1 #include <u.h> 2 #include <libc.h> 3 4 #define MASK 0x7fffffffL 5 #define NORM (1.0/(1.0+MASK)) 6 7 double frand(void)8 frand(void) 9 { 10 double x; 11 12 do { 13 x = lrand() * NORM; 14 x = (x + lrand()) * NORM; 15 } while(x >= 1); 16 return x; 17 } 18