C++ Class member access problem with templates

Question

Ive got a problem that if I have a template class, which in turn has a template method that takes a parameter of another instance of the class (with different template argum

Answer 1

They are different types: templates construct new types from a template.

You have to make other instantiations of your class friends:

template class MyClass
{
    T v;
public:
    MyClass(T v):v(v){}

    templatevoid foo(MyClass obj)
    {
        std::cout << v     << " ";
        std::cout << obj.v << " ";
        std::cout << v + obj.v << std::endl;
    }

    // Any other type of MyClass is a friend.
    template 
    friend class MyClass;

    // You can also specialize the above:
    friend class MyClass; // only if this is a MyClass will the
                               // other class let us access its privates
                               // (that is, when you try to access v in another
                               // object, only if you are a MyClass will
                               // this friend apply)
};