[Python-Dev] Mini-Pep: Simplifying the Integral ABC (original) (raw)

Guido van Rossum guido at python.org
Thu Jun 5 16:54:41 CEST 2008

On Thu, Jun 5, 2008 at 6:20 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

Terry Reedy wrote:

"Raymond Hettinger" <python at rcn.com> wrote in message news:2745D7EB7C064B16A88E433588021756 at RaymondLaptop1... | From: "Guido van Rossum" <guido at python.org> | > Unless more folks actually say they agree I don't want to go forward | > with this. There was quite a bit of discussion about PEP 3141 and it | > was accepted; striking this much from it with virtually no discussion | > seems wrong to me. | | Not sure how to generate more discussion. It seems self-evident | that an abc with lots of abstract methods is inherently less usable | and that bitwise operations go beyond the basic notion of "integeriness". On reading PEP3141 some months ago and again today, I thought and still do that all the methods that depend on a 2s-complement representation and implementation really belong to an implentation-defined subclass of Integral. But I am not sure of the purpose of the class and of including such concrete methods in an ABC, and so said nothing ;-). I think it definitely makes sense to separate out the number-as-sequence-of-bits operations from the main Integral ABC. This would involve moving: lshift, rshift, and, or, xor, invert (along with their reversed and in-place counterparts)

Agreed. Let's move these into a separate BinaryInteger class.

Note that this leaves the Integral ABC adding only long, index and 3-argument pow over and above the Rational ABC. If 3-argument pow goes (which appears likely), we're left with long and index.

Let's ditch 3-arg pow, but keep long (in 2.6) and index. Actually long can go too.

However, there's still a few additional public properties and methods inherited from higher up in the numeric stack which most existing integral types are unlikely to provide: .real, .imag, .conjugate(). Unlike the methods being relocated, however, these are absolutely trivial for all non-complex numeric types.

I definitely want to keep these. They're essential for people who want to use the higher-up classes in the numeric tower.

I think this is settled now; Raymond can update PEP 3141 (if he refrains from editorializing) and patch numbers.py.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

More information about the Python-Dev mailing list