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?

[Georg Bauhaus]

Pascal Obry wrote:

Georg Bauhaus <ba*****@future apps.de> writes:

Can templates recurse?

No. (Though you can mix recursive subprograms, nesting, and template
instantiation .)

Hum, since you answered "no" and I answered "yes" it seems there is something
about "templates recurse" that I did not understand. In short what is a
recursive template in C++ ?

In Ada, you cannot instantiate a generic within itself (as Marius
has said elsewhere). In C++, you can, and you should provide
termination lest the instantiation loop exhausts something (at
link time, I believe):

template<typena me T>
struct G {
G<G> r;
};

Georg

[Larry Kilgallen]

In article <11************ *********@z14g2 000cwz.googlegr oups.com>, "Hans Malherbe" <ha***********@ gmail.com> writes:

Somewhere in this thread Loduvic writes:

* in Ada, loop variables (a) are constants and (b) do not exist outside
of the loop

This is safer, but limiting.
In C++ may want to declare the variable outside the loop,
break out early and use the loop variable. Let me guess: You can't
break out early in Ada, right?
You can, but if I want to export the loop variable I use something like:

for each_fluvark in fluvark_array'r ange loop
...
if some_value = 42
then
last_value_of_f luvark_index := fluvark_index;
exit;
end if;
...
end loop;

making quite explicit the difference between the changing value of the
index and the final value at which we exited the loop.
A few other questions:

Do you have nested functions like Pascal have?

Even Bliss has nested functions. What Ada has that Pascal has in addition
to nested functions is uplevel addressing, allowing an inner function to
access data declared in outer scopes.

[Falk Tannhäuser]

Pascal Obry wrote:

Hum, since you answered "no" and I answered "yes" it seems there is something
about "templates recurse" that I did not understand. In short what is a
recursive template in C++ ?

One example in C++:

template<unsign ed N> struct factorial
{
static unsigned const value = N * factorial<N-1>::value;
};

// Partial template specialisation to terminate the recursion:
template<> struct factorial<0>
{
static unsigned const value = 1;
};

With this, 'factorial<7>:: value' will be a compile time constant equal to 5040.

Another example:

template<typena me T> struct pointer_info
{
typedef T base_type;
static unsigned const indir_level = 0;
};

// Partial template specialisation for types that are pointers:
template<typena me T> struct pointer_info<T* >
{
typedef typename pointer_info<T> ::base_type base_type;
static unsigned const indir_level = pointer_info<T> ::indir_level + 1;
};

With this, suppose that you have
typedef int***** foo_t;
Then 'pointer_info<f oo_t>::base_typ e' is a typedef (alias) for 'int' and
'pointer_info<f oo_t>::indir_le vel' is a compile time constant equal to 5.

Falk

[Jerry Coffin]

Martin Dowie wrote:

[ ... ]

Hey! I did add a smiley! I just thought it was an opinion from a
reputable source that tied in with the post. :-) :-)
Sorry -- I rarely add an explicit smiley. Regardless of how my messages
might read, I rarely take much of it _terribly_ seriously.

[ ... ]
Would I be allowed to use embedded SQL in the Ada code (GNADE)? Or a
binding to Postgres or MySQL (APQ) or similar (ODBC)?

For the question at hand, I'd postulate that an embedded SQL
implementation simply wouldn't do the job. Binding to MySQL or using
ODBC would undoubtedly work, but using MySQL, Oracle, MS SQL Server,
etc., puts us back in the situation where we basically just have SQL
talking to a server written in C.

Now, I have no problem with that at all -- but it certainly doesn't
seem to be in keeping with what Richard was advocating.

Then again, your headers indicate that you post with Mozilla
Thunderbird running on Windows, connecting through BT Internet. What
percentage of the millions of lines of code used to write and transmit
your message do you suppose was written in Ada, and what percentage in
C and C++? :-)

Ada advocate: "The world WOULD be better if you used Ada."
C++ advocate: "The world IS better because of the cool code I wrote."

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Pascal Obry]

Falk Tannhäuser <fa************ *@crf.canon.fr> writes:

One example in C++:

template<unsign ed N> struct factorial
{
static unsigned const value = N * factorial<N-1>::value;
};

// Partial template specialisation to terminate the recursion:
template<> struct factorial<0>
{
static unsigned const value = 1;
};

With this, 'factorial<7>:: value' will be a compile time constant equal to
5040.

Ok, thanks. This is definitly a recursive definition. AFAIK there is no such
thing in Ada.

Pascal.

--

--|------------------------------------------------------
--| Pascal Obry Team-Ada Member
--| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE
--|------------------------------------------------------
--| http://www.obry.org
--| "The best way to travel is by means of imagination"
--|
--| gpg --keyserver wwwkeys.pgp.net --recv-key C1082595

[Adrien Plisson]

Jerry Coffin wrote:

Ada advocate: "The world WOULD be better if you used Ada."
C++ advocate: "The world IS better because of the cool code I wrote."

about Air Traffic Control:

C++ Advocate: "The world WOULDN'T be safer if they used C++"
Ada Advocate: "The world IS safer, because of the cool system we wrote"
about buffer overflows:

Ada advocate: "Networks WOULD be more secure if you used Ada"
C++ advocate: "Networks WOULD be more secure if we used Ada"
--
rien

[Martin Dowie]

Jerry Coffin wrote:

Martin Dowie wrote:

Hey! I did add a smiley! I just thought it was an opinion from a
reputable source that tied in with the post. :-) :-)

Sorry -- I rarely add an explicit smiley. Regardless of how my messages
might read, I rarely take much of it _terribly_ seriously.

I'll bare that in mind...

....did you see my implicit smiley!
For the question at hand, I'd postulate that an embedded SQL
implementation simply wouldn't do the job. Binding to MySQL or using
ODBC would undoubtedly work, but using MySQL, Oracle, MS SQL Server,
etc., puts us back in the situation where we basically just have SQL
talking to a server written in C.
Not necessarily, esp in the fields that Richard comes across day-in-day
out. I did have a link at work that was for a web page for a Relational
Database written in Ada that Lockhead(?) had developed.

Then again, your headers indicate that you post with Mozilla
Thunderbird running on Windows, connecting through BT Internet. What
percentage of the millions of lines of code used to write and transmit
your message do you suppose was written in Ada, and what percentage in
C and C++? :-)
I have no idea - quite possibly 0% but there are plenty of Ada apps
around - just not mass public market ones (that I know of). On the other
had there is a chance the packets that delivered this email went through
some Ada...

http://www.linuxjournal.com/article/3675

Ada advocate: "The world WOULD be better if you used Ada."
C++ advocate: "The world IS better because of the cool code I wrote."

What on earth would the C advocate say!! ;-)

Cheers

-- Martin

[Martin Dowie]

Jerry Coffin wrote:

Martin Dowie wrote:

Hey! I did add a smiley! I just thought it was an opinion from a
reputable source that tied in with the post. :-) :-)

Sorry -- I rarely add an explicit smiley. Regardless of how my messages
might read, I rarely take much of it _terribly_ seriously.

I'll bare that in mind...

....did you see my implicit smiley!
For the question at hand, I'd postulate that an embedded SQL
implementation simply wouldn't do the job. Binding to MySQL or using
ODBC would undoubtedly work, but using MySQL, Oracle, MS SQL Server,
etc., puts us back in the situation where we basically just have SQL
talking to a server written in C.
Not necessarily, esp in the fields that Richard comes across day-in-day
out. I did have a link at work that was for a web page for a Relational
Database written in Ada that Lockheed(?) had developed.

Then again, your headers indicate that you post with Mozilla
Thunderbird running on Windows, connecting through BT Internet. What
percentage of the millions of lines of code used to write and transmit
your message do you suppose was written in Ada, and what percentage in
C and C++? :-)
I have no idea - quite possibly 0% but there are plenty of Ada apps
around - just not mass public market ones (that I know of). On the other
had there is a chance the packets that delivered this email went through
some Ada...

http://www.linuxjournal.com/article/3675

Ada advocate: "The world WOULD be better if you used Ada."
C++ advocate: "The world IS better because of the cool code I wrote."

What on earth would the C advocate say!! ;-)

Cheers

-- Martin

[Dmitry A. Kazakov]

On Wed, 9 Mar 2005 18:04:45 +0000 (UTC), Martin Dowie wrote:

Jerry Coffin wrote:

Ada advocate: "The world WOULD be better if you used Ada."
C++ advocate: "The world IS better because of the cool code I wrote."

What on earth would the C advocate say!! ;-)

C advocate: "The world WILL be better with the next cool patch for the cool
code I'm keep on writing."

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

[xpyttl]

"Martin Dowie" <ma**********@b topenworld.com> wrote in message
news:d0******** **@titan.btinte rnet.com...

What on earth would the C advocate say!! ;-)

Leave me alone, I've got work to do!

...