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authorChristian Heimes <christian@cheimes.de>2008-02-11 06:19:17 (GMT)
committerChristian Heimes <christian@cheimes.de>2008-02-11 06:19:17 (GMT)
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Merged revisions 60481,60485,60489-60492,60494-60496,60498-60499,60501-60503,60505-60506,60508-60509,60523-60524,60532,60543,60545,60547-60548,60552,60554,60556-60559,60561-60562,60569,60571-60572,60574,60576-60583,60585-60586,60589,60591,60594-60595,60597-60598,60600-60601,60606-60612,60615,60617,60619-60621,60623-60625,60627-60629,60631,60633,60635,60647,60650,60652,60654,60656,60658-60659,60664-60666,60668-60670,60672,60676,60678,60680-60683,60685-60686,60688,60690,60692-60694,60697-60706,60708-60712,60714-60724 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r60701 | georg.brandl | 2008-02-09 22:36:15 +0100 (Sat, 09 Feb 2008) | 2 lines Needs only 2.4 now. ........ r60702 | georg.brandl | 2008-02-09 22:38:54 +0100 (Sat, 09 Feb 2008) | 2 lines Docs are rst now. ........ r60703 | georg.brandl | 2008-02-09 23:00:00 +0100 (Sat, 09 Feb 2008) | 2 lines Fix link. ........ r60704 | georg.brandl | 2008-02-10 00:09:25 +0100 (Sun, 10 Feb 2008) | 2 lines Fix for newest doctools. ........ r60709 | raymond.hettinger | 2008-02-10 08:21:09 +0100 (Sun, 10 Feb 2008) | 1 line Clarify that decimal also supports fixed-point arithmetic. ........ r60710 | nick.coghlan | 2008-02-10 08:32:52 +0100 (Sun, 10 Feb 2008) | 1 line Add missing NEWS entry for r60695 ........ r60712 | mark.dickinson | 2008-02-10 15:58:38 +0100 (Sun, 10 Feb 2008) | 3 lines Turn classmethods into staticmethods, and avoid calling the constructor of subclasses of Rational. (See discussion in issue #1682.) ........ r60715 | mark.dickinson | 2008-02-10 16:19:58 +0100 (Sun, 10 Feb 2008) | 2 lines Typos in decimal comment and documentation ........ r60716 | skip.montanaro | 2008-02-10 16:31:54 +0100 (Sun, 10 Feb 2008) | 2 lines Get the saying right. ;-) ........ r60717 | skip.montanaro | 2008-02-10 16:32:16 +0100 (Sun, 10 Feb 2008) | 2 lines whoops - revert ........ r60718 | mark.dickinson | 2008-02-10 20:23:36 +0100 (Sun, 10 Feb 2008) | 2 lines Remove reference to Rational ........ r60719 | raymond.hettinger | 2008-02-10 21:35:16 +0100 (Sun, 10 Feb 2008) | 1 line Complete an open todo on pickletools -- add a pickle optimizer. ........ r60721 | mark.dickinson | 2008-02-10 22:29:51 +0100 (Sun, 10 Feb 2008) | 3 lines Rename rational.Rational to fractions.Fraction, to avoid name clash with numbers.Rational. See issue #1682 for related discussion. ........ r60722 | christian.heimes | 2008-02-11 03:26:22 +0100 (Mon, 11 Feb 2008) | 1 line The test requires the network resource ........ r60723 | mark.dickinson | 2008-02-11 04:11:55 +0100 (Mon, 11 Feb 2008) | 3 lines Put an extra space into the repr of a Fraction: Fraction(1, 2) instead of Fraction(1,2). ........
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-# Originally contributed by Sjoerd Mullender.
-# Significantly modified by Jeffrey Yasskin <jyasskin at gmail.com>.
-
-"""Rational, infinite-precision, real numbers."""
-
-import math
-import numbers
-import operator
-import re
-
-__all__ = ["Rational"]
-
-RationalAbc = numbers.Rational
-
-
-def gcd(a, b):
- """Calculate the Greatest Common Divisor of a and b.
-
- Unless b==0, the result will have the same sign as b (so that when
- b is divided by it, the result comes out positive).
- """
- while b:
- a, b = b, a%b
- return a
-
-
-_RATIONAL_FORMAT = re.compile(r"""
- \A\s* # optional whitespace at the start, then
- (?P<sign>[-+]?) # an optional sign, then
- (?=\d|\.\d) # lookahead for digit or .digit
- (?P<num>\d*) # numerator (possibly empty)
- (?: # followed by an optional
- /(?P<denom>\d+) # / and denominator
- | # or
- \.(?P<decimal>\d*) # decimal point and fractional part
- )?
- \s*\Z # and optional whitespace to finish
-""", re.VERBOSE)
-
-
-class Rational(RationalAbc):
- """This class implements rational numbers.
-
- Rational(8, 6) will produce a rational number equivalent to
- 4/3. Both arguments must be Integral. The numerator defaults to 0
- and the denominator defaults to 1 so that Rational(3) == 3 and
- Rational() == 0.
-
- Rationals can also be constructed from strings of the form
- '[-+]?[0-9]+((/|.)[0-9]+)?', optionally surrounded by spaces.
-
- """
-
- __slots__ = ('_numerator', '_denominator')
-
- # We're immutable, so use __new__ not __init__
- def __new__(cls, numerator=0, denominator=1):
- """Constructs a Rational.
-
- Takes a string like '3/2' or '1.5', another Rational, or a
- numerator/denominator pair.
-
- """
- self = super(Rational, cls).__new__(cls)
-
- if denominator == 1:
- if isinstance(numerator, str):
- # Handle construction from strings.
- input = numerator
- m = _RATIONAL_FORMAT.match(input)
- if m is None:
- raise ValueError('Invalid literal for Rational: ' + input)
- numerator = m.group('num')
- decimal = m.group('decimal')
- if decimal:
- # The literal is a decimal number.
- numerator = int(numerator + decimal)
- denominator = 10**len(decimal)
- else:
- # The literal is an integer or fraction.
- numerator = int(numerator)
- # Default denominator to 1.
- denominator = int(m.group('denom') or 1)
-
- if m.group('sign') == '-':
- numerator = -numerator
-
- elif (not isinstance(numerator, numbers.Integral) and
- isinstance(numerator, RationalAbc)):
- # Handle copies from other rationals.
- other_rational = numerator
- numerator = other_rational.numerator
- denominator = other_rational.denominator
-
- if (not isinstance(numerator, numbers.Integral) or
- not isinstance(denominator, numbers.Integral)):
- raise TypeError("Rational(%(numerator)s, %(denominator)s):"
- " Both arguments must be integral." % locals())
-
- if denominator == 0:
- raise ZeroDivisionError('Rational(%s, 0)' % numerator)
-
- g = gcd(numerator, denominator)
- self._numerator = int(numerator // g)
- self._denominator = int(denominator // g)
- return self
-
- @classmethod
- def from_float(cls, f):
- """Converts a finite float to a rational number, exactly.
-
- Beware that Rational.from_float(0.3) != Rational(3, 10).
-
- """
- if not isinstance(f, float):
- raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
- (cls.__name__, f, type(f).__name__))
- if math.isnan(f) or math.isinf(f):
- raise TypeError("Cannot convert %r to %s." % (f, cls.__name__))
- return cls(*f.as_integer_ratio())
-
- @classmethod
- def from_decimal(cls, dec):
- """Converts a finite Decimal instance to a rational number, exactly."""
- from decimal import Decimal
- if not isinstance(dec, Decimal):
- raise TypeError(
- "%s.from_decimal() only takes Decimals, not %r (%s)" %
- (cls.__name__, dec, type(dec).__name__))
- if not dec.is_finite():
- # Catches infinities and nans.
- raise TypeError("Cannot convert %s to %s." % (dec, cls.__name__))
- sign, digits, exp = dec.as_tuple()
- digits = int(''.join(map(str, digits)))
- if sign:
- digits = -digits
- if exp >= 0:
- return cls(digits * 10 ** exp)
- else:
- return cls(digits, 10 ** -exp)
-
- @classmethod
- def from_continued_fraction(cls, seq):
- 'Build a Rational from a continued fraction expessed as a sequence'
- n, d = 1, 0
- for e in reversed(seq):
- n, d = d, n
- n += e * d
- return cls(n, d) if seq else cls(0)
-
- def as_continued_fraction(self):
- 'Return continued fraction expressed as a list'
- n = self.numerator
- d = self.denominator
- cf = []
- while d:
- e = int(n // d)
- cf.append(e)
- n -= e * d
- n, d = d, n
- return cf
-
- def approximate(self, max_denominator):
- 'Best rational approximation with a denominator <= max_denominator'
- # XXX First cut at algorithm
- # Still needs rounding rules as specified at
- # http://en.wikipedia.org/wiki/Continued_fraction
- if self.denominator <= max_denominator:
- return self
- cf = self.as_continued_fraction()
- result = Rational(0)
- for i in range(1, len(cf)):
- new = self.from_continued_fraction(cf[:i])
- if new.denominator > max_denominator:
- break
- result = new
- return result
-
- @property
- def numerator(a):
- return a._numerator
-
- @property
- def denominator(a):
- return a._denominator
-
- def __repr__(self):
- """repr(self)"""
- return ('Rational(%r,%r)' % (self.numerator, self.denominator))
-
- def __str__(self):
- """str(self)"""
- if self.denominator == 1:
- return str(self.numerator)
- else:
- return '%s/%s' % (self.numerator, self.denominator)
-
- def _operator_fallbacks(monomorphic_operator, fallback_operator):
- """Generates forward and reverse operators given a purely-rational
- operator and a function from the operator module.
-
- Use this like:
- __op__, __rop__ = _operator_fallbacks(just_rational_op, operator.op)
-
- In general, we want to implement the arithmetic operations so
- that mixed-mode operations either call an implementation whose
- author knew about the types of both arguments, or convert both
- to the nearest built in type and do the operation there. In
- Rational, that means that we define __add__ and __radd__ as:
-
- def __add__(self, other):
- # Both types have numerators/denominator attributes,
- # so do the operation directly
- if isinstance(other, (int, Rational)):
- return Rational(self.numerator * other.denominator +
- other.numerator * self.denominator,
- self.denominator * other.denominator)
- # float and complex don't have those operations, but we
- # know about those types, so special case them.
- elif isinstance(other, float):
- return float(self) + other
- elif isinstance(other, complex):
- return complex(self) + other
- # Let the other type take over.
- return NotImplemented
-
- def __radd__(self, other):
- # radd handles more types than add because there's
- # nothing left to fall back to.
- if isinstance(other, RationalAbc):
- return Rational(self.numerator * other.denominator +
- other.numerator * self.denominator,
- self.denominator * other.denominator)
- elif isinstance(other, Real):
- return float(other) + float(self)
- elif isinstance(other, Complex):
- return complex(other) + complex(self)
- return NotImplemented
-
-
- There are 5 different cases for a mixed-type addition on
- Rational. I'll refer to all of the above code that doesn't
- refer to Rational, float, or complex as "boilerplate". 'r'
- will be an instance of Rational, which is a subtype of
- RationalAbc (r : Rational <: RationalAbc), and b : B <:
- Complex. The first three involve 'r + b':
-
- 1. If B <: Rational, int, float, or complex, we handle
- that specially, and all is well.
- 2. If Rational falls back to the boilerplate code, and it
- were to return a value from __add__, we'd miss the
- possibility that B defines a more intelligent __radd__,
- so the boilerplate should return NotImplemented from
- __add__. In particular, we don't handle RationalAbc
- here, even though we could get an exact answer, in case
- the other type wants to do something special.
- 3. If B <: Rational, Python tries B.__radd__ before
- Rational.__add__. This is ok, because it was
- implemented with knowledge of Rational, so it can
- handle those instances before delegating to Real or
- Complex.
-
- The next two situations describe 'b + r'. We assume that b
- didn't know about Rational in its implementation, and that it
- uses similar boilerplate code:
-
- 4. If B <: RationalAbc, then __radd_ converts both to the
- builtin rational type (hey look, that's us) and
- proceeds.
- 5. Otherwise, __radd__ tries to find the nearest common
- base ABC, and fall back to its builtin type. Since this
- class doesn't subclass a concrete type, there's no
- implementation to fall back to, so we need to try as
- hard as possible to return an actual value, or the user
- will get a TypeError.
-
- """
- def forward(a, b):
- if isinstance(b, (int, Rational)):
- return monomorphic_operator(a, b)
- elif isinstance(b, float):
- return fallback_operator(float(a), b)
- elif isinstance(b, complex):
- return fallback_operator(complex(a), b)
- else:
- return NotImplemented
- forward.__name__ = '__' + fallback_operator.__name__ + '__'
- forward.__doc__ = monomorphic_operator.__doc__
-
- def reverse(b, a):
- if isinstance(a, RationalAbc):
- # Includes ints.
- return monomorphic_operator(a, b)
- elif isinstance(a, numbers.Real):
- return fallback_operator(float(a), float(b))
- elif isinstance(a, numbers.Complex):
- return fallback_operator(complex(a), complex(b))
- else:
- return NotImplemented
- reverse.__name__ = '__r' + fallback_operator.__name__ + '__'
- reverse.__doc__ = monomorphic_operator.__doc__
-
- return forward, reverse
-
- def _add(a, b):
- """a + b"""
- return Rational(a.numerator * b.denominator +
- b.numerator * a.denominator,
- a.denominator * b.denominator)
-
- __add__, __radd__ = _operator_fallbacks(_add, operator.add)
-
- def _sub(a, b):
- """a - b"""
- return Rational(a.numerator * b.denominator -
- b.numerator * a.denominator,
- a.denominator * b.denominator)
-
- __sub__, __rsub__ = _operator_fallbacks(_sub, operator.sub)
-
- def _mul(a, b):
- """a * b"""
- return Rational(a.numerator * b.numerator, a.denominator * b.denominator)
-
- __mul__, __rmul__ = _operator_fallbacks(_mul, operator.mul)
-
- def _div(a, b):
- """a / b"""
- return Rational(a.numerator * b.denominator,
- a.denominator * b.numerator)
-
- __truediv__, __rtruediv__ = _operator_fallbacks(_div, operator.truediv)
-
- def __floordiv__(a, b):
- """a // b"""
- return math.floor(a / b)
-
- def __rfloordiv__(b, a):
- """a // b"""
- return math.floor(a / b)
-
- def __mod__(a, b):
- """a % b"""
- div = a // b
- return a - b * div
-
- def __rmod__(b, a):
- """a % b"""
- div = a // b
- return a - b * div
-
- def __pow__(a, b):
- """a ** b
-
- If b is not an integer, the result will be a float or complex
- since roots are generally irrational. If b is an integer, the
- result will be rational.
-
- """
- if isinstance(b, RationalAbc):
- if b.denominator == 1:
- power = b.numerator
- if power >= 0:
- return Rational(a.numerator ** power,
- a.denominator ** power)
- else:
- return Rational(a.denominator ** -power,
- a.numerator ** -power)
- else:
- # A fractional power will generally produce an
- # irrational number.
- return float(a) ** float(b)
- else:
- return float(a) ** b
-
- def __rpow__(b, a):
- """a ** b"""
- if b.denominator == 1 and b.numerator >= 0:
- # If a is an int, keep it that way if possible.
- return a ** b.numerator
-
- if isinstance(a, RationalAbc):
- return Rational(a.numerator, a.denominator) ** b
-
- if b.denominator == 1:
- return a ** b.numerator
-
- return a ** float(b)
-
- def __pos__(a):
- """+a: Coerces a subclass instance to Rational"""
- return Rational(a.numerator, a.denominator)
-
- def __neg__(a):
- """-a"""
- return Rational(-a.numerator, a.denominator)
-
- def __abs__(a):
- """abs(a)"""
- return Rational(abs(a.numerator), a.denominator)
-
- def __trunc__(a):
- """trunc(a)"""
- if a.numerator < 0:
- return -(-a.numerator // a.denominator)
- else:
- return a.numerator // a.denominator
-
- def __floor__(a):
- """Will be math.floor(a) in 3.0."""
- return a.numerator // a.denominator
-
- def __ceil__(a):
- """Will be math.ceil(a) in 3.0."""
- # The negations cleverly convince floordiv to return the ceiling.
- return -(-a.numerator // a.denominator)
-
- def __round__(self, ndigits=None):
- """Will be round(self, ndigits) in 3.0.
-
- Rounds half toward even.
- """
- if ndigits is None:
- floor, remainder = divmod(self.numerator, self.denominator)
- if remainder * 2 < self.denominator:
- return floor
- elif remainder * 2 > self.denominator:
- return floor + 1
- # Deal with the half case:
- elif floor % 2 == 0:
- return floor
- else:
- return floor + 1
- shift = 10**abs(ndigits)
- # See _operator_fallbacks.forward to check that the results of
- # these operations will always be Rational and therefore have
- # round().
- if ndigits > 0:
- return Rational(round(self * shift), shift)
- else:
- return Rational(round(self / shift) * shift)
-
- def __hash__(self):
- """hash(self)
-
- Tricky because values that are exactly representable as a
- float must have the same hash as that float.
-
- """
- # XXX since this method is expensive, consider caching the result
- if self.denominator == 1:
- # Get integers right.
- return hash(self.numerator)
- # Expensive check, but definitely correct.
- if self == float(self):
- return hash(float(self))
- else:
- # Use tuple's hash to avoid a high collision rate on
- # simple fractions.
- return hash((self.numerator, self.denominator))
-
- def __eq__(a, b):
- """a == b"""
- if isinstance(b, RationalAbc):
- return (a.numerator == b.numerator and
- a.denominator == b.denominator)
- if isinstance(b, numbers.Complex) and b.imag == 0:
- b = b.real
- if isinstance(b, float):
- return a == a.from_float(b)
- else:
- # XXX: If b.__eq__ is implemented like this method, it may
- # give the wrong answer after float(a) changes a's
- # value. Better ways of doing this are welcome.
- return float(a) == b
-
- def _subtractAndCompareToZero(a, b, op):
- """Helper function for comparison operators.
-
- Subtracts b from a, exactly if possible, and compares the
- result with 0 using op, in such a way that the comparison
- won't recurse. If the difference raises a TypeError, returns
- NotImplemented instead.
-
- """
- if isinstance(b, numbers.Complex) and b.imag == 0:
- b = b.real
- if isinstance(b, float):
- b = a.from_float(b)
- try:
- # XXX: If b <: Real but not <: RationalAbc, this is likely
- # to fall back to a float. If the actual values differ by
- # less than MIN_FLOAT, this could falsely call them equal,
- # which would make <= inconsistent with ==. Better ways of
- # doing this are welcome.
- diff = a - b
- except TypeError:
- return NotImplemented
- if isinstance(diff, RationalAbc):
- return op(diff.numerator, 0)
- return op(diff, 0)
-
- def __lt__(a, b):
- """a < b"""
- return a._subtractAndCompareToZero(b, operator.lt)
-
- def __gt__(a, b):
- """a > b"""
- return a._subtractAndCompareToZero(b, operator.gt)
-
- def __le__(a, b):
- """a <= b"""
- return a._subtractAndCompareToZero(b, operator.le)
-
- def __ge__(a, b):
- """a >= b"""
- return a._subtractAndCompareToZero(b, operator.ge)
-
- def __bool__(a):
- """a != 0"""
- return a.numerator != 0
-
- # support for pickling, copy, and deepcopy
-
- def __reduce__(self):
- return (self.__class__, (str(self),))
-
- def __copy__(self):
- if type(self) == Rational:
- return self # I'm immutable; therefore I am my own clone
- return self.__class__(self.numerator, self.denominator)
-
- def __deepcopy__(self, memo):
- if type(self) == Rational:
- return self # My components are also immutable
- return self.__class__(self.numerator, self.denominator)