how to exit from two nested for loop in matlab

问题

I have a while loop in which I have two for loops. I have a condition in the innermost for loop. Whenever that condition is satisfied I want to exit from both the two for loops and continue within the while loop:

while (1)
    for x=1:20
        for y=1:30
            if(condition)

            end
        end
    end
end

Does Matlab have something like a labeled statement in Java, or is there another way to do this?

回答1:

Here is a very simple answer leveraging the fact that testing numerous simple conditions is nearly free:

while (1)
    go = true;
    for x=1:20
        for y=1:30
            if go && condition
               go = false;

            end
        end
    end
end

This approach is very simple, easily generalized to any number of loops and avoids the abuse of error handling.

回答2:

One ever so slightly more elegant way than Luis Mendo's. ;-)

while (1)
    for x=1:20
        for y=1:30
            quit = (condition);
            if quit
                break;
            end
        end
        if quit
            break;
        end
    end
end

回答3:

Only slightly more elegant than A.Donda's answer (avoids testing the condition twice):

while 1
    for x=1:20
        for y=1:30
            quit = 0;
            if (condition)
                quit = 1;
                break;
            end
        end
        if quit
            break;
        end
    end
end

回答4:

A bit of abuse, a bit of overkill, but here it is: yet another way

while (1)
    try
        for x = 1 : 20
            for y = 1 : 30
                assert(~(condition), 'break')
            end
        end
    catch err
        if ~strcmp(err.message, 'break'), rethrow(err), end
    end
end

The nice thing about this approach is that it works with an arbitrary number of nested loops, and only evaluates condition once without having to store the result in a variable.

Inspired by tmpearce's comment.

回答5:

I'm aware of only one quite inelegant way to do this: check the condition twice.

while (1)
    for x=1:20
        for y=1:30
            if (condition)
                break;
            end
        end
        if (condition)
            break;
        end
    end
end

回答6:

Another possibility, which avoids using two break statements: if you don't do anything in the outer for loop except calling the inner for loop, you can merge them:

[yy xx] = ndgrid(1:20,1:30);
while 1
    for n = 1:numel(x)
        x = xx(n);
        y = yy(n);
        if (condition)
            break      
        end
    end
end

回答7:

immediate exit for both for loops and continue with the remain of while loop.

while (1)
    go=1 %

    for x=1:20
        if go==0;break; %

        for y=1:30
            if(condition)
                go=0;break; %
            end
        end
    end
end

来源：https://stackoverflow.com/questions/20302746/how-to-exit-from-two-nested-for-loop-in-matlab