What does the following code do?

Question

I was wondering what the following code does:

for (auto x:m) std::cout << x << " ";

I already know that auto is a way to leave it to the compiler to decide the type of the variable but I don't know what :m does.

m is probably a container: so for each element (x) in your container (m): print x — Alexis, Jul 22 '13 at 09:40
C++11 - the new ISO C++ standard [Unordered containers](http://www.stroustrup.com/C++11FAQ.html) — Grijesh Chauhan, Jul 22 '13 at 09:40
possible duplicate of [range-based for in c++11](http://stackoverflow.com/questions/9005835/range-based-for-in-c11) — awesoon, Jul 22 '13 at 09:41
m is surely a container. See second answer to [this question](http://stackoverflow.com/questions/12702561/c-iterate-through-vector-using-for-loop). — m0skit0, Jul 22 '13 at 09:43

score 0 · Accepted Answer · answered Jul 22 '13 at 09:41

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It is a C++11 range-based for loop syntax described here: http://www.cprogramming.com/c++11/c++11-ranged-for-loop.html

Here m should be a container, like std::vector. The code will iterate the container and put every element (accessed as x inside the loop) into the std::cout stream. Elements will be separated by space.

answered Jul 22 '13 at 09:41

Sergey K.

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does it work on c++10 as well? – fer y Jul 22 '13 at 11:45
You mean C++03? No, it does not. – Sergey K. Jul 22 '13 at 11:49

Pixelchemist · Answer 2 · 2013-07-22T10:22:30.863

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m is any type that follows the ranged concept (i.e. Container concept).

The loop iterates over all elements of m where x represents the currently iterated value.

edited Jul 22 '13 at 10:22

answered Jul 22 '13 at 09:41

Pixelchemist

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`m` can also be an array or a user defined type. It doesn't have to fully satisfy the container concept. – juanchopanza Jul 22 '13 at 10:12
@juanchopanza I didn't say `m` is a container. – Pixelchemist Jul 22 '13 at 10:22

What does the following code do?

2 Answers2