Nested for loop syntax & break behavior

[quinnj]

I noticed this today

In  [8]: for a = 1:3, b = 4:6
    b == 5 && break
    println("a = $a")
    println("b = $b")
end

a = 1
b = 4
a = 2
b = 4
a = 3
b = 4

(i.e. the break only breaks the inner loop).
I'm not saying this is wrong, but it might be good to add a sentence or two about it in the docs as one might think that the nested loop syntax only creates a single loop to break from.

[JeffBezanson]

And then there's always #330.
I always thought of this form as just a syntactic convenience, but maybe we are "wasting syntax" by not having this kind of loop mean something different --- namely that you want conceptually a "single" loop but over an n-d space.

[StefanKarpinski]

I'm rather in favor of that. It makes it a little easier to express a different behavior and the bonus is that I think the difference is not only useful but entirely intuitive. Imagining writing that paragraph in the manual doesn't make me wince.