Re: polymorphism (was compare swarm with repast)

[Nick Collier]

Hi,

When I saw the first message about java lacking polymorphism I was a bit
confused, but let it lie. Now with this second message I want to reply. 

Java _DOES_ support polymorphism as least as far as I understand it
(polymorphism that is). For example, if I have three agent types, A, B,
and C. The first of which, A,  is an interface (that is just method
signature declarations and no implementation) with say a step method.
The other two types, B and C, are concrete implementations of this
interface. They each provide a different implementation of the step
method that results in different agent behavior. So, I can treat B and C
here as type A, but whenever I call the step method on B and C their own
implementations are executed. B is polymorphic in that it appears as
both A and B to client code. A could also be a class here as well. This
is pretty much the way polymorphism works in C++ as well. (Methods in
java default to virtual.) Obj-C does much more run time binding etc., 
so perhaps its "more polymorphic," but Java certainly has polymorphism
as least as its commonly understood. A brief look at any of the 100's of
java books under polymorphism, as well as various design pattern books
with java examples confirms this. 

Nick

On Mon, 2002-08-12 at 09:45, M Lang / S Railsback wrote:
> Russell Standish wrote:
> > 
> > Problems with Java.
> > 
> > 1) Its slow
> > 2) Has too many incompatible versions
> > 3) Lacks operator overloading
> > 4) Lacks generic programming
> > 5) Lack multiple inheritance and polymorphism
> 
> Here are my two cent's worth, as someone who (a) has not yet given Java
> a serious try, and (b) has had the luxury of working with experienced C
> programmers on my Swarm projects.
> 
> a. I have *never* had a problem installing and running Swarm, using the
> packaged releases for Windows. 
> 
> b. Russell's problem #5 is to us a real one- the lack of polymorphism. I
> think this is the same issue Glen was getting at- Objective C gives you
> more flexibility to have agents of different classes all mixed up
> competing with each other, etc., and the model swarm not having to know
> what class agent it is telling to do what. I'm not sure how we could do
> some of our models without polymorphism.
> 
> c. Thanks for all the timely discussion as I am finishing up a draft
> book chapter on software for agent-based ecological models. (It is NOT a
> review of all the platforms out there, but instead an overview of things
> to think about for people getting started.) If someone is dying to
> review it for me, please send me a message.
> 
> Steve
> 
> -- 
> address@hidden
> Lang, Railsback & Assoc.
> 250 California Ave., Arcata CA 95521
> 707-822-0453; Fax 822-1868
> 
> 
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-- 
Nick Collier 
Social Science Research Computing 
University of Chicago 
http://repast.sourceforge.net



                  ==================================
   Swarm-Modelling is for discussion of Simulation and Modelling techniques
   esp. using Swarm.  For list administration needs (esp. [un]subscribing),
   please send a message to <address@hidden> with "help" in the
   body of the message.
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