/*** 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);

 }