Question

Help on vector says of front()

Returns a reference to the first element in the vector container.
Unlike member vector::begin, which returns an iterator to this same element, this > function returns a direct reference.

Help on vector says of begin()

Returns an iterator referring to the first element in the vector container.
Notice that unlike member vector::front, which returns a reference to the first element, > this function returns a random access iterator.

And this code outputs:

char arr[] = { 'A', 'B', 'C' };
vector<char> vec(arr, arr+sizeof(arr));
cout << "address of vec.front() " << (void*)&vec.front() << endl;
cout << "address of vec.begin() " << (void*)&vec.begin() << endl;

address of vec.front() 00401F90
address of vec.begin() 0030F494

I don’t understand what ‘direct reference’ means? In the case of begin() isn’t a random access iterator just a pointer?

Can someone please point out the difference?

Answer 1

In the case of begin() isn’t a random access iterator just a pointer?

No, an iterator has some pointer semantics, but it’s actually a class.

And even if it was, that should answer the question. It’s like asking why the address of a pointer isn’t the same as the address of the object it points to.

You’d get the same value if you dereference the iterator, which will give you the first element:

&(*vec.begin())

because

*vec.begin() == vec.front()