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author | Christian Heimes <christian@cheimes.de> | 2008-02-11 06:19:17 (GMT) |
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committer | Christian Heimes <christian@cheimes.de> | 2008-02-11 06:19:17 (GMT) |
commit | 3feef61742facb3cbf53f9df1cb89062452597f2 (patch) | |
tree | 766365e91d9f906fb8d7e5568708db1d385531ca /Lib/rational.py | |
parent | ba99c5887286147925fb02141c274e5b4dc84f4e (diff) | |
download | cpython-3feef61742facb3cbf53f9df1cb89062452597f2.zip cpython-3feef61742facb3cbf53f9df1cb89062452597f2.tar.gz cpython-3feef61742facb3cbf53f9df1cb89062452597f2.tar.bz2 |
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
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r60701 | georg.brandl | 2008-02-09 22:36:15 +0100 (Sat, 09 Feb 2008) | 2 lines
Needs only 2.4 now.
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r60702 | georg.brandl | 2008-02-09 22:38:54 +0100 (Sat, 09 Feb 2008) | 2 lines
Docs are rst now.
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r60703 | georg.brandl | 2008-02-09 23:00:00 +0100 (Sat, 09 Feb 2008) | 2 lines
Fix link.
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r60704 | georg.brandl | 2008-02-10 00:09:25 +0100 (Sun, 10 Feb 2008) | 2 lines
Fix for newest doctools.
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r60709 | raymond.hettinger | 2008-02-10 08:21:09 +0100 (Sun, 10 Feb 2008) | 1 line
Clarify that decimal also supports fixed-point arithmetic.
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r60710 | nick.coghlan | 2008-02-10 08:32:52 +0100 (Sun, 10 Feb 2008) | 1 line
Add missing NEWS entry for r60695
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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.)
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r60715 | mark.dickinson | 2008-02-10 16:19:58 +0100 (Sun, 10 Feb 2008) | 2 lines
Typos in decimal comment and documentation
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r60716 | skip.montanaro | 2008-02-10 16:31:54 +0100 (Sun, 10 Feb 2008) | 2 lines
Get the saying right. ;-)
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r60717 | skip.montanaro | 2008-02-10 16:32:16 +0100 (Sun, 10 Feb 2008) | 2 lines
whoops - revert
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r60718 | mark.dickinson | 2008-02-10 20:23:36 +0100 (Sun, 10 Feb 2008) | 2 lines
Remove reference to Rational
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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.
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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.
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r60722 | christian.heimes | 2008-02-11 03:26:22 +0100 (Mon, 11 Feb 2008) | 1 line
The test requires the network resource
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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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Diffstat (limited to 'Lib/rational.py')
-rwxr-xr-x | Lib/rational.py | 536 |
1 files changed, 0 insertions, 536 deletions
diff --git a/Lib/rational.py b/Lib/rational.py deleted file mode 100755 index 6002964..0000000 --- a/Lib/rational.py +++ /dev/null @@ -1,536 +0,0 @@ -# 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) |