Move item to a list without copying

Question

Given

std::list<std::vector<float>> foo;
std::vector<float> bar;

How should I move bar to the end of foo without copying data?

Is this ok?

foo.emplace_back(std::move(bar));

Answer 1

Is this ok?

foo.emplace_back(std::move(bar));

Yes, because:

1. std::move(bar) casts bar to an rvalue reference.

2. std::list::emplace_back takes any number of forwarding references and uses them to construct an element at the end.

3. std::vector::vector has an overload (6) that takes an rvalue reference, which moves the contents of the rhs vector without performing any copy.

Answer 2

Yes, the code in the Q is certainly OK. Even using push_back would be OK:

foo.push_back(std::move(bar));

Answer 3

How should I move bar to the end of foo without copying data?

Using the move constructor of std::vector:

foo.push_back(std::move(bar));

Is this ok?

foo.emplace_back(std::move(bar));

That is OK as well.