Source code for sympy.sets.fancysets
from __future__ import print_function, division
from sympy.core.basic import Basic
from sympy.core.compatibility import as_int, with_metaclass
from sympy.core.sets import Set, Interval, Intersection
from sympy.core.singleton import Singleton, S
from sympy.core.symbol import symbols
from sympy.core.sympify import sympify
from sympy.core.decorators import deprecated
[docs]class Naturals(with_metaclass(Singleton, Set)):
"""
Represents the natural numbers (or counting numbers) which are all
positive integers starting from 1. This set is also available as
the Singleton, S.Naturals.
Examples
========
>>> from sympy import S, Interval, pprint
>>> 5 in S.Naturals
True
>>> iterable = iter(S.Naturals)
>>> next(iterable)
1
>>> next(iterable)
2
>>> next(iterable)
3
>>> pprint(S.Naturals.intersect(Interval(0, 10)))
{1, 2, ..., 10}
See Also
========
Naturals0 : non-negative integers (i.e. includes 0, too)
Integers : also includes negative integers
"""
is_iterable = True
_inf = S.One
_sup = S.Infinity
def _intersect(self, other):
if other.is_Interval:
return Intersection(
S.Integers, other, Interval(self._inf, S.Infinity))
return None
def _contains(self, other):
from sympy.assumptions.ask import ask, Q
if ask(Q.positive(other)) and ask(Q.integer(other)):
return True
return False
def __iter__(self):
i = self._inf
while True:
yield i
i = i + 1
@property
def _boundary(self):
return self
[docs]class Naturals0(Naturals):
"""Represents the whole numbers which are all the non-negative integers,
inclusive of zero.
See Also
========
Naturals : positive integers; does not include 0
Integers : also includes the negative integers
"""
_inf = S.Zero
def _contains(self, other):
from sympy.assumptions.ask import ask, Q
if ask(Q.negative(other)) == False and ask(Q.integer(other)):
return True
return False
[docs]class Integers(with_metaclass(Singleton, Set)):
"""
Represents all integers: positive, negative and zero. This set is also
available as the Singleton, S.Integers.
Examples
========
>>> from sympy import S, Interval, pprint
>>> 5 in S.Naturals
True
>>> iterable = iter(S.Integers)
>>> next(iterable)
0
>>> next(iterable)
1
>>> next(iterable)
-1
>>> next(iterable)
2
>>> pprint(S.Integers.intersect(Interval(-4, 4)))
{-4, -3, ..., 4}
See Also
========
Naturals0 : non-negative integers
Integers : positive and negative integers and zero
"""
is_iterable = True
def _intersect(self, other):
from sympy.functions.elementary.integers import floor, ceiling
if other.is_Interval and other.measure < S.Infinity:
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):
from sympy.assumptions.ask import ask, Q
if ask(Q.integer(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 -S.Infinity
@property
def _sup(self):
return S.Infinity
@property
def _boundary(self):
return self
class Reals(with_metaclass(Singleton, Interval)):
def __new__(cls):
return Interval.__new__(cls, -S.Infinity, S.Infinity)
[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):
already_seen = set()
for i in self.base_set:
val = self.lamda(i)
if val in already_seen:
continue
else:
already_seen.add(val)
yield val
def _is_multivariate(self):
return len(self.lamda.variables) > 1
def _contains(self, other):
from sympy.solvers import solve
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
@deprecated(useinstead="ImageSet", issue=3958, deprecated_since_version="0.7.4")
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):
from sympy.functions.elementary.integers import ceiling
# 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):
from sympy.functions.elementary.integers import floor, ceiling
from sympy.functions.elementary.miscellaneous import Min, Max
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, S.Infinity))
if other == S.Integers:
return self
return None
def _contains(self, other):
from sympy.assumptions.ask import ask, Q
return (other >= self.inf and other <= self.sup and
ask(Q.integer((self.start - other)/self.step)))
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
@property
def _boundary(self):
return self
