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Postings from July 2002
Okay, now that the dust from YAPC has settled and the holidays and
such are done, it's time to get to some of the outstanding bits of
Parrot. I'm going to get the extension mechanism designed over the
next few days, but until then...
We need a multimethod dispatch for vtable calls. Right now we're
working on a "left side wins" scheme and, while we're going to keep
that (sort of) we really need a way to choose the method to call
based on the types on both sides of binary operators. (Unary
operators, luckily, are easier)
Basically what we need is a lookup matrix for each vtable method
(add, subtract, multiply, whatever) that we can index by left and
right types to get the actual method to call. The current
int/num/string/same scheme can stay, as they're multimethod already,
and handy shortcuts. The methods that take a generic unknown PMC are
the ones that need to do the multimethod lookup.
We can do this with the current vtable scheme as it is, since we
already have a slot to put this in, and I think we're going to have
languages that still do a left-side-win scheme.
Yes, this means we're going to have to do matricies (at least 2D
matricies), class dependencies (so derived classes can inherit from
parent classes so as not to leave gaps), and method registration at
PMC load time.
I'd hoped to avoid this, but...
I'll get more details together in a bit.
--
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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