#include "Math/Integrator.h"
#include "Math/WrappedFunction.h"
#include <iostream>

class formula 
{ 
public: 
   formula(); 
   formula(double newY); 
   ~formula(); 
   double operator() (double x){ return x*y; }; 
   void SetY( double newY) { y= newY; }
protected: 
   double x, y; 
}; 

formula::formula(){ 
   y = 1; 
} 

formula::formula(double newY){ 
   y = newY; 
} 

formula::~formula(){} 

void testIntegration() { 

   formula f(2.);
   ROOT::Math::WrappedFunction<formula> wf(f);
   
   ROOT::Math::Integrator ig(wf);

   std::cout << ig.Integral(0,1) << std::endl;

   // changing the parameter  in formula
   f.SetY(3.);
   // need to re-create a new WrappedFunction because we 
   // used formula by value   
   ig.SetFunction(ROOT::Math::WrappedFunction<formula>(f) );
   std::cout << ig.Integral(0,1) << std::endl;
   

   // it is more efficient to use in WrappedFunction a reference
   // but we have to be sure now that formula is not delete before 
   // WrappedFunction

   ROOT::Math::WrappedFunction<formula &> wf2(f);
   ig.SetFunction(wf2);
   f.SetY(5.);
   std::cout << ig.Integral(0,1) << std::endl;
   f.SetY(10.);
   std::cout << ig.Integral(0,1) << std::endl;
   
}