Re: Eiffel and Java

[paul.johnson@gecm.com (Paul Johnson)]

In article <1996Nov11.142547.4810@schbbs.mot.com>, shang@corp.mot.com says...
>
>In article <328592FC.64F26D66@sede.unijui.tche.br> "Marcos F. F. de Macedo"  
><marcosm@sede.unijui.tche.br> writes:

>> Interfaces in Java have nothing to do with this concepts. Interface in
>> Java is an implementation restriction (not a conceptual one) [...]

>Separation of the interface from implementation is a good thing.
>It is required by the practical software engineering needs to reduce
>the dependency among software components. 

Maybe, but along the way from interface to implementation there is space for 
partial implementations containing code that is reused between the final 
implementations.

A good example is the Eiffel "COMPARABLE" class, which defines all the 
comparison operators in terms of the "<" operator.  So for instance the 
implementation of ">=" is

   Result := not Current < other;

You can't do this in Java: every class that wants comparison operators 
(assuming such a thing can be defined in the language) needs to implement all 
of them every time.

Paul.

-- 
Paul Johnson            | GEC-Marconi Ltd is not responsible for my opinions. |
+44 1245 242244         +-----------+-----------------------------------------+
Work: <paul.johnson@gecm.com>       | You are lost in a twisty maze of little
Home: <Paul@treetop.demon.co.uk>    | standards, all different.