[Python-3000] New section for PEP 3124 (original) (raw)

Phillip J. Eby pje at telecommunity.com
Wed Jul 25 01:01:06 CEST 2007

At 03:16 PM 7/24/2007 -0700, Guido van Rossum wrote:

I'm confused why you spend so much time refuting the argument,

The purpose was to capture the arguments on both sides for posterity as part of the PEP.

Also, the paragraph starting with "As a result, the vast majority of overloads can be found adjacent to..." sounds like it isn't a big loss to require explicit decoration.

Perhaps these two bits should have been closer together, then:

On 7/24/07, Phillip J. Eby <pje at telecommunity.com> wrote:

The principal reasons to extend the behavior of a function that has not been specifically made generic are to:

* Add special cases not contemplated by the original function's author, such as support for additional types. * Be notified of an action in order to cause some related operation to be performed, either before the original operation is performed, after it, or both. This can include general-purpose operations like adding logging, timing, or tracing, as well as application-specific behavior. ... As a result, the vast majority of overloads can be found adjacent to either the function being overloaded, or to a *newly-defined type for which the overload is adding support*

Emphasis added to the last bit -- you can't add support for a newly-defined type to a previously-existing function that was not declared generic, unless arbitrary overloads are allowed.

For example, epydoc and pydoc contain functions that inspect the type of their arguments in order to decide what to with them. While it's arguable that in a GF world, the authors should have made those functions overloadable, it isn't reasonable to expect everyone to rewrite their code to make everything overloadable, nor to correctly anticipate every function for which extension might be needed.

As I tried to indicate with my "gut feelings" argument this is not something that's up to rational argument.

Of course... but the purpose was to document the experiences upon which my gut feelings are based, since that aspect of the PEP was not previously dealt with adequately.

In retrospect, the new section is weak mainly because it's phrased as a defense to a critique, rather than being written as a motivation for the proposed feature. So much for the attempt at a quick fix. :)

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