auto_ptr实现代码 (摘自<> Page 293)

template <class T>
class auto_ptr
{
public:
    explicit auto_ptr(T*p = 0) : pointee(p){}
    
    template<class U> auto_ptr(auto_ptr<U>& r);

    ~auto_ptr(){delete pointee;}

    template<class U> auto_ptr<T>& operator=(auto_ptr<U>& r);

    T& operator*() const {return *pointee;}
    T* operator->() const {return pointee;}
    T* get() const {return pointee;}
    T* release(){
        T* old = pointee;
        pointee = 0;
        return old;
    }

    void reset(T*p = 0){
        if(pointee != p) {
            delete pointee;
            pointee = p;
        }
    }

private:
    T* pointee;
    template<class U> friend class auto_ptr<U>;
};

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

template<class T>
    template<class U>
    inline auto_ptr<T>& operator=(auto_ptr<U>& r){
        if(this != &r) reset(r.release());
        return *this;
    }

另外 SGI C++中的auto_ptr
/*
 * Copyright (c) 1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation. Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose. It is provided "as is" without express or implied warranty.
 *
 */

#ifndef __SGI_STL_MEMORY
#define __SGI_STL_MEMORY

#include <stl_algobase.h>
#include <stl_alloc.h>
#include <stl_construct.h>
#include <stl_tempbuf.h>
#include <stl_uninitialized.h>
#include <stl_raw_storage_iter.h>


#if defined(__STL_MEMBER_TEMPLATES)

__STL_BEGIN_NAMESPACE

template <class _Tp> class auto_ptr {
private:
  _Tp* _M_ptr;

public:
  typedef _Tp element_type;
  explicit auto_ptr(_Tp* __p = 0) __STL_NOTHROW : _M_ptr(__p) {}
  auto_ptr(auto_ptr& __a) __STL_NOTHROW : _M_ptr(__a.release()) {}
  template <class _Tp1> auto_ptr(auto_ptr<_Tp1>& __a) __STL_NOTHROW
    : _M_ptr(__a.release()) {}
  auto_ptr& operator=(auto_ptr& __a) __STL_NOTHROW {
    if (&__a != this) {
      delete _M_ptr;
      _M_ptr = __a.release();
    }
    return *this;
  }
  template <class _Tp1>
  auto_ptr& operator=(auto_ptr<_Tp1>& __a) __STL_NOTHROW {
    if (__a.get() != this->get()) {
      delete _M_ptr;
      _M_ptr = __a.release();
    }
    return *this;
  }
  ~auto_ptr() __STL_NOTHROW { delete _M_ptr; }

  _Tp& operator*() const __STL_NOTHROW {
    return *_M_ptr;
  }
  _Tp* operator->() const __STL_NOTHROW {
    return _M_ptr;
  }
  _Tp* get() const __STL_NOTHROW {
    return _M_ptr;
  }
  _Tp* release() __STL_NOTHROW {
    _Tp* __tmp = _M_ptr;
    _M_ptr = 0;
    return __tmp;
  }
  void reset(_Tp* __p = 0) __STL_NOTHROW {
    delete _M_ptr;
    _M_ptr = __p;
  }

  // According to the C++ standard, these conversions are required. Most

  // present-day compilers, however, do not enforce that requirement---and,

  // in fact, most present-day compilers do not support the language

  // features that these conversions rely on.

  
#ifdef __SGI_STL_USE_AUTO_PTR_CONVERSIONS

private:
  template<class _Tp1> struct auto_ptr_ref {
    _Tp1* _M_ptr;
    auto_ptr_ref(_Tp1* __p) : _M_ptr(__p) {}
  };

public:
  auto_ptr(auto_ptr_ref<_Tp> __ref) __STL_NOTHROW
    : _M_ptr(__ref._M_ptr) {}
  template <class _Tp1> operator auto_ptr_ref<_Tp1>() __STL_NOTHROW
    { return auto_ptr_ref<_Tp>(this->release()); }
  template <class _Tp1> operator auto_ptr<_Tp1>() __STL_NOTHROW
    { return auto_ptr<_Tp1>(this->release()); }

#endif /* __SGI_STL_USE_AUTO_PTR_CONVERSIONS */
};

__STL_END_NAMESPACE
#endif /* member templates */

#endif /* __SGI_STL_MEMORY */


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