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From: Brian Rogoff <bpr@best.com>
Subject: Re: OO, C++, and something much better!
Date: 1997/02/24
Message-ID: <Pine.SGI.3.95.970224163110.19651B-100000@shellx.best.com>#1/1
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 comp.lang.eiffel,comp.lang.ada,comp.lang.c++,comp.lang.smalltalk,comp.object
Date: 1997-02-24T00:00:00+00:00
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On 24 Feb 1997, Jon S Anthony wrote:

> In article <Pine.SGI.3.95.970221115143.12989C-100000@shellx.best.com> Brian Rogoff <bpr@best.com> writes:
> 
> > On 21 Feb 1997, Eric W. Nikitin wrote:
> > > A language derived from Oberon, Lagoona, goes on to provide an additional
> > > feature called categories which are distinct from type, but allow 
> > > different types to be related via similar behaviors. ( Categories
> > > are similar to protocals in Objective-C and interfaces in Java ).
> > 
> > 	Something similar to this is provided in Ada by using generic 
> > packages with empty bodies. For example
> 
> Isn't this Lagoona category aspect basically the same as Class in Ada?
> A family of related types?
> 
> /Jon

	I can't say for sure, since I don't know Lagoona, and I don't know 
what a Lagoona "category" is. I looked at what it was being used for, and 
thought that it vaguely resembled an ML "signature", which I would
translate into Ada using a null bodied generic package. 

	"Category" is becoming one of those terms like "operator". I know 
the term from abstract algebra, but software folk use it in at least three
ways:

(1) The Lagoona way, new to me, and I still don't get it. Any Lagoona 
    users care to help? 
(2) The way I know (and love), from abstract algebra (any number of books
    discuss this, the one by Hilton&Wu is where I learned it)
(3) The Booch method uses the term for (in essence) Ada packages or C++ 
    namespaces (Robert Martin's book is my favorite source for this stuff,
    even though I prefer Ada to C++).   

-- Brian