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Postings from September 2001
At 04:35 PM 8/31/2001 -0500, Me wrote:
>Dan, I don't immediately see how per object/class dispatch
>control helps to make multimethods pluggable.
There's going to be a "method call" entry in the variable's vtable. You
want a different method call method, you change the entry. Probably by
changing the class shared vtable.
Globally overriding the "leftmost depth-first" (or breadth-first dispatch,
or dispatch with automatic redispatch) dispatch method's certainly
possible, and I know Damian'd like to do it, but I don't like the thought
of throwing in another level of indirection on a method call. Yeah, I know,
it's only a single extra pointer deref, and compared to the rest of the
code it's not much of a performance loss, but we have a lot of places where
it's "Just one more level of indirection" and those little pieces will
ultimately add up.
Not to say we won't, but I make it a point to question these decisions.
That way folks take the performance implications into account. I don't mind
*doing* them, mind, but I want people to think about the costs when
deciding the value of the feature.
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
dan@sidhe.org have teddy bears and even
teddy bears get drunk
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