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Re: loop problem

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On 20.10.2011 17:18, fattaneh wrote:
> hi all ,
> i have written this code , and it should be in while if num is not
> zero
> so it shouldn't print error , but num becomes zero and it wont come
> out of while
> i have written this code in visual studio c++
> 
> #include "stdafx.h"
Doesn't look much like standard...

> #include <stdio.h>
> using namespace System;
> 
> int main(array<System::String ^> ^args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
Definitely _not_ standard. The standard is one of:

int main()
int main(int argc, char* argv[])

or equivalent. (There are two other forms for argv that mean exactly the
same.)

> {
>     int num =5 ;
>     while (num !=0)
>     {
>         num-- ;
>         if(num ==0)
>         {
>             printf("error") ;   // it should never write this but it
> will write .
>         }
>     }
>     return 0;
> }
> 
> 
> could you help me to filnd out what the problem is ?
> 
> thanks of all . . .

Short: Move the decrement instruction to the other side of the loop!

Long: The condition of a while-loop is checked only on entry and on
repeat, not after every instruction inside the loop. Thus, if num is 1
at the beginning of the loop, it is decremented to 0, then the if fires.

HTH,
Markus

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loop problem fattaneh <fattaneh.69@gmail.com> - 2011-10-20 08:18 -0700
  Re: loop problem Leigh Johnston <leigh@i42.co.uk> - 2011-10-20 16:34 +0100
    Re: loop problem fattaneh <fattaneh.69@gmail.com> - 2011-10-20 08:39 -0700
  Re: loop problem Markus Wichmann <nullplan@gmx.net> - 2011-10-20 18:20 +0200

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