def test_range_interval_intersection():
p = symbols('p', positive=True)
assert isinstance(Range(3).intersect(Interval(p, p + 2)), Intersection)
assert Range(4).intersect(Interval(0, 3)) == Range(4)
assert Range(4).intersect(Interval(-oo, oo)) == Range(4)
assert Range(4).intersect(Interval(1, oo)) == Range(1, 4)
assert Range(4).intersect(Interval(1.1, oo)) == Range(2, 4)
assert Range(4).intersect(Interval(0.1, 3)) == Range(1, 4)
assert Range(4).intersect(Interval(0.1, 3.1)) == Range(1, 4)
assert Range(4).intersect(Interval.open(0, 3)) == Range(1, 3)
assert Range(4).intersect(Interval.open(0.1, 0.5)) is S.EmptySet
def test_continuous_domain():
x = Symbol('x')
assert continuous_domain(sin(x), x, Interval(0, 2*pi)) == Interval(0, 2*pi)
assert continuous_domain(tan(x), x, Interval(0, 2*pi)) == \
Union(Interval(0, pi/2, False, True), Interval(pi/2, 3*pi/2, True, True),
Interval(3*pi/2, 2*pi, True, False))
assert continuous_domain((x - 1)/((x - 1)**2), x, S.Reals) == \
Union(Interval(-oo, 1, True, True), Interval(1, oo, True, True))
assert continuous_domain(log(x) + log(4*x - 1), x, S.Reals) == \
Interval(1/4, oo, True, True)
assert continuous_domain(1/sqrt(x - 3), x, S.Reals) == Interval(3, oo, True, True)
assert continuous_domain(1/x - 2, x, S.Reals) == \
Union(Interval.open(-oo, 0), Interval.open(0, oo))
assert continuous_domain(1/(x**2 - 4) + 2, x, S.Reals) == \
Union(Interval.open(-oo, -2), Interval.open(-2, 2), Interval.open(2, oo))
def test_bool_as_set():
assert ITE(y <= 0, False, y >= 1).as_set() == Interval(1, oo)
assert And(x <= 2, x >= -2).as_set() == Interval(-2, 2)
assert Or(x >= 2, x <= -2).as_set() == Interval(-oo, -2) + Interval(2, oo)
assert Not(x > 2).as_set() == Interval(-oo, 2)
# issue 10240
assert Not(And(x > 2, x < 3)).as_set() == \
Union(Interval(-oo, 2), Interval(3, oo))
assert true.as_set() == S.UniversalSet
assert false.as_set() == EmptySet()
assert x.as_set() == S.UniversalSet
assert And(Or(x < 1, x > 3), x < 2).as_set() == Interval.open(-oo, 1)
assert And(x < 1, sin(x) < 3).as_set() == (x < 1).as_set()
raises(NotImplementedError, lambda: (sin(x) < 1).as_set())
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:
return S.EmptySet
s2 = _first_finite_point(r2, c)
if s2 is None:
return S.EmptySet
# replace the corresponding start or stop in
# the original Ranges with these points; the
# result must have at least one point since
# we know that s1 and s2 are in the Ranges
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
r1 = _updated_range(self, s1)
r2 = _updated_range(other, s2)
# work with them both in the increasing direction
if sign(r1.step) < 0:
r1 = r1.reversed
if sign(r2.step) < 0:
r2 = r2.reversed
# return clipped Range with positive step; it
# can't be empty at this point
start = max(r1.start, r2.start)
stop = min(r1.stop, r2.stop)
return Range(start, stop, step)
else:
return
def __eq__(self, other):
return other == Interval(-S.Infinity, S.Infinity)
def _intersect(self, other):
from sympy.solvers.diophantine import diophantine
if self.base_set is S.Integers:
g = None
if isinstance(other, ImageSet) and other.base_set is S.Integers:
g = other.lamda.expr
m = other.lamda.variables[0]
elif other is S.Integers:
m = g = Dummy('x')
if g is not None:
f = self.lamda.expr
n = self.lamda.variables[0]
# Diophantine sorts the solutions according to the alphabetic
# order of the variable names, since the result should not depend
# on the variable name, they are replaced by the dummy variables
# below
a, b = Dummy('a'), Dummy('b')
f, g = f.subs(n, a), g.subs(m, b)
solns_set = diophantine(f - g)
if solns_set == set():
return EmptySet()
solns = list(diophantine(f - g))
if len(solns) != 1:
return
# since 'a' < 'b', select soln for n
nsol = solns[0][0]
t = nsol.free_symbols.pop()
return imageset(Lambda(n, f.subs(a, nsol.subs(t, n))),
S.Integers)
if other == S.Reals:
from sympy.solvers.solveset import solveset_real
from sympy.core.function import expand_complex
if len(self.lamda.variables) > 1:
return None
f = self.lamda.expr
n = self.lamda.variables[0]
n_ = Dummy(n.name, real=True)
f_ = f.subs(n, n_)
re, im = f_.as_real_imag()
im = expand_complex(im)
return imageset(Lambda(n_, re),
self.base_set.intersect(solveset_real(im, n_)))
elif isinstance(other, Interval):
from sympy.solvers.solveset import (invert_real, invert_complex,
solveset)
f = self.lamda.expr
n = self.lamda.variables[0]
base_set = self.base_set
new_inf, new_sup = None, None
new_lopen, new_ropen = other.left_open, other.right_open
if f.is_real:
inverter = invert_real
else:
inverter = invert_complex
g1, h1 = inverter(f, other.inf, n)
g2, h2 = inverter(f, other.sup, n)
if all(isinstance(i, FiniteSet) for i in (h1, h2)):
if g1 == n:
if len(h1) == 1:
new_inf = h1.args[0]
if g2 == n:
if len(h2) == 1:
new_sup = h2.args[0]
# TODO: Design a technique to handle multiple-inverse
# functions
# Any of the new boundary values cannot be determined
if any(i is None for i in (new_sup, new_inf)):
return
range_set = S.EmptySet
if all(i.is_real for i in (new_sup, new_inf)):
# this assumes continuity of underlying function
# however fixes the case when it is decreasing
if new_inf > new_sup:
new_inf, new_sup = new_sup, new_inf
new_interval = Interval(new_inf, new_sup, new_lopen,
new_ropen)
range_set = base_set._intersect(new_interval)
else:
if other.is_subset(S.Reals):
solutions = solveset(f, n, S.Reals)
if not isinstance(range_set, (ImageSet, ConditionSet)):
range_set = solutions._intersect(other)
else:
return
if range_set is S.EmptySet:
return S.EmptySet
elif isinstance(range_set,
Range) and range_set.size is not S.Infinity:
range_set = FiniteSet(*list(range_set))
if range_set is not None:
return imageset(Lambda(n, f), range_set)
return
else:
return
def test_multivariate_bool_as_set():
x, y = symbols('x,y')
assert And(x >= 0, y >= 0).as_set() == Interval(0, oo)*Interval(0, oo)
assert Or(x >= 0, y >= 0).as_set() == S.Reals*S.Reals - \
Interval(-oo, 0, True, True)*Interval(-oo, 0, True, True)
def test_issue_8975():
assert Or(And(-oo < x, x <= -2), And(2 <= x, x < oo)).as_set() == \
Interval(-oo, -2) + Interval(2, oo)
def set(self):
return S.Reals * Interval(0, S.Infinity)
def test_continuous_domain():
x = Symbol("x")
assert continuous_domain(sin(x), x,
Interval(0, 2 * pi)) == Interval(0, 2 * pi)
assert continuous_domain(tan(x), x, Interval(0, 2 * pi)) == Union(
Interval(0, pi / 2, False, True),
Interval(pi / 2, pi * Rational(3, 2), True, True),
Interval(pi * Rational(3, 2), 2 * pi, True, False),
)
assert continuous_domain((x - 1) / ((x - 1)**2), x,
S.Reals) == Union(Interval(-oo, 1, True, True),
Interval(1, oo, True, True))
assert continuous_domain(log(x) + log(4 * x - 1), x,
S.Reals) == Interval(Rational(1, 4), oo, True,
True)
assert continuous_domain(1 / sqrt(x - 3), x,
S.Reals) == Interval(3, oo, True, True)
assert continuous_domain(1 / x - 2, x,
S.Reals) == Union(Interval.open(-oo, 0),
Interval.open(0, oo))
assert continuous_domain(1 / (x**2 - 4) + 2, x,
S.Reals) == Union(Interval.open(-oo, -2),
Interval.open(-2, 2),
Interval.open(2, oo))
def function_range(f, symbol, domain):
"""
Finds the range of a function in a given domain.
This method is limited by the ability to determine the singularities and
determine limits.
Examples
========
>>> from sympy import Symbol, S, exp, log, pi, sqrt, sin, tan
>>> from sympy.sets import Interval
>>> from sympy.calculus.util import function_range
>>> x = Symbol('x')
>>> function_range(sin(x), x, Interval(0, 2*pi))
[-1, 1]
>>> function_range(tan(x), x, Interval(-pi/2, pi/2))
(-oo, oo)
>>> function_range(1/x, x, S.Reals)
(-oo, oo)
>>> function_range(exp(x), x, S.Reals)
(0, oo)
>>> function_range(log(x), x, S.Reals)
(-oo, oo)
>>> function_range(sqrt(x), x , Interval(-5, 9))
[0, 3]
"""
from sympy.solvers.solveset import solveset
vals = S.EmptySet
period = periodicity(f, symbol)
if not any(period is i for i in (None, S.Zero)):
inf = domain.inf
inf_period = S.Zero if inf.is_infinite else inf
sup_period = inf_period + period
periodic_interval = Interval(inf_period, sup_period)
domain = domain.intersect(periodic_interval)
intervals = continuous_domain(f, symbol, domain)
range_int = S.EmptySet
if isinstance(intervals, Interval):
interval_iter = (intervals,)
else:
interval_iter = intervals.args
for interval in interval_iter:
critical_points = S.EmptySet
critical_values = S.EmptySet
bounds = ((interval.left_open, interval.inf, '+'),
(interval.right_open, interval.sup, '-'))
for is_open, limit_point, direction in bounds:
if is_open:
critical_values += FiniteSet(limit(f, symbol, limit_point, direction))
vals += critical_values
else:
vals += FiniteSet(f.subs(symbol, limit_point))
critical_points += solveset(f.diff(symbol), symbol, domain)
for critical_point in critical_points:
vals += FiniteSet(f.subs(symbol, critical_point))
left_open, right_open = False, False
if critical_values is not S.EmptySet:
if critical_values.inf == vals.inf:
left_open = True
if critical_values.sup == vals.sup:
right_open = True
range_int += Interval(vals.inf, vals.sup, left_open, right_open)
return range_int
def function_range(f, symbol, domain):
"""
Finds the range of a function in a given domain.
This method is limited by the ability to determine the singularities and
determine limits.
Examples
========
>>> from sympy import Symbol, S, exp, log, pi, sqrt, sin, tan
>>> from sympy.sets import Interval
>>> from sympy.calculus.util import function_range
>>> x = Symbol('x')
>>> function_range(sin(x), x, Interval(0, 2*pi))
Interval(-1, 1)
>>> function_range(tan(x), x, Interval(-pi/2, pi/2))
Interval(-oo, oo)
>>> function_range(1/x, x, S.Reals)
Union(Interval.open(-oo, 0), Interval.open(0, oo))
>>> function_range(exp(x), x, S.Reals)
Interval.open(0, oo)
>>> function_range(log(x), x, S.Reals)
Interval(-oo, oo)
>>> function_range(sqrt(x), x , Interval(-5, 9))
Interval(0, 3)
"""
from sympy.solvers.solveset import solveset
if isinstance(domain, EmptySet):
return S.EmptySet
period = periodicity(f, symbol)
if period is S.Zero:
# the expression is constant wrt symbol
return FiniteSet(f.expand())
if period is not None:
if isinstance(domain, Interval):
if (domain.inf - domain.sup).is_infinite:
domain = Interval(0, period)
elif isinstance(domain, Union):
for sub_dom in domain.args:
if isinstance(sub_dom, Interval) and \
((sub_dom.inf - sub_dom.sup).is_infinite):
domain = Interval(0, period)
intervals = continuous_domain(f, symbol, domain)
range_int = S.EmptySet
if isinstance(intervals,(Interval, FiniteSet)):
interval_iter = (intervals,)
elif isinstance(intervals, Union):
interval_iter = intervals.args
else:
raise NotImplementedError(filldedent('''
Unable to find range for the given domain.
'''))
for interval in interval_iter:
if isinstance(interval, FiniteSet):
for singleton in interval:
if singleton in domain:
range_int += FiniteSet(f.subs(symbol, singleton))
elif isinstance(interval, Interval):
vals = S.EmptySet
critical_points = S.EmptySet
critical_values = S.EmptySet
bounds = ((interval.left_open, interval.inf, '+'),
(interval.right_open, interval.sup, '-'))
for is_open, limit_point, direction in bounds:
if is_open:
critical_values += FiniteSet(limit(f, symbol, limit_point, direction))
vals += critical_values
else:
vals += FiniteSet(f.subs(symbol, limit_point))
solution = solveset(f.diff(symbol), symbol, interval)
if isinstance(solution, ConditionSet):
raise NotImplementedError('Unable to find critical points for %s'.format(f))
critical_points += solution
for critical_point in critical_points:
vals += FiniteSet(f.subs(symbol, critical_point))
left_open, right_open = False, False
if critical_values is not S.EmptySet:
if critical_values.inf == vals.inf:
left_open = True
if critical_values.sup == vals.sup:
right_open = True
range_int += Interval(vals.inf, vals.sup, left_open, right_open)
else:
raise NotImplementedError(filldedent('''
Unable to find range for the given domain.
'''))
return range_int
def interval(self):
return Interval(self.args[1][1], self.args[1][2])
def prove(Eq):
n = Symbol.n(integer=True, positive=True)
u = Symbol.u(domain=Interval(0, n, integer=True))
v = Symbol.v(domain=Interval(0, n, integer=True))
Eq << apply(n, u, v)
w, i, j = Eq[0].lhs.args
Q = Eq[2].lhs.base
Eq.x_slice_last, Eq.x_slice_domain = sets.imply.conditionset.apply(
Q[u]).split()
Eq << Eq.x_slice_domain.apply(
discrete.combinatorics.permutation.index.equality, v)
Eq.h_domain, Eq.x_h_equality = Eq[-1].split()
hv = Eq.x_h_equality.function.lhs.indices[0]
Eq << algebre.matrix.elementary.swap.invariant.permutation.apply(n + 1,
w=w)
Eq << Subset(Eq[-2].limits[0][1], Eq[-1].rhs, plausible=True)
Eq << sets.subset.forall.imply.forall.apply(Eq[-1], Eq[-2])
Eq << Eq[-1].subs(Eq[-1].rhs.this.definition)
Eq << Eq[-1].subs(i, n)
Eq << Eq[-1].subs(j, hv)
k = Eq[-1].function.lhs.function.arg.args[0].indices[-1]
Eq.Xv_definition = Eq[1].subs(j, v)
Eq << Eq.Xv_definition[k].set.union_comprehension((k, 0, n))
Eq.x_n1_set_comprehension = Eq[-2].subs(Eq[-1].reversed)
Eq << Eq.Xv_definition[n]
Eq << Eq[0].subs(i, n).subs(j, hv)[n]
Eq << Eq[-2].this.rhs.subs(Eq[-1])
Eq << Eq[-1].this.rhs.expand()
Eq << Eq[-1].subs(Eq.x_h_equality)
Eq << Eq[-1].this.function.as_Or()
Eq << (Eq[-1] & Eq.h_domain).split()
Eq <<= Eq.x_n1_set_comprehension & Eq[-1]
Eq.Xv_in_Qv, Eq.x_eq_swap_Xv = Eq[3].split()
Eq << Eq.Xv_in_Qv.definition
Eq.indexu_eq_indexu = Eq.x_eq_swap_Xv.function.rhs.args[0].indices[
1].this.subs(Eq.Xv_definition)
Eq.indexu_eq_indexv = Eq.x_slice_domain.apply(
discrete.combinatorics.permutation.index.swap, u, v, w=w)
Eq.indexu_contains, Eq.x_indexu_equality = Eq.x_slice_domain.apply(
discrete.combinatorics.permutation.index.equality, u).split()
Eq.equality_of_indexu_and_n = Eq.x_indexu_equality + Eq.x_slice_last.reversed
i = Symbol.i(domain=Interval(0, n, integer=True))
j = Symbol.j(domain=Interval(0, n, integer=True))
Eq << Eq.x_slice_domain.apply(
discrete.combinatorics.permutation.index.kronecker_delta.indexOf, i, j)
x = Eq[-1].variable.base
Eq << Eq[-1].subs(i, x[n]).split()
Eq << Eq[-2].subs(Eq.x_slice_last)
m = Symbol.m(domain=Interval(0, n, integer=True))
Eq.indexOf_indexed = Eq.x_slice_domain.apply(
discrete.combinatorics.permutation.index.indexOf_indexed, j=m)
Eq << Eq.indexOf_indexed.subs(m, n)
Eq << Eq[-2].subs(Eq[-1])
Eq << Eq[-1].subs(j, Eq.equality_of_indexu_and_n.function.lhs).split()
Eq << Eq[-2].subs(Eq.x_indexu_equality)
Eq << Eq.indexOf_indexed.subs(
m, Eq.equality_of_indexu_and_n.function.lhs.indices[0]).split()
Eq <<= Eq.indexu_contains & Eq[-2]
Eq << Eq[-3].subs(Eq[-1])
Eq << Eq[-1].subs(Eq.equality_of_indexu_and_n)
Eq << Eq[-1].this.function.lhs.as_Piecewise()
Eq << Eq[-1].this.function.as_Or()
Eq << Eq.indexu_eq_indexv.subs(Eq[-1].reversed)
Eq << Eq.indexu_eq_indexu.subs(Eq[-1])
Eq << Eq.x_eq_swap_Xv.subs(Eq[-1])
Eq << Eq[-1].subs(Eq.Xv_definition)
Eq << algebre.matrix.elementary.swap.multiply.left.apply(
x[:n + 1], i=n, j=Eq.h_domain.lhs, w=w)
Eq << Eq[-2].subs(Eq[-1])
def test_not_empty_in():
assert not_empty_in(FiniteSet(x, 2*x).intersect(Interval(1, 2, True, False)), x) == \
Interval(S(1)/2, 2, True, False)
assert not_empty_in(FiniteSet(x, x**2).intersect(Interval(1, 2)), x) == \
Union(Interval(-sqrt(2), -1), Interval(1, 2))
assert not_empty_in(FiniteSet(x**2 + x, x).intersect(Interval(2, 4)), x) == \
Union(Interval(-sqrt(17)/2 - S(1)/2, -2),
Interval(1, -S(1)/2 + sqrt(17)/2), Interval(2, 4))
assert not_empty_in(FiniteSet(x/(x - 1)).intersect(S.Reals), x) == \
Complement(S.Reals, FiniteSet(1))
assert not_empty_in(FiniteSet(a/(a - 1)).intersect(S.Reals), a) == \
Complement(S.Reals, FiniteSet(1))
assert not_empty_in(FiniteSet((x**2 - 3*x + 2)/(x - 1)).intersect(S.Reals), x) == \
Complement(S.Reals, FiniteSet(1))
assert not_empty_in(FiniteSet(3, 4, x/(x - 1)).intersect(Interval(2, 3)), x) == \
Union(Interval(S(3)/2, 2), FiniteSet(3))
assert not_empty_in(FiniteSet(x/(x**2 - 1)).intersect(S.Reals), x) == \
Complement(S.Reals, FiniteSet(-1, 1))
assert not_empty_in(FiniteSet(x, x**2).intersect(Union(Interval(1, 3, True, True),
Interval(4, 5))), x) == \
Union(Interval(-sqrt(5), -2), Interval(-sqrt(3), -1, True, True),
Interval(1, 3, True, True), Interval(4, 5))
assert not_empty_in(FiniteSet(1).intersect(Interval(3, 4)),
x) == S.EmptySet
assert not_empty_in(FiniteSet(x**2/(x + 2)).intersect(Interval(1, oo)), x) == \
Union(Interval(-2, -1, True, False), Interval(2, oo))
def test_union_RealSubSet():
assert (S.Complexes).union(Interval(1, 2)) == S.Complexes
assert (S.Complexes).union(S.Integers) == S.Complexes
def set(self):
k = len(self.alpha)
return Interval(0, 1)**k
def test_issue_16469():
x = Symbol("x", real=True)
f = abs(x)
assert function_range(f, x, S.Reals) == Interval(0, oo, False, True)
def set(self):
return Intersection(S.Naturals0, Interval(0, self.n))**len(self.p)
def test_multivariate_relational_as_set():
assert (x*y >= 0).as_set() == Interval(0, oo)*Interval(0, oo) + \
Interval(-oo, 0)*Interval(-oo, 0)
def test_core_interval():
for c in (Interval, Interval(0, 2)):
check(c)
def test_issue_8777():
assert And(x > 2, x < oo).as_set() == Interval(2, oo, left_open=True)
assert And(x >= 1, x < oo).as_set() == Interval(1, oo)
assert (x < oo).as_set() == Interval(-oo, oo)
assert (x > -oo).as_set() == Interval(-oo, oo)
def function_range(f, symbol, domain):
"""
Finds the range of a function in a given domain.
This method is limited by the ability to determine the singularities and
determine limits.
Parameters
==========
f : :py:class:`~.Expr`
The concerned function.
symbol : :py:class:`~.Symbol`
The variable for which the range of function is to be determined.
domain : :py:class:`~.Interval`
The domain under which the range of the function has to be found.
Examples
========
>>> from sympy import Interval, Symbol, S, exp, log, pi, sqrt, sin, tan
>>> from sympy.calculus.util import function_range
>>> x = Symbol('x')
>>> function_range(sin(x), x, Interval(0, 2*pi))
Interval(-1, 1)
>>> function_range(tan(x), x, Interval(-pi/2, pi/2))
Interval(-oo, oo)
>>> function_range(1/x, x, S.Reals)
Union(Interval.open(-oo, 0), Interval.open(0, oo))
>>> function_range(exp(x), x, S.Reals)
Interval.open(0, oo)
>>> function_range(log(x), x, S.Reals)
Interval(-oo, oo)
>>> function_range(sqrt(x), x, Interval(-5, 9))
Interval(0, 3)
Returns
=======
:py:class:`~.Interval`
Union of all ranges for all intervals under domain where function is
continuous.
Raises
======
NotImplementedError
If any of the intervals, in the given domain, for which function
is continuous are not finite or real,
OR if the critical points of the function on the domain cannot be found.
"""
if domain is S.EmptySet:
return S.EmptySet
period = periodicity(f, symbol)
if period == S.Zero:
# the expression is constant wrt symbol
return FiniteSet(f.expand())
from sympy.series.limits import limit
from sympy.solvers.solveset import solveset
if period is not None:
if isinstance(domain, Interval):
if (domain.inf - domain.sup).is_infinite:
domain = Interval(0, period)
elif isinstance(domain, Union):
for sub_dom in domain.args:
if isinstance(sub_dom, Interval) and \
((sub_dom.inf - sub_dom.sup).is_infinite):
domain = Interval(0, period)
intervals = continuous_domain(f, symbol, domain)
range_int = S.EmptySet
if isinstance(intervals, (Interval, FiniteSet)):
interval_iter = (intervals, )
elif isinstance(intervals, Union):
interval_iter = intervals.args
else:
raise NotImplementedError(
filldedent('''
Unable to find range for the given domain.
'''))
for interval in interval_iter:
if isinstance(interval, FiniteSet):
for singleton in interval:
if singleton in domain:
range_int += FiniteSet(f.subs(symbol, singleton))
elif isinstance(interval, Interval):
vals = S.EmptySet
critical_points = S.EmptySet
critical_values = S.EmptySet
bounds = ((interval.left_open, interval.inf, '+'),
(interval.right_open, interval.sup, '-'))
for is_open, limit_point, direction in bounds:
if is_open:
critical_values += FiniteSet(
limit(f, symbol, limit_point, direction))
vals += critical_values
else:
vals += FiniteSet(f.subs(symbol, limit_point))
solution = solveset(f.diff(symbol), symbol, interval)
if not iterable(solution):
raise NotImplementedError(
'Unable to find critical points for {}'.format(f))
if isinstance(solution, ImageSet):
raise NotImplementedError(
'Infinite number of critical points for {}'.format(f))
critical_points += solution
for critical_point in critical_points:
vals += FiniteSet(f.subs(symbol, critical_point))
left_open, right_open = False, False
if critical_values is not S.EmptySet:
if critical_values.inf == vals.inf:
left_open = True
if critical_values.sup == vals.sup:
right_open = True
range_int += Interval(vals.inf, vals.sup, left_open, right_open)
else:
raise NotImplementedError(
filldedent('''
Unable to find range for the given domain.
'''))
return range_int
def __new__(cls):
return Interval.__new__(cls, -S.Infinity, S.Infinity)
def bspline_basis(d, knots, n, x):
"""
The $n$-th B-spline at $x$ of degree $d$ with knots.
Explanation
===========
B-Splines are piecewise polynomials of degree $d$. They are defined on a
set of knots, which is a sequence of integers or floats.
Examples
========
The 0th degree splines have a value of 1 on a single interval:
>>> from sympy import bspline_basis
>>> from sympy.abc import x
>>> d = 0
>>> knots = tuple(range(5))
>>> bspline_basis(d, knots, 0, x)
Piecewise((1, (x >= 0) & (x <= 1)), (0, True))
For a given ``(d, knots)`` there are ``len(knots)-d-1`` B-splines
defined, that are indexed by ``n`` (starting at 0).
Here is an example of a cubic B-spline:
>>> bspline_basis(3, tuple(range(5)), 0, x)
Piecewise((x**3/6, (x >= 0) & (x <= 1)),
(-x**3/2 + 2*x**2 - 2*x + 2/3,
(x >= 1) & (x <= 2)),
(x**3/2 - 4*x**2 + 10*x - 22/3,
(x >= 2) & (x <= 3)),
(-x**3/6 + 2*x**2 - 8*x + 32/3,
(x >= 3) & (x <= 4)),
(0, True))
By repeating knot points, you can introduce discontinuities in the
B-splines and their derivatives:
>>> d = 1
>>> knots = (0, 0, 2, 3, 4)
>>> bspline_basis(d, knots, 0, x)
Piecewise((1 - x/2, (x >= 0) & (x <= 2)), (0, True))
It is quite time consuming to construct and evaluate B-splines. If
you need to evaluate a B-spline many times, it is best to lambdify them
first:
>>> from sympy import lambdify
>>> d = 3
>>> knots = tuple(range(10))
>>> b0 = bspline_basis(d, knots, 0, x)
>>> f = lambdify(x, b0)
>>> y = f(0.5)
Parameters
==========
d : integer
degree of bspline
knots : list of integer values
list of knots points of bspline
n : integer
$n$-th B-spline
x : symbol
See Also
========
bspline_basis_set
References
==========
.. [1] https://en.wikipedia.org/wiki/B-spline
"""
# make sure x has no assumptions so conditions don't evaluate
xvar = x
x = Dummy()
knots = tuple(sympify(k) for k in knots)
d = int(d)
n = int(n)
n_knots = len(knots)
n_intervals = n_knots - 1
if n + d + 1 > n_intervals:
raise ValueError("n + d + 1 must not exceed len(knots) - 1")
if d == 0:
result = Piecewise(
(S.One, Interval(knots[n], knots[n + 1]).contains(x)), (0, True)
)
elif d > 0:
denom = knots[n + d + 1] - knots[n + 1]
if denom != S.Zero:
B = (knots[n + d + 1] - x) / denom
b2 = bspline_basis(d - 1, knots, n + 1, x)
else:
b2 = B = S.Zero
denom = knots[n + d] - knots[n]
if denom != S.Zero:
A = (x - knots[n]) / denom
b1 = bspline_basis(d - 1, knots, n, x)
else:
b1 = A = S.Zero
result = _add_splines(A, b1, B, b2, x)
else:
raise ValueError("degree must be non-negative: %r" % n)
# return result with user-given x
return result.xreplace({x: xvar})
def __hash__(self):
return hash(Interval(-S.Infinity, S.Infinity))
def test_not_empty_in():
assert not_empty_in(
FiniteSet(x, 2 * x).intersect(Interval(1, 2, True, False)),
x) == Interval(S.Half, 2, True, False)
assert not_empty_in(FiniteSet(x, x**2).intersect(Interval(1, 2)),
x) == Union(Interval(-sqrt(2), -1), Interval(1, 2))
assert not_empty_in(FiniteSet(x**2 + x, x).intersect(Interval(2, 4)),
x) == Union(
Interval(-sqrt(17) / 2 - S.Half, -2),
Interval(1,
Rational(-1, 2) + sqrt(17) / 2),
Interval(2, 4),
)
assert not_empty_in(FiniteSet(x / (x - 1)).intersect(S.Reals),
x) == Complement(S.Reals, FiniteSet(1))
assert not_empty_in(FiniteSet(a / (a - 1)).intersect(S.Reals),
a) == Complement(S.Reals, FiniteSet(1))
assert not_empty_in(
FiniteSet((x**2 - 3 * x + 2) / (x - 1)).intersect(S.Reals),
x) == Complement(S.Reals, FiniteSet(1))
assert not_empty_in(
FiniteSet(3, 4, x / (x - 1)).intersect(Interval(2, 3)),
x) == Interval(-oo, oo)
assert not_empty_in(
FiniteSet(4, x / (x - 1)).intersect(Interval(2, 3)),
x) == Interval(S(3) / 2, 2)
assert not_empty_in(FiniteSet(x / (x**2 - 1)).intersect(S.Reals),
x) == Complement(S.Reals, FiniteSet(-1, 1))
assert not_empty_in(
FiniteSet(x, x**2).intersect(
Union(Interval(1, 3, True, True), Interval(4, 5))),
x,
) == Union(
Interval(-sqrt(5), -2),
Interval(-sqrt(3), -1, True, True),
Interval(1, 3, True, True),
Interval(4, 5),
)
assert not_empty_in(FiniteSet(1).intersect(Interval(3, 4)),
x) == S.EmptySet
assert not_empty_in(
FiniteSet(x**2 / (x + 2)).intersect(Interval(1, oo)),
x) == Union(Interval(-2, -1, True, False), Interval(2, oo))
raises(ValueError, lambda: not_empty_in(x))
raises(ValueError, lambda: not_empty_in(Interval(0, 1), x))
raises(NotImplementedError,
lambda: not_empty_in(FiniteSet(x).intersect(S.Reals), x, a))
def _intersect(self, other):
if other.is_Interval:
return Intersection(S.Integers, other,
Interval(self._inf, S.Infinity))
return None
def test_normalize_theta_set():
# Interval
assert normalize_theta_set(Interval(pi, 2*pi)) == \
Union(FiniteSet(0), Interval.Ropen(pi, 2*pi))
assert normalize_theta_set(Interval(9*pi/2, 5*pi)) == Interval(pi/2, pi)
assert normalize_theta_set(Interval(-3*pi/2, pi/2)) == Interval.Ropen(0, 2*pi)
assert normalize_theta_set(Interval.open(-3*pi/2, pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.open(pi/2, 2*pi))
assert normalize_theta_set(Interval.open(-7*pi/2, -3*pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.open(pi/2, 2*pi))
assert normalize_theta_set(Interval(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.Ropen(3*pi/2, 2*pi))
assert normalize_theta_set(Interval.open(-pi/2, pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.open(3*pi/2, 2*pi))
assert normalize_theta_set(Interval(-4*pi, 3*pi)) == Interval.Ropen(0, 2*pi)
assert normalize_theta_set(Interval(-3*pi/2, -pi/2)) == Interval(pi/2, 3*pi/2)
assert normalize_theta_set(Interval.open(0, 2*pi)) == Interval.open(0, 2*pi)
assert normalize_theta_set(Interval.Ropen(-pi/2, pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.Ropen(3*pi/2, 2*pi))
assert normalize_theta_set(Interval.Lopen(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.open(3*pi/2, 2*pi))
assert normalize_theta_set(Interval(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.Ropen(3*pi/2, 2*pi))
assert normalize_theta_set(Interval.open(4*pi, 9*pi/2)) == Interval.open(0, pi/2)
assert normalize_theta_set(Interval.Lopen(4*pi, 9*pi/2)) == Interval.Lopen(0, pi/2)
assert normalize_theta_set(Interval.Ropen(4*pi, 9*pi/2)) == Interval.Ropen(0, pi/2)
assert normalize_theta_set(Interval.open(3*pi, 5*pi)) == \
Union(Interval.Ropen(0, pi), Interval.open(pi, 2*pi))
# FiniteSet
assert normalize_theta_set(FiniteSet(0, pi, 3*pi)) == FiniteSet(0, pi)
assert normalize_theta_set(FiniteSet(0, pi/2, pi, 2*pi)) == FiniteSet(0, pi/2, pi)
assert normalize_theta_set(FiniteSet(0, -pi/2, -pi, -2*pi)) == FiniteSet(0, pi, 3*pi/2)
assert normalize_theta_set(FiniteSet(-3*pi/2, pi/2)) == \
FiniteSet(pi/2)
assert normalize_theta_set(FiniteSet(2*pi)) == FiniteSet(0)
# Unions
assert normalize_theta_set(Union(Interval(0, pi/3), Interval(pi/2, pi))) == \
Union(Interval(0, pi/3), Interval(pi/2, pi))
assert normalize_theta_set(Union(Interval(0, pi), Interval(2*pi, 7*pi/3))) == \
Interval(0, pi)
# ValueError for non-real sets
raises(ValueError, lambda: normalize_theta_set(S.Complexes))
def normalize_theta_set(theta):
"""
Normalize a Real Set `theta` in the Interval [0, 2*pi). It returns
a normalized value of theta in the Set. For Interval, a maximum of
one cycle [0, 2*pi], is returned i.e. for theta equal to [0, 10*pi],
returned normalized value would be [0, 2*pi). As of now intervals
with end points as non-multiples of `pi` is not supported.
Raises
======
NotImplementedError
The algorithms for Normalizing theta Set are not yet
implemented.
ValueError
The input is not valid, i.e. the input is not a real set.
RuntimeError
It is a bug, please report to the github issue tracker.
Examples
========
>>> from sympy.sets.fancysets import normalize_theta_set
>>> from sympy import Interval, FiniteSet, pi
>>> normalize_theta_set(Interval(9*pi/2, 5*pi))
[pi/2, pi]
>>> normalize_theta_set(Interval(-3*pi/2, pi/2))
[0, 2*pi)
>>> normalize_theta_set(Interval(-pi/2, pi/2))
[0, pi/2] U [3*pi/2, 2*pi)
>>> normalize_theta_set(Interval(-4*pi, 3*pi))
[0, 2*pi)
>>> normalize_theta_set(Interval(-3*pi/2, -pi/2))
[pi/2, 3*pi/2]
>>> normalize_theta_set(FiniteSet(0, pi, 3*pi))
{0, pi}
"""
from sympy.functions.elementary.trigonometric import _pi_coeff as coeff
if theta.is_Interval:
interval_len = theta.measure
# one complete circle
if interval_len >= 2 * S.Pi:
if interval_len == 2 * S.Pi and theta.left_open and theta.right_open:
k = coeff(theta.start)
return Union(Interval(0, k * S.Pi, False, True),
Interval(k * S.Pi, 2 * S.Pi, True, True))
return Interval(0, 2 * S.Pi, False, True)
k_start, k_end = coeff(theta.start), coeff(theta.end)
if k_start is None or k_end is None:
raise NotImplementedError(
"Normalizing theta without pi as coefficient is "
"not yet implemented")
new_start = k_start * S.Pi
new_end = k_end * S.Pi
if new_start > new_end:
return Union(Interval(S.Zero, new_end, False, theta.right_open),
Interval(new_start, 2 * S.Pi, theta.left_open, True))
else:
return Interval(new_start, new_end, theta.left_open,
theta.right_open)
elif theta.is_FiniteSet:
new_theta = []
for element in theta:
k = coeff(element)
if k is None:
raise NotImplementedError('Normalizing theta without pi as '
'coefficient, is not Implemented.')
else:
new_theta.append(k * S.Pi)
return FiniteSet(*new_theta)
elif theta.is_Union:
return Union(
*[normalize_theta_set(interval) for interval in theta.args])
elif theta.is_subset(S.Reals):
raise NotImplementedError(
"Normalizing theta when, it is of type %s is not "
"implemented" % type(theta))
else:
raise ValueError(" %s is not a real set" % (theta))
def test_ComplexRegion_from_real():
c1 = ComplexRegion(Interval(0, 1) * Interval(0, 2 * S.Pi), polar=True)
raises(ValueError, lambda: c1.from_real(c1))
assert c1.from_real(Interval(-1, 1)) == ComplexRegion(Interval(-1, 1) * FiniteSet(0), False)
def test_is_convex():
assert is_convex(1 / x, x, domain=Interval(0, oo)) == True
assert is_convex(1 / x, x, domain=Interval(-oo, 0)) == False
assert is_convex(x**2, x, domain=Interval(0, oo)) == True
assert is_convex(log(x), x) == False
raises(NotImplementedError, lambda: is_convex(log(x), x, a))
def test_normalize_theta_set():
# Interval
assert normalize_theta_set(Interval(pi, 2*pi)) == \
Union(FiniteSet(0), Interval.Ropen(pi, 2*pi))
assert normalize_theta_set(Interval(pi*Rational(9, 2), 5*pi)) == Interval(pi/2, pi)
assert normalize_theta_set(Interval(pi*Rational(-3, 2), pi/2)) == Interval.Ropen(0, 2*pi)
assert normalize_theta_set(Interval.open(pi*Rational(-3, 2), pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.open(pi/2, 2*pi))
assert normalize_theta_set(Interval.open(pi*Rational(-7, 2), pi*Rational(-3, 2))) == \
Union(Interval.Ropen(0, pi/2), Interval.open(pi/2, 2*pi))
assert normalize_theta_set(Interval(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.Ropen(pi*Rational(3, 2), 2*pi))
assert normalize_theta_set(Interval.open(-pi/2, pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.open(pi*Rational(3, 2), 2*pi))
assert normalize_theta_set(Interval(-4*pi, 3*pi)) == Interval.Ropen(0, 2*pi)
assert normalize_theta_set(Interval(pi*Rational(-3, 2), -pi/2)) == Interval(pi/2, pi*Rational(3, 2))
assert normalize_theta_set(Interval.open(0, 2*pi)) == Interval.open(0, 2*pi)
assert normalize_theta_set(Interval.Ropen(-pi/2, pi/2)) == \
Union(Interval.Ropen(0, pi/2), Interval.Ropen(pi*Rational(3, 2), 2*pi))
assert normalize_theta_set(Interval.Lopen(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.open(pi*Rational(3, 2), 2*pi))
assert normalize_theta_set(Interval(-pi/2, pi/2)) == \
Union(Interval(0, pi/2), Interval.Ropen(pi*Rational(3, 2), 2*pi))
assert normalize_theta_set(Interval.open(4*pi, pi*Rational(9, 2))) == Interval.open(0, pi/2)
assert normalize_theta_set(Interval.Lopen(4*pi, pi*Rational(9, 2))) == Interval.Lopen(0, pi/2)
assert normalize_theta_set(Interval.Ropen(4*pi, pi*Rational(9, 2))) == Interval.Ropen(0, pi/2)
assert normalize_theta_set(Interval.open(3*pi, 5*pi)) == \
Union(Interval.Ropen(0, pi), Interval.open(pi, 2*pi))
# FiniteSet
assert normalize_theta_set(FiniteSet(0, pi, 3*pi)) == FiniteSet(0, pi)
assert normalize_theta_set(FiniteSet(0, pi/2, pi, 2*pi)) == FiniteSet(0, pi/2, pi)
assert normalize_theta_set(FiniteSet(0, -pi/2, -pi, -2*pi)) == FiniteSet(0, pi, pi*Rational(3, 2))
assert normalize_theta_set(FiniteSet(pi*Rational(-3, 2), pi/2)) == \
FiniteSet(pi/2)
assert normalize_theta_set(FiniteSet(2*pi)) == FiniteSet(0)
# Unions
assert normalize_theta_set(Union(Interval(0, pi/3), Interval(pi/2, pi))) == \
Union(Interval(0, pi/3), Interval(pi/2, pi))
assert normalize_theta_set(Union(Interval(0, pi), Interval(2*pi, pi*Rational(7, 3)))) == \
Interval(0, pi)
# ValueError for non-real sets
raises(ValueError, lambda: normalize_theta_set(S.Complexes))
# NotImplementedError for subset of reals
raises(NotImplementedError, lambda: normalize_theta_set(Interval(0, 1)))
# NotImplementedError without pi as coefficient
raises(NotImplementedError, lambda: normalize_theta_set(Interval(1, 2*pi)))
raises(NotImplementedError, lambda: normalize_theta_set(Interval(2*pi, 10)))
raises(NotImplementedError, lambda: normalize_theta_set(FiniteSet(0, 3, 3*pi)))
def __new__(cls):
return Interval.__new__(cls, -S.Infinity, S.Infinity)
def test_function_range():
x, y, a, b = symbols("x y a b")
assert function_range(sin(x), x, Interval(-pi / 2,
pi / 2)) == Interval(-1, 1)
assert function_range(sin(x), x, Interval(0, pi)) == Interval(0, 1)
assert function_range(tan(x), x, Interval(0, pi)) == Interval(-oo, oo)
assert function_range(tan(x), x, Interval(pi / 2, pi)) == Interval(-oo, 0)
assert function_range((x + 3) / (x - 2), x,
Interval(-5,
5)) == Union(Interval(-oo, Rational(2, 7)),
Interval(Rational(8, 3), oo))
assert function_range(1 / (x**2), x, Interval(-1, 1)) == Interval(1, oo)
assert function_range(exp(x), x, Interval(-1,
1)) == Interval(exp(-1), exp(1))
assert function_range(log(x) - x, x, S.Reals) == Interval(-oo, -1)
assert function_range(sqrt(3 * x - 1), x,
Interval(0, 2)) == Interval(0, sqrt(5))
assert function_range(x * (x - 1) - (x**2 - x), x, S.Reals) == FiniteSet(0)
assert function_range(x * (x - 1) - (x**2 - x) + y, x,
S.Reals) == FiniteSet(y)
assert function_range(sin(x), x, Union(Interval(-5, -3),
FiniteSet(4))) == Union(
Interval(-sin(3), 1),
FiniteSet(sin(4)))
assert function_range(cos(x), x, Interval(-oo, -4)) == Interval(-1, 1)
assert function_range(cos(x), x, S.EmptySet) == S.EmptySet
raises(
NotImplementedError,
lambda: function_range(exp(x) * (sin(x) - cos(x)) / 2 - x, x, S.Reals),
)
raises(NotImplementedError,
lambda: function_range(sin(x) + x, x, S.Reals)) # issue 13273
raises(NotImplementedError, lambda: function_range(log(x), x, S.Integers))
raises(NotImplementedError,
lambda: function_range(sin(x) / 2, x, S.Naturals))
