C++ Linker Error in Constructor
<p>I keep getting Linker Error undefined reference to <code>Poisson::Poisson(int, int)</code>
I want to use <code>Poisson::Poisson(int, double)</code> as I am clearly trying to do and cannot figure out why it won't let me!</p>

<pre><code>#include "Distribution.h"
using namespace std;

class Poisson : public Distribution
{
 public:
 // Constructors
 Poisson(int inittrials, double initlambda);
 Poisson();           //Sets trials (k) = 10, lambda = 5

 // Knowledge responsibilities
 double GetLambda() const;  
 // Returns the time zone

 double calcProb();
 double calcExpVal();
 double calcVar();



private:                                     
  double lambda;
};
</code></pre>

<p>now for my cpp file</p>

<pre><code>#include "Poisson.h"
#include &lt;iostream&gt;
#include &lt;string&gt;
using namespace std;

Poisson::Poisson(int inittrials, double initlambda) 
  : Distribution(inittrials)
{ 
  lambda = initlambda; 
  updateNickname("Probability of Exactly k Occurences of an event");
  updateProbEqn("f(k, lambda) = (((lambda)^k) * e(^-lambda))/ k!");
  updateExpValEqn("E(X) = Lambda");
  updateVarEqn("VAR(X) = Lambda");
}

//************************************************************

Poisson::Poisson()
{ lambda = 5.0; }

//************************************************************

double Poisson::GetLambda() const
{ return lambda; }

//************************************************************

double Poisson::calcProb()
{
   double numerator;
   double denomanator;       
   //numerator = (GetLambda())^(GetTrials()) * (2.71828183)^((-1)*GetLambda());
}

double Poisson::calcExpVal()
{
}
double Poisson::calcVar()
{
}
</code></pre>
