#ifdef ZX81_RNG /* * This is my favorite tiny RNG, If you had a ZX81 you may recognise it :-) * (RdeBath) */ #include <stdlib.h> #define MAXINT (((unsigned)-1)>>1) static unsigned int sseed = 0; int rand() { return (sseed = (((sseed + 1L) * 75L) % 65537L) - 1) & MAXINT; } void srand(seed) unsigned int seed; { sseed = seed; } #else /* * This generator is a combination of three linear congruential generators * with periods or 2^15-405, 2^15-1041 and 2^15-1111. It has a period that * is the product of these three numbers. */ static int seed1 = 1; static int seed2 = 1; static int seed3 = 1; #define MAXINT (((unsigned)-1)>>1) #define CRANK(a,b,c,m,s) \ q = s/a; \ s = b*(s-a*q) - c*q; \ if(s<0) s+=m; int rand() { register int q; CRANK(206, 157, 31, 32363, seed1); CRANK(217, 146, 45, 31727, seed2); CRANK(222, 142, 133, 31657, seed3); return seed1 ^ seed2 ^ seed3; } void srand(seed) unsigned int seed; { seed &= MAXINT; seed1 = seed % 32362 + 1; seed2 = seed % 31726 + 1; seed3 = seed % 31656 + 1; } #endif