C ++：编译器看不到重载运算符

Question

I have stuck on my try to implement linked list iterator class. Compiler is complaining when I use overloaded "!=" operator here:

for (itr = (test0.begin()); itr != (test0.end()); ++itr)
{
    cout << *itr;
}

Here is the error:

error: no match for ‘operator!=’ in ‘itr != SinglyLinkedList<Object>::end() [with Object = int]()’

I don't understand why it can't find the match, because both test0.end() and itr are iterators.

Here is the code of overloaded operator:

bool operator!= (iterator &rhs)
{
    return (this->current != rhs.current);
}

Thanks in advance.

Answer 1

I suspect that this is because of const-correctness:

bool operator!= (iterator const &rhs) const
{
    return (this->current != rhs.current);
}