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My first C++ problem :(

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Join Date: Dec 2007

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OmniX

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My first C++ problem :(

Jul 17th, 2008

I have just started using C++ for the first time and I love it!!!

First problem I have encoutered proably a simple one but

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for (int a=0; a<10; a++) {
 for (int b=0; b<10; b++) {
  for (int c=0; c<10; c++) {
   if (b == 5) {
    break; beak; break; break;
   }
  }
 }
}
for (int a=0; a<10; a++) {
 for (int b=0; b<10; b++) {
  for (int c=0; c<10; c++) {
   if (b == 5) {
    break; beak; break; break;
   }
  }
 }
}

Now the idea is if b is equal to 5 then it breaks out of the if loop, the for loop c, the for loop b, the for loop a.

Am I doing it right?

If not can someoone please correct me?

Thankyou, Regards X

PS: While on the topic what happens if I only wanted to break out of the if loop or if loop + for loop a or if loop + for loop a + for loop b. Thanks Again.

Last edited by OmniX; Jul 17th, 2008 at 11:15 am.

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Narue

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Re: My first C++ problem :(

Jul 17th, 2008

>Now the idea is if b is equal to 5 then it breaks out of
>the if loop, the for loop c, the for loop b, the for loop a.
Nope. You can write as many breaks as you want, but only the first one will have any effect, and it'll break you out of the inner-most loop (the c loop).

>If not can someoone please correct me?
You have options here, but the best option is not to get into such a situation to begin with. If you need to break out of a nested loop, it's usually best (if you can manage it) to refactor the nested loops into a function and then use the return value to break:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for ( int a = 0; a < 10; a++ ) {
  if ( !some_function() )
    break;
}
 
...
 
bool some_function()
{
  for ( int b = 0; b < 10; b++ ) {
    for ( int c = 0; c < 10; c++ ) {
      if ( b == 5 )
        return false;
    }
  }
 
  return true;
}
for ( int a = 0; a < 10; a++ ) {
  if ( !some_function() )
    break;
}

...

bool some_function()
{
  for ( int b = 0; b < 10; b++ ) {
    for ( int c = 0; c < 10; c++ ) {
      if ( b == 5 )
        return false;
    }
  }

  return true;
}

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Join Date: Dec 2007

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OmniX

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Re: My first C++ problem :(

Jul 17th, 2008

That would be a good idea use of functions but I am not able to in this problem

If i set it to a bool function then return false it will break me out completly, correct?

I require to just break out for loops a, b, c when required what would I do in that case?

Eg.
Break out of for loop a:
Break out of for loop a, b:
Break out of for loop a, b, c:

Thanks, Regards X

"You never stop learning." - OmniX

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Join Date: Mar 2005

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invisal

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Re: My first C++ problem :(

Jul 17th, 2008

Then use goto

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for (int a=0; a<10; a++) {
  for (int b=0; b<10; b++) {
   for (int c=0; c<10; c++) {
     if (b == 5)
          goto endloop;
   }
 }
}
endloop:
for (int a=0; a<10; a++) {
  for (int b=0; b<10; b++) {
   for (int c=0; c<10; c++) {
     if (b == 5)
          goto endloop;
   }
 }
}
endloop:

Last edited by invisal; Jul 17th, 2008 at 1:07 pm.

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Join Date: Dec 2007

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OmniX

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Re: My first C++ problem :(

Jul 17th, 2008

Thanks!!!

Very nice, so I can have multiple goto statements also?

a;
b;
c;

goto a;

goto b;

goto c;

Something like that?

"You never stop learning." - OmniX

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Join Date: Mar 2005

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invisal

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Re: My first C++ problem :(

Jul 17th, 2008

Of course you can have multiple of them. However, try to avoid using it as much as possible since most of the time goto can be replaced with a loop. For some case such as break multiple-level of loops, goto is inevitable.

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Behind every smile is a tear.
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Narue

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Re: My first C++ problem :(

Jul 17th, 2008

>For some case such as break multiple-level of loops, goto is inevitable.
I wouldn't say inevitable, but goto can be the cleanest solution if you have deep nesting and can't refactor it. The alternative is to use flags and check them at each level, which is a "pure" structured solution, but it's almost always ugly as sin.

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