/*** This is a portable random number generator whose origins are

 *** unknown.  As far as can be told, this is public domain software.

/*** portable random number generator */

/*** Note that every variable used here must have at least 31 bits

 *** of precision, exclusive of sign.  Long integers should be enough.

 *** The generator is the congruential:  i = 7**5 * i mod (2^31-1).

 ***/

#define MULTIPLIER 16807

#define MODULUS    2147483647

static long saved_seed;

/*** set_random - initialize constants and seed */

void set_random(seed)

long seed;

{

  saved_seed = seed;

}

/*** ng_random - generate a random integer in the interval [a,b] (b >= a >= 0) */

long ng_random(a, b)

long a, b;

{

  register long hi, lo;

  hi = MULTIPLIER * (saved_seed >> 16);

  lo = MULTIPLIER * (saved_seed & 0xffff);

  hi += (lo>>16);

  lo &= 0xffff;

  lo += (hi>>15);

  hi &= 0x7fff;

  lo -= MODULUS;

  if ((saved_seed = (hi<<16) + lo) < 0)

    saved_seed += MODULUS;

  if (b <= a)

    return b;

  return a + saved_seed % (b - a + 1);

}