Teaching new tricks to an old dog (C++ -->Ada)

[Turamnvia Suouriviaskimatta]

I 'm following various posting in "comp.lang. ada, comp.lang.c++ ,
comp.realtime, comp.software-eng" groups regarding selection of a
programming language of C, C++ or Ada for safety critical real-time
applications. The majority of expert/people recommend Ada for safety
critical real-time applications. I've many years of experience in C/C++ (and
Delphi) but no Ada knowledge.

May I ask if it is too difficult to move from C/C++ to Ada?
What is the best way of learning Ada for a C/C++ programmer?

[Larry Kilgallen]

In article <11************ *@corp.supernew s.com>, CTips <ct***@bestweb. net> writes:

On some implementations (on RISC architectures) a register is reserved
for the static-chain. This means one less register for *every* function
(or maybe only for enclosed functions?) when used with a language that
support this kind of nested functions.
It does not have much to do with whether one language supports it,
so long as _some_ language supports it.

If I have a call chain:

Ada => C => Ada

that second Ada subprogram might want to access a variable in the first
Ada subprogram. So the C implementation must pass the context along.
As I understand it, that is the job of the "Bound Procedure Value"
construct in the VMS Calling Standard. Such relationships between
languages must be defined by the calling standard for the platform,
meaning that the C compiler should honor it as well. I imagine that
HP Ada and HP Pascal interact properly in this regard -- I have no idea
about HP C.
C++ probably left it out because of its C heritage, while Ada probably
dropped it in because of its Pascal heritage. IMHO, its probably not
worth the cost.

If that is your opinion, I would say you have not done enough programing
in a language where it is provided.

[Ed Falis]

On 14 Mar 2005 19:00:00 -0500, Robert A Duff
<bo*****@shell0 1.TheWorld.com> wrote:

But if you want to hide most of the data of some abstraction, and
there's no "natural" meaning of "<", then you have to think ahead, and
define some "<" operation just in case somebody wants to put the thing
into a container. (Or, of course, go back and add that in to an
existing data type when you find it's needed.)

Bertrand Meyer went pretty heavily into this situation with his
"open-closed" principle in Eiffel - largely why he's a big fan of multiple
inheritance. This in a sense follows your paranthetical remark.

[Jerry Coffin]

Randy Brukardt wrote:

[ ... ]

This statement is false. I was going to try to explain precisely what
happened, but it probably is better to just point to the articles on that topic that were published at the time. See:
http://www.adaic.com/compilers/index.html
and in particular:
http://www.adaic.com/compilers/acaa.html

I see it, but I also see things like this:

----- quote -----
Q. What about NIST? Isn't Ada still a FIPS standard, with requirements
for NIST validation?

A. FIPS 119-1 is still valid, and section 11.4 states that
"Implementation s of FIPS Ada shall be validated in accordance with the
NIST Computer Systems Laboratory (CSL) validation procedures for FIPS
Ada". However, such validation procedures no longer exist, since NIST
had delegated Ada validation authority to AJPO, and AJPO did not
re-delegate this authority.
--- end quote ---

(from: http://sw-eng.falls-church.va.us/ajpofaq.html) which seems to
agree reasonably closely with what I said. Some of it appears to be
obsolete -- FIPS pub 119-1 is NOT valid anymore; it has been withdrawn.
That has little to do with events that happened years ago though.

I'd also note that the relationship between the ACAA and the ISO seems
to be rather one-sided -- while you emphasize your relationship with
the ISO rather heavily on your web site, the ISO seems to mention you
rather a bit less -- a search for "ACAA" on the ISO web site more or
less implies that they've never even heard of you.

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Randy Brukardt]

"Jerry Coffin" <jc*****@taeus. com> wrote in message
news:11******** **************@ z14g2000cwz.goo glegroups.com.. .

Randy Brukardt wrote: .... I see it, but I also see things like this: <Misleading junk snipped>
.... (from: http://sw-eng.falls-church.va.us/ajpofaq.html) which seems to
agree reasonably closely with what I said.
Ah, yes, the imfamous "Ada is dead site". (It doesn't say that anymore, but
it once did.) That site was created by someone how posted all kinds of
misinformation; people seem to believe it because they registered the old
AJPO domain name. Of course, anyone can post anything on the net, and it can
be hard to tell what's accurate and what isn't.
I'd also note that the relationship between the ACAA and the ISO seems
to be rather one-sided -- while you emphasize your relationship with
the ISO rather heavily on your web site, the ISO seems to mention you
rather a bit less -- a search for "ACAA" on the ISO web site more or
less implies that they've never even heard of you.

Since the ACAA is defined in an ISO standard (specifically ISO/IEC 18009),
and ISO makes money by *selling* their standards, you're hardly going to
find anything there. I don't think you can find much about Ada there,
either. The ACAA I run is an instantiation of that described by that
standard.

You might be able to find out more on the WG9 web site (WG9 is the Ada
Working Group within ISO/IEC JTC1 SC22), but it is pretty sparse:
http://www.open-std.org/JTC1/SC22/WG9/

Randy.

[Dmitry A. Kazakov]

On Tue, 15 Mar 2005 00:10:27 GMT, Dr. Adrian Wrigley wrote:

On Mon, 14 Mar 2005 23:46:33 +0000, Hyman Rosen wrote:

Dr. Adrian Wrigley wrote:

This means that you can't write an implementation of a template/generic
function using a map/hash without changing some/all the implementations
and interfaces up the instantiation tree (am I right?).

No, you are wrong. Simply write your comparison or hash function at the
point where you need it. Use the public accessors to get the data you
need to perform the operations.

That's the point... there aren't any public accessor functions
for opaque data types such as non-limited generic formal parameters.

Then the data are inherently non-sortable. That was designer's decision,
and that is *the* contract. To define "<" would mean to break that
contract.

There are lot of situations where some ad-hoc generated comparison will not
work. Especially if objects are in fact handles to something that may
change asynchronously to the container.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

[Dmitry A. Kazakov]

On 14 Mar 2005 16:02:43 -0500, Robert A Duff wrote:

"Dmitry A. Kazakov" <ma*****@dmit ry-kazakov.de> writes:

It can be formulated in two words: "contract model" is what C++ templates
lack.
Which is both a benefit and a drawback. C++ templates are somewhat more
powerful that Ada generics, because of the lack of contract model, and
implicit instantiation.

I think that the reason is not contracts but inflexible contracts. Ada
formal generic parameters are not ADTs. So there is no way to define a
formal generic type Ordered. Instead of that ADTs are defined ad-hoc:

generic
type Foo is private;
function "<" (Left, Right : Foo) return Boolean is <>;
package ...

What is worse is that these ad-hoc ADTs are not named, so in fact it is a
kind of that flawed structural type equivalence reborn.
But I don't think that addresses Dr. Wrigley's complaint (which applies
to both Ada and C++).

Indirectly it does, because what he wants is to get more that is in the
contract ... (:-))

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

[Jean-Pierre Rosen]

Greg Comeau a écrit :

Other posts seems to disagree. I don't see how they could disagree with the mere fact that Adalog is a
registered ACAL, but anyway...
Please clarify for us.
Also include how and why your company is the _official_ lab.
(I'm not challenging you, but seems to me a mixed message
is coming through this thread.)

The ACAA (see Randy's posts) is the official office for issuing
conformance certificates. These certificates are issued after
conformance testing has been performed by an ACAA approved laboratory,
called and ACAL. Adalog has been approved by ACAA, and this is easily
checked by going to the ACAA site!

People arguing that there is no more validation office are simply wrong,
and I hope it is misinformation and not malice.
--
---------------------------------------------------------
J-P. Rosen (ro***@adalog.f r)
Visit Adalog's web site at http://www.adalog.fr

[Georg Bauhaus]

Dmitry A. Kazakov wrote:

I think that the reason is not contracts but inflexible contracts. Ada
formal generic parameters are not ADTs. So there is no way to define a
formal generic type Ordered.

Hm. Do you mean, a contract type cannot be _defined_ in the
generic formal part of a unit?
Otherwise, why not just write

generic
type Ordered is new Has_Less_Than with private;
package ...

where Has_Less_Than is an abstract type with a "<" operation.

(Or use multiple interfaces and Ada 2005.)

[Hans Malherbe]

Dr. Adrian Wrigley wrote:

That's the point... there aren't any public accessor
functions

It's a good point. If you design a library you not only have to decide
up front whether you want to let users put your class in ordered
containers but whether you want to allow containers at all (Generic
algorithms freely make copies of elements and assume value semantics).

I have to ask myself though: If I am denied access to information that
lets me implement a < operator, am I supposed to be able to sort it?

Groete
Hans

[Dmitry A. Kazakov]

On Tue, 15 Mar 2005 11:51:33 +0100, Georg Bauhaus wrote:

Dmitry A. Kazakov wrote:

I think that the reason is not contracts but inflexible contracts. Ada
formal generic parameters are not ADTs. So there is no way to define a
formal generic type Ordered.

Hm. Do you mean, a contract type cannot be _defined_ in the
generic formal part of a unit?
Otherwise, why not just write

generic
type Ordered is new Has_Less_Than with private;
package ...

where Has_Less_Than is an abstract type with a "<" operation.

In which case it simple does not need to be generic! Ordered here is a
normal ADT, which class is Has_Less_Than'C lass. So the package should work
directly with the class and be non-generic. End of story.

What I meant was:

generic
type Ordered is Has_Less_Than; -- This is not Ada!
package ...

Here Has_Less_Than is not a type but a [generic] class of types, like
"private", "limited private", "range <>", etc. It is almost same but not
the same. This is actually why I strongly believe that generics are
superfluous and should be replaced by better ADTs (now normal ones, one
storey below). In other words there is no need to make a fuss with types
ADT (=classes of formal generic types) when we are far from being ready
with the normal ones!

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de