Re: [boost] Boost.Multimethod proposal

Subject: Re: [boost] Boost.Multimethod proposal
From: Edward Diener (eldiener_at_[hidden])
Date: 2009-08-22 23:58:52

Jeffrey Bosboom wrote:
> Edward Diener wrote:
>> What is a practical use for multi-methods ?
> 
> Multimethods (assuming this library uses the term as it's commonly 
> understood) are like virtual functions that are dispatched on the 
> dynamic types of their arguments as well as the type of *this.  You can 
> get this effect through double dispatch, but it requires a bit of 
> plumbing and requires two virtual calls (which for some people is a 
> large amount of overhead).  (Of course, multimethods have overhead too.)

This does not explain the practical purpose of multimethods. I know what 
virtual functions are, of course. What in multimethods improves on the 
polymorphic capabilities of virtual functions that make them a practical 
choice for use over normal polymorphism.