ref: e9b045956ac6aa241777d15e52d87c87dd7c6d80
dir: /libc/frand.c/
#include <u.h>
#include <libc.h>
#define MASK 0x7fffffffL
#define NORM (1.0/(1.0+MASK))
double
frand(void)
{
double x;
do {
x = lrand() * NORM;
x = (x + lrand()) * NORM;
} while(x >= 1);
return x;
}