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From: Ioannis Vranos <ivr@remove.this.grad.com>
Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: Fri, 11 Mar 2005 06:06:55 +0200
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Xref: g2news1.google.com comp.lang.ada:9087 comp.lang.c++:45052
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Date: 2005-03-11T06:06:55+02:00
List-Id: <comp.lang.ada>

fmdf@tiscali.it wrote:

> -- over.adb
> 
> with Ada.Text_IO;
> use Ada.Text_IO;
> 
> procedure Over is
> -- Pragma Suppress( Range_Check );
> type Var_T is range 0 .. 100;
> package Var_IO is new Ada.Text_IO.Integer_IO( Var_T );
> Var : Var_T := 0;
> 
> begin
>     for Index in 0 .. 100 loop -- range check failing is expected
>         Var := Var + 1;
>     end loop;
>     Var_IO.Put ( Var );
>     New_Line;
> exception
>     when Constraint_Error =>
>         Put_Line ( "Constrained Error" );
>     when others =>
>         Put_Line ( "Unknown Error" );
> end Over;
> 
> 
> Ada example is less than half longer than C++, it is most expressive,



Your C++ code in a bit better shape (and more spaces, I like to add 
spaces to make the code more readable):


#include <iostream>
#include <stdexcept>


class Var_T
{
  public:
      Var_T( const int& i = int() )
      {
          if ( i >= 0 && i <= 100 )
              Var = i;

          else throw std::out_of_range("raised \"Out of Range\"");
      }

      Var_T& operator++( )
      {
          assign( ++Var );

          return *this;
      }

      bool assign( const int& i )
      {
          if ( i >= 0 && i <= 100 )
              Var = i;

          else throw std::out_of_range("raised \"Out of Range\"");

          return true;
      }

      int rvalue() const { return Var; }


  private:
      int Var;
  };



inline std::ostream& operator<<( std::ostream &out, const Var_T &obj )
{
     out << obj.rvalue();

     return out;
}


int main() try
{
     Var_T Var;

     for ( int i = 0; i <= 100; ++i ) // range check error expected
          ++Var;

     std::cout << Var << "\n";
}

catch(std::exception &ERR)
{
     std::cerr << ERR.what() << "\n";
}












> it catches all exceptions (not only out of range) and it suppresses all
> range checks when uncommenting "Pragma".
> 
> What dou you think of this kind of Ada unefficient and too many lines
> of code example?


At first personally I do not think Ada is inefficient, but I have the 
feeling that C++ is more powerful.

About the run-time checks one can easily implement a macro mechanism to 
disable checks too, with the definition of a constant like before the 
compilation like:


#define NOCHECKS


Second, templates can be used for compile-time constraints, but I do not 
know these stuff yet, so perhaps someone may provide this. And then one 
could provide such a checking mechanism via templates (not of course to 
mention once again template metaprogramming where an increment operation 
could become compile-time).



-- 
Ioannis Vranos

http://www23.brinkster.com/noicys