undefined reference to `elast_opt()' collect2: ld returned 1 exit status
<p>I've written some oop code that use dealii library.</p>

<p>class <code>elastic</code> is defined in prelim header as:</p>

<pre><code>using namespace dealii;

template &lt;int dim&gt;
class elastic
{
  public:

    elastic(const Triangulation&lt;dim&gt;   *triang);
     ~elastic() ;

        void  run() ;

  private:
. 
.
.
</code></pre>

<p>and in another header that includes header:</p>

<pre><code>template &lt;int dim&gt;

  elastic&lt;dim&gt;::elastic(const Triangulation&lt;dim&gt;   *triang): dof_handler (triangulation), fe (FE_Q&lt;dim&gt;(1))

  {triangulation.copy_triangulation  (*triang);}
</code></pre>

<p>and my main is written below:</p>

<pre><code>#include "prelim.h"

using namespace dealii;

int main()

{
  deallog.depth_console (0);    
  elastic&lt;2&gt;    *elast_opt();    
  for ( iter=0; iter&lt;5 ; ++iter)    
      elast_opt()-&gt;run();    
  return 0;
}
</code></pre>

<p>When I compile I get these errors:</p>

<pre><code>....../main.cc:16: undefined reference to `elast_opt()'
collect2: ld returned 1 exit status
make: *** [main] Error 1
</code></pre>
