ref: 6d3e368f2d0796e366d2df8ed56e3b6fe0c42182
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;
}