[Python-Dev] Mini-Pep: Simplifying the Integral ABC

[Alex Martelli]

On Fri, Jun 6, 2008 at 11:01 AM, Guido van Rossum <guido at python.org> wrote:
> On Thu, Jun 5, 2008 at 8:45 PM, Raymond Hettinger <python at rcn.com> 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