[Python-Dev] NotImplemented reaching top-level

[Nick Coghlan]

Armin Rigo wrote:
> Hi Reinhold,
> 
> On Sun, Dec 25, 2005 at 12:37:53PM +0100, Reinhold Birkenfeld wrote:
>>> that nobody fully understands the convoluted code paths of abstract.c
>>> any more :-(
>> Time for a rewrite?
> 
> Of course, speaking of a rewrite, PyPy does the "right thing" in these
> two areas.  Won't happen to CPython, though.  There are too much
> backward-compatibility issues with the PyTypeObject structure; I think
> we're doomed with patching the bugs as they show up.
> 
> Looking up in the language reference, I see no mention of NotImplemented
> in the page about __add__, __radd__, etc.  I guess it's a documentation
> bug as well, isn't it?  The current code base tries to implement the
> following behavior: Returning NotImplemented from any of the binary
> special methods (__xxx__, __rxxx__, __ixxx__) makes Python proceed as if
> the method was not defined in the first place.
> 
> If we agree on this, I could propose a doc fix, a test, and appropriate
> bug fixes.

That sounds like the right definition to me (I believe this behaviour is what 
Raymond and Facundo were aiming for with the last round of updates to Decimal).

Regards,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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