[Python-Dev] PEP 246, redux

[Clark C. Evans]

Alex,

  This is wonderful work, thank you for keeping the ball in the air;
  I'm honored to keep my name as a co-author -- kinda like a free lunch.

Phillip,

  Once again, thank you!  Without PyProtocols and your advocacy,
  this proposal might have been buried in the historical bit-bucket.

On Mon, Jan 10, 2005 at 12:43:44PM -0500, Phillip J. Eby wrote:
| -1 if this introduces a performance penalty to a wide range of 
| adaptations (i.e. those using abstract base classes), just to support 
| people who want to create deliberate Liskov violations.  I personally 
| don't think that we should pander to Liskov violators, especially since 
| Guido seems to be saying that there will be some kind of interface 
| objects available in future Pythons.

I particularly like Alex's Liskov violation error; although it is
not hugely common, it does happen, and there should be a way for a 
class to indicate that it's only being used for implementation.

Perhaps... if the class doesn't have a __conform__ method, then its
adaptation is automatic (that is, only the class can raise this
case).  The rationale for only enabling one of the two paths is that
the base class would have been in-place before the derived class was
created; therefore, it is highly unlikely that __adapt__ would ever
be of help.  Therefore, there might be a performance penalty, but it'd 
be really small, simply checking to see if the slot is filled in.

Best,

Clark