const vector implies const elements?

Question

Does const vector mean that its elements are constas well?

In the code below,

v[0].set (1234); in void g (

Answer 1

The first version

v[0].set (1234); 

does not compile because it tries to change the vector's first element returned to it by reference. The compiler thinks it's a change because set(int) is not marked const.

The second version, on the other hand, only reads from the vector

(*v[0]).set(1234);

and calls set on the result of the dereference of a constant reference to a pointer that it gets back.

When you call v[0] on a const vector, you get back a const reference to A. When element type is a pointer, calling set on it is OK. You could change the second example to

v[0]->set(1234);

and get the same result as before. This is because you get a reference to a pointer that is constant, but the item pointed to by that pointer is not constant.