Multiple Dispatch in Ada 95 (Was Re: Real OO)

[rogoff@sccm.Stanford.EDU (Brian Rogoff)]

Don Harrison writes:
   Jon S Anthony writes:
   ::> In Ada, with the second, third, fourth, ... and nth
   :> operands of the same specific type controlling dispatching, by the
   :> time the compiler gets to the end of the routine signature, it is
   :> rolling it's eyes and crying: "Good grief, I heard you the first
   :> time!!!"
   :
   :Don, are you really this clueless or are you just being facetious?
   :The reason I say this is that the above doesn't even work as a joke,
   :because it is rooted in an error (instead of a clever observation).

   Mostly facetious. But I do find it slightly ridiculous to say that there are
   multiple controlling operands if it only works if they happen to have the same
   dynamic type. (No, I'm not saying that it should be possible for them to be
   different). The fact that you get an exception if the types differ is not as
   plain as in the Eiffel paradigm, IMO. 

This raises an interesting question. Why doesn't Ada 95 support 
multimethods? I'm sure this was discussed somewhere, I just haven't 
seen it. Does multiple dispatch break something, or was it mainly an 
implementation thing? Could we see it in a future version of Ada?

While Don clearly prefers the "Eiffel way", I think that multiple dispatch 
would fit in more neatly with the current Ada 95 scheme, which I like. 

-- Brian