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POThe purpose behind empty struct?
 

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  1. POThe purpose behind empty struct?
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    <p>Declarations of auto_ptr from C++ Standard Library</p> <pre><code>namespace std { template &lt;class Y&gt; struct auto_ptr_ref {}; template &lt;class X&gt; class auto_ptr { public: typedef X element_type; // 20.4.5.1 construct/copy/destroy: explicit auto_ptr(X* p =0) throw(); auto_ptr(auto_ptr&amp;) throw(); template &lt;class Y&gt; auto_ptr(auto_ptr&lt;Y&gt;&amp;) throw(); auto_ptr&amp; operator=(auto_ptr&amp;) throw(); template &lt;class Y&gt; auto_ptr&amp; operator=(auto_ptr&lt;Y&gt;&amp;) throw(); auto_ptr&amp; operator=(auto_ptr_ref&lt;X&gt;) throw(); ~auto_ptr() throw(); // 20.4.5.2 members: X&amp; operator*() const throw(); X* operator-&gt;() const throw(); X* get() const throw(); X* release() throw(); void reset(X* p =0) throw(); // 20.4.5.3 conversions: auto_ptr(auto_ptr_ref&lt;X&gt;) throw(); template &lt;class Y&gt; operator auto_ptr_ref&lt;Y&gt;() throw(); template &lt;class Y&gt; operator auto_ptr&lt;Y&gt;() throw(); }; </code></pre> <p>}</p> <p>I don't understand the purpose of this part:</p> <pre><code>template &lt;class Y&gt; struct auto_ptr_ref {}; </code></pre> <p>Without declaring any variable, how can these be valid:</p> <pre><code>auto_ptr&amp; operator=(auto_ptr_ref&lt;X&gt;) throw(); </code></pre> <p>and these too:</p> <pre><code>auto_ptr(auto_ptr_ref&lt;X&gt;) throw(); template &lt;class Y&gt; operator auto_ptr_ref&lt;Y&gt;() throw(); </code></pre> <p><strong>Edit:</strong> and also (I just notice) I don't understand how the "operator" are used for the last two lines. Isn't the syntax something like "return-type operatoroperand;", where is the return type? operand? </p>
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    1. COah i simply never know about that though (still new to here)
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    2. CO@user385261: When you are new to a website, read their FAQ. It's not there for kicks.
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      1. USLightness Races in Orbit
 

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