Silly compile error using lists / iterators (C++)

Question

The following does not compile, and I cannot for the life of me see why!

#include <list>
using namespace std;

list<char> myList;
list<int>::iterator it;

it = myList.begin();

The error:

error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::list<_Ty>::_Iterator<_Secure_validation>' (or there is no acceptable conversion)

Answer 1

This happens because list<char> and list<int> are two different classes. So their iterators are different types too.
If you look at std::list class code you will see something like:

typedef _Iterator<_SECURE_VALIDATION_DEFAULT> iterator;

or

typedef _Iterator<bla_bla_bla> iterator;

That means new type is defined by each distinct class list. In other words each list defines its own iterator type.

Change your code to this:

list<char>::iterator it;

Answer 2

Because the type of the iterator is different:

list<char> myList; // char
list<int>::iterator it; // int

Beware that the type of the list or any other container is not only the template type parameter, but all other template parameters as well. For example:

list<char, MyAllocator> mylist;
list<char, YourAllocator> yourlist;
// typeof mylist != type of yourlist      (!!!)