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- #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, z;
- 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
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