Python sympy.piecewise_fold函数代码示例

def test_piecewise_integrate1c():
    for i, g in enumerate([
        Piecewise((1 - x, Interval(0, 1).contains(x)),
            (1 + x, Interval(-1, 0).contains(x)), (0, True)),
        Piecewise((0, Or(x <= -1, x >= 1)), (1 - x, x > 0),
            (1 + x, True))]):
        gy1 = g.integrate((x, y, 1))
        g1y = g.integrate((x, 1, y))
        for yy in (-2, 0, 2):
            assert g.integrate((x, yy, 1)) == gy1.subs(y, yy)
            assert g.integrate((x, 1, yy)) == g1y.subs(y, yy)
        assert piecewise_fold(gy1.rewrite(Piecewise)) == Piecewise(
            (1, y <= -1),
            (-y**2/2 - y + 1/2, y <= 0),
            (y**2/2 - y + 1/2, y < 1),
            (0, True))
        assert piecewise_fold(g1y.rewrite(Piecewise)) == Piecewise(
            (-1, y <= -1),
            (y**2/2 + y - 1/2, y <= 0),
            (-y**2/2 + y - 1/2, y < 1),
            (0, True))
        # g1y and gy1 should simplify if the condition that y < 1
        # is applied, e.g. Min(1, Max(-1, y)) --> Max(-1, y)
        assert gy1 == Piecewise(
            (-Min(1, Max(-1, y))**2/2 - Min(1, Max(-1, y)) +
                Min(1, Max(0, y))**2 + 1/2, y < 1),
            (0, True))
        assert g1y == Piecewise(
            (Min(1, Max(-1, y))**2/2 + Min(1, Max(-1, y)) -
                Min(1, Max(0, y))**2 - 1/2, y < 1),
            (0, True))

 def supply(self):
     aggregate = sp.Piecewise((0, True))
     for firm, n in self.firms():
         supply = firm.supply()
         if isinstance(supply, sp.relational.Relational):
             aggregate = sp.piecewise_fold(aggregate + firm.supply())
         else:
             aggregate = sp.piecewise_fold(aggregate + n*firm.supply())
     return aggregate

def test_piecewise_fold_expand():
    p1 = Piecewise((1,Interval(0,1,False,True)),(0,True))

    p2 = piecewise_fold(expand((1-x)*p1))
    assert p2 == Piecewise((1 - x, Interval(0,1,False,True)), \
        (Piecewise((-x, Interval(0,1,False,True)), (0, True)), True))

    p2 = expand(piecewise_fold((1-x)*p1))
    assert p2 == Piecewise((1 - x, Interval(0,1,False,True)), (0, True))

def test_issue_10087():
    a, b = Piecewise((x, x > 1), (2, True)), Piecewise((x, x > 3), (3, True))
    m = a*b
    f = piecewise_fold(m)
    for i in (0, 2, 4):
        assert m.subs(x, i) == f.subs(x, i)
    m = a + b
    f = piecewise_fold(m)
    for i in (0, 2, 4):
        assert m.subs(x, i) == f.subs(x, i)

 def test_surplus(self):
     """Practice problem 2.2
     """
     sp.var('A x p')
     cons = Consumer(x, p, 2*A * sp.sqrt(x))
     self.assertEqual(sp.piecewise_fold(cons.surplus()),
                      sp.Piecewise((0, p < 0),
                                   (-A**2/p + 2*A*sp.sqrt(A**2/p**2), True)))
     self.assertEqual(sp.piecewise_fold(cons.surplus_at(p*2)),
                      sp.Piecewise((0, 2*p < 0),
                                   (-A**2/(2*p) + A*sp.sqrt(A**2/p**2), True)))

def test_piecewise_fold():

    p = Piecewise((x, x < 1), (1, 1 <= x))

    assert piecewise_fold(x*p) == Piecewise((x**2, x < 1), (x, 1 <= x))
    assert piecewise_fold(p+p) == Piecewise((2*x, x < 1), (2, 1 <= x))

    p1 = Piecewise((0, x < 0), (x, x <= 1), (0, True))
    p2 = Piecewise((0, x < 0), (1 - x, x <=1), (0, True))

    p = 4*p1 + 2*p2
    assert integrate(piecewise_fold(p),(x,-oo,oo)) == integrate(2*x + 2, (x, 0, 1))

def test_piecewise_fold():
    p = Piecewise((x, x < 1), (1, 1 <= x))

    assert piecewise_fold(x*p) == Piecewise((x**2, x < 1), (x, 1 <= x))
    assert piecewise_fold(p + p) == Piecewise((2*x, x < 1), (2, 1 <= x))
    assert piecewise_fold(Piecewise((1, x < 0), (2, True))
                          + Piecewise((10, x < 0), (-10, True))) == \
        Piecewise((11, x < 0), (-8, True))

    p1 = Piecewise((0, x < 0), (x, x <= 1), (0, True))
    p2 = Piecewise((0, x < 0), (1 - x, x <= 1), (0, True))

    p = 4*p1 + 2*p2
    assert integrate(
        piecewise_fold(p), (x, -oo, oo)) == integrate(2*x + 2, (x, 0, 1))

    assert piecewise_fold(
        Piecewise((1, y <= 0), (-Piecewise((2, y >= 0)), True)
        )) == Piecewise((1, y <= 0), (-2, y >= 0))

    assert piecewise_fold(Piecewise((x, ITE(x > 0, y < 1, y > 1)))
        ) == Piecewise((x, ((x <= 0) | (y < 1)) & ((x > 0) | (y > 1))))

    a, b = (Piecewise((2, Eq(x, 0)), (0, True)),
        Piecewise((x, Eq(-x + y, 0)), (1, Eq(-x + y, 1)), (0, True)))
    assert piecewise_fold(Mul(a, b, evaluate=False)
        ) == piecewise_fold(Mul(b, a, evaluate=False))

    def b_spline(self, n, k):
        """
        Calculates the B-Spline b and returns it in a symbolic representation
        :param n: n in b^n
        :param k: k in b_k
        :return: kth-b_spline of degree n
        """
        x = sympy.symbols('x')
        spline = None

        if n in self.b_splines and k in self.b_splines[n]:
            return self.b_splines[n][k]

        if n == 0:
            spline = sympy.Piecewise((1, (x < sympy.S(self.knot_list[k + 1])) & (x >= sympy.S(self.knot_list[k]))),
                                     (0, True))
        else:
            gamma_k = (x - sympy.S(self.knot_list[k])) / (sympy.S(self.knot_list[k + n]) - sympy.S(self.knot_list[k]))
            gamma_k_plus_1 = (x - sympy.S(self.knot_list[k + 1])) / (
                sympy.S(self.knot_list[k + 1 + n]) - sympy.S(self.knot_list[k + 1]))
            spline = sympy.piecewise_fold(
                gamma_k * self.b_spline(n - 1, k) + (1 - gamma_k_plus_1) * self.b_spline(
                    n - 1, k + 1))

        self.add_spline(spline, n, k)
        return spline

def test_issue_14240():
    assert piecewise_fold(
        Piecewise((1, a), (2, b), (4, True)) +
        Piecewise((8, a), (16, True))
        ) == Piecewise((9, a), (18, b), (20, True))
    assert piecewise_fold(
        Piecewise((2, a), (3, b), (5, True)) *
        Piecewise((7, a), (11, True))
        ) == Piecewise((14, a), (33, b), (55, True))
    # these will hang if naive folding is used
    assert piecewise_fold(Add(*[
        Piecewise((i, a), (0, True)) for i in range(40)])
        ) == Piecewise((780, a), (0, True))
    assert piecewise_fold(Mul(*[
        Piecewise((i, a), (0, True)) for i in range(1, 41)])
        ) == Piecewise((factorial(40), a), (0, True))

 def _stress(self):
     z = sympy.Symbol('z')
     x = sympy.Symbol('x')
     props = self.laminate.piecewise_cr()
     strain = self.strain
     stress = sympy.piecewise_fold(props * self.strain)
     return stress

def test_piecewise_fold_piecewise_in_cond_2():
    p1 = Piecewise((cos(x), x < 0), (0, True))
    p2 = Piecewise((0, Eq(p1, 0)), (1 / p1, True))
    p3 = Piecewise(
        (0, (x >= 0) | Eq(cos(x), 0)),
        (1/cos(x), x < 0),
        (zoo, True))  # redundant b/c all x are already covered
    assert(piecewise_fold(p2) == p3)

def test_piecewise_fold_piecewise_in_cond():
    p1 = Piecewise((cos(x), x < 0), (0, True))
    p2 = Piecewise((0, Eq(p1, 0)), (p1 / Abs(p1), True))
    p3 = piecewise_fold(p2)
    assert p2.subs(x, -pi / 2) == 0.0
    assert p2.subs(x, 1) == 0.0
    assert p2.subs(x, -pi / 4) == 1.0
    p4 = Piecewise((0, Eq(p1, 0)), (1, True))
    assert piecewise_fold(p4) == Piecewise((0, Or(And(Eq(cos(x), 0), x < 0), Not(x < 0))), (1, True))

    r1 = 1 < Piecewise((1, x < 1), (3, True))
    assert piecewise_fold(r1) == Not(x < 1)

    p5 = Piecewise((1, x < 0), (3, True))
    p6 = Piecewise((1, x < 1), (3, True))
    p7 = piecewise_fold(Piecewise((1, p5 < p6), (0, True)))
    assert Piecewise((1, And(Not(x < 1), x < 0)), (0, True))

def test_piecewise_integrate1ca():
    y = symbols('y', real=True)
    g = Piecewise(
        (1 - x, Interval(0, 1).contains(x)),
        (1 + x, Interval(-1, 0).contains(x)),
        (0, True)
        )
    gy1 = g.integrate((x, y, 1))
    g1y = g.integrate((x, 1, y))

    assert g.integrate((x, -2, 1)) == gy1.subs(y, -2)
    assert g.integrate((x, 1, -2)) == g1y.subs(y, -2)
    assert g.integrate((x, 0, 1)) == gy1.subs(y, 0)
    assert g.integrate((x, 1, 0)) == g1y.subs(y, 0)
    # XXX Make test pass without simplify
    assert g.integrate((x, 2, 1)) == gy1.subs(y, 2).simplify()
    assert g.integrate((x, 1, 2)) == g1y.subs(y, 2).simplify()

    assert piecewise_fold(gy1.rewrite(Piecewise)) == \
        Piecewise(
            (1, y <= -1),
            (-y**2/2 - y + S(1)/2, y <= 0),
            (y**2/2 - y + S(1)/2, y < 1),
            (0, True))
    assert piecewise_fold(g1y.rewrite(Piecewise)) == \
        Piecewise(
            (-1, y <= -1),
            (y**2/2 + y - S(1)/2, y <= 0),
            (-y**2/2 + y - S(1)/2, y < 1),
            (0, True))

    # g1y and gy1 should simplify if the condition that y < 1
    # is applied, e.g. Min(1, Max(-1, y)) --> Max(-1, y)
    # XXX Make test pass without simplify
    assert gy1.simplify() == Piecewise(
        (
            -Min(1, Max(-1, y))**2/2 - Min(1, Max(-1, y)) +
            Min(1, Max(0, y))**2 + S(1)/2, y < 1),
        (0, True)
        )
    assert g1y.simplify() == Piecewise(
        (
            Min(1, Max(-1, y))**2/2 + Min(1, Max(-1, y)) -
            Min(1, Max(0, y))**2 - S(1)/2, y < 1),
        (0, True))

def test_stackoverflow_43852159():
    f = lambda x: Piecewise((1 , (x >= -1) & (x <= 1)) , (0, True))
    Conv = lambda x: integrate(f(x - y)*f(y), (y, -oo, +oo))
    cx = Conv(x)
    assert cx.subs(x, -1.5) == cx.subs(x, 1.5)
    assert cx.subs(x, 3) == 0
    assert piecewise_fold(f(x - y)*f(y)) == Piecewise(
        (1, (y >= -1) & (y <= 1) & (x - y >= -1) & (x - y <= 1)),
        (0, True))

def test_piecewise_fold():
    p = Piecewise((x, x < 1), (1, 1 <= x))

    assert piecewise_fold(x*p) == Piecewise((x**2, x < 1), (x, 1 <= x))
    assert piecewise_fold(p + p) == Piecewise((2*x, x < 1), (2, 1 <= x))
    assert piecewise_fold(Piecewise((1, x < 0), (2, True))
                          + Piecewise((10, x < 0), (-10, True))) == \
        Piecewise((11, x < 0), (-8, True))

    p1 = Piecewise((0, x < 0), (x, x <= 1), (0, True))
    p2 = Piecewise((0, x < 0), (1 - x, x <= 1), (0, True))

    p = 4*p1 + 2*p2
    assert integrate(
        piecewise_fold(p), (x, -oo, oo)) == integrate(2*x + 2, (x, 0, 1))

    assert piecewise_fold(
        Piecewise((1, y <= 0), (-Piecewise((2, y >= 0)), True)
        )) == Piecewise((1, y <= 0), (-2, y >= 0))