[pypy-dev] Re: type problems

[Michael Hudson]

Samuele Pedroni <pedronis at bluewin.ch> writes:

> I agree with this.
>
> At 17:45 07.07.2003 +0200, Michael Hudson wrote:
>> I wrote this on the train yesterday.  Some of it is a bit out of
>> date from talking on IRC today, but not all of it.
>>
>> A tip for making the multimethod implementation more comprehensible:
>> separate finding the method to call from calling it.  Also,
>> consistently using common lisp terminology would help *me*, if
>> no-one else.
>
> it makes sense in general, one problem is that delegation is very
> specific to our multimethods, there is no such notion in CL,Dylan,...

Well, OK, but in other places.  Applicable methods is one notion that
certainly is transferable.

I also notice that raising FailedToImplement is very like calling
call-next-method except that control flow never returns.

I think it makes sense to have compute-applicable-methods or whatever
be a generator.

>
>
>>   And, finally, presuming that the implementation isn't going to
>> change drastically another four or five times, documentation would
>> be good!  As Samuele and Armin are probably too close to write this,
>> perhaps I'll have a stab.  Also, disentangling them from the
>> StdObjSpace implementation (if possible) would probably reduce the
>> general level of incomprehension.
>>
>> I want a spec for the applicable method computation algorithm -- a
>> sufficiently detailed description to allow implementation by someone
>> unfamiliar with our present one.  I would also like an explanation
>> of why our algorithm is so flaming complicated.
>
> a formal spec for what it happens would be very good indeed. If we
> cannot write it then we should change the code so that we can write
> one.

This is part of the plan :-)

> If dispatch table compression is the way we want to follow it
> becomes important e.g. to know whether our rules are monotonic
> (table compression algos I know about need that) and to reformulate
> delegation relationships as some kind of subtyping rel.

If you say so :-)

I do notice delegation is what screws a naive attempt to memoize more
of the applicable method computation.

Cheers,
M.

-- 
  [3] Modem speeds being what they are, large .avi files were
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