From: Friedrich Dominicus <frido@...>
Date: 2002-09-12T15:19:30+09:00
Subject: Re: Multimethods (was Re: Larry Wall's comments on Ruby)

matz@ruby-lang.org (Yukihiro Matsumoto) writes:

> Hi,
> 
> In message "Multimethods (was Re: Larry Wall's comments on Ruby)"
>     on 02/09/11, Dan Sugalski <dan@sidhe.org> writes:
> 
> |Multimethod dispatch is reasonably simple. It's when you have 
> |multiple methods with the same name, which are only differentiated by 
> |their method signature. At runtime, the types of the arguments are 
> |checked and you dispatch to the matching method. If no method 
> |matches, or more than one method matches equally well, an exception 
> |is thrown.
> 
> In my definition, this is not multi-method, because a method still
> belongs to certain class.
I think you're right with your definition. And you are right with
multi-methods go beyond that. But it's quite easy to understand, while
using the used definitions for overloading. 

The edge is small I guess. AFAIK do not all function in C++ e.g do
have to belong to classes. And therefor one could have multi-methods
there too. It's just very unusual use I guess.

>  I call this "overloading method".  I'm not
> against overloading method.  
This is a terrible difficult area IMHO. I used it and found it useful
sometimes on the other hand I'm convinced that use stand near the
other. 


> This has power of multi-method, and
> simplicity of ordinary method. 
It depends on how you think objects and methods to have to work
together. Most OO langauge includes Ruby see methods as "element of an
object" This does not hold for CLOS. You loose the tight relationship
but gain a new level of flexibility. 

Till some years I was in the first boat (heavily influences by Eiffel)
but now I sit in the other. If you like I invite you to check out the
GoF book and see how having the latter simplifies the mentioned
patterns there. Well I guess with ruby you do not need many pattern
from the GoF book, that's due to the flexibilty of ruby.


> Just like mix-in compared to MI.
May be. I'm used to MI since years. I do not find mix-ins easier to
understand nor more clear. It's a different approach which obviously
work for you.

Regards
Friedrich