Merges the two values

def merge(self, other):
        """
        Merges the two values
        """
        other = self.coerce(other)
        if list_diff(self.domain, other.domain) != []:
            raise Exception("Incomparable orderings. Different domains")
        if self.is_equal(other):
            # pick among dependencies
            return self
        elif other.is_entailed_by(self):
            return self
        elif self.is_entailed_by(other):
            self.low, self.high = other.low, other.high
        elif self.is_contradictory(other):
            raise Contradiction("Cannot merge %s and %s" % (self, other))
        else:
            # information in both
            to_i = self.to_i
            self.low = self.domain[max(map(to_i, [self.low, other.low]))]
            self.high =self.domain[min(map(to_i, [self.high, other.high]))]
        return self