Question

Is this the right way to use C++11 rvalue-references and move semantics to implement a convenience wrapper for std::reverse()?

template <class BIDirContainer> inline BIDirContainer&& reverse(BIDirContainer a) {
    std::reverse(begin(a), end(a));
    return std::move(a); 
}

The code works in my test case but I am unsure its about performance: should I use && here or is it unneccesary?

Answer 1

I would say the right way to do it is to return by value from your function:

template <class BIDirContainer> inline BIDirContainer reverse(BIDirContainer a) {
    std::reverse(begin(a), end(a));
    return a; 
}

and then give BIDirContainer a move constructor if it doesn’t have one. Then this kind of expression:

BIDirContainer x = ...;
BIDirContainer backwards{reverse(x)};

should move the contents of the temporary a in your reverse function into backwards.