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What does double ampersand return type mean?

I came across a syntax like this:

int&& move(int&& x)
{
    return x;
}

which supposedly implements the function std::move

, but I don't quite understand what the return type (& &) means.

I've googled and couldn't answer, can someone please explain this to me?

EDIT:

Most of my confusion comes from the fact that the function return already has an r value, so I don't understand that && can change there .. not sure if I make sense or not.

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2 answers


From: http://www.stroustrup.com/C++11FAQ.html#rval

&&

indicates an "rvalue reference". An rvalue reference can bind to rvalues ​​(but not lvalues):



X a;
X f();
X& r1 = a;      // bind r1 to a (an lvalue)
X& r2 = f();    // error: f() is an rvalue; can't bind

X&& rr1 = f();  // fine: bind rr1 to temporary
X&& rr2 = a;    // error: bind a is an lvalue
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In this case, the move function uses what is called rvalue references

a relatively new C ++ function. This is explained well in this article .



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