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]

Wes Groleau wrote:

That is the approach perl takes to multiple inheritance. At least
I think so--I haven't finished studying it. What does C++ or Eiffel
do when multiple inheritance creates two meanings for the same name?

What do you mean by two meanings?

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Ed Falis]

On 23 Mar 2005 18:16:42 -0800, Jerry Coffin <jc*****@taeus. com> wrote:

Sorry, but if you think a class is called a tagged record in Ada,
you don't understand the language.

I'll openly admit that my knowledge of Ada 95 is _extremely_ limited
(I'm afraid I quit using Ada before 1995). Perhaps I need to take
another look in this area.
OTOH, doing a bit more looking, if I've misunderstood the situation, at
least I have some company. For example:

This is just a matter of simile. A tagged type and derivatives of tagged
types provide dispatching and other typical OOP facilities. Where the
concept differs from the class concept is that visibility is orthogonal,
provided by packages and other more traditional Ada facilities, while the
class concept combines the two.

- Ed

[Wes Groleau]

Ioannis Vranos wrote:

Wes Groleau wrote:

That is the approach perl takes to multiple inheritance. At least
I think so--I haven't finished studying it. What does C++ or Eiffel
do when multiple inheritance creates two meanings for the same name?

What do you mean by two meanings?

Class Wagon has method Draw.
Class Picture has method Draw.

If you multiply inherit to make
Class Picture_Of_A_Wa gon, what does the method Draw do?

This was one of the arguments against having multiple
inheritance. But I think it's a silly argument. One
could just as logically argue that the "use" clause
should not exist because two packages might have Draw
subprograms. Or that overloading should not be allowed
because it's possible to write something ambiguous.

Ada's answer for the former is that if and only if the
situation _actually_ arises, neither of the choices is visible.

For the latter, the code just won't compile.

--
Wes Groleau

"There ain't nothin' in this world that's worth being a snot over."
-- Larry Wall

[Ed Falis]

On Wed, 23 Mar 2005 21:42:58 -0500, Wes Groleau
<gr**********@f reeshell.org> wrote:

That is the approach perl takes to multiple inheritance. At least
I think so--I haven't finished studying it. What does C++ or Eiffel
do when multiple inheritance creates two meanings for the same name?

Eiffel has very nice and elegant facilities for resolving ambiguities. A
lot of thought went into the situation of "diamond inheritance", where an
ultimate base class is inherited via two distinct ancestors, and how to
resolve it. Eiffel is in many ways Ada's beautiful niece. But Ada is a
lot more portable.

- Ed

[Ioannis Vranos]

Jim Rogers wrote:

My reading of the information at that url indicates that GMP allows
the specification of precision, but not the specification of a limited
range of valid values.

Since I have had enough with this signed value range of Ada, here is a
quick implementation of mine and some uses of it.

I am sure one can create a better one or a container directly that
supports ranges, if he devotes some time, so the question again arises,
since it is possible and nothing exists, probably it is not considered
useful to have such a feature in C++:
#include <vector>
#include <algorithm>
#include <cstdlib>

template <class T>
class range
{
std::vector<T> array;
T min, max;

public:
range(const T &mi, const T &ma):array(m a-mi+1), min(mi), max(ma)
{
using namespace std;

if(max-min<=0)
;//throw some exception

for(typename vector<T>::size _type i=0; i<array.size() ; ++i)
array[i]=min+i;
}

const T &operator[](const T &index)
{
// Add range checking max>=index>=min if desirable

return array[index-min+1];
}

operator T() { return array.size(); }

};
int main()
{
using namespace std;

range<int> r(-100, -20);

vector<int> vec(r);

vec[r[-65]]=3;
}


--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Ioannis Vranos]

Ioannis Vranos wrote:

Jim Rogers wrote:

My reading of the information at that url indicates that GMP allows
the specification of precision, but not the specification of a limited
range of valid values.

Since I have had enough with this signed value range of Ada, here is a
quick implementation of mine and some uses of it.

I am sure one can create a better one or a container directly that
supports ranges, if he devotes some time, so the question again arises,
since it is possible and nothing exists, probably it is not considered
useful to have such a feature in C++:
#include <vector>
#include <algorithm>
#include <cstdlib>

template <class T>
class range
{
std::vector<T> array;
T min, max;

public:
range(const T &mi, const T &ma):array(m a-mi+1), min(mi), max(ma)
{
using namespace std;

if(max-min<=0)
;//throw some exception

for(typename vector<T>::size _type i=0; i<array.size() ; ++i)
array[i]=min+i;
}

const T &operator[](const T &index)
{
// Add range checking max>=index>=min if desirable

fixed: return array[index-min]; }

operator T() { return array.size(); }

};
int main()
{
using namespace std;

range<int> r(-100, -20);

vector<int> vec(r);

vec[r[-65]]=3;
}

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Jerry Coffin]

Jim Rogers wrote:

[ ... ]

For instance the following macro can cause some serious problems when
mis-applied:

#define SWAP(A,B) ((temp) = (A);(A) = (B); (B) = (temp))

char s1[30];
int i;

SWAP(S1, i);

In many cases it is safer to define an in-line function than to
define a macro.

I don't see a particularly serious problem here -- the code simply
won't compile. At the moment you have some syntactical problems and
sloppiness that's overlooked by Ada comilers (because Ada is
case-insensitive).

Even ignoring those, however, it will fail because of a
type-difference. To give a concrete example, after (partially) fixing
your code above, Visual C++ says:

swap.cpp(7) : error C2440: '=' : cannot convert from 'int' to 'char
[30]'
There are no conversions to array types, although there are
conversions to references or pointers to arrays

Modulo trivial things like ':=' vs. '=', 'int' vs. 'Integer', etc., I
suspect that's on the same general order as you'd expect to see from an
Ada compiler given code that attempted to assign an Integer to an array
of characters.

I think most C++ programmers, however, would tend to agree that in this
case you'd generally be better off using std::swap.

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Ioannis Vranos]

Wes Groleau wrote:

Class Wagon has method Draw.
Class Picture has method Draw.

If you multiply inherit to make
Class Picture_Of_A_Wa gon, what does the method Draw do?

In C++ you will get an error message until you define a newer version of
Draw for Picture_Of_A_Wa gon class.

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Georg Bauhaus]

Ioannis Vranos wrote:

fixed: return array[index-min];

See? This is when proper language support comes in handy.
Georg

[Georg Bauhaus]

Ioannis Vranos wrote:

Jim Rogers wrote:

My reading of the information at that url indicates that GMP allows
the specification of precision, but not the specification of a limited
range of valid values.

Jim doesn't mention fpt ranges in the context of arrays.
Just a floating point type whose values range between 0.0 and 1.0.
And a description of the use of this type that has a range constraint.
No arrays or signs in sight.

Since I have had enough with this signed value range of Ada,

Forget about the sign, as you did in your code with min and max.
This is not a sign issue. This isn't limited to array bounds
checking. It has to do with types and with values that match at compile
time.
For a start, add a template parameter to class range from which
the compiler can infer the min and max values.