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POc++ templated friend class
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  1. POc++ templated friend class
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    copied!<p>I'm trying to write an implementation of a 2-3-4 tree in c++. I'm it's been a while since I've used templates, and I'm getting some errors. Here's my extremely basic code framework:<br> node.h:</p> <pre><code> #ifndef TTFNODE_H #define TTFNODE_H template &lt;class T&gt; class TreeNode { private: TreeNode(); TreeNode(T item); T data[3]; TreeNode&lt;T&gt;* child[4]; friend class TwoThreeFourTree&lt;T&gt;; int nodeType; }; #endif </code></pre> <p>node.cpp:</p> <pre><code>#include "node.h" using namespace std; template &lt;class T&gt; //default constructor TreeNode&lt;T&gt;::TreeNode(){ } template &lt;class T&gt; //paramerter receving constructor TreeNode&lt;T&gt;::TreeNode(T item){ data[0] = item; nodeType = 2; } </code></pre> <p>TwoThreeFourTree.h</p> <pre><code>#include "node.h" #ifndef TWO_H #define TWO_H enum result {same, leaf,lchild,lmchild,rmchild, rchild}; template &lt;class T&gt; class TwoThreeFourTree { public: TwoThreeFourTree(); private: TreeNode&lt;T&gt; * root; }; #endif </code></pre> <p>TwoThreeFourTree.cpp:</p> <pre><code>#include "TwoThreeFourTree.h" #include &lt;iostream&gt; #include &lt;string&gt; using namespace std; template &lt;class T&gt; TwoThreeFourTree&lt;T&gt;::TwoThreeFourTree(){ root = NULL; } </code></pre> <p>And main.cpp:</p> <pre><code>#include "TwoThreeFourTree.h" #include &lt;string&gt; #include &lt;iostream&gt; #include &lt;fstream&gt; using namespace std; int main(){ ifstream inFile; string filename = "numbers.txt"; inFile.open (filename.c_str()); int curInt = 0; TwoThreeFourTree &lt;TreeNode&gt; Tree; while(!inFile.eof()){ inFile &gt;&gt; curInt; cout &lt;&lt; curInt &lt;&lt; " " &lt;&lt; endl; } inFile.close(); } </code></pre> <p>And when I try to compile from the command line with: g++ main.cpp node.cpp TwoThreeFourTree.cpp</p> <p>I get the following errors: </p> <pre><code>In file included from TwoThreeFourTree.h:1, from main.cpp:1: node.h:12: error: ‘TwoThreeFourTree’ is not a template main.cpp: In function ‘int main()’: main.cpp:13: error: type/value mismatch at argument 1 in template parameter list for ‘template&lt;class T&gt; class TwoThreeFourTree’ main.cpp:13: error: expected a type, got ‘TreeNode’ main.cpp:13: error: invalid type in declaration before ‘;’ token In file included from node.cpp:1: node.h:12: error: ‘TwoThreeFourTree’ is not a template In file included from TwoThreeFourTree.h:1, from TwoThreeFourTree.cpp:1: node.h:12: error: ‘TwoThreeFourTree’ is not a template </code></pre> <p>My main question is why it's saying "error: ‘TwoThreeFourTree’ is not a template". Does anyone have any ideas? Thanks for all advice/help in advance... Dan</p>
 

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