parameters: (monomorphic_operator, fallback_operator)
return_statement: return forward, reverse
docstring: 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, long, 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, 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.
docstring_summary: Generates forward and reverse operators given a purely-rational
          operator and a function from the operator module.
docstring_tokens: Generates forward and reverse operators given a purely - rational operator and a function from the operator module .
function: 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, long, 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, 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, long, 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, 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
function_tokens: def _operator_fallbacks ( monomorphic_operator , fallback_operator ) : def forward ( a , b ) : if isinstance ( b , ( int , long , 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 , 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