test_assumptions.py 文件源码

def test_special_assumptions():
    x = Symbol('x')
    z2 = z = Symbol('z', zero=True)
    assert z2 == z == S.Zero
    assert (2*z).is_positive is False
    assert (2*z).is_negative is False
    assert (2*z).is_zero is True
    assert (z2*z).is_positive is False
    assert (z2*z).is_negative is False
    assert (z2*z).is_zero is True

    e = -3 - sqrt(5) + (-sqrt(10)/2 - sqrt(2)/2)**2
    assert (e < 0) is S.false
    assert (e > 0) is S.false
    assert (e == 0) is False  # it's not a literal 0
    assert e.equals(0) is True