¿Es rvalue la referencia lvalue?

Is rvalue reference lvalue?

An rvalue reference behaves just like an lvalue reference except that it can bind to a temporary (an rvalue), whereas you can not bind a (non const) lvalue reference to an rvalue.

Put simply, an lvalue is an object reference and an rvalue is a value. The difference between lvalues and rvalues plays a role in the writing and understanding of expressions. An lvalue always has a defined region of storage, so you can take its address. An rvalue is an expression that is not an lvalue.

An lvalue refers to an object that persists beyond a single expression. An rvalue is a temporary value that does not persist beyond the expression that uses it.

A non- const lvalue reference will only bind to non- const lvalue s of the same type, or a class derived from the referenced type. A const lvalue reference on the other hand will also bind to rvalue s, though again the object bound to the reference must have the same type as the referenced type, or a class derived from the referenced type.

An lvalue reference to const type is a reference that can be initialized with rvalues and lvalues alike (rendering constant and non-constant types). Thus, by selecting from the choice of three reference kinds, you can choose which expressions to pick. This is very useful when you define function overloads that differ only by reference type:

In return statement, ans is an lvalue, but since it is an automatic object and it is obvious it is not going to be used after the return, for the purpose of optimization it is treated ‘as if it was a temporary’, or more precisely: as an rvalue. It can be bound to an rvalue reference.

Every name (of an object or of a reference) is an lvalue. node.is_empty () most probably returns a temporary of type bool. All expressions that return temporaries are rvalues. Expression node.left () most probably returns an lvalue reference to another node. Any expression that returns an lvalue reference is an lvalue.