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POIssues with unordered_map
 

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  1. POIssues with unordered_map
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    <p>I'm trying to implement various data structures and algorithms for learning purposes.</p> <p>At the moment I'm trying to implement a Graph class template but I'm having issues with trying to use STL <code>unordered_map</code> (and <code>consequently priority_queue</code> in the future). </p> <p>Basically what happens at the moment is, for some reason, the template types don't match up when trying to initialize the vertex map within the graph. From what I understand, since I only plan to use key types from the native C++ types, as long as my value type is a pointer I shouldn't need to do any extra work apart from a copy constructor for my custom vertex class. The default comparer/hasher should suffice. But it doesn't and the error I'm receiving is kind of incomprehensible. </p> <p>The error:</p> <pre><code>Error 1 error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::unordered_map&lt;T,graph&lt;T&gt;::vertex *,std::hash&lt;int&gt;,std::equal_to&lt;_Kty&gt;,std::allocator&lt;std::pair&lt;const _Kty,_Ty&gt;&gt;&gt;' (or there is no acceptable conversion) </code></pre> <p>The code:</p> <pre><code>#include "stdafx.h" #include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;unordered_map&gt; #include &lt;numeric&gt; #include &lt;functional&gt; using namespace std; class vertex; template &lt;class T&gt; class graph { public: graph() { verts = unordered_map&lt;T, vertex*&gt;(); } ~graph() { for each(auto v in verts) delete(v); delete(verts); } private: unordered_map&lt;T, vertex*&gt; verts; // --- Inner Classes --- struct path { vertex *dest; double cost; path(vertex *d = nullptr, double c = 0.0) : dest(d) : cost(c) {} inline int compare(const path&amp; p) { auto other = p.cost; return cost &lt; other ? -1 : cost &gt; other ? 1 : 0; } }; struct edge { vertex *dest; double cost; edge(vertex *d = nullptr, double c = 0.0) : dest(d) : cost(c) {} }; class vertex { public: // Vertex relationships T name; vector&lt;edge&gt;* adj; // Path Finding Information double distance; vertex *prev; int scratch; void reset_path_finding() { distance = double.infinity(); prev = nullptr; scratch = 0; } vertex(T name = default(T)) : name(name) : adj(new vector&lt;edge&gt;) : distance(double.infinity()) : prev(nullptr) : scratch(0) {} vertex(const vertex&amp; v) { name = v.name; adj = v.adj; distance = v.distance; prev = v.prev; scratch = v.scratch; } ~vertex() { delete(adj); } private: }; }; int main() { graph&lt;int&gt; myGraph = graph&lt;int&gt;(); cout &lt;&lt; "Press any key to continue..." &lt;&lt; endl; int x; cin &gt;&gt; x; return 0; } </code></pre>
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    1. COCan you please point the line in the source the error is about?
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    2. COBy the way, when you declare a variable (class member, local or global) like the local `myGraph` in the `main` function or `verts` in the `graph` class, you don't have to initialize the way you do. Just declaring it will be enough.
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