Problem separating .h and .cpp file
<p>I am writing a class and need to separate the declarations from the implementation, but I keep receiving "undefined reference" errors when compiling and linking my test program.  It works fine when I include the implementation in the .h file, so I believe I am doing something wrong in there.  I just can't figure out what.</p>

<p><strong>Huge_Integer.h</strong></p>

<pre><code>#ifndef HUGE_INTEGER_H
#define HUGE_INTEGER_H

#include &lt;vector&gt;
#include &lt;string&gt;

using namespace std;

class Huge_Integer
{
   public:
      Huge_Integer();
      Huge_Integer(string);
      void input();
      string output();
      void add(Huge_Integer);
      void subtract(Huge_Integer);
      bool is_equal_to(Huge_Integer);
      bool is_not_equal_to(Huge_Integer);
      bool is_greater_than(Huge_Integer);
      bool is_less_than(Huge_Integer);
      bool is_greater_than_or_equal_to(Huge_Integer);
      bool is_less_than_or_equal_to(Huge_Integer);
   private:
      vector&lt;int&gt; value;
};

#endif
</code></pre>

<p><strong>Huge_Integer.cpp</strong></p>

<pre><code>#include&lt;vector&gt;
#include&lt;string&gt;
#include&lt;iostream&gt;

#include "Huge_Integer.h"

using namespace std;

// all stubs for now...

Huge_Integer::Huge_Integer()
{
   cout &lt;&lt; "object created\n";
}

Huge_Integer::Huge_Integer(string s)
{
   cout &lt;&lt; "object created\n";
}

//etc...
</code></pre>

<p>It also works if I put <code>#include "Huge_Integer.cpp"</code> in my test file, but I shouldn't have to do that, right?</p>

<p>I am using MinGW.</p>

<p>Thanks in advance!</p>

<p>Edit: Added stubs from my .cpp file</p>
