func (ip Addr) v6(i uint8) uint8 {
	return uint8(*(ip.addr.halves()[(i/8)%2]) >> ((7 - i%8) * 8))
}

// v6u16 returns the i'th 16-bit word of ip. If ip is an IPv4 address,
// this accesses the IPv4-mapped IPv6 address form of the IP.
func (ip Addr) v6u16(i uint8) uint16 {
	return uint16(*(ip.addr.halves()[(i/4)%2]) >> ((3 - i%4) * 16))
}

// isZero reports whether ip is the zero value of the IP type.