AN `auto_ptr` IMPLEMENTATION

(Please note that an update on auto_ptr is now available.)

Items 9, 10, 26, 31 and 32 attest to the remarkable utility of the auto_ptr template. Unfortunately, few compilers currently provide an implementation. Items 9 and 28 sketch how you might write one yourself, but it's nice to have more than a sketch when embarking on real-world projects.

Below are two presentations of a complete implementation for auto_ptr. The first presentation documents the class interface and implements all the member functions outside the class definition. The second implements each member function within the class definition. Stylistically, the second presentation is inferior to the first, because it fails to separate the class interface from its implementation. However, auto_ptr is a simple class, and the second presentation brings that out much more clearly than does the first.

Here is auto_ptr with its interface documented:

template<class T>
class auto_ptr {
public:
 explicit auto_ptr(T *p = 0);    // see Item 5 for a 
     // description of ""explicit""

 template<class U>               // copy constructor member
 auto_ptr(auto_ptr<U>& rhs);     // template (see Item 28):
     // initialize a new auto_ptr
     // with any compatible 
     // auto_ptr


 ~auto_ptr();


 template<class U>
 auto_ptr<T>&  operator=(auto_ptr<U>& rhs);
     // assignment operator 
     // member template (see
     // Item 28): assign from any
     // compatible auto_ptr 


 T& operator*() const;           // see Item 28   
 T* operator->() const;          // see Item 28


 T* get() const;                 // return value of current
     // dumb pointer


 T* release();                   // relinquish ownership of
     // current dumb pointer and
     // return its value


 void reset(T *p = 0);           // delete owned pointer;
     // assume ownership of p
private:
 T *pointee;
};


template<class T>
inline auto_ptr<T>::auto_ptr(T *p)
: pointee(p)
{}


template<class T>
 template<class U>
 inline auto_ptr<T>::auto_ptr(auto_ptr<U>& rhs)
 : pointee(rhs.release())
 {}


template<class T>
inline auto_ptr<T>::~auto_ptr()
{ delete pointee; }


template<class T>
 template<class U>
 inline auto_ptr<T>&  auto_ptr<T>::operator=(auto_ptr<U>& rh"

AN auto_ptr IMPLEMENTATION

AN `auto_ptr` IMPLEMENTATION