Question

I use this C++ code for storing x to the variable val.

class Hello
{
  int val;
public:
  Hello(int x) : val(x) {}
};

However, when I saw this code, I cannot see how Super can store value t or o.

template<typename T>
class K : public std::auto_ptr<T>
{
    typedef std::auto_ptr<T> Super;
public:
    K() : Super() { }
    K(T* t) : Super(t) { }
    K(K<T>& o) : Super(o) { }
};

How does this code work?

Answer 1

Could’ve been written as

template<typename T>
class K : public std::auto_ptr<T>
{
public:
    K() : std::auto_ptr<T>() { }
    K(T* t) : std::auto_ptr<T>(t) { }
    K(K<T>& o) : std::auto_ptr<T>(o) { }
};

Which is just more verbose to initialize the base class. A typedef is cleaner most of the time if you have to deal with templated base classes.