declare a variable such as:
//
// long int x;
//
// to hold the random number

#include

long int seed()
// post: return four digit number based upon time
{
  // declarations
  long int t, z;
  int x, x1, x2, x3, x4;
  long * s;

  // instructions
  t = time(s);
  x = t - (t/10000)*10000;
  x1 = x/1000;
  x = x - x1*1000;
  x2 = x/100;
  x = x - x2*100;
  x3 = x/10;
  x4 = x - x3*10;
  z = x3*1000 + x1*100 + x4*10 + x2;
  return z;
} // end seed

long int random(long int x)
// pre:  x > 0
// post: return next psuedo-random number by linear congruential method
{
  // declaration
  long int z;

  // instructions
  z = (25173*x + 13849) % 65536;
  return z;
} // end random

long int rnd(long int& x, long int range)
// pre:  x and range > 0
// post: x = next pseudo-random number in sequence
//           return next pseudo-random number in 1, ..., range
//
// PROOF:  0 <=          x          <  65536
//         0 <=       x/65536       <  1
//         0 <=   (x/65536)*range   <  range
//         0 <=   (x/65536)*range   <= range - 1
//         1 <= (x/65536)*range + 1 <= range
{
  // declaration
  long int y;

  // instructions
  x = random(x);
  y = (x*(range)/65536) + 1;
  return y;
} // end rnd