Question

Sorry about the confusing title, did not know what to title it.
I have this function:

static void smooth5(IntVector*& v)
{
    IntVector* tmp = new IntVector();
    for(int i=0; i<v->size(); i+=2)
        tmp->push_back(v->at(i));
    delete v;
    v = tmp;
}

and in the main I do this:

IntVector* v = new IntVector();

v->push_back(0);
v->push_back(1);
v->push_back(2);
v->push_back(3);

smooth5(v);

//print the contents of v

When I print the contents of v, the output is 0 2.
But I did not understand what

IntVector*& v

really means when v is a pointer to an object on the heap. Can someone please explain?

Answer 1

IntVector*& declares a reference to a pointer. Using this as a function argument allows smooth5 to modify the caller’s copy of v.

It is similar to but more readable than passing a pointer to a pointer – IntVector**.

In your example, smooth5 deletes the caller’s IntVector and points it to its tmp variable instead.