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?

[Ioannis Vranos]

Pascal Obry wrote:

Ioannis Vranos <iv*@remove.thi s.grad.com> writes:

arrays. The [0, +] style maps closely what is happening in the machine.

Certainly. But the Ada model can maps more closely to the domain problem.
And this is an important point. We are not writting software for the machine
but to solve problems. Most of the time you just don't care how such data will
be handled by the machine (i.e. how the compiler will generate the code).

C++ maps on both. However I guess Ada maps on both too since it is a
systems programming language. :-)
Now may you explain how the ability to use negative subranges for built
in array indices makes Ada better for any domain problem?

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Pascal Obry]

Ioannis Vranos <iv*@remove.thi s.grad.com> writes:

Now may you explain how the ability to use negative subranges for built in
array indices makes Ada better for any domain problem?

For a domain problem where you have to create an area centered on (0,0)
for example. What about a vector representing altitude, the sub-zero values
being under the water. Just some examples, I bet you'll be able to think about
lot more :)

Pascal.

--

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--| Pascal Obry Team-Ada Member
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[Vinzent 'Gadget' Hoefler]

Ioannis Vranos wrote:

Georg Bauhaus wrote:

I forgot to say here that the cost of map's operator[] is O(log(n))
which is fairly cheap for large amount of data.

compare O(log(n)) to O(1) where n is 1, 1000, 1_000_000.
Make this access a part of an inner loop.

If you do the maths, you will see that log(10^6) isn't that large.

Yeah, right. Binary searches are not much slower. Only about 10 or 20
times. Seem, you just rendered hashing algorithms obsolete.
Vinzent.

--
worst case: The wrong assumption there actually is one.

[Ioannis Vranos]

Pascal Obry wrote:

For a domain problem where you have to create an area centered on (0,0)
for example. What about a vector representing altitude, the sub-zero values
being under the water. Just some examples, I bet you'll be able to think about
lot more :)

I think an associative container like map fits better to this. What do
you do in Ada if you want to associate product names with prices, in the
style
productlist["something"]= 71.2;
or a name with a number (string with string) in an address book
application for example?
namelist["Obry Pascal"]="321-45563";
Also may you tell me if that famous compile-time boundary checking
applies (can be used) to user-defined containers too?

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Pascal Obry]

Ioannis Vranos <iv*@remove.thi s.grad.com> writes:

I think an associative container like map fits better to this. What do you do
in Ada if you want to associate product names with prices, in the style
productlist["something"]= 71.2;
or a name with a number (string with string) in an address book application
for example?
namelist["Obry Pascal"]="321-45563";
We use a map, using the Ada.Containers STL like library.
Also may you tell me if that famous compile-time boundary checking applies
(can be used) to user-defined containers too?

What do you mean by that ? You want to restric a map index ?

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

[Ioannis Vranos]

Pascal Obry wrote:

Also may you tell me if that famous compile-time boundary checking applies
(can be used) to user-defined containers too?

What do you mean by that ? You want to restric a map index ?

In the "STL like" library do you have something like valarray or vector?

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Georg Bauhaus]

Ioannis Vranos wrote:

Georg Bauhaus wrote:

I forgot to say here that the cost of map's operator[] is O(log(n))
which is fairly cheap for large amount of data.

compare O(log(n)) to O(1) where n is 1, 1000, 1_000_000.
Make this access a part of an inner loop.

If you do the maths, you will see that log(10^6) isn't that large.

Compare log(10^6) to 1.

I can't see how O(log(n)) isn't huge when compared to
O(1), in an inner loop for containers of size 10^6.
Georg

[Georg Bauhaus]

Ioannis Vranos wrote:

What do
you do in Ada if you want to associate product names with prices, in the
style

Once again you are trying to escape the problem...
We are not discussing the value of a map. We are not
debating it either.

A map *is* most valuable. A map is *not* a vector.
Sometimes you *need* a vector. A vector is *not* a convenient
replacement for a map in C++.

And of course there are maps for Ada, but this is OT.

[Ioannis Vranos]

Georg Bauhaus wrote:

Compare log(10^6) to 1.

I can't see how O(log(n)) isn't huge when compared to
O(1), in an inner loop for containers of size 10^6.

OK, but besides the fact that only explicit entries in map occupy space,
and the rest keys return 0, which means that the search and counting of
a value is faster than an array in case that no the entire range is
under use, there are also third-party hashed containers, including
hashed maps.

Also, as I said it is not difficult to define an array that takes
arbitrary signed ranges, but this does not make much sense in C++.
In other words, the direct equivalent of your array is probably
valarray/vector, ignoring the signed ranges.
BTW, the compile-time boundary checks you have been mentioning, sounds
like they are restricted to built-in arrays, which means is not of much use.
Also the lack of a "STL like" library in Ada until now probably sounds
like that Ada lacks much of the high-level abstraction that C++ provides.

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Ioannis Vranos]

Georg Bauhaus wrote:

Once again you are trying to escape the problem...
We are not discussing the value of a map. We are not
debating it either.

A map *is* most valuable. A map is *not* a vector.
Sometimes you *need* a vector. A vector is *not* a convenient
replacement for a map in C++.

And of course there are maps for Ada, but this is OT.

OK, one can use a vector then. And as I said in other messages, it is
not difficult to define an array that takes arbitrary signed ranges, but
this does not make much sense in C++.
In other words, the direct equivalent of your array is probably
valarray/vector, ignoring the signed ranges.
--
Ioannis Vranos

http://www23.brinkster.com/noicys