#define IB1 1
#define IB2 2
#define IB5 16
#define IB18 131072
#define MASK (IB1+IB2+IB5)

int irbit2(unsigned long *iseed)
{
	if (*iseed & IB18) {
		*iseed=((*iseed ^ MASK) << 1) | IB1;
		return 1;
	} else {
		*iseed <<= 1;
		return 0;
	}
}
#undef MASK
#undef IB18
#undef IB5
#undef IB2
#undef IB1
/* (C) Copr. 1986-92 Numerical Recipes Software $!6)D$|2$3. */