Re: Ada -vs- GNAT

["Robert I. Eachus" <rieachus@attbi.com>]

Stephen Leake wrote:

 
> GNAT is open source; if you want an Ada variant, go fund it! As Robert
> keeps pointing out, that was one of the original motivations behind
> producing an open source Ada compiler; people (mainly universities)
> would be free to play around with the language. Yet no one has done it
> yet in a serious way.


I have to disagree here.  I think that you will find that a lot of ACT 
customers have taken that approach.  However, a strong perception during 
both the Ada 83 and Ada95 standardization process was that Ada should be 
extensible in a natural way with attribute, pragmas, and packages.  And 
also that any of these that are generally useful, even if just in a 
specific doman, and are ready for standardization, belong in the standard.

I'd hate to have to try to count the GNAT features that were needed by a 
specific customer, added to GNAT, then migrated into the area of 
generally used.  Several of these attributes and pragmas are migrating 
into the standard, even if they officially have yet to do so, others 
actually made it into the Ada 95 standard before it was approved.

I think that this conservatism is a very good thing.  There are features 
(or mis-features depending on your point of view) that were added in Ada 
95, and as they became used a need for additional language features 
became obvious. These are usually first seen in GNAT, but quickly appear 
in the other Ada compilers.  If the need is there, once the ARG can 
determine what the best way to implement the functionality is, it 
migrates into all compilers fairly quickly.

So Ada really is a much more dynamic standard than people think, and 
today's Ada 95 is much better than the Ada 95 of 1995.  But since the 
perception is that, of course all these features are part of the 
standard and there is no fragmenting of the Ada language, a lot of 
people make the mistake of assuming that this innovation and evolution 
is not going on.  In practice it is, just slow enough--and compatibly 
enough--that users don't notice.