ref: 7f7c098f85fba9612ea2aa3901b7f5fae3b209f5
dir: /sys/src/cmd/unix/drawterm/libc/nrand.c/
#include <u.h>
#include <libc.h>
#define MASK 0x7fffffffL
int
nrand(int n)
{
long slop, v;
if(n < 0)
return n;
slop = MASK % n;
do
v = lrand();
while(v <= slop);
return v % n;
}