[Python-3000] defop ?

[Antoine Pitrou]

Le mercredi 22 novembre 2006 à 12:47 -0800, Guido van Rossum a écrit :
> > class DefOpDescriptor:
> >     def __init__(self, genfunc, implfunc):
> >         self.genfunc = genfunc
> >         self.implfunc = implfunc
> >     def __call__(self, *args, **kargs):
> >         # Directly call the implementation (why not)
> >         self.implfunc(*args, **kargs)
> 
> I'm not sure how/when __call__ would be used.
> 
> Shouldn't you implement a __get__ descriptor instead?

Hmmm yes, thanks for pointing that out :-o. It will (or should) work
better like this:

    def __get__(self, obj, objtype):
        return types.MethodType(self.implfunc, obj, objtype)

Besides, if we don't want to allow direct calls of the implementation
without going through generic method dispath (see below), we don't need
__get__ at all.

> Aha, cool. You forgot to add that now the method name chosen must be
> unique. This works fine to describe @defop, and I like it better than
> using sys._getframe(). But it doesn't really work for the defop
> syntax, unless that makes up a unique (random?) name for each
> occurrence.

Indeed it could mangle a unique name, like __private does.

Also, DefOpDescriptors could be removed from the class dictionary at
class construction, and appended to a __generic_overloads__ attribute.
This would keep the class dict clean, and produce better documentation
by separating generic function implementations from other methods in the
documentation.

(it probably still sounds a bit hackish)