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From: olehjalmar kristensen - Sun Microsystems - Trondheim Norway
 <ok145024@sun.com>
Newsgroups: comp.lang.ada
Subject: Re: Is the Writing on the Wall for Ada?
Date: 08 Sep 2003 09:49:23 +0200
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Date: 2003-09-08T07:49:24+00:00
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>>>>> "HR" == Hyman Rosen <hyrosen@mail.com> writes:

    HR> David Marceau wrote:
    >> Interfaces are the way to separating the differences between versions of
    >> components.

    HR> That is a very interesting point of view. Oh wait, no it isn't. It's just a
    HR> wrong point of view. The way interfaces are used in Java, and in C++ for that
    HR> matter, is as a specification for the the methods supported by an object.
    HR> It doesn't matter how this got that way, so we may as well assume that your
    HR> little history lesson is true, since it's uninteresting regardless.

    HR> Write an interface, and now you have a specification for how a component may
    HR> be invoked, without any code implementing such a component. Write the code
    HR> which conforms to the interface, and you're done. The compiler makes sure that
    HR> if an interface is expected, it is supplied, and if it's to be implemented,
    HR> nothing is missing.

    HR> That's your separately compilable specification and implementation. What about
    HR> this fails to work?

In theory, nothing. But I've actually managed to create instances of
classes with pure virtual functions. Kind of funny when it blows up at
run time with "pure virtual function called". That's a criticism of the
compiler of course, not the language as such.

And then you don't have the compiler forcing you to actually write a
separate interface, of course.