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Subject: Re: [boost] Boost.Multimethod proposal
From: David Bergman (David.Bergman_at_[hidden])
Date: 2009-08-23 13:16:20

On Aug 23, 2009, at 10:00 AM, Mathias Gaunard wrote:

> OvermindDL1 wrote:
>> Hmm, I know LISP has a well optimized multimethod implementation
>> written in pure LISP, wonder how easily that method could be
>> transferred to C++, although more verbose...
> Lisp is dynamically typed, so the implementation of multimethods is
> simply that of overloading.

This sentence is a bit oxymoronic. A dynamically typed language has no
way to overload anything, i.e. overloading is a feature found in
languages where type can be expressed and dispatched upon.
Disregarding the oxymoronic quality, why is this implication natural
(dynamic ---> multimethod == overloading...)?

That said, yes, in CLOS one can extract type information (a tag) and
match it against the special form arguments provided to a "method" (ad-
hoc multipolymorphic operator...). So, in that sense, CLOS is not
completely dynamic, since type information can be expressed statically
(in these special 'defmethod' forms) and matched against through a
specialized pattern matching mechanism.


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