Python solvers.denoms函数代码示例

def _solve_radical(f, symbol, solveset_solver):
    """ Helper function to solve equations with radicals """
    eq, cov = unrad(f)
    if not cov:
        result = solveset_solver(eq, symbol) - \
            Union(*[solveset_solver(g, symbol) for g in denoms(f, [symbol])])
    else:
        y, yeq = cov
        if not solveset_solver(y - I, y):
            yreal = Dummy('yreal', real=True)
            yeq = yeq.xreplace({y: yreal})
            eq = eq.xreplace({y: yreal})
            y = yreal
        g_y_s = solveset_solver(yeq, symbol)
        f_y_sols = solveset_solver(eq, y)
        result = Union(*[imageset(Lambda(y, g_y), f_y_sols)
                         for g_y in g_y_s])

    return FiniteSet(*[s for s in result if checksol(f, symbol, s) is True])

def heurisch_wrapper(f, x, rewrite=False, hints=None, mappings=None, retries=3,
                     degree_offset=0, unnecessary_permutations=None):
    """
    A wrapper around the heurisch integration algorithm.

    This method takes the result from heurisch and checks for poles in the
    denominator. For each of these poles, the integral is reevaluated, and
    the final integration result is given in terms of a Piecewise.

    Examples
    ========

    >>> from sympy.core import symbols
    >>> from sympy.functions import cos
    >>> from sympy.integrals.heurisch import heurisch, heurisch_wrapper
    >>> n, x = symbols('n x')
    >>> heurisch(cos(n*x), x)
    sin(n*x)/n
    >>> heurisch_wrapper(cos(n*x), x)
    Piecewise((x, n == 0), (sin(n*x)/n, True))

    See Also
    ========

    heurisch
    """
    f = sympify(f)
    if x not in f.free_symbols:
        return f*x

    res = heurisch(f, x, rewrite, hints, mappings, retries, degree_offset,
                   unnecessary_permutations)
    if not isinstance(res, Basic):
        return res
    # We consider each denominator in the expression, and try to find
    # cases where one or more symbolic denominator might be zero. The
    # conditions for these cases are stored in the list slns.
    slns = []
    for d in denoms(res):
        try:
            slns += solve(d, dict=True, exclude=(x,))
        except NotImplementedError:
            pass
    if not slns:
        return res
    slns = list(uniq(slns))
    # Remove the solutions corresponding to poles in the original expression.
    slns0 = []
    for d in denoms(f):
        try:
            slns0 += solve(d, dict=True, exclude=(x,))
        except NotImplementedError:
            pass
    slns = [s for s in slns if s not in slns0]
    if not slns:
        return res
    if len(slns) > 1:
        eqs = []
        for sub_dict in slns:
            eqs.extend([Eq(key, value) for key, value in sub_dict.items()])
        slns = solve(eqs, dict=True, exclude=(x,)) + slns
    # For each case listed in the list slns, we reevaluate the integral.
    pairs = []
    for sub_dict in slns:
        expr = heurisch(f.subs(sub_dict), x, rewrite, hints, mappings, retries,
                        degree_offset, unnecessary_permutations)
        cond = And(*[Eq(key, value) for key, value in sub_dict.items()])
        pairs.append((expr, cond))
    pairs.append((heurisch(f, x, rewrite, hints, mappings, retries,
                           degree_offset, unnecessary_permutations), True))
    return Piecewise(*pairs)

def _invalid_solutions(f, symbol, domain):
    bad = S.EmptySet
    for d in denoms(f):
        bad += _solveset(d, symbol, domain, _check=False)
    return bad

def solve_univariate_inequality(expr, gen, relational=True):
    """Solves a real univariate inequality.

    Examples
    ========

    >>> from sympy.solvers.inequalities import solve_univariate_inequality
    >>> from sympy.core.symbol import Symbol
    >>> x = Symbol('x')

    >>> solve_univariate_inequality(x**2 >= 4, x)
    Or(And(-oo < x, x <= -2), And(2 <= x, x < oo))

    >>> solve_univariate_inequality(x**2 >= 4, x, relational=False)
    (-oo, -2] U [2, oo)

    """

    from sympy.solvers.solvers import solve, denoms

    # This keeps the function independent of the assumptions about `gen`.
    # `solveset` makes sure this function is called only when the domain is
    # real.
    d = Dummy(real=True)
    expr = expr.subs(gen, d)
    _gen = gen
    gen = d

    if expr is S.true:
        rv = S.Reals
    elif expr is S.false:
        rv = S.EmptySet
    else:
        e = expr.lhs - expr.rhs
        parts = n, d = e.as_numer_denom()
        if all(i.is_polynomial(gen) for i in parts):
            solns = solve(n, gen, check=False)
            singularities = solve(d, gen, check=False)
        else:
            solns = solve(e, gen, check=False)
            singularities = []
            for d in denoms(e):
                singularities.extend(solve(d, gen))

        include_x = expr.func(0, 0)

        def valid(x):
            v = e.subs(gen, x)
            try:
                r = expr.func(v, 0)
            except TypeError:
                r = S.false
            if r in (S.true, S.false):
                return r
            if v.is_real is False:
                return S.false
            else:
                v = v.n(2)
                if v.is_comparable:
                    return expr.func(v, 0)
                return S.false

        start = S.NegativeInfinity
        sol_sets = [S.EmptySet]
        try:
            reals = _nsort(set(solns + singularities), separated=True)[0]
        except NotImplementedError:
            raise NotImplementedError('sorting of these roots is not supported')
        for x in reals:
            end = x

            if end in [S.NegativeInfinity, S.Infinity]:
                if valid(S(0)):
                    sol_sets.append(Interval(start, S.Infinity, True, True))
                    break

            pt = ((start + end)/2 if start is not S.NegativeInfinity else
                (end/2 if end.is_positive else
                (2*end if end.is_negative else
                end - 1)))
            if valid(pt):
                sol_sets.append(Interval(start, end, True, True))

            if x in singularities:
                singularities.remove(x)
            elif include_x:
                sol_sets.append(FiniteSet(x))

            start = end

        end = S.Infinity

        # in case start == -oo then there were no solutions so we just
        # check a point between -oo and oo (e.g. 0) else pick a point
        # past the last solution (which is start after the end of the
        # for-loop above
        pt = (0 if start is S.NegativeInfinity else
            (start/2 if start.is_negative else
            (2*start if start.is_positive else
            start + 1)))
#.........这里部分代码省略.........

def solve_univariate_inequality(expr, gen, relational=True):
    """Solves a real univariate inequality.

    Examples
    ========

    >>> from sympy.solvers.inequalities import solve_univariate_inequality
    >>> from sympy.core.symbol import Symbol
    >>> x = Symbol('x', real=True)

    >>> solve_univariate_inequality(x**2 >= 4, x)
    Or(And(-oo < x, x <= -2), And(2 <= x, x < oo))

    >>> solve_univariate_inequality(x**2 >= 4, x, relational=False)
    (-oo, -2] U [2, oo)

    """

    from sympy.solvers.solvers import solve, denoms

    e = expr.lhs - expr.rhs
    parts = n, d = e.as_numer_denom()
    if all(i.is_polynomial(gen) for i in parts):
        solns = solve(n, gen, check=False)
        singularities = solve(d, gen, check=False)
    else:
        solns = solve(e, gen, check=False)
        singularities = []
        for d in denoms(e):
            singularities.extend(solve(d, gen))

    include_x = expr.func(0, 0)

    def valid(x):
        v = e.subs(gen, x)
        try:
            r = expr.func(v, 0)
        except TypeError:
            r = S.false
        if r in (S.true, S.false):
            return r
        if v.is_real is False:
            return S.false
        else:
            v = v.n(2)
            if v.is_comparable:
                return expr.func(v, 0)
            return S.false

    start = S.NegativeInfinity
    sol_sets = [S.EmptySet]
    try:
        reals = _nsort(set(solns + singularities), separated=True)[0]
    except NotImplementedError:
        raise NotImplementedError('sorting of these roots is not supported')
    for x in reals:
        end = x

        if end in [S.NegativeInfinity, S.Infinity]:
            if valid(S(0)):
                sol_sets.append(Interval(start, S.Infinity, True, True))
                break

        if valid((start + end)/2 if start != S.NegativeInfinity else end - 1):
            sol_sets.append(Interval(start, end, True, True))

        if x in singularities:
            singularities.remove(x)
        elif include_x:
            sol_sets.append(FiniteSet(x))

        start = end

    end = S.Infinity

    if valid(start + 1):
        sol_sets.append(Interval(start, end, True, True))

    rv = Union(*sol_sets)
    return rv if not relational else rv.as_relational(gen)

def _solve_inequality(ie, s, linear=False):
    """Return the inequality with s isolated on the left, if possible.
    If the relationship is non-linear, a solution involving And or Or
    may be returned. False or True are returned if the relationship
    is never True or always True, respectively.

    If `linear` is True (default is False) an `s`-dependent expression
    will be isoloated on the left, if possible
    but it will not be solved for `s` unless the expression is linear
    in `s`. Furthermore, only "safe" operations which don't change the
    sense of the relationship are applied: no division by an unsigned
    value is attempted unless the relationship involves Eq or Ne and
    no division by a value not known to be nonzero is ever attempted.

    Examples
    ========

    >>> from sympy import Eq, Symbol
    >>> from sympy.solvers.inequalities import _solve_inequality as f
    >>> from sympy.abc import x, y

    For linear expressions, the symbol can be isolated:

    >>> f(x - 2 < 0, x)
    x < 2
    >>> f(-x - 6 < x, x)
    x > -3

    Sometimes nonlinear relationships will be False

    >>> f(x**2 + 4 < 0, x)
    False

    Or they may involve more than one region of values:

    >>> f(x**2 - 4 < 0, x)
    (-2 < x) & (x < 2)

    To restrict the solution to a relational, set linear=True
    and only the x-dependent portion will be isolated on the left:

    >>> f(x**2 - 4 < 0, x, linear=True)
    x**2 < 4

    Division of only nonzero quantities is allowed, so x cannot
    be isolated by dividing by y:

    >>> y.is_nonzero is None  # it is unknown whether it is 0 or not
    True
    >>> f(x*y < 1, x)
    x*y < 1

    And while an equality (or unequality) still holds after dividing by a
    non-zero quantity

    >>> nz = Symbol('nz', nonzero=True)
    >>> f(Eq(x*nz, 1), x)
    Eq(x, 1/nz)

    the sign must be known for other inequalities involving > or <:

    >>> f(x*nz <= 1, x)
    nz*x <= 1
    >>> p = Symbol('p', positive=True)
    >>> f(x*p <= 1, x)
    x <= 1/p

    When there are denominators in the original expression that
    are removed by expansion, conditions for them will be returned
    as part of the result:

    >>> f(x < x*(2/x - 1), x)
    (x < 1) & Ne(x, 0)
    """
    from sympy.solvers.solvers import denoms
    if s not in ie.free_symbols:
        return ie
    if ie.rhs == s:
        ie = ie.reversed
    if ie.lhs == s and s not in ie.rhs.free_symbols:
        return ie
    expr = ie.lhs - ie.rhs
    rv = None
    try:
        p = Poly(expr, s)
        if p.degree() == 0:
            rv = ie.func(p.as_expr(), 0)
        elif not linear and p.degree() > 1:
            # handle in except clause
            raise NotImplementedError
    except (PolynomialError, NotImplementedError):
        if not linear:
            try:
                return reduce_rational_inequalities([[ie]], s)
            except PolynomialError:
                return solve_univariate_inequality(ie, s)
        else:
            p = Poly(expr)

    e = expanded = p.as_expr()  # this is in exanded form
#.........这里部分代码省略.........

def solve_univariate_inequality(expr, gen, relational=True, domain=S.Reals, continuous=False):
    """Solves a real univariate inequality.

    Parameters
    ==========

    expr : Relational
        The target inequality
    gen : Symbol
        The variable for which the inequality is solved
    relational : bool
        A Relational type output is expected or not
    domain : Set
        The domain over which the equation is solved
    continuous: bool
        True if expr is known to be continuous over the given domain
        (and so continuous_domain() doesn't need to be called on it)

    Raises
    ======

    NotImplementedError
        The solution of the inequality cannot be determined due to limitation
        in `solvify`.

    Notes
    =====

    Currently, we cannot solve all the inequalities due to limitations in
    `solvify`. Also, the solution returned for trigonometric inequalities
    are restricted in its periodic interval.

    See Also
    ========

    solvify: solver returning solveset solutions with solve's output API

    Examples
    ========

    >>> from sympy.solvers.inequalities import solve_univariate_inequality
    >>> from sympy import Symbol, sin, Interval, S
    >>> x = Symbol('x')

    >>> solve_univariate_inequality(x**2 >= 4, x)
    ((2 <= x) & (x < oo)) | ((x <= -2) & (-oo < x))

    >>> solve_univariate_inequality(x**2 >= 4, x, relational=False)
    Union(Interval(-oo, -2), Interval(2, oo))

    >>> domain = Interval(0, S.Infinity)
    >>> solve_univariate_inequality(x**2 >= 4, x, False, domain)
    Interval(2, oo)

    >>> solve_univariate_inequality(sin(x) > 0, x, relational=False)
    Interval.open(0, pi)

    """
    from sympy import im
    from sympy.calculus.util import (continuous_domain, periodicity,
        function_range)
    from sympy.solvers.solvers import denoms
    from sympy.solvers.solveset import solveset_real, solvify, solveset
    from sympy.solvers.solvers import solve

    # This keeps the function independent of the assumptions about `gen`.
    # `solveset` makes sure this function is called only when the domain is
    # real.
    _gen = gen
    _domain = domain
    if gen.is_real is False:
        rv = S.EmptySet
        return rv if not relational else rv.as_relational(_gen)
    elif gen.is_real is None:
        gen = Dummy('gen', real=True)
        try:
            expr = expr.xreplace({_gen: gen})
        except TypeError:
            raise TypeError(filldedent('''
When gen is real, the relational has a complex part
which leads to an invalid comparison like I < 0.
            '''))

    rv = None

    if expr is S.true:
        rv = domain

    elif expr is S.false:
        rv = S.EmptySet

    else:
        e = expr.lhs - expr.rhs
        period = periodicity(e, gen)
        if period is not None:
            frange = function_range(e, gen, domain)

            rel = expr.rel_op
            if rel == '<' or rel == '<=':
                if expr.func(frange.sup, 0):
#.........这里部分代码省略.........

def solve_univariate_inequality(expr, gen, relational=True, domain=S.Reals, continuous=False):
    """Solves a real univariate inequality.

    Parameters
    ==========

    expr : Relational
        The target inequality
    gen : Symbol
        The variable for which the inequality is solved
    relational : bool
        A Relational type output is expected or not
    domain : Set
        The domain over which the equation is solved
    continuous: bool
        True if expr is known to be continuous over the given domain
        (and so continuous_domain() doesn't need to be called on it)

    Raises
    ======

    NotImplementedError
        The solution of the inequality cannot be determined due to limitation
        in `solvify`.

    Notes
    =====

    Currently, we cannot solve all the inequalities due to limitations in
    `solvify`. Also, the solution returned for trigonometric inequalities
    are restricted in its periodic interval.

    See Also
    ========

    solvify: solver returning solveset solutions with solve's output API

    Examples
    ========

    >>> from sympy.solvers.inequalities import solve_univariate_inequality
    >>> from sympy import Symbol, sin, Interval, S
    >>> x = Symbol('x')

    >>> solve_univariate_inequality(x**2 >= 4, x)
    ((2 <= x) & (x < oo)) | ((x <= -2) & (-oo < x))

    >>> solve_univariate_inequality(x**2 >= 4, x, relational=False)
    (-oo, -2] U [2, oo)

    >>> domain = Interval(0, S.Infinity)
    >>> solve_univariate_inequality(x**2 >= 4, x, False, domain)
    [2, oo)

    >>> solve_univariate_inequality(sin(x) > 0, x, relational=False)
    (0, pi)

    """
    from sympy.calculus.util import (continuous_domain, periodicity,
        function_range)
    from sympy.solvers.solvers import denoms
    from sympy.solvers.solveset import solveset_real, solvify

    # This keeps the function independent of the assumptions about `gen`.
    # `solveset` makes sure this function is called only when the domain is
    # real.
    d = Dummy(real=True)
    expr = expr.subs(gen, d)
    _gen = gen
    gen = d
    rv = None

    if expr is S.true:
        rv = domain

    elif expr is S.false:
        rv = S.EmptySet

    else:
        e = expr.lhs - expr.rhs
        period = periodicity(e, gen)
        if period is not None:
            frange = function_range(e, gen, domain)

            rel = expr.rel_op
            if rel == '<' or rel == '<=':
                if expr.func(frange.sup, 0):
                    rv = domain
                elif not expr.func(frange.inf, 0):
                    rv = S.EmptySet

            elif rel == '>' or rel == '>=':
                if expr.func(frange.inf, 0):
                    rv = domain
                elif not expr.func(frange.sup, 0):
                    rv = S.EmptySet

            inf, sup = domain.inf, domain.sup
            if sup - inf is S.Infinity:
                domain = Interval(0, period, False, True)
#.........这里部分代码省略.........