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Newsgroups: comp.lang.ada
Message-ID: <940908231244_73672.2025_DHR48-1@CompuServe.COM>
Date: Thu, 8 Sep 1994 19:12:45 EDT
Sender: Ada programming language <INFO-ADA@NDSUVM1.BITNET>
From: Ken Garlington <73672.2025@COMPUSERVE.COM>
Subject: Ada 9X features
Comments: To: "comp.lang.ada" <info-ada@vm1.nodak.edu>
Date: 1994-09-08T19:12:45-04:00
List-Id: <comp.lang.ada>

I would disagree with Bevin Brett's assessment of Ada 9X requirements bloat in
one area: the ability to have access values that don't reference the heap. We
have a number of constant data structures where the use of access values
greatly simplifies the data description and the corresponding algorithms. In
the "good" old JOVIAL days, it was pretty simple to get the compiler/linker to
build this as a static structure in ROM. (From what I understand, this can also
be done in C.)

We can use Ada 83 access types, which are much clearer to read and understand
than the JOVIAL equivalent. However, we just can't afford the elaboration time,
nor the extra memory, needed to copy these large data structure into the heap.
So, we have to do nasty tricks with UNCHECKED_CONVERSION and SYSTEM.ADDRESS to
get the data structure the way we want.

When we, as a most decidedly non-academic group of Ada practitioners, were
asked what we would want in Ada 9X, we wrote MRs that discussed our problems in
this area, fully expecting to be told, "Oh, there's a simple way to do that in
Ada 83 - you just..." or "Well, you just don't have an Ada mindset..." However,
neither of these happened. Even more to our surprise, an implementation has
been proposed for Ada 9X which looks like it will work perfectly.

I can't say that I will use everything in Ada 9X. I can't defend everything
that's been added. But I hope that those features that were added based on
inputs from the "grunts" in the field are treated with the same importance as
those proposed by the vendors, even if they aren't quite as interesting...