From: Christoph <chr_news@...>
Date: 2002-09-12T04:37:58+09:00
Subject: Re: Multimethods (was Re: Larry Wall's comments on Ruby)


"Hal E. Fulton" wrote in
....
> Do people really consider that a "multiple-receiver"
> model??
>
> I had envisioned some kind of bizarre framework
> where you could do (obj1,obj2).method in an
> order-independent fashion.

What you are talking about is called symmetric
dispatch - interestingly enough even so it is easy
 to cook up a notion of anti-symmetric dispatch
that could handle arithmetic binary operator
 ``-''   I could not find a single google hit on the
subject.

Anyway the two subject are not necessarily
distinct. One can imagine a system  were

    obj1 + obj2 is equivalent to

the (symmetric if you like) dispatched version

          (obj1, obj2).add

>
> In any case, I wouldn't favor adding this to Ruby,
> as variables have no types; and thus how do you
> define a method "signature"?

Well in the given case the signature would be zero - the
crucial point is that  (obj1,obj2)  would not be an
ordinary object but a (possible symmetric) double
or bi-object with a (symmetric) bi-type. Note however
that I am not even sure if such a system has ever been
 implemented in a languages (like Ruby) were classes
(types) live within the Objectspace (are ``real'' objects).

Anyway I would be quite happy with a trail balloon
using more conventional  multiple-dispatch.

....

/Christoph