Source code for sympy.functions.elementary.integers

from __future__ import print_function, division

from sympy.core.singleton import S
from sympy.core.function import Function
from sympy.core import Add
from sympy.core.evalf import get_integer_part, PrecisionExhausted
from sympy.core.numbers import Integer
from sympy.core.relational import Gt, Lt, Ge, Le
from sympy.core.symbol import Symbol


###############################################################################
######################### FLOOR and CEILING FUNCTIONS #########################
###############################################################################


[docs]class RoundFunction(Function): """The base class for rounding functions.""" @classmethod def eval(cls, arg): from sympy import im if arg.is_integer or arg.is_finite is False: return arg if arg.is_imaginary or (S.ImaginaryUnit*arg).is_real: i = im(arg) if not i.has(S.ImaginaryUnit): return cls(i)*S.ImaginaryUnit return cls(arg, evaluate=False) v = cls._eval_number(arg) if v is not None: return v # Integral, numerical, symbolic part ipart = npart = spart = S.Zero # Extract integral (or complex integral) terms terms = Add.make_args(arg) for t in terms: if t.is_integer or (t.is_imaginary and im(t).is_integer): ipart += t elif t.has(Symbol): spart += t else: npart += t if not (npart or spart): return ipart # Evaluate npart numerically if independent of spart if npart and ( not spart or npart.is_real and (spart.is_imaginary or (S.ImaginaryUnit*spart).is_real) or npart.is_imaginary and spart.is_real): try: r, i = get_integer_part( npart, cls._dir, {}, return_ints=True) ipart += Integer(r) + Integer(i)*S.ImaginaryUnit npart = S.Zero except (PrecisionExhausted, NotImplementedError): pass spart += npart if not spart: return ipart elif spart.is_imaginary or (S.ImaginaryUnit*spart).is_real: return ipart + cls(im(spart), evaluate=False)*S.ImaginaryUnit else: return ipart + cls(spart, evaluate=False) def _eval_is_finite(self): return self.args[0].is_finite def _eval_is_real(self): return self.args[0].is_real def _eval_is_integer(self): return self.args[0].is_real
[docs]class floor(RoundFunction): """ Floor is a univariate function which returns the largest integer value not greater than its argument. This implementation generalizes floor to complex numbers by taking the floor of the real and imaginary parts separately. Examples ======== >>> from sympy import floor, E, I, S, Float, Rational >>> floor(17) 17 >>> floor(Rational(23, 10)) 2 >>> floor(2*E) 5 >>> floor(-Float(0.567)) -1 >>> floor(-I/2) -I >>> floor(S(5)/2 + 5*I/2) 2 + 2*I See Also ======== sympy.functions.elementary.integers.ceiling References ========== .. [1] "Concrete mathematics" by Graham, pp. 87 .. [2] http://mathworld.wolfram.com/FloorFunction.html """ _dir = -1 @classmethod def _eval_number(cls, arg): if arg.is_Number: return arg.floor() elif any(isinstance(i, j) for i in (arg, -arg) for j in (floor, ceiling)): return arg if arg.is_NumberSymbol: return arg.approximation_interval(Integer)[0] def _eval_nseries(self, x, n, logx): r = self.subs(x, 0) args = self.args[0] args0 = args.subs(x, 0) if args0 == r: direction = (args - args0).leadterm(x)[0] if direction.is_positive: return r else: return r - 1 else: return r def _eval_rewrite_as_ceiling(self, arg): return -ceiling(-arg) def _eval_rewrite_as_frac(self, arg): return arg - frac(arg) def _eval_Eq(self, other): if isinstance(self, floor): if (self.rewrite(ceiling) == other) or \ (self.rewrite(frac) == other): return S.true def __le__(self, other): if self.args[0] == other and other.is_real: return S.true return Le(self, other, evaluate=False) def __gt__(self, other): if self.args[0] == other and other.is_real: return S.false return Gt(self, other, evaluate=False)
[docs]class ceiling(RoundFunction): """ Ceiling is a univariate function which returns the smallest integer value not less than its argument. This implementation generalizes ceiling to complex numbers by taking the ceiling of the real and imaginary parts separately. Examples ======== >>> from sympy import ceiling, E, I, S, Float, Rational >>> ceiling(17) 17 >>> ceiling(Rational(23, 10)) 3 >>> ceiling(2*E) 6 >>> ceiling(-Float(0.567)) 0 >>> ceiling(I/2) I >>> ceiling(S(5)/2 + 5*I/2) 3 + 3*I See Also ======== sympy.functions.elementary.integers.floor References ========== .. [1] "Concrete mathematics" by Graham, pp. 87 .. [2] http://mathworld.wolfram.com/CeilingFunction.html """ _dir = 1 @classmethod def _eval_number(cls, arg): if arg.is_Number: return arg.ceiling() elif any(isinstance(i, j) for i in (arg, -arg) for j in (floor, ceiling)): return arg if arg.is_NumberSymbol: return arg.approximation_interval(Integer)[1] def _eval_nseries(self, x, n, logx): r = self.subs(x, 0) args = self.args[0] args0 = args.subs(x, 0) if args0 == r: direction = (args - args0).leadterm(x)[0] if direction.is_positive: return r + 1 else: return r else: return r def _eval_rewrite_as_floor(self, arg): return -floor(-arg) def _eval_rewrite_as_frac(self, arg): return arg + frac(-arg) def _eval_Eq(self, other): if isinstance(self, ceiling): if (self.rewrite(floor) == other) or \ (self.rewrite(frac) == other): return S.true def __lt__(self, other): if self.args[0] == other and other.is_real: return S.false return Lt(self, other, evaluate=False) def __ge__(self, other): if self.args[0] == other and other.is_real: return S.true return Ge(self, other, evaluate=False)
[docs]class frac(Function): r"""Represents the fractional part of x For real numbers it is defined [1]_ as .. math:: x - \lfloor{x}\rfloor Examples ======== >>> from sympy import Symbol, frac, Rational, floor, ceiling, I >>> frac(Rational(4, 3)) 1/3 >>> frac(-Rational(4, 3)) 2/3 returns zero for integer arguments >>> n = Symbol('n', integer=True) >>> frac(n) 0 rewrite as floor >>> x = Symbol('x') >>> frac(x).rewrite(floor) x - floor(x) for complex arguments >>> r = Symbol('r', real=True) >>> t = Symbol('t', real=True) >>> frac(t + I*r) I*frac(r) + frac(t) See Also ======== sympy.functions.elementary.integers.floor sympy.functions.elementary.integers.ceiling References =========== .. [1] http://en.wikipedia.org/wiki/Fractional_part .. [2] http://mathworld.wolfram.com/FractionalPart.html """ @classmethod def eval(cls, arg): from sympy import AccumBounds, im def _eval(arg): if arg is S.Infinity or arg is S.NegativeInfinity: return AccumBounds(0, 1) if arg.is_integer: return S.Zero if arg.is_number: if arg is S.NaN: return S.NaN elif arg is S.ComplexInfinity: return None else: return arg - floor(arg) return cls(arg, evaluate=False) terms = Add.make_args(arg) real, imag = S.Zero, S.Zero for t in terms: # Two checks are needed for complex arguments # see issue-7649 for details if t.is_imaginary or (S.ImaginaryUnit*t).is_real: i = im(t) if not i.has(S.ImaginaryUnit): imag += i else: real += t else: real += t real = _eval(real) imag = _eval(imag) return real + S.ImaginaryUnit*imag def _eval_rewrite_as_floor(self, arg): return arg - floor(arg) def _eval_rewrite_as_ceiling(self, arg): return arg + ceiling(-arg) def _eval_Eq(self, other): if isinstance(self, frac): if (self.rewrite(floor) == other) or \ (self.rewrite(ceiling) == other): return S.true