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<H2>auto_ptr </H2>
<HR><PRE>     Memory Management</PRE><HR>
<A NAME="Summary"><H3>Summary</H3></A>
<P>A simple, smart pointer class.</P>
<H3>Contents</H3>
<UL>
<A HREF="#Synopsis"><LI>Synopsis</LI></A>
<A HREF="#Description"><LI>Description</LI></A>
<A HREF="#Interface"><LI>Interface</LI></A>
<A HREF="#Constructors and Destructors"><LI>Constructors and Destructors</LI></A>
<A HREF="#Operators"><LI>Operators</LI></A>
<A HREF="#Member Functions"><LI>Member Functions</LI></A>
<A HREF="#Example"><LI>Example</LI></A>
</UL>
<A NAME="Synopsis"><H3>Synopsis</H3></A>
<PRE>#include &#60;memory></PRE>
<PRE>template &#60;class X> class auto_ptr;</PRE>
<A NAME="Description"><H3>Description</H3></A>
<P>The template class <B><I>auto_ptr</B></I> holds onto a pointer obtained via <SAMP>new</SAMP> and deletes that object when the <B><I>auto_ptr</B></I> object itself is destroyed (such as when leaving block scope).  <B><I>auto_ptr</B></I> can be used to make calls to operator <SAMP>new</SAMP> exception-safe.  The <B><I>auto_ptr</B></I> class provides semantics of strict ownership:  an object may be safely pointed to by only one <B><I>auto_ptr</B></I>, so copying an <B><I>auto_ptr</B></I> copies the pointer <I>and</I> transfers ownership to the destination. </P>
<A NAME="Interface"><H3>Interface</H3></A>
<PRE>template &#60;class X> class auto_ptr {</PRE>
<PRE>
   public:
     // constructor/copy/destroy
     explicit auto_ptr (X* = 0);
     auto_ptr (const auto_ptr&#60;X>&#38;);
     void operator= (const auto_ptr&#60;X>&#38;);
     ~auto_ptr ();
     // members
     X&#38; operator* () const;
     X* operator-> () const;
     X* get () const;
     X* release ();
     void reset (X* = 0);
 };</PRE>
<A NAME="Constructors and Destructors"><H3>Constructors and Destructors</H3></A>
<PRE>explicit 
<B>auto_ptr </B>(X* p = 0);</PRE>
<UL><P>Constructs an object of class <SAMP>auto_ptr&#60;X></SAMP>, initializing the held pointer to <SAMP>p</SAMP>.  Requires that <SAMP>p</SAMP> points to an object of class <SAMP>X</SAMP> or a class derived from <SAMP>X</SAMP> for which <SAMP>delete p</SAMP> is defined and accessible, or that <SAMP>p</SAMP> is a null pointer.</P>
</UL>
<PRE><B>auto_ptr </B>(const auto_ptr&#60;X>&#38; a);</PRE>
<UL><P>Copy constructor. Constructs an object of class <SAMP>auto_ptr&#60;X></SAMP>, and copies the argument <SAMP>a</SAMP> to <SAMP>*this</SAMP>.  <SAMP>*this</SAMP> becomes the new owner of the underlying pointer.</P>
</UL>
<PRE>~<B>auto_ptr</B> ();</PRE>
<UL><P>Deletes the underlying pointer.</P>
</UL>
<A NAME="Operators"><H3>Operators</H3></A>
<PRE>void 
<B>operator=</B> (const auto_ptr&#60;X>&#38; a);</PRE>
<UL><P>Assignment operator.  Copies the argument <SAMP>a</SAMP> to <SAMP>*this</SAMP>.  <SAMP>*this</SAMP> becomes the new owner of the underlying pointer.  If <SAMP>*this</SAMP> already owned a pointer, then that pointer is deleted first.</P>
</UL>
<PRE>X&#38; 
<B>operator*</B> () const;</PRE>
<UL><P> Returns a reference to the object to which the  underlying pointer points.</P>
</UL>
<PRE>X* 
<B>operator-> </B>() const;</PRE>
<UL><P>Returns the underlying pointer.</P>
</UL>
<A NAME="Member Functions"><H3>Member Functions</H3></A>
<PRE>X* 
<B>get</B> () const;</PRE>
<UL><P>Returns the underlying pointer.</P>
</UL>
<PRE>X*
<B>release</B>();</PRE>
<UL><P>Releases ownership of the underlying pointer.  Returns that pointer.</P>
</UL>
<PRE>void 
<B>reset</B> (X* p = 0);</PRE>
<UL><P>Requires that <SAMP>p</SAMP> points to an object of class <SAMP>X</SAMP> or a class derived from<SAMP> X</SAMP> for which <SAMP>delete p </SAMP>is defined and accessible, or <SAMP>p </SAMP>is a null pointer.   Deletes the current underlying pointer, then resets it to <SAMP>p</SAMP>.</P>
</UL>
<A NAME="Example"><H3>Example</H3></A>
<PRE>   //
   // auto_ptr.cpp
   //
   #include &#60;iostream.h>
   #include &#60;memory>
   //
   // A simple structure.
   //
   struct X
   {
       X (int i = 0) : m_i(i) { }
       int get() const { return m_i; }
       int m_i;
   };
   int main ()
   {
      //
      // b will hold a pointer to an X.
      //
      auto_ptr&#60;X> b(new X(12345));
      //
      // a will now be the owner of the underlying pointer.
      //
      auto_ptr&#60;X> a = b;
      //
      // Output the value contained by the underlying pointer.
      //
      cout &#60;&#60; a->get() &#60;&#60; endl;
      //
      // The pointer will be deleted when a is destroyed on 
      // leaving scope.
      //
      return 0;
   }
Output : 
12345</PRE>
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