def cmp(other)
			if (!other.kind_of?(IPv6))
				raise ArgumentError, "Expected an IPv6 object for 'other' but got a #{other.class}."
			end
			if (self.addr > other.addr)
				return 1
			elsif (self.addr < other.addr)
				return -1
			end
			return 0
		end
def cmp(other)
			if (!other.kind_of?(IPv6))
				raise ArgumentError, "Expected an IPv6 object for 'other' but got a #{other.class}."
			end
			if (self.addr > other.addr)
				return 1
			elsif (self.addr < other.addr)
				return -1
			end
			return 0
		end
cmp compares equality with another IPv6. Return:
 * 1 if this IPv6 is numerically greater
 * 0 if the two are equal
 * -1 if this IPv6 is numerically less