Source code for diofant.sets.fancysets

from ..core import Basic, Expr, Integer, Lambda, Rational, S, oo
from ..core.compatibility import as_int
from ..core.singleton import Singleton
from ..core.sympify import converter, sympify
from ..logic import false, true
from ..utilities.iterables import cantor_product
from .sets import EmptySet, FiniteSet, Intersection, Interval, Set

[docs]class Naturals(Set, metaclass=Singleton): """The set of natural numbers. 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 ======== >>> 5 in S.Naturals True >>> iterable = iter(S.Naturals) >>> next(iterable) 1 >>> next(iterable) 2 >>> next(iterable) 3 >>> S.Naturals.intersection(Interval(0, 10)) Range(1, 11, 1) See Also ======== Naturals0 : non-negative integers Integers : also includes negative integers """ is_iterable = True _inf = Integer(1) _sup = oo def _intersection(self, other): if other.is_Interval: return Intersection( S.Integers, other, Interval(self._inf, oo, False, True)) def _contains(self, other): if not isinstance(other, Expr): return false elif other.is_positive and other.is_integer: return true elif other.is_integer is False or other.is_positive is False: 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): """The set of natural numbers, starting from 0. Represents the whole numbers which are all the non-negative integers, inclusive of zero. See Also ======== Naturals : positive integers Integers : also includes the negative integers """ _inf = Integer(0) def _contains(self, other): if not isinstance(other, Expr): return false elif other.is_integer and other.is_nonnegative: return true elif other.is_integer is False or other.is_nonnegative is False: return false
[docs]class Integers(Set, metaclass=Singleton): """The set of all integers. Represents all integers: positive, negative and zero. This set is also available as the Singleton, S.Integers. Examples ======== >>> 5 in S.Naturals True >>> iterable = iter(S.Integers) >>> next(iterable) 0 >>> next(iterable) 1 >>> next(iterable) -1 >>> next(iterable) 2 >>> S.Integers.intersection(Interval(-4, 4)) Range(-4, 5, 1) See Also ======== Naturals0 : non-negative integers Integers : positive and negative integers and zero """ is_iterable = True def _intersection(self, other): from ..functions import floor, ceiling if other is Interval(-oo, oo, True, True) or other is S.Reals: return self elif other.is_Interval: s = Range(ceiling(other.left), floor(other.right) + 1) return s.intersection(other) # take out endpoints if open interval def _contains(self, other): if not isinstance(other, Expr): return false elif other.is_integer: return true elif other.is_integer is False: return false def __iter__(self): yield Integer(0) i = Integer(1) while True: yield i yield -i i = i + 1 @property def _inf(self): return -oo @property def _sup(self): return oo @property def _boundary(self): return self def _eval_imageset(self, f): from ..core import Wild expr = f.expr if len(f.variables) > 1: return n = f.variables[0] a = Wild('a') b = Wild('b') match = expr.match(a*n + b) if match[a].is_negative: expr = -expr match = expr.match(a*n + b) if match[a] == 1 and match[b].is_integer: expr = expr - match[b] return ImageSet(Lambda(n, expr), S.Integers)
[docs]class Rationals(Set, metaclass=Singleton): """The set of all rationals.""" def _contains(self, other): if other.is_rational: return true elif other.is_rational is False: return false @property def _inf(self): return -oo @property def _sup(self): return oo @property def _boundary(self): return self def __iter__(self): seen = [] pairs = cantor_product(S.Integers, S.Naturals) while True: n, d = next(pairs) r = Rational(n, d) if r not in seen: seen.append(r) yield r
class Reals(Interval, metaclass=Singleton): def __new__(cls): return Interval.__new__(cls, -oo, oo, True, True)
[docs]class ImageSet(Set): """Image of a set under a mathematical function. Examples ======== >>> squares = ImageSet(Lambda(x, x**2), S.Naturals) >>> 4 in squares True >>> 5 in squares False >>> FiniteSet(0, 1, 2, 3, 4, 5, 6, 7, 9, 10).intersection(squares) {1, 4, 9} >>> square_iterable = iter(squares) >>> for i in range(4): ... next(square_iterable) 1 4 9 16 If you want to get value for `x` = 2, 1/2 etc. (Please check whether the `x` value is in `base_set` or not before passing it as args) >>> squares.lamda(2) 4 >>> squares.lamda(Rational(1, 2)) 1/4 """ 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 _contains(self, other): from ..solvers import solve L = self.lamda if len(self.lamda.variables) > 1: return # pragma: no cover solns = solve(L.expr - other, L.variables[0]) for soln in solns: if soln[L.variables[0]] in self.base_set: return true return false @property def is_iterable(self): return self.base_set.is_iterable def _intersection(self, other): from ..core import Dummy from ..solvers.diophantine import diophantine from .sets import imageset if self.base_set is S.Integers: if isinstance(other, ImageSet) and other.base_set is S.Integers: f, g = self.lamda.expr, other.lamda.expr n, m = self.lamda.variables[0], other.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: t = list(solns[0][0].free_symbols)[0] else: return # pragma: no cover # since 'a' < 'b' return imageset(Lambda(t, f.subs({a: solns[0][0]})), S.Integers) if other == S.Reals: from ..solvers.diophantine import diophantine from ..core import expand_complex if len(self.lamda.variables) > 1 or self.base_set is not S.Integers: return # pragma: no cover f = self.lamda.expr n = self.lamda.variables[0] n_ = Dummy(, integer=True) f_ = f.subs({n: n_}) re, im = map(expand_complex, f_.as_real_imag()) sols = list(diophantine(im, n_)) if all(s[0].has(n_) is False for s in sols): s = FiniteSet(*[s[0] for s in sols]) elif len(sols) == 1 and sols[0][0].has(n_): s = imageset(Lambda(n_, sols[0][0]), S.Integers) else: return # pragma: no cover return imageset(Lambda(n_, re), self.base_set.intersection(s))
[docs]class Range(Set): """Represents a range of integers. Examples ======== >>> list(Range(5)) [0, 1, 2, 3, 4] >>> list(Range(10, 15)) [10, 11, 12, 13, 14] >>> list(Range(10, 20, 2)) [10, 12, 14, 16, 18] >>> list(Range(20, 10, -2)) [12, 14, 16, 18, 20] """ is_iterable = True def __new__(cls, *args): from ..functions import ceiling if len(args) == 1 and isinstance(args[0], range): args = args[0].start, args[0].stop, args[0].step # expand range slc = slice(*args) start, stop, step = slc.start or 0, slc.stop, slc.step or 1 try: start, stop, step = [w if w in [-oo, oo] else Integer(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") if not step.is_finite: raise ValueError("Infinite step is not allowed") if start == stop: return S.EmptySet 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 if n.is_finite: start, stop = sorted((start, start + (n - 1)*step)) else: start, stop = sorted((start, stop - step)) step = abs(step) if (start, stop) == (-oo, oo): raise ValueError("Both the start and end value of " "Range cannot be unbounded") else: 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 _intersection(self, other): from ..functions import floor, ceiling, 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 if inf.is_finite and self.inf.is_finite: off = (inf - self.inf) % self.step else: off = Integer(0) if off: inf += self.step - off return Range(inf, sup + 1, self.step) if other == S.Naturals: return self._intersection(Interval(1, oo, False, True)) if other == S.Integers: return self def _contains(self, other): if (((self.start - other)/self.step).is_integer or ((self.stop - other)/self.step).is_integer): return sympify(other >= self.inf and other <= self.sup, strict=True) else: return false def __iter__(self): if self.start == -oo: i = self.stop - self.step step = -self.step else: i = self.start step = self.step while(i < self.stop and i >= self.start): yield i i += step def __len__(self): return int((self.stop - self.start)//self.step) def __bool__(self): return True def _ith_element(self, i): return self.start + i*self.step @property def _last_element(self): if self.stop is oo: return oo elif self.start == -oo: return self.stop - self.step else: 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
converter[range] = Range