def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def test_ccode_Rational():
    assert ccode(Rational(3, 7)) == "3.0L/7.0L"
    assert ccode(Rational(18, 9)) == "2"
    assert ccode(Rational(3, -7)) == "-3.0L/7.0L"
    assert ccode(Rational(-3, -7)) == "3.0L/7.0L"
    assert ccode(x + Rational(3, 7)) == "x + 3.0L/7.0L"
    assert ccode(Rational(3, 7)*x) == "(3.0L/7.0L)*x"