/

# Source code for sympy.sets.fancysets

from __future__ import print_function, division

from sympy import (Dummy, S, symbols, Lambda, pi, Basic, sympify, ask, Q, Min,
Max)
from sympy.functions.elementary.integers import floor, ceiling
from sympy.functions.elementary.complexes import sign
from sympy.core.compatibility import iterable, as_int, with_metaclass
from sympy.core.sets import Set, Interval, FiniteSet, Intersection
from sympy.core.singleton import Singleton, S
from sympy.core.decorators import deprecated
from sympy.solvers import solve

oo = S.Infinity

[docs]class Naturals(with_metaclass(Singleton, Set)):
"""
Represents the Natural Numbers. The Naturals are available as a singleton
as S.Naturals

Examples
========

>>> from sympy import S, Interval, pprint
>>> 5 in S.Naturals
True
>>> iterable = iter(S.Naturals)
>>> print(next(iterable))
1
>>> print(next(iterable))
2
>>> print(next(iterable))
3
>>> pprint(S.Naturals.intersect(Interval(0, 10)))
{1, 2, ..., 10}
"""

is_iterable = True
_inf = S.One
_sup = oo

def _intersect(self, other):
if other.is_Interval:
return Intersection(S.Integers, other, Interval(self._inf, oo))
return None

def _contains(self, other):
return True
return False

def __iter__(self):
i = self._inf
while True:
yield i
i = i + 1

class Naturals0(Naturals):
""" The Natural Numbers starting at 0

S.Naturals - starts at 1
"""
_inf = S.Zero

def _contains(self, other):
return True
return False

[docs]class Integers(with_metaclass(Singleton, Set)):
"""
Represents the Integers. The Integers are available as a singleton
as S.Integers

Examples
========

>>> from sympy import S, Interval, pprint
>>> 5 in S.Naturals
True
>>> iterable = iter(S.Integers)
>>> print(next(iterable))
0
>>> print(next(iterable))
1
>>> print(next(iterable))
-1
>>> print(next(iterable))
2

>>> pprint(S.Integers.intersect(Interval(-4, 4)))
{-4, -3, ..., 4}
"""

is_iterable = True

def _intersect(self, other):
if other.is_Interval and other.measure < oo:
s = Range(ceiling(other.left), floor(other.right) + 1)
return s.intersect(other)  # take out endpoints if open interval
return None

def _contains(self, other):
return True
return False

def __iter__(self):
yield S.Zero
i = S(1)
while True:
yield i
yield -i
i = i + 1

@property
def _inf(self):
return -oo

@property
def _sup(self):
return oo

class Reals(with_metaclass(Singleton, Interval)):

def __new__(cls):
return Interval.__new__(cls, -oo, oo)

[docs]class ImageSet(Set):
"""
Image of a set under a mathematical function

Examples
--------
>>> from sympy import Symbol, S, ImageSet, FiniteSet, Lambda

>>> x = Symbol('x')
>>> N = S.Naturals
>>> squares = ImageSet(Lambda(x, x**2), N) # {x**2 for x in N}
>>> 4 in squares
True
>>> 5 in squares
False

>>> FiniteSet(0, 1, 2, 3, 4, 5, 6, 7, 9, 10).intersect(squares)
{1, 4, 9}

>>> square_iterable = iter(squares)
>>> for i in range(4):
...     next(square_iterable)
1
4
9
16
"""
def __new__(cls, lamda, base_set):
return Basic.__new__(cls, lamda, base_set)

lamda = property(lambda self: self.args[0])
base_set = property(lambda self: self.args[1])

def __iter__(self):
for i in self.base_set:
val = self.lamda(i)
if val in already_seen:
continue
else:
yield val

def _is_multivariate(self):
return len(self.lamda.variables) > 1

def _contains(self, other):
L = self.lamda
if self._is_multivariate():
solns = solve([expr - val for val, expr in zip(other, L.expr)],
L.variables)
else:
solns = solve(L.expr - other, L.variables[0])

for soln in solns:
try:
if soln in self.base_set:
return True
except TypeError:
if soln.evalf() in self.base_set:
return True
return False

@property
def is_iterable(self):
return self.base_set.is_iterable

def TransformationSet(*args, **kwargs):
"""Deprecated alias for the ImageSet constructor."""
return ImageSet(*args, **kwargs)

class Range(Set):
"""
Represents a range of integers.

Examples
========

>>> from sympy import Range
>>> list(Range(5)) # 0 to 5
[0, 1, 2, 3, 4]
>>> list(Range(10, 15)) # 10 to 15
[10, 11, 12, 13, 14]
>>> list(Range(10, 20, 2)) # 10 to 20 in steps of 2
[10, 12, 14, 16, 18]
>>> list(Range(20, 10, -2)) # 20 to 10 backward in steps of 2
[12, 14, 16, 18, 20]

"""

is_iterable = True

def __new__(cls, *args):
# expand range
slc = slice(*args)
start, stop, step = slc.start or 0, slc.stop, slc.step or 1
try:
start, stop, step = [S(as_int(w)) for w in (start, stop, step)]
except ValueError:
raise ValueError("Inputs to Range must be Integer Valued\n" +
"Use ImageSets of Ranges for other cases")
n = ceiling((stop - start)/step)
if n <= 0:
return S.EmptySet

# normalize args: regardless of how they are entered they will show
# canonically as Range(inf, sup, step) with step > 0
start, stop = sorted((start, start + (n - 1)*step))
step = abs(step)

return Basic.__new__(cls, start, stop + step, step)

start = property(lambda self: self.args[0])
stop = property(lambda self: self.args[1])
step = property(lambda self: self.args[2])

def _intersect(self, other):
if other.is_Interval:
osup = other.sup
oinf = other.inf
# if other is [0, 10) we can only go up to 9
if osup.is_integer and other.right_open:
osup -= 1
if oinf.is_integer and other.left_open:
oinf += 1

# Take the most restrictive of the bounds set by the two sets
# round inwards
inf = ceiling(Max(self.inf, oinf))
sup = floor(Min(self.sup, osup))
# if we are off the sequence, get back on
off = (inf - self.inf) % self.step
if off:
inf += self.step - off

return Range(inf, sup + 1, self.step)

if other == S.Naturals:
return self._intersect(Interval(1, oo))

if other == S.Integers:
return self

return None

def _contains(self, other):
return (other >= self.inf and other <= self.sup and

def __iter__(self):
i = self.start
while(i < self.stop):
yield i
i = i + self.step

def __len__(self):
return ((self.stop - self.start)//self.step)

def _ith_element(self, i):
return self.start + i*self.step

@property
def _last_element(self):
return self._ith_element(len(self) - 1)

@property
def _inf(self):
return self.start

@property
def _sup(self):
return self.stop - self.step