New idea! I missed an obvious solution. Let the binary methods in Integral be mixins instead of abstract methods. That minimizes
the burden on the class implementer while providing maximum support for clients.
class Integral(Rational):
...
def __lshift__(self, other):
"""self << other"""
return long(self) << long(other)
def __xor__(self, other):
"""self ^ other"""
return long(self) ^ long(other)
I worried a bit about changing type, but this kind of thing is already baked
into numbers.py:
@property
def imag(self):
"""Real numbers have no imaginary component."""
return 0
@property
def denominator(self):
"""Integers have a denominator of 1."""
return 1
Raymond
----- Original Message -----
From: "Alex Martelli" <[EMAIL PROTECTED]>
To: "Guido van Rossum" <[EMAIL PROTECTED]>
Cc: "Raymond Hettinger" <[EMAIL PROTECTED]>; <python-dev@python.org>
Sent: Friday, June 06, 2008 11:40 AM
Subject: Re: [Python-Dev] Mini-Pep: Simplifying the Integral ABC
On Fri, Jun 6, 2008 at 11:01 AM, Guido van Rossum <[EMAIL PROTECTED]> wrote:
On Thu, Jun 5, 2008 at 8:45 PM, Raymond Hettinger <[EMAIL PROTECTED]> wrote:
Does anyone actually need an int lookalike with binary methods but
cannot just inherit from int?
Does anyone actually need an int lookalike with operations like +, -
etc. but cannot just inherit from int? If the answer is yes, is there
a compelling reason why they wouldn't want to support binary methods
as well?
Yes, there's a use case for implementing long integers as arrays of
decimal digits -- addition is roughly as efficient as for binary
integers (x86 chips still have instructions to help with that), and
emitting as decimal digits is MUCH more efficient of course -- so if
I/O in decimal form is the most common operation, with a little
arithmetic (particularly sums), you could gain performance; binary
operations, however, would be as inefficient as decimal form
conversion is for ordinary binary ints, and not needed for the typical
applications that would use these "decimal coded integers"
(accounting), so why not save the implementer of such an extension
from having to write that unneeded and slow extra code?
Alex
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