def union_sets(self, o): # noqa:F811
""" Returns the union of self and o
for use with sympy.sets.Set, if possible. """
from sympy.sets import Union, FiniteSet
# if its a FiniteSet, merge any points
# we contain and return a union with the rest
if o.is_FiniteSet:
other_points = [p for p in o if not self._contains(p)]
if len(other_points) == len(o):
return None
return Union(self, FiniteSet(*other_points))
if self._contains(o):
return self
return None
def _set_pow(x, exponent):
"""
Powers in interval arithmetic
https://en.wikipedia.org/wiki/Interval_arithmetic
"""
s1 = x.start**exponent
s2 = x.end**exponent
if ((s2 > s1) if exponent > 0 else (x.end > -x.start)) == True:
left_open = x.left_open
right_open = x.right_open
# TODO: handle unevaluated condition.
sleft = s2
else:
# TODO: `s2 > s1` could be unevaluated.
left_open = x.right_open
right_open = x.left_open
sleft = s1
if x.start.is_positive:
return Interval(
Min(s1, s2),
Max(s1, s2), left_open, right_open)
elif x.end.is_negative:
return Interval(
Min(s1, s2),
Max(s1, s2), left_open, right_open)
# Case where x.start < 0 and x.end > 0:
if exponent.is_odd:
if exponent.is_negative:
if x.start.is_zero:
return Interval(s2, oo, x.right_open)
if x.end.is_zero:
return Interval(-oo, s1, True, x.left_open)
return Union(Interval(-oo, s1, True, x.left_open), Interval(s2, oo, x.right_open))
else:
return Interval(s1, s2, x.left_open, x.right_open)
elif exponent.is_even:
if exponent.is_negative:
if x.start.is_zero:
return Interval(s2, oo, x.right_open)
if x.end.is_zero:
return Interval(s1, oo, x.left_open)
return Interval(0, oo)
else:
return Interval(S.Zero, sleft, S.Zero not in x, left_open)
def test_booleans():
""" test basic unions and intersections """
half = Rational(1, 2)
p1, p2, p3, p4 = map(Point, [(0, 0), (1, 0), (5, 1), (0, 1)])
p5, p6, p7 = map(Point, [(3, 2), (1, -1), (0, 2)])
l1 = Line(Point(0, 0), Point(1, 1))
l2 = Line(Point(half, half), Point(5, 5))
l3 = Line(p2, p3)
l4 = Line(p3, p4)
poly1 = Polygon(p1, p2, p3, p4)
poly2 = Polygon(p5, p6, p7)
poly3 = Polygon(p1, p2, p5)
assert Union(l1, l2).equals(l1)
assert Intersection(l1, l2).equals(l1)
assert Intersection(l1, l4) == FiniteSet(Point(1, 1))
assert Intersection(Union(l1, l4),
l3) == FiniteSet(Point(-S(1) / 3, -S(1) / 3),
Point(5, 1))
assert Intersection(l1, FiniteSet(Point(7, -7))) == EmptySet()
assert Intersection(Circle(Point(0, 0), 3),
Line(p1, p2)) == FiniteSet(Point(-3, 0), Point(3, 0))
assert Intersection(l1, FiniteSet(p1)) == FiniteSet(p1)
assert Union(l1, FiniteSet(p1)) == l1
fs = FiniteSet(Point(S(1) / 3, 1), Point(S(2) / 3, 0),
Point(S(9) / 5,
S(1) / 5), Point(S(7) / 3, 1))
# test the intersection of polygons
assert Intersection(poly1, poly2) == fs
# make sure if we union polygons with subsets, the subsets go away
assert Union(poly1, poly2, fs) == Union(poly1, poly2)
# make sure that if we union with a FiniteSet that isn't a subset,
# that the points in the intersection stop being listed
assert Union(poly1, FiniteSet(Point(0, 0),
Point(3,
5))) == Union(poly1,
FiniteSet(Point(3, 5)))
# intersect two polygons that share an edge
assert Intersection(poly1, poly3) == Union(
FiniteSet(Point(S(3) / 2, 1), Point(2, 1)),
Segment(Point(0, 0), Point(1, 0)))
def _solve_abs(f, symbol):
""" Helper function to solve equation involving absolute value function """
p, q, r = Wild('p'), Wild('q'), Wild('r')
pattern_match = f.match(p*Abs(q) + r) or {}
if not pattern_match.get(p, S.Zero).is_zero:
f_p, f_q, f_r = pattern_match[p], pattern_match[q], pattern_match[r]
q_pos_cond = solve_univariate_inequality(f_q >= 0, symbol,
relational=False)
q_neg_cond = solve_univariate_inequality(f_q < 0, symbol,
relational=False)
sols_q_pos = solveset_real(f_p*f_q + f_r,
symbol).intersect(q_pos_cond)
sols_q_neg = solveset_real(f_p*(-f_q) + f_r,
symbol).intersect(q_neg_cond)
return Union(sols_q_pos, sols_q_neg)
else:
return ConditionSet(symbol, Eq(f, 0), S.Complexes)
def _invert_complex(f, g_ys, symbol):
""" Helper function for invert_complex """
if not f.has(symbol):
raise ValueError("Inverse of constant function doesn't exist")
if f is symbol:
return (f, g_ys)
n = Dummy('n')
if f.is_Add:
# f = g + h
g, h = f.as_independent(symbol)
if g != S.Zero:
return _invert_complex(h, imageset(Lambda(n, n - g), g_ys), symbol)
if f.is_Mul:
# f = g*h
g, h = f.as_independent(symbol)
if g != S.One:
return _invert_complex(h, imageset(Lambda(n, n / g), g_ys), symbol)
if hasattr(f, 'inverse') and \
not isinstance(f, TrigonometricFunction) and \
not isinstance(f, exp):
if len(f.args) > 1:
raise ValueError("Only functions with one argument are supported.")
return _invert_complex(f.args[0],
imageset(Lambda(n,
f.inverse()(n)), g_ys), symbol)
if isinstance(f, exp):
if isinstance(g_ys, FiniteSet):
exp_invs = Union(*[
imageset(
Lambda(n,
I * (2 * n * pi + arg(g_y)) +
log(Abs(g_y))), S.Integers) for g_y in g_ys
if g_y != 0
])
return _invert_complex(f.args[0], exp_invs, symbol)
return (f, g_ys)
def test_booleans():
""" test basic unions and intersections """
assert Union(l1, l2).equals(l1)
assert Intersection(l1, l2).equals(l1)
assert Intersection(l1, l4) == FiniteSet(Point(1,1))
assert Intersection(Union(l1, l4), l3) == FiniteSet(Point(-1/3, -1/3), Point(5, 1))
assert Intersection(l1, FiniteSet(Point(7,-7))) == EmptySet()
assert Intersection(Circle(Point(0,0), 3), Line(p1,p2)) == FiniteSet(Point(-3,0), Point(3,0))
assert Intersection(l1, FiniteSet(p1)) == FiniteSet(p1)
assert Union(l1, FiniteSet(p1)) == l1
fs = FiniteSet(Point(1/3, 1), Point(2/3, 0), Point(9/5, 1/5), Point(7/3, 1))
# test the intersection of polygons
assert Intersection(poly1, poly2) == fs
# make sure if we union polygons with subsets, the subsets go away
assert Union(poly1, poly2, fs) == Union(poly1, poly2)
# make sure that if we union with a FiniteSet that isn't a subset,
# that the points in the intersection stop being listed
assert Union(poly1, FiniteSet(Point(0,0), Point(3,5))) == Union(poly1, FiniteSet(Point(3,5)))
# intersect two polygons that share an edge
assert Intersection(poly1, poly3) == Union(FiniteSet(Point(3/2, 1), Point(2, 1)), Segment(Point(0, 0), Point(1, 0)))
def _intersect(self, o):
""" Returns a sympy.sets.Set of intersection objects,
if possible. """
from sympy.sets import Set, FiniteSet, Union
from sympy.geometry import Point
try:
inter = self.intersection(o)
except NotImplementedError:
# sympy.sets.Set.reduce expects None if an object
# doesn't know how to simplify
return None
# put the points in a FiniteSet
points = FiniteSet(*[p for p in inter if isinstance(p, Point)])
non_points = [p for p in inter if not isinstance(p, Point)]
return Union(*(non_points + [points]))
def _solve_abs(f, symbol):
""" Helper function to solve equation involving absolute value function """
from sympy.solvers.inequalities import solve_univariate_inequality
assert f.has(Abs)
p, q, r = Wild('p'), Wild('q'), Wild('r')
pattern_match = f.match(p*Abs(q) + r)
if not pattern_match[p].is_zero:
f_p, f_q, f_r = pattern_match[p], pattern_match[q], pattern_match[r]
q_pos_cond = solve_univariate_inequality(f_q >= 0, symbol,
relational=False)
q_neg_cond = solve_univariate_inequality(f_q < 0, symbol,
relational=False)
sols_q_pos = solveset_real(f_p*f_q + f_r,
symbol).intersect(q_pos_cond)
sols_q_neg = solveset_real(f_p*(-f_q) + f_r,
symbol).intersect(q_neg_cond)
return Union(sols_q_pos, sols_q_neg)
else:
raise NotImplementedError
def test_SetExpr_Interval_div():
# TODO: some expressions cannot be calculated due to bugs (currently
# commented):
assert SetExpr(Interval(-3, -2))/SetExpr(Interval(-2, 1)) == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(2, 3))/SetExpr(Interval(-2, 2)) == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-3, -2))/SetExpr(Interval(0, 4)) == SetExpr(Interval(-oo, Rational(-1, 2)))
assert SetExpr(Interval(2, 4))/SetExpr(Interval(-3, 0)) == SetExpr(Interval(-oo, Rational(-2, 3)))
assert SetExpr(Interval(2, 4))/SetExpr(Interval(0, 3)) == SetExpr(Interval(Rational(2, 3), oo))
# assert SetExpr(Interval(0, 1))/SetExpr(Interval(0, 1)) == SetExpr(Interval(0, oo))
# assert SetExpr(Interval(-1, 0))/SetExpr(Interval(0, 1)) == SetExpr(Interval(-oo, 0))
assert SetExpr(Interval(-1, 2))/SetExpr(Interval(-2, 2)) == SetExpr(Interval(-oo, oo))
assert 1/SetExpr(Interval(-1, 2)) == SetExpr(Union(Interval(-oo, -1), Interval(S.Half, oo)))
assert 1/SetExpr(Interval(0, 2)) == SetExpr(Interval(S.Half, oo))
assert (-1)/SetExpr(Interval(0, 2)) == SetExpr(Interval(-oo, Rational(-1, 2)))
# assert 1/SetExpr(Interval(-oo, 0)) == SetExpr(Interval.open(-oo, 0))
assert 1/SetExpr(Interval(-1, 0)) == SetExpr(Interval(-oo, -1))
def _solve_real_trig(f, symbol):
""" Helper to solve trigonometric equations """
f = trigsimp(f)
f = f.rewrite(exp)
f = together(f)
g, h = fraction(f)
y = Dummy('y')
g, h = g.expand(), h.expand()
g, h = g.subs(exp(I * symbol), y), h.subs(exp(I * symbol), y)
if g.has(symbol) or h.has(symbol):
return ConditionSet(symbol, Eq(f, 0), S.Reals)
solns = solveset_complex(g, y) - solveset_complex(h, y)
if isinstance(solns, FiniteSet):
return Union(
*[invert_complex(exp(I * symbol), s, symbol)[1] for s in solns])
elif solns is S.EmptySet:
return S.EmptySet
else:
return ConditionSet(symbol, Eq(f, 0), S.Reals)
def _solve_abs(f, symbol, domain):
""" Helper function to solve equation involving absolute value function """
if not domain.is_subset(S.Reals):
raise ValueError(filldedent('''
Absolute values cannot be inverted in the
complex domain.'''))
p, q, r = Wild('p'), Wild('q'), Wild('r')
pattern_match = f.match(p*Abs(q) + r) or {}
if not pattern_match.get(p, S.Zero).is_zero:
f_p, f_q, f_r = pattern_match[p], pattern_match[q], pattern_match[r]
q_pos_cond = solve_univariate_inequality(f_q >= 0, symbol,
relational=False)
q_neg_cond = solve_univariate_inequality(f_q < 0, symbol,
relational=False)
sols_q_pos = solveset_real(f_p*f_q + f_r,
symbol).intersect(q_pos_cond)
sols_q_neg = solveset_real(f_p*(-f_q) + f_r,
symbol).intersect(q_neg_cond)
return Union(sols_q_pos, sols_q_neg)
else:
return ConditionSet(symbol, Eq(f, 0), domain)
def intersection_sets(self, o): # noqa:F811
""" Returns a sympy.sets.Set of intersection objects,
if possible. """
from sympy.geometry.point import Point
try:
# if o is a FiniteSet, find the intersection directly
# to avoid infinite recursion
if o.is_FiniteSet:
inter = FiniteSet(*(p for p in o if self.contains(p)))
else:
inter = self.intersection(o)
except NotImplementedError:
# sympy.sets.Set.reduce expects None if an object
# doesn't know how to simplify
return None
# put the points in a FiniteSet
points = FiniteSet(*[p for p in inter if isinstance(p, Point)])
non_points = [p for p in inter if not isinstance(p, Point)]
return Union(*(non_points + [points]))
def _solve_as_poly(f, symbol, solveset_solver, invert_func):
"""
Solve the equation using polynomial techniques if it already is a
polynomial equation or, with a change of variables, can be made so.
"""
result = None
if f.is_polynomial(symbol):
solns = roots(f,
symbol,
cubics=True,
quartics=True,
quintics=True,
domain='EX')
num_roots = sum(solns.values())
if degree(f, symbol) <= num_roots:
result = FiniteSet(*solns.keys())
else:
poly = Poly(f, symbol)
solns = poly.all_roots()
if poly.degree() <= len(solns):
result = FiniteSet(*solns)
else:
raise NotImplementedError("Couldn't find all roots "
"of the equation %s" % f)
else:
poly = Poly(f)
if poly is None:
raise NotImplementedError("Could not convert %s to Poly" % f)
gens = [g for g in poly.gens if g.has(symbol)]
if len(gens) == 1:
poly = Poly(poly, gens[0])
gen = poly.gen
deg = poly.degree()
poly = Poly(poly.as_expr(), poly.gen, composite=True)
poly_solns = FiniteSet(
*roots(poly, cubics=True, quartics=True, quintics=True).keys())
if len(poly_solns) < deg:
raise NotImplementedError("Couldn't find all the roots of "
"the equation %s" % f)
if gen != symbol:
y = Dummy('y')
lhs, rhs_s = invert_func(gen, y, symbol)
if lhs is symbol:
result = Union(*[rhs_s.subs(y, s) for s in poly_solns])
else:
raise NotImplementedError("inversion of %s not handled" %
gen)
else:
raise NotImplementedError("multiple generators not handled"
" by solveset")
if result is not None:
if isinstance(result, FiniteSet):
# this is to simplify solutions like -sqrt(-I) to sqrt(2)/2
# - sqrt(2)*I/2. We are not expanding for solution with free
# variables because that makes the solution more complicated. For
# example expand_complex(a) returns re(a) + I*im(a)
if all([
s.free_symbols == set() and not isinstance(s, RootOf)
for s in result
]):
s = Dummy('s')
result = imageset(Lambda(s, expand_complex(s)), result)
return result
else:
raise NotImplementedError
def _solve_as_poly(f, symbol, domain=S.Complexes):
"""
Solve the equation using polynomial techniques if it already is a
polynomial equation or, with a change of variables, can be made so.
"""
result = None
if f.is_polynomial(symbol):
solns = roots(f, symbol, cubics=True, quartics=True,
quintics=True, domain='EX')
num_roots = sum(solns.values())
if degree(f, symbol) <= num_roots:
result = FiniteSet(*solns.keys())
else:
poly = Poly(f, symbol)
solns = poly.all_roots()
if poly.degree() <= len(solns):
result = FiniteSet(*solns)
else:
result = ConditionSet(symbol, Eq(f, 0), domain)
else:
poly = Poly(f)
if poly is None:
result = ConditionSet(symbol, Eq(f, 0), domain)
gens = [g for g in poly.gens if g.has(symbol)]
if len(gens) == 1:
poly = Poly(poly, gens[0])
gen = poly.gen
deg = poly.degree()
poly = Poly(poly.as_expr(), poly.gen, composite=True)
poly_solns = FiniteSet(*roots(poly, cubics=True, quartics=True,
quintics=True).keys())
if len(poly_solns) < deg:
result = ConditionSet(symbol, Eq(f, 0), domain)
if gen != symbol:
y = Dummy('y')
inverter = invert_real if domain.is_subset(S.Reals) else invert_complex
lhs, rhs_s = inverter(gen, y, symbol)
if lhs == symbol:
result = Union(*[rhs_s.subs(y, s) for s in poly_solns])
else:
result = ConditionSet(symbol, Eq(f, 0), domain)
else:
result = ConditionSet(symbol, Eq(f, 0), domain)
if result is not None:
if isinstance(result, FiniteSet):
# this is to simplify solutions like -sqrt(-I) to sqrt(2)/2
# - sqrt(2)*I/2. We are not expanding for solution with free
# variables because that makes the solution more complicated. For
# example expand_complex(a) returns re(a) + I*im(a)
if all([s.free_symbols == set() and not isinstance(s, RootOf)
for s in result]):
s = Dummy('s')
result = imageset(Lambda(s, expand_complex(s)), result)
if isinstance(result, FiniteSet):
result = result.intersection(domain)
return result
else:
return ConditionSet(symbol, Eq(f, 0), domain)
def _invert_real(f, g_ys, symbol):
"""Helper function for _invert."""
if f == symbol:
return (f, g_ys)
n = Dummy('n', real=True)
if hasattr(f, 'inverse') and not isinstance(f, (
TrigonometricFunction,
HyperbolicFunction,
)):
if len(f.args) > 1:
raise ValueError("Only functions with one argument are supported.")
return _invert_real(f.args[0],
imageset(Lambda(n, f.inverse()(n)), g_ys),
symbol)
if isinstance(f, Abs):
pos = Interval(0, S.Infinity)
neg = Interval(S.NegativeInfinity, 0)
return _invert_real(f.args[0],
Union(imageset(Lambda(n, n), g_ys).intersect(pos),
imageset(Lambda(n, -n), g_ys).intersect(neg)), symbol)
if f.is_Add:
# f = g + h
g, h = f.as_independent(symbol)
if g is not S.Zero:
return _invert_real(h, imageset(Lambda(n, n - g), g_ys), symbol)
if f.is_Mul:
# f = g*h
g, h = f.as_independent(symbol)
if g is not S.One:
return _invert_real(h, imageset(Lambda(n, n/g), g_ys), symbol)
if f.is_Pow:
base, expo = f.args
base_has_sym = base.has(symbol)
expo_has_sym = expo.has(symbol)
if not expo_has_sym:
res = imageset(Lambda(n, real_root(n, expo)), g_ys)
if expo.is_rational:
numer, denom = expo.as_numer_denom()
if numer == S.One or numer == - S.One:
return _invert_real(base, res, symbol)
else:
if numer % 2 == 0:
n = Dummy('n')
neg_res = imageset(Lambda(n, -n), res)
return _invert_real(base, res + neg_res, symbol)
else:
return _invert_real(base, res, symbol)
else:
if not base.is_positive:
raise ValueError("x**w where w is irrational is not "
"defined for negative x")
return _invert_real(base, res, symbol)
if not base_has_sym:
return _invert_real(expo,
imageset(Lambda(n, log(n)/log(base)), g_ys), symbol)
if isinstance(f, TrigonometricFunction):
if isinstance(g_ys, FiniteSet):
def inv(trig):
if isinstance(f, (sin, csc)):
F = asin if isinstance(f, sin) else acsc
return (lambda a: n*pi + (-1)**n*F(a),)
if isinstance(f, (cos, sec)):
F = acos if isinstance(f, cos) else asec
return (
lambda a: 2*n*pi + F(a),
lambda a: 2*n*pi - F(a),)
if isinstance(f, (tan, cot)):
return (lambda a: n*pi + f.inverse()(a),)
n = Dummy('n', integer=True)
invs = S.EmptySet
for L in inv(f):
invs += Union(*[imageset(Lambda(n, L(g)), S.Integers) for g in g_ys])
return _invert_real(f.args[0], invs, symbol)
return (f, g_ys)
def _invert_real(f, g_ys, symbol):
""" Helper function for invert_real """
if not f.has(symbol):
raise ValueError("Inverse of constant function doesn't exist")
if f is symbol:
return (f, g_ys)
n = Dummy('n')
if hasattr(f, 'inverse') and not isinstance(f, TrigonometricFunction) and \
not isinstance(f, HyperbolicFunction):
if len(f.args) > 1:
raise ValueError("Only functions with one argument are supported.")
return _invert_real(f.args[0], imageset(Lambda(n,
f.inverse()(n)), g_ys),
symbol)
if isinstance(f, Abs):
return _invert_real(
f.args[0],
Union(
imageset(Lambda(n, n), g_ys).intersect(Interval(0, oo)),
imageset(Lambda(n, -n), g_ys).intersect(Interval(-oo, 0))),
symbol)
if f.is_Add:
# f = g + h
g, h = f.as_independent(symbol)
if g != S.Zero:
return _invert_real(h, imageset(Lambda(n, n - g), g_ys), symbol)
if f.is_Mul:
# f = g*h
g, h = f.as_independent(symbol)
if g != S.One:
return _invert_real(h, imageset(Lambda(n, n / g), g_ys), symbol)
if f.is_Pow:
base, expo = f.args
base_has_sym = base.has(symbol)
expo_has_sym = expo.has(symbol)
if not expo_has_sym:
res = imageset(Lambda(n, real_root(n, expo)), g_ys)
if expo.is_rational:
numer, denom = expo.as_numer_denom()
if numer == S.One or numer == -S.One:
return _invert_real(base, res, symbol)
else:
if numer % 2 == 0:
n = Dummy('n')
neg_res = imageset(Lambda(n, -n), res)
return _invert_real(base, res + neg_res, symbol)
else:
return _invert_real(base, res, symbol)
else:
if not base.is_positive:
raise ValueError("x**w where w is irrational is not "
"defined for negative x")
return _invert_real(base, res, symbol)
if not base_has_sym:
return _invert_real(expo,
imageset(Lambda(n,
log(n) / log(base)), g_ys),
symbol)
if isinstance(f, sin):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
sin_invs = Union(*[imageset(Lambda(n, n*pi + (-1)**n*asin(g_y)), \
S.Integers) for g_y in g_ys])
return _invert_real(f.args[0], sin_invs, symbol)
if isinstance(f, csc):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
csc_invs = Union(*[imageset(Lambda(n, n*pi + (-1)**n*acsc(g_y)), \
S.Integers) for g_y in g_ys])
return _invert_real(f.args[0], csc_invs, symbol)
if isinstance(f, cos):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
cos_invs_f1 = Union(*[imageset(Lambda(n, 2*n*pi + acos(g_y)), \
S.Integers) for g_y in g_ys])
cos_invs_f2 = Union(*[imageset(Lambda(n, 2*n*pi - acos(g_y)), \
S.Integers) for g_y in g_ys])
cos_invs = Union(cos_invs_f1, cos_invs_f2)
return _invert_real(f.args[0], cos_invs, symbol)
if isinstance(f, sec):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
sec_invs_f1 = Union(*[imageset(Lambda(n, 2*n*pi + asec(g_y)), \
S.Integers) for g_y in g_ys])
sec_invs_f2 = Union(*[imageset(Lambda(n, 2*n*pi - asec(g_y)), \
S.Integers) for g_y in g_ys])
sec_invs = Union(sec_invs_f1, sec_invs_f2)
return _invert_real(f.args[0], sec_invs, symbol)
if isinstance(f, tan) or isinstance(f, cot):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
tan_cot_invs = Union(*[imageset(Lambda(n, n*pi + f.inverse()(g_y)), \
S.Integers) for g_y in g_ys])
return _invert_real(f.args[0], tan_cot_invs, symbol)
return (f, g_ys)
def solveset_complex(f, symbol):
""" Solve a complex valued equation.
Parameters
==========
f : Expr
The target equation
symbol : Symbol
The variable for which the equation is solved
Returns
=======
Set
A set of values for `symbol` for which `f` equal to
zero. An `EmptySet` is returned if no solution is found.
A `ConditionSet` is returned as an unsolved object if algorithms
to evaluate complete solutions are not yet implemented.
`solveset_complex` claims to be complete in the solution set that
it returns.
Raises
======
NotImplementedError
The algorithms to solve inequalities in complex domain are
not yet implemented.
ValueError
The input is not valid.
RuntimeError
It is a bug, please report to the github issue tracker.
See Also
========
solveset_real: solver for real domain
Examples
========
>>> from sympy import Symbol, exp
>>> from sympy.solvers.solveset import solveset_complex
>>> from sympy.abc import x, a, b, c
>>> solveset_complex(a*x**2 + b*x +c, x)
{-b/(2*a) - sqrt(-4*a*c + b**2)/(2*a), -b/(2*a) + sqrt(-4*a*c + b**2)/(2*a)}
* Due to the fact that complex extension of my real valued functions are
multivariate even some simple equations can have infinitely many
solution.
>>> solveset_complex(exp(x) - 1, x)
ImageSet(Lambda(_n, 2*_n*I*pi), Integers())
"""
if not symbol.is_Symbol:
raise ValueError(" %s is not a symbol" % (symbol))
f = sympify(f)
original_eq = f
if not isinstance(f, (Expr, Number)):
raise ValueError(" %s is not a valid sympy expression" % (f))
f = together(f)
# Without this equations like a + 4*x**2 - E keep oscillating
# into form a/4 + x**2 - E/4 and (a + 4*x**2 - E)/4
if not fraction(f)[1].has(symbol):
f = expand(f)
if f.is_zero:
return S.Complexes
elif not f.has(symbol):
result = EmptySet()
elif f.is_Mul and all([_is_finite_with_finite_vars(m) for m in f.args]):
result = Union(*[solveset_complex(m, symbol) for m in f.args])
else:
lhs, rhs_s = invert_complex(f, 0, symbol)
if lhs == symbol:
result = rhs_s
elif isinstance(rhs_s, FiniteSet):
equations = [lhs - rhs for rhs in rhs_s]
result = EmptySet()
for equation in equations:
if equation == f:
if any(
_has_rational_power(g, symbol)[0]
for g in equation.args):
result += _solve_radical(equation, symbol,
solveset_complex)
else:
result += _solve_as_rational(
equation,
symbol,
solveset_solver=solveset_complex,
as_poly_solver=_solve_as_poly_complex)
else:
result += solveset_complex(equation, symbol)
else:
result = ConditionSet(symbol, Eq(f, 0), S.Complexes)
if isinstance(result, FiniteSet):
result = [
s for s in result
if isinstance(s, RootOf) or domain_check(original_eq, symbol, s)
]
return FiniteSet(*result)
else:
return result
def _(f, x):
return Union(*(imageset(f, arg) for arg in x.args))
def solveset_real(f, symbol):
""" Solves a real valued equation.
Parameters
==========
f : Expr
The target equation
symbol : Symbol
The variable for which the equation is solved
Returns
=======
Set
A set of values for `symbol` for which `f` is equal to
zero. An `EmptySet` is returned if no solution is found.
A `ConditionSet` is returned as unsolved object if algorithms
to evaluate complete solutions are not yet implemented.
`solveset_real` claims to be complete in the set of the solution it
returns.
Raises
======
NotImplementedError
Algorithms to solve inequalities in complex domain are
not yet implemented.
ValueError
The input is not valid.
RuntimeError
It is a bug, please report to the github issue tracker.
See Also
=======
solveset_complex : solver for complex domain
Examples
========
>>> from sympy import Symbol, exp, sin, sqrt, I
>>> from sympy.solvers.solveset import solveset_real
>>> x = Symbol('x', real=True)
>>> a = Symbol('a', real=True, finite=True, positive=True)
>>> solveset_real(x**2 - 1, x)
{-1, 1}
>>> solveset_real(sqrt(5*x + 6) - 2 - x, x)
{-1, 2}
>>> solveset_real(x - I, x)
EmptySet()
>>> solveset_real(x - a, x)
{a}
>>> solveset_real(exp(x) - a, x)
{log(a)}
* In case the equation has infinitely many solutions an infinitely indexed
`ImageSet` is returned.
>>> solveset_real(sin(x) - 1, x)
ImageSet(Lambda(_n, 2*_n*pi + pi/2), Integers())
* If the equation is true for any arbitrary value of the symbol a `S.Reals`
set is returned.
>>> solveset_real(x - x, x)
(-oo, oo)
"""
if not symbol.is_Symbol:
raise ValueError(" %s is not a symbol" % (symbol))
f = sympify(f)
if not isinstance(f, (Expr, Number)):
raise ValueError(" %s is not a valid sympy expression" % (f))
original_eq = f
f = together(f)
# In this, unlike in solveset_complex, expression should only
# be expanded when fraction(f)[1] does not contain the symbol
# for which we are solving
if not symbol in fraction(f)[1].free_symbols and f.is_rational_function():
f = expand(f)
if f.has(Piecewise):
f = piecewise_fold(f)
result = EmptySet()
if f.expand().is_zero:
return S.Reals
elif not f.has(symbol):
return EmptySet()
elif f.is_Mul and all([_is_finite_with_finite_vars(m) for m in f.args]):
# if f(x) and g(x) are both finite we can say that the solution of
# f(x)*g(x) == 0 is same as Union(f(x) == 0, g(x) == 0) is not true in
# general. g(x) can grow to infinitely large for the values where
# f(x) == 0. To be sure that we are not silently allowing any
# wrong solutions we are using this technique only if both f and g are
# finite for a finite input.
result = Union(*[solveset_real(m, symbol) for m in f.args])
elif _is_function_class_equation(TrigonometricFunction, f, symbol) or \
_is_function_class_equation(HyperbolicFunction, f, symbol):
result = _solve_real_trig(f, symbol)
elif f.is_Piecewise:
result = EmptySet()
expr_set_pairs = f.as_expr_set_pairs()
for (expr, in_set) in expr_set_pairs:
solns = solveset_real(expr, symbol).intersect(in_set)
result = result + solns
else:
lhs, rhs_s = invert_real(f, 0, symbol)
if lhs == symbol:
result = rhs_s
elif isinstance(rhs_s, FiniteSet):
equations = [lhs - rhs for rhs in rhs_s]
for equation in equations:
if equation == f:
if any(
_has_rational_power(g, symbol)[0]
for g in equation.args):
result += _solve_radical(equation, symbol,
solveset_real)
elif equation.has(Abs):
result += _solve_abs(f, symbol)
else:
result += _solve_as_rational(
equation,
symbol,
solveset_solver=solveset_real,
as_poly_solver=_solve_as_poly_real)
else:
result += solveset_real(equation, symbol)
else:
result = ConditionSet(symbol, Eq(f, 0), S.Reals)
if isinstance(result, FiniteSet):
result = [
s for s in result
if isinstance(s, RootOf) or domain_check(original_eq, symbol, s)
]
return FiniteSet(*result).intersect(S.Reals)
else:
return result.intersect(S.Reals)
def function_sets(f, x):
return Union(imageset(f, arg) for arg in x.args)
def test_SetExpr_Interval_pow():
assert SetExpr(Interval(0, 2))**2 == SetExpr(Interval(0, 4))
assert SetExpr(Interval(-1, 1))**2 == SetExpr(Interval(0, 1))
assert SetExpr(Interval(1, 2))**2 == SetExpr(Interval(1, 4))
assert SetExpr(Interval(-1, 2))**3 == SetExpr(Interval(-1, 8))
assert SetExpr(Interval(-1, 1))**0 == SetExpr(FiniteSet(1))
#assert SetExpr(Interval(1, 2))**(S(5)/2) == SetExpr(Interval(1, 4*sqrt(2)))
#assert SetExpr(Interval(-1, 2))**(S.One/3) == SetExpr(Interval(-1, 2**(S.One/3)))
#assert SetExpr(Interval(0, 2))**(S.One/2) == SetExpr(Interval(0, sqrt(2)))
#assert SetExpr(Interval(-4, 2))**(S(2)/3) == SetExpr(Interval(0, 2*2**(S.One/3)))
#assert SetExpr(Interval(-1, 5))**(S.One/2) == SetExpr(Interval(0, sqrt(5)))
#assert SetExpr(Interval(-oo, 2))**(S.One/2) == SetExpr(Interval(0, sqrt(2)))
#assert SetExpr(Interval(-2, 3))**(S(-1)/4) == SetExpr(Interval(0, oo))
assert SetExpr(Interval(1, 5))**(-2) == SetExpr(Interval(S.One / 25, 1))
assert SetExpr(Interval(-1, 3))**(-2) == SetExpr(Interval(0, oo))
assert SetExpr(Interval(0, 2))**(-2) == SetExpr(Interval(S.One / 4, oo))
assert SetExpr(Interval(-1, 2))**(-3) == SetExpr(
Union(Interval(-oo, -1), Interval(S(1) / 8, oo)))
assert SetExpr(Interval(-3, -2))**(-3) == SetExpr(
Interval(S(-1) / 8, -S.One / 27))
assert SetExpr(Interval(-3, -2))**(-2) == SetExpr(
Interval(S.One / 9, S.One / 4))
#assert SetExpr(Interval(0, oo))**(S.One/2) == SetExpr(Interval(0, oo))
#assert SetExpr(Interval(-oo, -1))**(S.One/3) == SetExpr(Interval(-oo, -1))
#assert SetExpr(Interval(-2, 3))**(-S.One/3) == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-oo, 0))**(-2) == SetExpr(Interval.open(0, oo))
assert SetExpr(Interval(-2, 0))**(-2) == SetExpr(Interval(S.One / 4, oo))
assert SetExpr(Interval(S.One / 3, S.One / 2))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(0, S.One / 2))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(S.One / 2, 1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(0, 1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(2, 3))**oo == SetExpr(FiniteSet(oo))
assert SetExpr(Interval(1, 2))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(S.One / 2, 3))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(-S.One / 3,
-S.One / 4))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(-1, -S.One / 2))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-3, -2))**oo == SetExpr(FiniteSet(-oo, oo))
assert SetExpr(Interval(-2, -1))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-2, -S.One / 2))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-S.One / 2,
S.One / 2))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(-S.One / 2, 1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(-S(2) / 3, 2))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(-1, 1))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-1, S.One / 2))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-1, 2))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-2, S.One / 2))**oo == SetExpr(Interval(-oo, oo))
assert (SetExpr(Interval(1, 2))**x).dummy_eq(
SetExpr(ImageSet(Lambda(_d, _d**x), Interval(1, 2))))
assert SetExpr(Interval(2, 3))**(-oo) == SetExpr(FiniteSet(0))
assert SetExpr(Interval(0, 2))**(-oo) == SetExpr(Interval(0, oo))
assert (SetExpr(Interval(-1, 2))**(-oo)).dummy_eq(
SetExpr(ImageSet(Lambda(_d, _d**(-oo)), Interval(-1, 2))))
def _set_function(f, x):
from sympy.functions.elementary.miscellaneous import Min, Max
from sympy.solvers.solveset import solveset
from sympy.core.function import diff, Lambda
from sympy.series import limit
from sympy.calculus.singularities import singularities
from sympy.sets import Complement
# TODO: handle functions with infinitely many solutions (eg, sin, tan)
# TODO: handle multivariate functions
expr = f.expr
if len(expr.free_symbols) > 1 or len(f.variables) != 1:
return
var = f.variables[0]
if expr.is_Piecewise:
result = S.EmptySet
domain_set = x
for (p_expr, p_cond) in expr.args:
if p_cond is true:
intrvl = domain_set
else:
intrvl = p_cond.as_set()
intrvl = Intersection(domain_set, intrvl)
if p_expr.is_Number:
image = FiniteSet(p_expr)
else:
image = imageset(Lambda(var, p_expr), intrvl)
result = Union(result, image)
# remove the part which has been `imaged`
domain_set = Complement(domain_set, intrvl)
if domain_set.is_EmptySet:
break
return result
if not x.start.is_comparable or not x.end.is_comparable:
return
try:
sing = [i for i in singularities(expr, var)
if i.is_real and i in x]
except NotImplementedError:
return
if x.left_open:
_start = limit(expr, var, x.start, dir="+")
elif x.start not in sing:
_start = f(x.start)
if x.right_open:
_end = limit(expr, var, x.end, dir="-")
elif x.end not in sing:
_end = f(x.end)
if len(sing) == 0:
solns = list(solveset(diff(expr, var), var))
extr = [_start, _end] + [f(i) for i in solns
if i.is_real and i in x]
start, end = Min(*extr), Max(*extr)
left_open, right_open = False, False
if _start <= _end:
# the minimum or maximum value can occur simultaneously
# on both the edge of the interval and in some interior
# point
if start == _start and start not in solns:
left_open = x.left_open
if end == _end and end not in solns:
right_open = x.right_open
else:
if start == _end and start not in solns:
left_open = x.right_open
if end == _start and end not in solns:
right_open = x.left_open
return Interval(start, end, left_open, right_open)
else:
return imageset(f, Interval(x.start, sing[0],
x.left_open, True)) + \
Union(*[imageset(f, Interval(sing[i], sing[i + 1], True, True))
for i in range(0, len(sing) - 1)]) + \
imageset(f, Interval(sing[-1], x.end, True, x.right_open))
def _set_function(f, x):
return Union(imageset(f, arg) for arg in x.args)
def dispatch_on_operation(x, y, op):
return Union(*[dispatch_on_operation(i, y, op) for i in x])
def _solveset(f, symbol, domain, _check=False):
"""Helper for solveset to return a result from an expression
that has already been sympify'ed and is known to contain the
given symbol."""
# _check controls whether the answer is checked or not
from sympy.simplify.simplify import signsimp
orig_f = f
f = together(f)
if f.is_Mul:
_, f = f.as_independent(symbol, as_Add=False)
if f.is_Add:
a, h = f.as_independent(symbol)
m, h = h.as_independent(symbol, as_Add=False)
f = a/m + h # XXX condition `m != 0` should be added to soln
f = piecewise_fold(f)
# assign the solvers to use
solver = lambda f, x, domain=domain: _solveset(f, x, domain)
if domain.is_subset(S.Reals):
inverter_func = invert_real
else:
inverter_func = invert_complex
inverter = lambda f, rhs, symbol: inverter_func(f, rhs, symbol, domain)
result = EmptySet()
if f.expand().is_zero:
return domain
elif not f.has(symbol):
return EmptySet()
elif f.is_Mul and all(_is_finite_with_finite_vars(m, domain)
for m in f.args):
# if f(x) and g(x) are both finite we can say that the solution of
# f(x)*g(x) == 0 is same as Union(f(x) == 0, g(x) == 0) is not true in
# general. g(x) can grow to infinitely large for the values where
# f(x) == 0. To be sure that we are not silently allowing any
# wrong solutions we are using this technique only if both f and g are
# finite for a finite input.
result = Union(*[solver(m, symbol) for m in f.args])
elif _is_function_class_equation(TrigonometricFunction, f, symbol) or \
_is_function_class_equation(HyperbolicFunction, f, symbol):
result = _solve_trig(f, symbol, domain)
elif f.is_Piecewise:
dom = domain
result = EmptySet()
expr_set_pairs = f.as_expr_set_pairs()
for (expr, in_set) in expr_set_pairs:
if in_set.is_Relational:
in_set = in_set.as_set()
if in_set.is_Interval:
dom -= in_set
solns = solver(expr, symbol, in_set)
result += solns
else:
lhs, rhs_s = inverter(f, 0, symbol)
if lhs == symbol:
# do some very minimal simplification since
# repeated inversion may have left the result
# in a state that other solvers (e.g. poly)
# would have simplified; this is done here
# rather than in the inverter since here it
# is only done once whereas there it would
# be repeated for each step of the inversion
if isinstance(rhs_s, FiniteSet):
rhs_s = FiniteSet(*[Mul(*
signsimp(i).as_content_primitive())
for i in rhs_s])
result = rhs_s
elif isinstance(rhs_s, FiniteSet):
for equation in [lhs - rhs for rhs in rhs_s]:
if equation == f:
if any(_has_rational_power(g, symbol)[0]
for g in equation.args) or _has_rational_power(
equation, symbol)[0]:
result += _solve_radical(equation,
symbol,
solver)
elif equation.has(Abs):
result += _solve_abs(f, symbol, domain)
else:
result += _solve_as_rational(equation, symbol, domain)
else:
result += solver(equation, symbol)
else:
result = ConditionSet(symbol, Eq(f, 0), domain)
if _check:
if isinstance(result, ConditionSet):
# it wasn't solved or has enumerated all conditions
# -- leave it alone
return result
# whittle away all but the symbol-containing core
# to use this for testing
fx = orig_f.as_independent(symbol, as_Add=True)[1]
fx = fx.as_independent(symbol, as_Add=False)[1]
if isinstance(result, FiniteSet):
# check the result for invalid solutions
result = FiniteSet(*[s for s in result
if isinstance(s, RootOf)
or domain_check(fx, symbol, s)])
return result
def _set_function(f, x): # noqa:F811
return Union(*(imageset(f, arg) for arg in x.args))
def test_SetExpr_Interval_pow():
assert SetExpr(Interval(0, 2))**2 == SetExpr(Interval(0, 4))
assert SetExpr(Interval(-1, 1))**2 == SetExpr(Interval(0, 1))
assert SetExpr(Interval(1, 2))**2 == SetExpr(Interval(1, 4))
assert SetExpr(Interval(-1, 2))**3 == SetExpr(Interval(-1, 8))
assert SetExpr(Interval(-1, 1))**0 == SetExpr(FiniteSet(1))
#assert SetExpr(Interval(1, 2))**Rational(5, 2) == SetExpr(Interval(1, 4*sqrt(2)))
#assert SetExpr(Interval(-1, 2))**Rational(1, 3) == SetExpr(Interval(-1, 2**Rational(1, 3)))
#assert SetExpr(Interval(0, 2))**S.Half == SetExpr(Interval(0, sqrt(2)))
#assert SetExpr(Interval(-4, 2))**Rational(2, 3) == SetExpr(Interval(0, 2*2**Rational(1, 3)))
#assert SetExpr(Interval(-1, 5))**S.Half == SetExpr(Interval(0, sqrt(5)))
#assert SetExpr(Interval(-oo, 2))**S.Half == SetExpr(Interval(0, sqrt(2)))
#assert SetExpr(Interval(-2, 3))**(Rational(-1, 4)) == SetExpr(Interval(0, oo))
assert SetExpr(Interval(1,
5))**(-2) == SetExpr(Interval(Rational(1, 25), 1))
assert SetExpr(Interval(-1, 3))**(-2) == SetExpr(Interval(0, oo))
assert SetExpr(Interval(0,
2))**(-2) == SetExpr(Interval(Rational(1, 4), oo))
assert SetExpr(Interval(-1, 2))**(-3) == SetExpr(
Union(Interval(-oo, -1), Interval(Rational(1, 8), oo)))
assert SetExpr(Interval(-3, -2))**(-3) == SetExpr(
Interval(Rational(-1, 8), Rational(-1, 27)))
assert SetExpr(Interval(-3, -2))**(-2) == SetExpr(
Interval(Rational(1, 9), Rational(1, 4)))
#assert SetExpr(Interval(0, oo))**S.Half == SetExpr(Interval(0, oo))
#assert SetExpr(Interval(-oo, -1))**Rational(1, 3) == SetExpr(Interval(-oo, -1))
#assert SetExpr(Interval(-2, 3))**(Rational(-1, 3)) == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-oo, 0))**(-2) == SetExpr(Interval.open(0, oo))
assert SetExpr(Interval(-2,
0))**(-2) == SetExpr(Interval(Rational(1, 4), oo))
assert SetExpr(Interval(Rational(1, 3),
S.Half))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(0, S.Half))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(S.Half, 1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(0, 1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(2, 3))**oo == SetExpr(FiniteSet(oo))
assert SetExpr(Interval(1, 2))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(S.Half, 3))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(Rational(-1, 3),
Rational(-1, 4)))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(-1, Rational(-1,
2)))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-3, -2))**oo == SetExpr(FiniteSet(-oo, oo))
assert SetExpr(Interval(-2, -1))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-2, Rational(-1,
2)))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(Rational(-1, 2),
S.Half))**oo == SetExpr(FiniteSet(0))
assert SetExpr(Interval(Rational(-1, 2),
1))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(Rational(-2, 3),
2))**oo == SetExpr(Interval(0, oo))
assert SetExpr(Interval(-1, 1))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-1, S.Half))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-1, 2))**oo == SetExpr(Interval(-oo, oo))
assert SetExpr(Interval(-2, S.Half))**oo == SetExpr(Interval(-oo, oo))
assert (SetExpr(Interval(1, 2))**x).dummy_eq(
SetExpr(ImageSet(Lambda(_d, _d**x), Interval(1, 2))))
assert SetExpr(Interval(2, 3))**(-oo) == SetExpr(FiniteSet(0))
assert SetExpr(Interval(0, 2))**(-oo) == SetExpr(Interval(0, oo))
assert (SetExpr(Interval(-1, 2))**(-oo)).dummy_eq(
SetExpr(ImageSet(Lambda(_d, _d**(-oo)), Interval(-1, 2))))
def _invert_real(f, g_ys, symbol):
""" Helper function for invert_real """
if not f.has(symbol):
raise ValueError("Inverse of constant function doesn't exist")
if f is symbol:
return (f, g_ys)
n = Dummy('n')
if hasattr(f, 'inverse') and not isinstance(f, TrigonometricFunction):
if len(f.args) > 1:
raise ValueError("Only functions with one argument are supported.")
return _invert_real(f.args[0], imageset(Lambda(n,
f.inverse()(n)), g_ys),
symbol)
if isinstance(f, Abs):
g_ys = g_ys - FiniteSet(*[g_y for g_y in g_ys if g_y.is_negative])
return _invert_real(f.args[0],
Union(g_ys, imageset(Lambda(n, -n), g_ys)), symbol)
if f.is_Add:
# f = g + h
g, h = f.as_independent(symbol)
if g != S.Zero:
return _invert_real(h, imageset(Lambda(n, n - g), g_ys), symbol)
if f.is_Mul:
# f = g*h
g, h = f.as_independent(symbol)
if g != S.One:
return _invert_real(h, imageset(Lambda(n, n / g), g_ys), symbol)
if f.is_Pow:
base, expo = f.args
base_has_sym = base.has(symbol)
expo_has_sym = expo.has(symbol)
if not expo_has_sym:
res = imageset(Lambda(n, Pow(n, 1 / expo)), g_ys)
if expo.is_rational:
numer, denom = expo.as_numer_denom()
if numer == S.One or numer == -S.One:
return _invert_real(base, res, symbol)
else:
if numer % 2 == 0:
n = Dummy('n')
neg_res = imageset(Lambda(n, -n), res)
return _invert_real(base, res + neg_res, symbol)
else:
return _invert_real(base, res, symbol)
else:
if not base.is_positive:
raise ValueError("x**w where w is irrational is not "
"defined for negative x")
return _invert_real(base, res, symbol)
if not base_has_sym:
return _invert_real(expo,
imageset(Lambda(n,
log(n) / log(base)), g_ys),
symbol)
if isinstance(f, tan) or isinstance(f, cot):
n = Dummy('n')
if isinstance(g_ys, FiniteSet):
tan_cot_invs = Union(*[
imageset(Lambda(n, n * pi + f.inverse()(g_y)), S.Integers)
for g_y in g_ys
])
return _invert_real(f.args[0], tan_cot_invs, symbol)
return (f, g_ys)
