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From: stt@henning.camb.inmet.com (Tucker Taft)
Subject: Re: C/C++ knocks the ....
Date: 1996/02/18
Message-ID: <DMzHIw.8G1.0.-s@inmet.camb.inmet.com>#1/1
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organization: Intermetrics, Inc.
newsgroups: comp.lang.ada
Date: 1996-02-18T00:00:00+00:00
List-Id: <comp.lang.ada>

Matt Kennel (kennel@msr.epm.ornl.gov) wrote:
: ...
: As for Ada, I'm not yet fully convinced abou the package vs 
: type thing.  C++ might be ugly because you can have all sorts of
: elements outside classes, but in Eiffel you cannot.

: Eiffel intentionally makes the unit of namespace and of type
: the same. 

: The question is, do the benefits of having them completely separate
: make up for the extra work and complexity of having to double the
: number of 'mental units' in most idiomatic programs.  (and without
: MI you have to go a bit further) 

: Yes, Ada has them on orthogonal axes.  Eiffel only has "one axis"
: but it may empirically be along the major princpal component with
: only a small deviation in other directions. 

On the other hand, various Eiffel implementations have felt the
need to add yet another language on top for doing "configuration"
of large systems (I think it is called "GRACE"?).  This seems
to indicate that programmers have a need to deal with larger groupings
than that represented by a single class.  Although one could conceivably
just create larger and larger classes, at some point the model of a "type"
breaks down, whereas the notion of a package scales nicely to the
notion of a subsystem, as in Ada 95.  

It is interesting to note that Java has the notion 
of "package" for defining groups of classes.  This seems 
like a reasonable compromise, though it still loses out on some of the
other advantages of defining abstractions using a package rather than a
class, such as symmetry of parameters in binary operations, and elimination
of the pesky "once" or "static" qualifiers of Eiffel/C++/Java that are
needed to turn a "component" of a type into a component of a module.

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA