Current File : //lib/python3/dist-packages/sympy/sets/handlers/functions.py
from sympy import Set, symbols, exp, log, S, Wild, Dummy, oo, Float
from sympy.core import Expr, Add
from sympy.core.function import Lambda, _coeff_isneg, FunctionClass
from sympy.logic.boolalg import true
from sympy.multipledispatch import dispatch
from sympy.sets import (imageset, Interval, FiniteSet, Union, ImageSet,
EmptySet, Intersection, Range)
from sympy.sets.fancysets import Integers, Naturals, Reals
from sympy.functions.elementary.exponential import match_real_imag
_x, _y = symbols("x y")
FunctionUnion = (FunctionClass, Lambda)
@dispatch(FunctionClass, Set) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
return None
@dispatch(FunctionUnion, FiniteSet) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
return FiniteSet(*map(f, x))
@dispatch(Lambda, Interval) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
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 not var.is_real:
if expr.subs(var, Dummy(real=True)).is_real is False:
return
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 S.EmptySet:
break
return result
if not x.start.is_comparable or not x.end.is_comparable:
return
try:
from sympy.polys.polyutils import _nsort
sing = list(singularities(expr, var, x))
if len(sing) > 1:
sing = _nsort(sing)
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:
soln_expr = solveset(diff(expr, var), var)
if not (isinstance(soln_expr, FiniteSet) or soln_expr is EmptySet):
return
solns = list(soln_expr)
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))
@dispatch(FunctionClass, Interval) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
if f == exp:
return Interval(exp(x.start), exp(x.end), x.left_open, x.right_open)
elif f == log:
return Interval(log(x.start), log(x.end), x.left_open, x.right_open)
return ImageSet(Lambda(_x, f(_x)), x)
@dispatch(FunctionUnion, Union) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
return Union(*(imageset(f, arg) for arg in x.args))
@dispatch(FunctionUnion, Intersection) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
from sympy.sets.sets import is_function_invertible_in_set
# If the function is invertible, intersect the maps of the sets.
if is_function_invertible_in_set(f, x):
return Intersection(*(imageset(f, arg) for arg in x.args))
else:
return ImageSet(Lambda(_x, f(_x)), x)
@dispatch(FunctionUnion, type(EmptySet)) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
return x
@dispatch(FunctionUnion, Set) # type: ignore # noqa:F811
def _set_function(f, x): # noqa:F811
return ImageSet(Lambda(_x, f(_x)), x)
@dispatch(FunctionUnion, Range) # type: ignore # noqa:F811
def _set_function(f, self): # noqa:F811
from sympy.core.function import expand_mul
if not self:
return S.EmptySet
if not isinstance(f.expr, Expr):
return
if self.size == 1:
return FiniteSet(f(self[0]))
if f is S.IdentityFunction:
return self
x = f.variables[0]
expr = f.expr
# handle f that is linear in f's variable
if x not in expr.free_symbols or x in expr.diff(x).free_symbols:
return
if self.start.is_finite:
F = f(self.step*x + self.start) # for i in range(len(self))
else:
F = f(-self.step*x + self[-1])
F = expand_mul(F)
if F != expr:
return imageset(x, F, Range(self.size))
@dispatch(FunctionUnion, Integers) # type: ignore # noqa:F811
def _set_function(f, self): # noqa:F811
expr = f.expr
if not isinstance(expr, Expr):
return
n = f.variables[0]
if expr == abs(n):
return S.Naturals0
# f(x) + c and f(-x) + c cover the same integers
# so choose the form that has the fewest negatives
c = f(0)
fx = f(n) - c
f_x = f(-n) - c
neg_count = lambda e: sum(_coeff_isneg(_) for _ in Add.make_args(e))
if neg_count(f_x) < neg_count(fx):
expr = f_x + c
a = Wild('a', exclude=[n])
b = Wild('b', exclude=[n])
match = expr.match(a*n + b)
if match and match[a] and (
not match[a].atoms(Float) and
not match[b].atoms(Float)):
# canonical shift
a, b = match[a], match[b]
if a in [1, -1]:
# drop integer addends in b
nonint = []
for bi in Add.make_args(b):
if not bi.is_integer:
nonint.append(bi)
b = Add(*nonint)
if b.is_number and a.is_real:
# avoid Mod for complex numbers, #11391
br, bi = match_real_imag(b)
if br and br.is_comparable and a.is_comparable:
br %= a
b = br + S.ImaginaryUnit*bi
elif b.is_number and a.is_imaginary:
br, bi = match_real_imag(b)
ai = a/S.ImaginaryUnit
if bi and bi.is_comparable and ai.is_comparable:
bi %= ai
b = br + S.ImaginaryUnit*bi
expr = a*n + b
if expr != f.expr:
return ImageSet(Lambda(n, expr), S.Integers)
@dispatch(FunctionUnion, Naturals) # type: ignore # noqa:F811
def _set_function(f, self): # noqa:F811
expr = f.expr
if not isinstance(expr, Expr):
return
x = f.variables[0]
if not expr.free_symbols - {x}:
if expr == abs(x):
if self is S.Naturals:
return self
return S.Naturals0
step = expr.coeff(x)
c = expr.subs(x, 0)
if c.is_Integer and step.is_Integer and expr == step*x + c:
if self is S.Naturals:
c += step
if step > 0:
if step == 1:
if c == 0:
return S.Naturals0
elif c == 1:
return S.Naturals
return Range(c, oo, step)
return Range(c, -oo, step)
@dispatch(FunctionUnion, Reals) # type: ignore # noqa:F811
def _set_function(f, self): # noqa:F811
expr = f.expr
if not isinstance(expr, Expr):
return
return _set_function(f, Interval(-oo, oo))
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