Example #1
0
def test_doit():
    p1 = Piecewise((x, x < 1), (x**2, -1 <= x), (x, 3 < x))
    p2 = Piecewise((x, x < 1), (Integral(2 * x), -1 <= x), (x, 3 < x))
    assert p2.doit() == p1
    assert p2.doit(deep=False) == p2
Example #2
0
def test_doit():
    p1 = Piecewise((x, x < 1), (x**2, -1 <= x), (x, 3 < x))
    p2 = Piecewise((x, x < 1), (Integral(2 * x), -1 <= x), (x, 3 < x))
    assert p2.doit() == p1
    assert p2.doit(deep=False) == p2
Example #3
0
def test_piecewise():

    # Test canonization
    assert Piecewise((x, x < 1), (0, True)) == Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, True), (1, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, False), (-1, 1 > 2)) == \
        Piecewise((x, x < 1))
    assert Piecewise((x, x < 1), (0, x < 1), (0, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, x < 2), (0, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (x, x < 2), (0, True)) == \
        Piecewise((x, Or(x < 1, x < 2)), (0, True))
    assert Piecewise((x, x < 1), (x, x < 2), (x, True)) == x
    assert Piecewise((x, True)) == x
    pytest.raises(TypeError, lambda: Piecewise(x))
    pytest.raises(TypeError, lambda: Piecewise((x, x**2)))

    # Test subs
    p = Piecewise((-1, x < -1), (x**2, x < 0), (log(x), x >= 0))
    p_x2 = Piecewise((-1, x**2 < -1), (x**4, x**2 < 0), (log(x**2), x**2 >= 0))
    assert p.subs(x, x**2) == p_x2
    assert p.subs(x, -5) == -1
    assert p.subs(x, -1) == 1
    assert p.subs(x, 1) == log(1)

    # More subs tests
    p2 = Piecewise((1, x < pi), (-1, x < 2 * pi), (0, x > 2 * pi))
    p3 = Piecewise((1, Eq(x, 0)), (1 / x, True))
    p4 = Piecewise((1, Eq(x, 0)), (2, 1 / x > 2))
    assert p2.subs(x, 2) == 1
    assert p2.subs(x, 4) == -1
    assert p2.subs(x, 10) == 0
    assert p3.subs(x, 0.0) == 1
    assert p4.subs(x, 0.0) == 1

    f, g, h = symbols('f,g,h', cls=Function)
    pf = Piecewise((f(x), x < -1), (f(x) + h(x) + 2, x <= 1))
    pg = Piecewise((g(x), x < -1), (g(x) + h(x) + 2, x <= 1))
    assert pg.subs(g, f) == pf

    assert Piecewise((1, Eq(x, 0)), (0, True)).subs(x, 0) == 1
    assert Piecewise((1, Eq(x, 0)), (0, True)).subs(x, 1) == 0
    assert Piecewise((1, Eq(x, y)), (0, True)).subs(x, y) == 1
    assert Piecewise((1, Eq(x, z)), (0, True)).subs(x, z) == 1
    assert Piecewise((1, Eq(exp(x), cos(z))), (0, True)).subs(x, z) == \
        Piecewise((1, Eq(exp(z), cos(z))), (0, True))
    assert Piecewise((1, Eq(x, y * (y + 1))),
                     (0, True)).subs(x, y**2 + y).simplify() == 1

    p5 = Piecewise((0, Eq(cos(x) + y, 0)), (1, True))
    assert p5.subs(y, 0) == Piecewise((0, Eq(cos(x), 0)), (1, True))

    # Test evalf
    assert p.evalf() == p
    assert p.evalf(subs={x: -2}) == -1
    assert p.evalf(subs={x: -1}) == 1
    assert p.evalf(subs={x: 1}) == log(1)

    # Test doit
    f_int = Piecewise((Integral(x, (x, 0, 1)), x < 1))
    assert f_int.doit() == Piecewise((1.0 / 2.0, x < 1))

    # Test differentiation
    f = x
    fp = x * p
    dp = Piecewise((0, x < -1), (2 * x, x < 0), (1 / x, x >= 0))
    fp_dx = x * dp + p
    assert diff(p, x) == dp
    assert diff(f * p, x) == fp_dx

    # Test simple arithmetic
    assert x * p == fp
    assert x * p + p == p + x * p
    assert p + f == f + p
    assert p + dp == dp + p
    assert p - dp == -(dp - p)

    # Test power
    dp2 = Piecewise((0, x < -1), (4 * x**2, x < 0), (1 / x**2, x >= 0))
    assert dp**2 == dp2

    # Test _eval_interval
    f1 = x * y + 2
    f2 = x * y**2 + 3
    peval = Piecewise((f1, x < 0), (f2, x > 0))
    peval_interval = f1.subs(x, 0) - f1.subs(x, -1) + f2.subs(x, 1) - f2.subs(
        x, 0)
    assert peval._eval_interval(x, 0, 0) == 0
    assert peval._eval_interval(x, -1, 1) == peval_interval
    peval2 = Piecewise((f1, x < 0), (f2, True))
    assert peval2._eval_interval(x, 0, 0) == 0
    assert peval2._eval_interval(x, 1, -1) == -peval_interval
    assert peval2._eval_interval(x, -1, -2) == f1.subs(x, -2) - f1.subs(x, -1)
    assert peval2._eval_interval(x, -1, 1) == peval_interval
    assert peval2._eval_interval(x, None, 0) == peval2.subs(x, 0)
    assert peval2._eval_interval(x, -1, None) == -peval2.subs(x, -1)

    # Test integration
    p_int = Piecewise((-x, x < -1), (x**3 / 3.0, x < 0),
                      (-x + x * log(x), x >= 0))
    assert integrate(p, x) == p_int
    p = Piecewise((x, x < 1), (x**2, -1 <= x), (x, 3 < x))
    assert integrate(p, (x, -2, 2)) == 5.0 / 6.0
    assert integrate(p, (x, 2, -2)) == -5.0 / 6.0
    p = Piecewise((0, x < 0), (1, x < 1), (0, x < 2), (1, x < 3), (0, True))
    assert integrate(p, (x, -oo, oo)) == 2
    p = Piecewise((x, x < -10), (x**2, x <= -1), (x, 1 < x))
    pytest.raises(ValueError, lambda: integrate(p, (x, -2, 2)))

    # Test commutativity
    assert p.is_commutative is True
Example #4
0
def test_piecewise():

    # Test canonization
    assert Piecewise((x, x < 1), (0, True)) == Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, True), (1, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, False), (-1, 1 > 2)) == \
        Piecewise((x, x < 1))
    assert Piecewise((x, x < 1), (0, x < 1), (0, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (0, x < 2), (0, True)) == \
        Piecewise((x, x < 1), (0, True))
    assert Piecewise((x, x < 1), (x, x < 2), (0, True)) == \
        Piecewise((x, Or(x < 1, x < 2)), (0, True))
    assert Piecewise((x, x < 1), (x, x < 2), (x, True)) == x
    assert Piecewise((x, True)) == x
    pytest.raises(TypeError, lambda: Piecewise(x))
    pytest.raises(TypeError, lambda: Piecewise((x, x**2)))
    assert Piecewise((0, Eq(z, 0, evaluate=False)), (1, True)) == 1

    # Test subs
    p = Piecewise((-1, x < -1), (x**2, x < 0), (log(x), x >= 0))
    p_x2 = Piecewise((-1, x**2 < -1), (x**4, x**2 < 0), (log(x**2), x**2 >= 0))
    assert p.subs({x: x**2}) == p_x2
    assert p.subs({x: -5}) == -1
    assert p.subs({x: -1}) == 1
    assert p.subs({x: 1}) == log(1)

    # More subs tests
    p2 = Piecewise((1, x < pi), (-1, x < 2*pi), (0, x > 2*pi))
    p3 = Piecewise((1, Eq(x, 0)), (1/x, True))
    p4 = Piecewise((1, Eq(x, 0)), (2, 1/x > 2))
    assert p2.subs({x: 2}) == 1
    assert p2.subs({x: 4}) == -1
    assert p2.subs({x: 10}) == 0
    assert p3.subs({x: 0.0}) == 1
    assert p4.subs({x: 0.0}) == 1

    f, g, h = symbols('f,g,h', cls=Function)
    pf = Piecewise((f(x), x < -1), (f(x) + h(x) + 2, x <= 1))
    pg = Piecewise((g(x), x < -1), (g(x) + h(x) + 2, x <= 1))
    assert pg.subs({g: f}) == pf

    assert Piecewise((1, Eq(x, 0)), (0, True)).subs({x: 0}) == 1
    assert Piecewise((1, Eq(x, 0)), (0, True)).subs({x: 1}) == 0
    assert Piecewise((1, Eq(x, y)), (0, True)).subs({x: y}) == 1
    assert Piecewise((1, Eq(x, z)), (0, True)).subs({x: z}) == 1
    assert Piecewise((1, Eq(exp(x), cos(z))), (0, True)).subs({x: z}) == \
        Piecewise((1, Eq(exp(z), cos(z))), (0, True))
    assert Piecewise((1, Eq(x, y*(y + 1))),
                     (0, True)).subs({x: y**2 + y}).simplify() == 1

    p5 = Piecewise( (0, Eq(cos(x) + y, 0)), (1, True))
    assert p5.subs({y: 0}) == Piecewise( (0, Eq(cos(x), 0)), (1, True))

    # Test evalf
    assert p.evalf() == p
    assert p.evalf(subs={x: -2}) == -1
    assert p.evalf(subs={x: -1}) == 1
    assert p.evalf(subs={x: 1}) == log(1)

    # Test doit
    f_int = Piecewise((Integral(x, (x, 0, 1)), x < 1))
    assert f_int.doit() == Piecewise( (1.0/2.0, x < 1) )

    # Test differentiation
    f = x
    fp = x*p
    dp = Piecewise((0, x < -1), (2*x, x < 0), (1/x, x >= 0))
    fp_dx = x*dp + p
    assert diff(p, x) == dp
    assert diff(f*p, x) == fp_dx

    # Test simple arithmetic
    assert x*p == fp
    assert x*p + p == p + x*p
    assert p + f == f + p
    assert p + dp == dp + p
    assert p - dp == -(dp - p)

    # Test power
    dp2 = Piecewise((0, x < -1), (4*x**2, x < 0), (1/x**2, x >= 0))
    assert dp**2 == dp2

    # Test _eval_interval
    f1 = x*y + 2
    f2 = x*y**2 + 3
    peval = Piecewise( (f1, x < 0), (f2, x > 0))
    peval_interval = (f1.subs({x: 0}) - f1.subs({x: -1}) +
                      f2.subs({x: 1}) - f2.subs({x: 0}))
    assert peval._eval_interval(x, 0, 0) == 0
    assert peval._eval_interval(x, -1, 1) == peval_interval
    peval2 = Piecewise((f1, x < 0), (f2, True))
    assert peval2._eval_interval(x, 0, 0) == 0
    assert peval2._eval_interval(x, 1, -1) == -peval_interval
    assert peval2._eval_interval(x, -1, -2) == (f1.subs({x: -2}) -
                                                f1.subs({x: -1}))
    assert peval2._eval_interval(x, -1, 1) == peval_interval
    assert peval2._eval_interval(x, None, 0) == peval2.subs({x: 0})
    assert peval2._eval_interval(x, -1, None) == -peval2.subs({x: -1})

    # Test integration
    p_int = Piecewise((-x, x < -1), (x**3/3.0, x < 0), (-x + x*log(x), x >= 0))
    assert integrate(p, x) == p_int
    p = Piecewise((x, x < 1), (x**2, -1 <= x), (x, 3 < x))
    assert integrate(p, (x, -2, 2)) == 5.0/6.0
    assert integrate(p, (x, 2, -2)) == -5.0/6.0
    p = Piecewise((0, x < 0), (1, x < 1), (0, x < 2), (1, x < 3), (0, True))
    assert integrate(p, (x, -oo, oo)) == 2
    p = Piecewise((x, x < -10), (x**2, x <= -1), (x, 1 < x))
    pytest.raises(ValueError, lambda: integrate(p, (x, -2, 2)))

    # Test commutativity
    assert p.is_commutative is True