Double Dispatch in Eiffel

[r***@gmail.com]

Seeing as how this message exchange is from November of 1992 and it is April of 2013 (21 years later), I am going to make a leap of faith assumption that you have handled your homework assignment and moved on. :-) That said -- I have just added a couple of Eiffel examples to the WikiPedia double-dispatch article with the present version of Eiffel in Eiffel Studio 7.2 using agents. Still, I am intrigued by Bertrand's suggestion for a FIGURE_PAIR class because after doing the agent-based example, there is a question in me about turning the pattern into a component such as what Kristine Arnout accomplished with some of the GO4 Design Patterns a number of years back (referring to her doctorate paper on the matter).

Cheers!
Larry

comp.lang.eiffel (please see there for details of the problem),

I'm having some trouble implementing double-dispatching in
Eiffel. I'm working on the solution to a homework problem
I assigned,

^^^^^^^^

Here is a brief view on this subject. (As this is a homework
assignment and I don't want to get into trouble with Mr. Hyatt's
2. If that is not the case, what this means from the perspective of
object-oriented design is that you have identified a *new data
abstraction*: figure pair. Then you should write the corresponding
deferred class \fIFIGURE_PAIR\fR, and provide effective descendants for
each useful combination
The details are left to the reader, both because the question was
homework-related of this problem and because it is pleasant to rediscover
them for oneself. (I'll post them later if anyone feels it's necessary.)

Hi Bertrand,
I don't see how you would construct the pair object, which is
an instance of some subclass of FIGURE_PAIR (which subclass?), so
you can call pair.intersect(). Can you please elucidate?
Thanks.
--dave yost

[Simon Willcocks]

Post by r***@gmail.com
Seeing as how this message exchange is from November of 1992

My usenet archives only go back to 2007. I'll have to try Dejanews. ;-)