[Python-Dev] PEP 246, redux

[Paul Moore]

On Wed, 12 Jan 2005 00:33:22 +0100, Alex Martelli <aleax at aleax.it> wrote:
> By imposing transitivity, you're essentially asserting that, if a
> programmer forgets to code and register an A -> C direct adapter, this
> is never a problem, as long as A -> B and B -> C adapters are
> registered, because A -> B -> C will give results just as good as the
> direct A -> C would have, so there's absolutely no reason to trouble
> the programmer about the trivial detail that transitivity is being
> used.
[...]
> paragraph, then this is just weird: since you're implicitly asserting
> that any old A->?->C transitive adaptation is just as good as a direct
> A->C, why should you worry about there being more than one such 2-step
> adaptation available?  Roll the dice to pick one and just proceed.

I know this is out-of-context picking, but I don't think I've ever
seen anyone state that A->?->C is "just as good as" a direct A->C. I
would have thought it self-evident that a shorter adaptation path is
always better. And specifically, I know that Philip has stated that
PyProtocols applies a shorter-is-better algorithm.

Having pointed this out, I'll go back to lurking. You two are doing a
great job of converging on something so far, so I'll let you get on
with it.

Paul.