From: Dan Sugalski <dan@...>
Date: 2002-09-12T15:35:16+09:00
Subject: Re: Multimethods (was Re: Larry Wall's comments on Ruby)

At 12:57 AM +0900 9/12/02, Christoph wrote:
>"Dan Sugalski"  wrote in
>....
>>  That's pretty much multimethods. They're terribly useful, as they cut
>>  out a lot of checks for the second type in methods. (Checks which
>>  tend to be slow, error prone, and missing stuff)
>
>Thanks Dan, for making such an eloquent case for multimethods.
>Personal I cannot image (surely an effect of being single and
>simple minded;-) how their use could be less complex then the
>alternatives like Rubys coerce framework  or double-dispatch ..

Their big problem is that they introduce methods that don't live in 
any class. If you have the methods:

    add(int, num)
    add(num, int)
    add(bignum, int)

those three, while methods, don't live in any class, so if you did:

    foo.add(bar)

you may well not be executing the add method defined in the foo 
class--you may be executing the one defined in the bar class, or the 
baz class, or maybe in some standalone code you loaded.

Not, mind, that I think that's enough to make it not happen, but I'm 
not a language designer. :)
-- 
                                         Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
dan@sidhe.org                         have teddy bears and even
                                       teddy bears get drunk