I don\'t understand very well the std::move
function
template
typename remove_reference::type&&
move(T&& a)
Because rvalue reference to lvalue reference would decay to lvalue reference, and returing lvalue reference would have different semantics from those you would expect from move
.
Edit: Huh, why the downvote? Check out this code:
template < typename T > T&& func(T&& x) { return x; }
int main()
{
int x;
int &y = func(x);
}
Further reading: http://www.justsoftwaresolutions.co.uk/cplusplus/rvalue_references_and_perfect_forwarding.html
Think about what happens if T
is an lvalue reference, for example MyClass &
. In that case, T &&
would become MyClass & &&
, and due to reference collapsing rules, this would be transformed into MyClass &
again. To achieve the right result, typename remove_reference<MyClass&>::type&&
first removes any reference decorations from the type, so MyClass &
is mapped to MyClass
, and then the rvalue reference is applied to it, yielding MyClass &&
.