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POfatal error LNK1120: 1 unresolved externals
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  1. POfatal error LNK1120: 1 unresolved externals
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    copied!<p>I am compiling the following code and I am receiving an error. I want to practice templates in boost and I do not know how to handle this problem </p> <pre><code>#include &lt;stdafx.h&gt; #include &lt;iostream&gt; #include &lt;string&gt; #include &lt;boost/function.hpp&gt; #include &lt;boost/array.hpp&gt; using namespace std; template&lt;typename R,typename D&gt; class GenericFunction { private: boost::function&lt;R (D)&gt; f; protected: GenericFunction(); public: GenericFunction(const boost::function&lt;R (D)&gt;&amp; myFunction); R evaluate(const D&amp; value) const ; R operator ()(const D&amp; value) const; }; template &lt;typename R, typename D, int N&gt; class ScalarValuedFunction:public GenericFunction&lt;R,boost::array&lt;D, N&gt;&gt; { public: ScalarValuedFunction(const boost::function&lt;R (const boost::array&lt;D, N&gt;)&gt; &amp;myF); }; template&lt;typename Numeric, std::size_t N&gt; Numeric Norm(const boost::array&lt;Numeric , N&gt;&amp; Vec) { Numeric Result=Vec[0]*Vec[0]; for (std::size_t i=1; i&lt;Vec.size();i++) { Result+=Vec[i]*Vec[i]; } return Result; } int main () { const int N=4; boost::array&lt;double, N&gt; arr={0.2,.3,1.1,4}; ScalarValuedFunction&lt;double, double, N&gt; myfun(Norm&lt;double,N&gt;); } </code></pre> <p>and receiving the following error,</p> <pre><code>ConsoleApplication2.obj : error LNK2019: unresolved external symbol "public: __thiscall ScalarValuedFunction&lt;double,double,4&gt;::ScalarValuedFunction&lt;double,double,4&gt;(class boost::function&lt;double __cdecl(class boost::array&lt;double,4&gt;)&gt; const &amp;)" (??0?$ScalarValuedFunction@NN$03@@QAE@ABV?$function@$$A6ANV?$array@N$03@boost@@@Z@boost@@@Z) referenced in function _main 1&gt;c:\users\university\documents\visual studio 2012\Projects\ConsoleApplication2\Debug\ConsoleApplication2.exe : fatal error LNK1120: 1 unresolved externals </code></pre> <p>please someone tell me what is wrong with my code? </p>
 

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