The point is that the local variable referencing the map is a different entity than the map itself. Foo gets a copy of that local variable, and the copy referen

The point is that the local variable referencing the map is a different entity than the map itself. Foo gets a copy of that local variable, and the copy references the same map object. And the fact that C++ references can be used for assignment is essentially their whole point, not "a quirk".