statistics

1 files changed, 645 insertions, 0 deletions

diff --git a/modules/language/python/module/fractions.py b/modules/language/python/module/fractions.py
new file mode 100644
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+++ b/modules/language/python/module/fractions.py
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+module(fractions)
+
+# Originally contributed by Sjoerd Mullender.
+# Significantly modified by Jeffrey Yasskin <jyasskin at gmail.com>.
+
+"""Fraction, infinite-precision, real numbers."""
+
+from decimal import Decimal
+import math
+import numbers
+import operator
+import re
+import sys
+
+__all__ = ['Fraction', 'gcd']
+
+
+
+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).
+    """
+    import warnings
+    warnings.warn('fractions.gcd() is deprecated. Use math.gcd() instead.',
+                  DeprecationWarning, 2)
+    if type(a) is int is type(b):
+        if (b or a) < 0:
+            return -math.gcd(a, b)
+        return math.gcd(a, b)
+    return _gcd(a, b)
+
+def _gcd(a, b):
+    # Supports non-integers for backward compatibility.
+    while b:
+        a, b = b, a%b
+    return a
+
+# Constants related to the hash implementation;  hash(x) is based
+# on the reduction of x modulo the prime _PyHASH_MODULUS.
+_PyHASH_MODULUS = sys.hash_info.modulus
+# Value to be used for rationals that reduce to infinity modulo
+# _PyHASH_MODULUS.
+_PyHASH_INF = sys.hash_info.inf
+
+_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
+       (?:/(?P<denom>\d+))?    # an optional denominator
+    |                          # or
+       (?:\.(?P<decimal>\d*))? # an optional fractional part
+       (?:E(?P<exp>[-+]?\d+))? # and optional exponent
+    )
+    \s*\Z                      # and optional whitespace to finish
+""", re.VERBOSE | re.IGNORECASE)
+
+
+class Fraction(numbers.Rational):
+    """This class implements rational numbers.
+
+    In the two-argument form of the constructor, Fraction(8, 6) will
+    produce a rational number equivalent to 4/3. Both arguments must
+    be Rational. The numerator defaults to 0 and the denominator
+    defaults to 1 so that Fraction(3) == 3 and Fraction() == 0.
+
+    Fractions can also be constructed from:
+
+      - numeric strings similar to those accepted by the
+        float constructor (for example, '-2.3' or '1e10')
+
+      - strings of the form '123/456'
+
+      - float and Decimal instances
+
+      - other Rational instances (including integers)
+
+    """
+
+    __slots__ = ('_numerator', '_denominator')
+
+    # We're immutable, so use __new__ not __init__
+    def __new__(cls, numerator=0, denominator=None, *, _normalize=True):
+        """Constructs a Rational.
+
+        Takes a string like '3/2' or '1.5', another Rational instance, a
+        numerator/denominator pair, or a float.
+
+        Examples
+        --------
+
+        >>> Fraction(10, -8)
+        Fraction(-5, 4)
+        >>> Fraction(Fraction(1, 7), 5)
+        Fraction(1, 35)
+        >>> Fraction(Fraction(1, 7), Fraction(2, 3))
+        Fraction(3, 14)
+        >>> Fraction('314')
+        Fraction(314, 1)
+        >>> Fraction('-35/4')
+        Fraction(-35, 4)
+        >>> Fraction('3.1415') # conversion from numeric string
+        Fraction(6283, 2000)
+        >>> Fraction('-47e-2') # string may include a decimal exponent
+        Fraction(-47, 100)
+        >>> Fraction(1.47)  # direct construction from float (exact conversion)
+        Fraction(6620291452234629, 4503599627370496)
+        >>> Fraction(2.25)
+        Fraction(9, 4)
+        >>> Fraction(Decimal('1.47'))
+        Fraction(147, 100)
+
+        """
+        self = super(Fraction, cls).__new__(cls)
+
+        if denominator is None:
+            if type(numerator) is int:
+                self._numerator = numerator
+                self._denominator = 1
+                return self
+
+            elif isinstance(numerator, numbers.Rational):
+                self._numerator = numerator.numerator
+                self._denominator = numerator.denominator
+                return self
+
+            elif isinstance(numerator, (float, Decimal)):
+                # Exact conversion
+                self._numerator, self._denominator = numerator.as_integer_ratio()
+                return self
+
+            elif isinstance(numerator, str):
+                # Handle construction from strings.
+                m = _RATIONAL_FORMAT.match(numerator)
+                if m is None:
+                    raise ValueError('Invalid literal for Fraction: %r' %
+                                     numerator)
+                numerator = int(m.group('num') or '0')
+                denom = m.group('denom')
+                if denom:
+                    denominator = int(denom)
+                else:
+                    denominator = 1
+                    decimal = m.group('decimal')
+                    if decimal:
+                        scale = 10**len(decimal)
+                        numerator = numerator * scale + int(decimal)
+                        denominator *= scale
+                    exp = m.group('exp')
+                    if exp:
+                        exp = int(exp)
+                        if exp >= 0:
+                            numerator *= 10**exp
+                        else:
+                            denominator *= 10**-exp
+                if m.group('sign') == '-':
+                    numerator = -numerator
+
+            else:
+                raise TypeError("argument should be a string "
+                                "or a Rational instance")
+
+        elif type(numerator) is int is type(denominator):
+            pass # *very* normal case
+
+        elif (isinstance(numerator, numbers.Rational) and
+            isinstance(denominator, numbers.Rational)):
+            numerator, denominator = (
+                numerator.numerator * denominator.denominator,
+                denominator.numerator * numerator.denominator
+                )
+        else:
+            raise TypeError("both arguments should be "
+                            "Rational instances")
+
+        if denominator == 0:
+            raise ZeroDivisionError('Fraction(%s, 0)' % numerator)
+        if _normalize:
+            if type(numerator) is int is type(denominator):
+                # *very* normal case
+                g = math.gcd(numerator, denominator)
+                if denominator < 0:
+                    g = -g
+            else:
+                g = _gcd(numerator, denominator)
+            numerator //= g
+            denominator //= g
+        self._numerator = numerator
+        self._denominator = denominator
+        return self
+
+    @classmethod
+    def from_float(cls, f):
+        """Converts a finite float to a rational number, exactly.
+
+        Beware that Fraction.from_float(0.3) != Fraction(3, 10).
+
+        """
+        if isinstance(f, numbers.Integral):
+            return cls(f)
+        elif not isinstance(f, float):
+            raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
+                            (cls.__name__, f, type(f).__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 isinstance(dec, numbers.Integral):
+            dec = Decimal(int(dec))
+        elif not isinstance(dec, Decimal):
+            raise TypeError(
+                "%s.from_decimal() only takes Decimals, not %r (%s)" %
+                (cls.__name__, dec, type(dec).__name__))
+        return cls(*dec.as_integer_ratio())
+
+    def limit_denominator(self, max_denominator=1000000):
+        """Closest Fraction to self with denominator at most max_denominator.
+
+        >>> Fraction('3.141592653589793').limit_denominator(10)
+        Fraction(22, 7)
+        >>> Fraction('3.141592653589793').limit_denominator(100)
+        Fraction(311, 99)
+        >>> Fraction(4321, 8765).limit_denominator(10000)
+        Fraction(4321, 8765)
+
+        """
+        # Algorithm notes: For any real number x, define a *best upper
+        # approximation* to x to be a rational number p/q such that:
+        #
+        #   (1) p/q >= x, and
+        #   (2) if p/q > r/s >= x then s > q, for any rational r/s.
+        #
+        # Define *best lower approximation* similarly.  Then it can be
+        # proved that a rational number is a best upper or lower
+        # approximation to x if, and only if, it is a convergent or
+        # semiconvergent of the (unique shortest) continued fraction
+        # associated to x.
+        #
+        # To find a best rational approximation with denominator <= M,
+        # we find the best upper and lower approximations with
+        # denominator <= M and take whichever of these is closer to x.
+        # In the event of a tie, the bound with smaller denominator is
+        # chosen.  If both denominators are equal (which can happen
+        # only when max_denominator == 1 and self is midway between
+        # two integers) the lower bound---i.e., the floor of self, is
+        # taken.
+
+        if max_denominator < 1:
+            raise ValueError("max_denominator should be at least 1")
+        if self._denominator <= max_denominator:
+            return Fraction(self)
+
+        p0, q0, p1, q1 = 0, 1, 1, 0
+        n, d = self._numerator, self._denominator
+        while True:
+            a = n//d
+            q2 = q0+a*q1
+            if q2 > max_denominator:
+                break
+            p0, q0, p1, q1 = p1, q1, p0+a*p1, q2
+            n, d = d, n-a*d
+
+        k = (max_denominator-q0)//q1
+        bound1 = Fraction(p0+k*p1, q0+k*q1)
+        bound2 = Fraction(p1, q1)
+        if abs(bound2 - self) <= abs(bound1-self):
+            return bound2
+        else:
+            return bound1
+
+    @property
+    def numerator(a):
+        return a._numerator
+
+    @property
+    def denominator(a):
+        return a._denominator
+
+    def __repr__(self):
+        """repr(self)"""
+        return '%s(%s, %s)' % (self.__class__.__name__,
+                               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
+        Fraction, 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, Fraction)):
+                    return Fraction(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, numbers.Rational):
+                    return Fraction(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
+        Fraction. I'll refer to all of the above code that doesn't
+        refer to Fraction, float, or complex as "boilerplate". 'r'
+        will be an instance of Fraction, which is a subtype of
+        Rational (r : Fraction <: Rational), and b : B <:
+        Complex. The first three involve 'r + b':
+
+            1. If B <: Fraction, int, float, or complex, we handle
+               that specially, and all is well.
+            2. If Fraction 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 Rational
+               here, even though we could get an exact answer, in case
+               the other type wants to do something special.
+            3. If B <: Fraction, Python tries B.__radd__ before
+               Fraction.__add__. This is ok, because it was
+               implemented with knowledge of Fraction, 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 Fraction in its implementation, and that it
+        uses similar boilerplate code:
+
+            4. If B <: Rational, 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, Fraction)):
+                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, numbers.Rational):
+                # 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"""
+        da, db = a.denominator, b.denominator
+        return Fraction(a.numerator * db + b.numerator * da,
+                        da * db)
+
+    __add__, __radd__ = _operator_fallbacks(_add, operator.add)
+
+    def _sub(a, b):
+        """a - b"""
+        da, db = a.denominator, b.denominator
+        return Fraction(a.numerator * db - b.numerator * da,
+                        da * db)
+
+    __sub__, __rsub__ = _operator_fallbacks(_sub, operator.sub)
+
+    def _mul(a, b):
+        """a * b"""
+        return Fraction(a.numerator * b.numerator, a.denominator * b.denominator)
+
+    __mul__, __rmul__ = _operator_fallbacks(_mul, operator.mul)
+
+    def _div(a, b):
+        """a / b"""
+        return Fraction(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, numbers.Rational):
+            if b.denominator == 1:
+                power = b.numerator
+                if power >= 0:
+                    return Fraction(a._numerator ** power,
+                                    a._denominator ** power,
+                                    _normalize=False)
+                elif a._numerator >= 0:
+                    return Fraction(a._denominator ** -power,
+                                    a._numerator ** -power,
+                                    _normalize=False)
+                else:
+                    return Fraction((-a._denominator) ** -power,
+                                    (-a._numerator) ** -power,
+                                    _normalize=False)
+            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, numbers.Rational):
+            return Fraction(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 Fraction"""
+        return Fraction(a._numerator, a._denominator, _normalize=False)
+
+    def __neg__(a):
+        """-a"""
+        return Fraction(-a._numerator, a._denominator, _normalize=False)
+
+    def __abs__(a):
+        """abs(a)"""
+        return Fraction(abs(a._numerator), a._denominator, _normalize=False)
+
+    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 Fraction and therefore have
+        # round().
+        if ndigits > 0:
+            return Fraction(round(self * shift), shift)
+        else:
+            return Fraction(round(self / shift) * shift)
+
+    def __hash__(self):
+        """hash(self)"""
+
+        # XXX since this method is expensive, consider caching the result
+
+        # In order to make sure that the hash of a Fraction agrees
+        # with the hash of a numerically equal integer, float or
+        # Decimal instance, we follow the rules for numeric hashes
+        # outlined in the documentation.  (See library docs, 'Built-in
+        # Types').
+
+        # dinv is the inverse of self._denominator modulo the prime
+        # _PyHASH_MODULUS, or 0 if self._denominator is divisible by
+        # _PyHASH_MODULUS.
+        dinv = pow(self._denominator, _PyHASH_MODULUS - 2, _PyHASH_MODULUS)
+        if not dinv:
+            hash_ = _PyHASH_INF
+        else:
+            hash_ = abs(self._numerator) * dinv % _PyHASH_MODULUS
+        result = hash_ if self >= 0 else -hash_
+        return -2 if result == -1 else result
+
+    def __eq__(a, b):
+        """a == b"""
+        if type(b) is int:
+            return a._numerator == b and a._denominator == 1
+        if isinstance(b, numbers.Rational):
+            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):
+            if math.isnan(b) or math.isinf(b):
+                # comparisons with an infinity or nan should behave in
+                # the same way for any finite a, so treat a as zero.
+                return 0.0 == b
+            else:
+                return a == a.from_float(b)
+        else:
+            # Since a doesn't know how to compare with b, let's give b
+            # a chance to compare itself with a.
+            return NotImplemented
+
+    def _richcmp(self, other, op):
+        """Helper for comparison operators, for internal use only.
+
+        Implement comparison between a Rational instance `self`, and
+        either another Rational instance or a float `other`.  If
+        `other` is not a Rational instance or a float, return
+        NotImplemented. `op` should be one of the six standard
+        comparison operators.
+
+        """
+        # convert other to a Rational instance where reasonable.
+        if isinstance(other, numbers.Rational):
+            return op(self._numerator * other.denominator,
+                      self._denominator * other.numerator)
+        if isinstance(other, float):
+            if math.isnan(other) or math.isinf(other):
+                return op(0.0, other)
+            else:
+                return op(self, self.from_float(other))
+        else:
+            return NotImplemented
+
+    def __lt__(a, b):
+        """a < b"""
+        return a._richcmp(b, operator.lt)
+
+    def __gt__(a, b):
+        """a > b"""
+        return a._richcmp(b, operator.gt)
+
+    def __le__(a, b):
+        """a <= b"""
+        return a._richcmp(b, operator.le)
+
+    def __ge__(a, b):
+        """a >= b"""
+        return a._richcmp(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) == Fraction:
+            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) == Fraction:
+            return self     # My components are also immutable
+        return self.__class__(self._numerator, self._denominator)