Should std::array have move constructor?

c++, c++11, move-semantics

Solution

`std::array` has a compiler generated move constructor, which allows all the elements of one instance to be moved into another. This is handy if the elements are efficiently moveable or if they are only movable:

#include <array>
#include <iostream>

struct Foo
{
  Foo()=default;
  Foo(Foo&&)
  {
    std::cout << "Foo(Foo&&)\n";
  }
  Foo& operator=(Foo&&)
  {
    std::cout << "operator=(Foo&&)\n";
    return *this;
  }
};

int main()
{
  std::array<Foo, 10> a;
  std::array<Foo, 10> b = std::move(a);
}

So I would say `std::array` should have a move copy constructor, specially since it comes for free. Not to have one would require for it to be actively disabled, and I cannot see any benefit in that.

Problem

Moving can't be implemented efficiently (O(1)) on std::array, so why does it have move constructor ?

Original source