Bob Rogers <[EMAIL PROTECTED]> wrote:
> From: Leopold Toetsch <[EMAIL PROTECTED]>
> 1) is there a MultiSub object with one short name that holds all
> possible long names (and function references)?
> If yes, who is creating it: the Perl6 compiler emits code to do so or
> it's up to Parrot to do the right thing?
> FWIW, Common Lisp specifies a "generic function" [1] that collects all
> methods defined for a given operation name. (In Perl/Parrot, the
> generic function name for your examples would be the string "foo"; in
> Lisp, it would be the symbol "FOO" in some package, but the practical
> difference should be slight.) The important thing is that the GF has
> all the information required to make method dispatch decisions.
That sounds exactly like the MultiSub object that gathers a candidate
list of all subroutines with the same short name.
> ... But on the other hand, the CL community has
> more than 15 years of experience with MMD, so I wanted to be sure
> everyone was aware of it.
Yeah, that's really helpful.
> 2) namespaces of (multi) subs.
> A non-multi method is in the classes' namespace. In Parrot terms that's
> currently:
> %globals{"\0class_name"}{"method_name"}
> I'm not quite sure, if the method hash shouldn't live inside the class.
> Is naming at this level really important here?
Well, the short name of the multi sub has to be stored somewhere.
> ... The operation itself
> needs a name (so that people can call it), and classes need class names
> (maybe), but all methods are implicitly named by the combination of
> operation plus argument signature.
Yes. That's the "long name" in Perl6 design documents.
> ... Which would seem to mean that,
> unlike perl5, the package in which a multimethod is defined doesn't
> matter; all that is captured by the argument signature.
Yep. You can define a multi sub anywhere.
> ... Or is it
> possible to have more than one method with the identical signature? And
> if so, what does that mean?
There can be identical signatures in different scopes. Within one scope,
I don't know.
> The "long name" is therefore a list of class names, which suggests
> that the single-dispatch naming above is backwards. Of course, I'm
> probably out of my depth here . . .
The "long name" contains the signature. The "short name" is the bare
"foo".
> A multi method is similar, except that their can be more then one
> with the same short name (which probably means that there has to be a
> MultiSub object holding the long names)
> I'm not sure it is meaningful to give a sub a "short name,"
You call it by the short name.
> %globals{"foo"} --> MultiSub{"foo_A_B" => Sub, ...}
> This sounds right to me. Or perhaps
> %globals{"foo"} --> MultiSub{["foo", 'A', 'B'] => Sub, ...}
Yep, something like that.
> just to belabor the point a bit.
> What about a not so global multi:
> multi sub foo(A $a, B $b) {...}
> Thanks for clarifying,
> leo
> Is this really different? After all, the operation "foo" should be just
> a string in either case.
Sure. But the string "foo" has to live in some namespace. But, it it's
not marked as global it's probably in either a package or a module, so
again it has it's namespace.
> -- Bob Rogers
leo
