Get out of multiple loops?

Question

Possible Duplicate:
Breaking out of a nested loop

I have this code

foreach (___)
{
    foreach (___)
    {
        foreach (___)
        {
            if (condition)
            {
                //break out of all loops
            }
        }
    }
}

But break only "breaks" the most inner loop (sorry for my english) and I want to leave them all...

I was thinking about :

1. GOTO, but I've always been told to not use it
2. A sort of boolean-flag

Is there any more elegant way ? like provided by C# ?

Thanks in advance for any help !

Answer 1

A very elegant solution to this is to move the entire nest of loops to a separate method and return; when you want to break out of all loops.

Answer 2

A goto is perfectly fine here:

foreach (___)
{
    foreach (___)
    {
        if (condition)
        {
            goto done;
        }
    }
}
done: ;

Answer 3

The best way is probably to refactor to smaller methods with return statements. But if you need a lot of variables in scope you can always use a delegate.

   Action work = delegate
        {
            foreach (___)
            {
                 foreach (___)
                 {
                       foreach (___)
                       {
                            if (condition)
                            {
                                 return;
                            }
                       }
                  }
             }

        };

  work();

Answer 4

Years ago, when I was in school, we had informatics with a pretty out of the books stupid teacher. One rule was "no goto". I had an algorithm with multiple loops that grew to many times the size without goto.

There are good reasons, and breaking out of multiple loops is one.

Answer 5

Maybe this is the only valid reason to use goto.

Answer 6

bool bLoopBreak = false;

foreach (___)
{
    foreach (___)
    {
        foreach (___)
        {
            if (condition)
            {
                bLoopBreak = true;
                break;
                //break out of all loops
            }
        }
        if (bLoopBreak) break;
    }
    if (bLoopBreak) break;
}

Answer 7

Don't be afraid to use goto in a case like this. break and continue are just syntactic sugar for goto, and is sparingly and commented correctly it can make code clearer than lots of nested checks to see if you should stop looping.

Answer 8

PHP lets you do this:

foreach (___)
{
    foreach (___)
    {
        foreach (___)
        {
            break 3; // get out of all 3 loops
        }
    }
}

I don't know a whole lot about C# but it may have a similar feature.

Answer 9

Just to throw an alternative in there: You could also throw an exception inside the loop. In C#/Java/Python this is reasonably cheap to do. (In C++, not so much.)

Note that Python has a StopIteration exception for a similar case, so it's not unheard of, although it might be a bit unorthodox in C#-land. ;)

Sometimes, you get the exception for free, and thus it can be used, but you'd better document it if you are taking that approach.

try {
    foreach (___) {
        foreach (___) {
            if(your condition true)  {
                throw new IterationDone(); // or use a singleton to avoid allocating
            }
        }
    }
    // not found
catch (IterationDone e) {
    // yay    
}

I've made the answer a community wiki, so that it can be seen and discussed. (I don't advocate it as the first and best solution, it's just A solution, and thus deserves to be here...)