Re: Ada student homework ?

[Robert Dewar <robert_dewar@my-deja.com>]

In article <uUWR5.441619$i5.7656071@news1.frmt1.sfba.home.com>,
  tmoran@acm.org wrote:

> Obviously.  But is it really true that *any* app using the
> facilities of MS Windows can be developed as easily, or
> easier, with GtkAda?

No, these are different tools, there are things that can be
done more easily with CLAW, but there are also things that
can be done more easily with GtkAda (in some respects the
facilities of GtkAda are higher level than those in CLAW,
but they certainly do not cover the full range of
functionality).
>
> Is there a release sequence of
> GtkAda versions that have been developed and tested with
> multiple Ada Windows, and
> instead tie you to ACT's Ada compiler?

That's a bit confused, but I assume you are asking whether
there are GtkAda versions that work with various Ada 95
compilers.

For this you have to ask other vendors. Unlike the situation
with a proprietary product like CLAW, anyone can take the
sources and adapt and distribute this for their own compiler.

ACT is in the business of making sure GtkAda works for GNU.
However, we try to generally maintain compatibility. We are
certainly aware that Rational for example has been at least
fiddling with GtkAda, and we have been happy to cooperate
with them on this.
I was talking more of compatiblity between operating systems
and architectures. We actually find that far more of our
users are concerned with this kind of portability, than with
portability to other compilers.

> Portability is not cheap.  Having worked on the development
> testing of CLAW on four different Ada compilers, including
> GNAT, ove the last few years I am acutely aware of that fact.
> It's also true that software vendors usually have strong
> economic incentives to promote lock-in to their products.

Right, which is why open source development works well, it
tends to counteract that. When sources are proprietary, people
have little chance to deal with that problem. In your case,
since CLAW is not open, you have to do all the work of making
sure it works on multiple Ada compilers. In the case of GtkAda,
different vendors can distribute that work among themselves.

Since GtkAda is part of the GNU project, the primary target is
of course GNU based tools (GNAT in particular), and now that the
GtkAda developers work for ACT that is certainly their primary
responsibility. However, as the release notes make clear we
generally try to avoid any compiler dependencies, and when
Rational has reported portability problems, we have been
able to fix them in the public sources without any difficulties.
Note that GNAT.HTable itself should be perfectly portable to
other Ada compilers, and there is nothing to stop Ada vendors
from taking components from the GNAT library (indeed for a while
Aonix was distributing some of our Annex G components with their
Ada 95 compiler, and may still be doing so for all I know, and
that's perfectly fine, providing that this is made clear and
appropriate licensing conditions are made clear to users (e.g.
appropriate copy of the GPL distributed with the product).

Robert Dewar
Ada Core Technologies


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