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code not working to the end

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  code not working to the end net user <netuser501@gmail.com> - 2011-06-29 16:03 -0700
    Re: code not working to the end Ian Collins <ian-news@hotmail.com> - 2011-06-30 11:16 +1200

#7256 — code not working to the end

hi,

Anything to improve for someone learning in the code below...

/* 1- Compute a n*2 value for 64 iterations */
/* 2- Maximum integer variable iterations for n*2 */
/* 3- Computer the number of iteration needed to reach the value in
question 1 */
int main()
try
{
        long double var_long_double = 1 ;
        long double var_long_double2 = 1 ;
        unsigned int var_integer = 1 ;
        unsigned int var_integer2 = 1 ;
        int i = 1 ;
        int nb = 1 ;
        // QUESTION 1
        while (i < 64)
        {
                var_long_double *= 2 ;
                i++ ;
        }
        cout << "\n1- Value for 64 iteration : " << var_long_double ;
        //QUESTION 2
        while (var_integer > 0)
        {
                cout << "\n" << nb << "\tvar_int : " << var_integer ;
                var_integer *= 2 ;
                nb++ ;
                if (var_integer > 0)
                        var_integer2 = var_integer ;
        }
        cout << "\n\n2- Number as integer variable for " << nb << "
incrementations : " << var_integer2 ;
        // QUESTION 3
        i = 1 ;
        while (var_long_double >= 0)
        {
                var_long_double /= 2 ;
                if (var_long_double >= 0)
                        var_long_double2 = var_long_double ;
                else
                        break ;
                i++ ;
        }
        cout << "\n3-Number of maximum iteration for i as int " << i
<<
"\n" ;
        cout << "\n\n" ;
        system("pause") ;
        return 0 ;
}

catch (runtime_error e)
{
        cout << e.what() << '\n' ;
        keep_window_open("~") ;
}

catch(...)
{
        cout << "Exiting\n" ;
        keep_window_open("~") ;
}

I am running this on a 64 bits computer using Windev.
Above the fact that I don't see the code above very reliable, I don't
understand why I get to -2 147 483 648 with an unsigned int variable.
From my understanding it should be 4 294 967 295...

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#7257

On 06/30/11 11:03 AM, net user wrote:
> hi,
>
> Anything to improve for someone learning in the code below...

It would have been helpful to have posted the real code!

> /* 1- Compute a n*2 value for 64 iterations */
> /* 2- Maximum integer variable iterations for n*2 */
> /* 3- Computer the number of iteration needed to reach the value in
> question 1 */
> int main()
> try
> {
>          long double var_long_double = 1 ;
>          long double var_long_double2 = 1 ;
>          unsigned int var_integer = 1 ;
>          unsigned int var_integer2 = 1 ;
>          int i = 1 ;
>          int nb = 1 ;

Declaring these where they are used is better style.

>          // QUESTION 1
>          while (i<  64)

A for loop would have been clearer.

>          {
>                  var_long_double *= 2 ;
>                  i++ ;
>          }
>          cout<<  "\n1- Value for 64 iteration : "<<  var_long_double ;
>          //QUESTION 2
>          while (var_integer>  0)

A for loop would have been clearer.

>          {
>                  cout<<  "\n"<<  nb<<  "\tvar_int : "<<  var_integer ;

This outputs 2^(n-1)).

>                  var_integer *= 2 ;
>                  nb++ ;
>                  if (var_integer>  0)
>                          var_integer2 = var_integer ;
>          }
>          cout<<  "\n\n2- Number as integer variable for "<<  nb<<  "
> incrementations : "<<  var_integer2 ;
>          // QUESTION 3
>          i = 1 ;
>          while (var_long_double>= 0)

This will run for (almost) ever.
>          {
>                  var_long_double /= 2 ;

var_long_double will never become zero.

>                  if (var_long_double>= 0)
>                          var_long_double2 = var_long_double ;
>                  else
>                          break ;
>                  i++ ;
>          }
>          cout<<  "\n3-Number of maximum iteration for i as int "<<  i
> <<
> "\n" ;
>          cout<<  "\n\n" ;
>          system("pause") ;
>          return 0 ;
> }
>
> catch (runtime_error e)

Catching exceptions by value is not a good idea, catch by const reference.

> {
>          cout<<  e.what()<<  '\n' ;
>          keep_window_open("~") ;
> }
>
> catch(...)
> {
>          cout<<  "Exiting\n" ;
>          keep_window_open("~") ;
> }
>
> I am running this on a 64 bits computer using Windev.
> Above the fact that I don't see the code above very reliable, I don't
> understand why I get to -2 147 483 648 with an unsigned int variable.
>  From my understanding it should be 4 294 967 295...

Where do you get that value?

-- 
Ian Collins

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