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POStuck on C++ template - deriving from std::map
 

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  1. POStuck on C++ template - deriving from std::map
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    <p>I'm going to extend the existing std::map class and add a new function to it:</p> <pre><code>template&lt;typename key_type, typename value_type&gt; class CleanableMap : public Cleanable, public std::map&lt;key_type, value_type&gt; { CleanableMap(const CleanableMap&amp; in); //not implemented CleanableMap&amp; operator=(const CleanableMap&amp; in); //not implemented public: CleanableMap() {} CleanableMap(const std::map&lt;key_type, value_type&gt;&amp; in) { *this = in; } virtual ~CleanableMap() {} std::map&lt;key_type, value_type&gt;&amp; operator=(const std::map&lt;key_type, value_type&gt;&amp; in) { *((std::map&lt;key_type, value_type&gt;*)this) = in; return *this; } }; </code></pre> <p>I've got a copy constructor and assignment operator such that I can simply assign an existing std::map of the same type to my new map:</p> <pre><code>CleanableMap&lt;DWORD, DWORD&gt; cm; std::map&lt;DWORD, DWORD&gt; stdm; cm = stdm; </code></pre> <p>The problem is, the compiler is complaining with an error that doesn't make sense -- I've explicitly coded for what it's complaining about:</p> <pre><code>1&gt;c:\dev\proj\commonfunc.cpp(399) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::map&lt;_Kty,_Ty&gt;' (or there is no acceptable conversion) 1&gt; with 1&gt; [ 1&gt; _Kty=DWORD, 1&gt; _Ty=DWORD 1&gt; ] 1&gt; c:\dev\proj\templates.h(245): could be 'CleanableMap&lt;key_type,value_type&gt; &amp;CleanableMap&lt;key_type,value_type&gt;::operator =(const CleanableMap&lt;key_type,value_type&gt; &amp;)' 1&gt; with 1&gt; [ 1&gt; key_type=DWORD, 1&gt; value_type=DWORD 1&gt; ] 1&gt; c:\dev\proj\templates.h(250): or 'std::map&lt;_Kty,_Ty&gt; &amp;CleanableMap&lt;key_type,value_type&gt;::operator =(const std::map&lt;_Kty,_Ty&gt; &amp;)' 1&gt; with 1&gt; [ 1&gt; _Kty=unsigned long, &lt;--- where did it come up with that? 1&gt; _Ty=std::pair&lt;const DWORD,DWORD&gt;, &lt;--- where did it come up with that? 1&gt; key_type=DWORD, 1&gt; value_type=DWORD 1&gt; ] 1&gt; while trying to match the argument list '(CleanableMap&lt;key_type,value_type&gt;, std::map&lt;_Kty,_Ty&gt;)' 1&gt; with 1&gt; [ 1&gt; key_type=DWORD, 1&gt; value_type=DWORD 1&gt; ] 1&gt; and 1&gt; [ 1&gt; _Kty=DWORD, 1&gt; _Ty=DWORD 1&gt; ] </code></pre> <p>There 'could be' it mentions on line 245 doesn't make sense -- there is no assignment operator like that (well, it's private. Removing it completely doesn't change anything).</p> <p>The 'could be' it mentions on line 250 is the assignment operator that I defined, but it was somehow deduced some other non-matching template types. Where did it get those??</p> <p>Help!!! :)</p>
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