Python complexes.sign函数代码示例

 def eval(cls, n, m, z=None):
     if z is not None:
         n, z, m = n, m, z
         k = 2 * z / pi
         if n == S.Zero:
             return elliptic_f(z, m)
         elif n == S.One:
             return elliptic_f(z, m) + (sqrt(1 - m * sin(z) ** 2) * tan(z) - elliptic_e(z, m)) / (1 - m)
         elif k.is_integer:
             return k * elliptic_pi(n, m)
         elif m == S.Zero:
             return atanh(sqrt(n - 1) * tan(z)) / sqrt(n - 1)
         elif n == m:
             return elliptic_f(z, n) - elliptic_pi(1, z, n) + tan(z) / sqrt(1 - n * sin(z) ** 2)
         elif n in (S.Infinity, S.NegativeInfinity):
             return S.Zero
         elif m in (S.Infinity, S.NegativeInfinity):
             return S.Zero
         elif z.could_extract_minus_sign():
             return -elliptic_pi(n, -z, m)
     else:
         if n == S.Zero:
             return elliptic_k(m)
         elif n == S.One:
             return S.ComplexInfinity
         elif m == S.Zero:
             return pi / (2 * sqrt(1 - n))
         elif m == S.One:
             return -S.Infinity / sign(n - 1)
         elif n == m:
             return elliptic_e(n) / (1 - n)
         elif n in (S.Infinity, S.NegativeInfinity):
             return S.Zero
         elif m in (S.Infinity, S.NegativeInfinity):
             return S.Zero

 def _updated_range(r, first):
     st = sign(r.step)*step
     if r.start.is_finite:
         rv = Range(first, r.stop, st)
     else:
         rv = Range(r.start, first + st, st)
     return rv

    def _eval_rewrite_as_sign(self, arg):
        """Represents the Heaviside function in the form of sign function.

        Examples
        ========

        >>> from sympy import Heaviside, Symbol, sign
        >>> x = Symbol('x', real=True)

        >>> Heaviside(x).rewrite(sign)
        sign(x)/2 + 1/2

        >>> Heaviside(x - 2).rewrite(sign)
        sign(x - 2)/2 + 1/2

        >>> Heaviside(x**2 - 2*x + 1).rewrite(sign)
        sign(x**2 - 2*x + 1)/2 + 1/2

        >>> y = Symbol('y')

        >>> Heaviside(y).rewrite(sign)
        Heaviside(y)

        >>> Heaviside(y**2 - 2*y + 1).rewrite(sign)
        Heaviside(y**2 - 2*y + 1)

        See Also
        ========

        sign

        """
        if arg.is_real:
            return (sign(arg)+1)/2

def real_root(arg, n=None, evaluate=None):
    """Return the real nth-root of arg if possible. If n is omitted then
    all instances of (-n)**(1/odd) will be changed to -n**(1/odd); this
    will only create a real root of a principal root -- the presence of
    other factors may cause the result to not be real.

    The parameter evaluate determines if the expression should be evaluated.
    If None, its value is taken from global_evaluate.

    Examples
    ========

    >>> from sympy import root, real_root, Rational
    >>> from sympy.abc import x, n

    >>> real_root(-8, 3)
    -2
    >>> root(-8, 3)
    2*(-1)**(1/3)
    >>> real_root(_)
    -2

    If one creates a non-principal root and applies real_root, the
    result will not be real (so use with caution):

    >>> root(-8, 3, 2)
    -2*(-1)**(2/3)
    >>> real_root(_)
    -2*(-1)**(2/3)


    See Also
    ========

    sympy.polys.rootoftools.rootof
    sympy.core.power.integer_nthroot
    root, sqrt
    """
    from sympy.functions.elementary.complexes import Abs, im, sign
    from sympy.functions.elementary.piecewise import Piecewise
    if n is not None:
        return Piecewise(
            (root(arg, n, evaluate=evaluate), Or(Eq(n, S.One), Eq(n, S.NegativeOne))),
            (Mul(sign(arg), root(Abs(arg), n, evaluate=evaluate), evaluate=evaluate),
            And(Eq(im(arg), S.Zero), Eq(Mod(n, 2), S.One))),
            (root(arg, n, evaluate=evaluate), True))
    rv = sympify(arg)
    n1pow = Transform(lambda x: -(-x.base)**x.exp,
                      lambda x:
                      x.is_Pow and
                      x.base.is_negative and
                      x.exp.is_Rational and
                      x.exp.p == 1 and x.exp.q % 2)
    return rv.xreplace(n1pow)

 def _first_finite_point(r1, c):
     if c == r1.start:
         return c
     # st is the signed step we need to take to
     # get from c to r1.start
     st = sign(r1.start - c)*step
     # use Range to calculate the first point:
     # we want to get as close as possible to
     # r1.start; the Range will not be null since
     # it will at least contain c
     s1 = Range(c, r1.start + st, st)[-1]
     if s1 == r1.start:
         pass
     else:
         # if we didn't hit r1.start then, if the
         # sign of st didn't match the sign of r1.step
         # we are off by one and s1 is not in r1
         if sign(r1.step) != sign(st):
             s1 -= st
     if s1 not in r1:
         return
     return s1

    def _eval_rewrite_as_sign(self, arg, H0=None):
        """Represents the Heaviside function in the form of sign function.
        The value of the second argument of Heaviside must specify Heaviside(0)
        = 1/2 for rewritting as sign to be strictly equivalent.  For easier
        usage, we also allow this rewriting when Heaviside(0) is undefined.

        Examples
        ========

        >>> from sympy import Heaviside, Symbol, sign
        >>> x = Symbol('x', real=True)

        >>> Heaviside(x).rewrite(sign)
        sign(x)/2 + 1/2

        >>> Heaviside(x, 0).rewrite(sign)
        Heaviside(x, 0)

        >>> Heaviside(x - 2).rewrite(sign)
        sign(x - 2)/2 + 1/2

        >>> Heaviside(x**2 - 2*x + 1).rewrite(sign)
        sign(x**2 - 2*x + 1)/2 + 1/2

        >>> y = Symbol('y')

        >>> Heaviside(y).rewrite(sign)
        Heaviside(y)

        >>> Heaviside(y**2 - 2*y + 1).rewrite(sign)
        Heaviside(y**2 - 2*y + 1)

        See Also
        ========

        sign

        """
        if arg.is_real:
            if H0 is None or H0 == S.Half:
                return (sign(arg)+1)/2

 def _eval_power(self, e):
     if e.is_Rational and self.is_number:
         from sympy.core.evalf import pure_complex
         from sympy.core.mul import _unevaluated_Mul
         from sympy.core.exprtools import factor_terms
         from sympy.core.function import expand_multinomial
         from sympy.functions.elementary.complexes import sign
         from sympy.functions.elementary.miscellaneous import sqrt
         ri = pure_complex(self)
         if ri:
             r, i = ri
             if e.q == 2:
                 D = sqrt(r**2 + i**2)
                 if D.is_Rational:
                     # (r, i, D) is a Pythagorean triple
                     root = sqrt(factor_terms((D - r)/2))**e.p
                     return root*expand_multinomial((
                         # principle value
                         (D + r)/abs(i) + sign(i)*S.ImaginaryUnit)**e.p)
             elif e == -1:
                 return _unevaluated_Mul(
                     r - i*S.ImaginaryUnit,
                     1/(r**2 + i**2))

 def _eval_rewrite_as_sign(self, arg):
     if arg.is_real:
         return (sign(arg)+1)/2

def test_sympy__functions__elementary__complexes__sign():
    from sympy.functions.elementary.complexes import sign
    assert _test_args(sign(x))

    def _intersect(self, other):
        from sympy.functions.elementary.integers import ceiling, floor
        from sympy.functions.elementary.complexes import sign

        if other is S.Naturals:
            return self._intersect(Interval(1, S.Infinity))

        if other is S.Integers:
            return self

        if other.is_Interval:
            if not all(i.is_number for i in other.args[:2]):
                return

            # In case of null Range, return an EmptySet.
            if self.size == 0:
                return S.EmptySet

            # trim down to self's size, and represent
            # as a Range with step 1.
            start = ceiling(max(other.inf, self.inf))
            if start not in other:
                start += 1
            end = floor(min(other.sup, self.sup))
            if end not in other:
                end -= 1
            return self.intersect(Range(start, end + 1))

        if isinstance(other, Range):
            from sympy.solvers.diophantine import diop_linear
            from sympy.core.numbers import ilcm

            # non-overlap quick exits
            if not other:
                return S.EmptySet
            if not self:
                return S.EmptySet
            if other.sup < self.inf:
                return S.EmptySet
            if other.inf > self.sup:
                return S.EmptySet

            # work with finite end at the start
            r1 = self
            if r1.start.is_infinite:
                r1 = r1.reversed
            r2 = other
            if r2.start.is_infinite:
                r2 = r2.reversed

            # this equation represents the values of the Range;
            # it's a linear equation
            eq = lambda r, i: r.start + i*r.step

            # we want to know when the two equations might
            # have integer solutions so we use the diophantine
            # solver
            a, b = diop_linear(eq(r1, Dummy()) - eq(r2, Dummy()))

            # check for no solution
            no_solution = a is None and b is None
            if no_solution:
                return S.EmptySet

            # there is a solution
            # -------------------

            # find the coincident point, c
            a0 = a.as_coeff_Add()[0]
            c = eq(r1, a0)

            # find the first point, if possible, in each range
            # since c may not be that point
            def _first_finite_point(r1, c):
                if c == r1.start:
                    return c
                # st is the signed step we need to take to
                # get from c to r1.start
                st = sign(r1.start - c)*step
                # use Range to calculate the first point:
                # we want to get as close as possible to
                # r1.start; the Range will not be null since
                # it will at least contain c
                s1 = Range(c, r1.start + st, st)[-1]
                if s1 == r1.start:
                    pass
                else:
                    # if we didn't hit r1.start then, if the
                    # sign of st didn't match the sign of r1.step
                    # we are off by one and s1 is not in r1
                    if sign(r1.step) != sign(st):
                        s1 -= st
                if s1 not in r1:
                    return
                return s1

            # calculate the step size of the new Range
            step = abs(ilcm(r1.step, r2.step))
            s1 = _first_finite_point(r1, c)
            if s1 is None:
#.........这里部分代码省略.........