#include "TF2.h"
#include "TF12.h"
#include "Math/Integrator.h"
#include <memory>

struct FitFunction { 

   std::shared_ptr<TF2> main;
   std::shared_ptr<TF1> part;
   std::shared_ptr<TF12> f12A;
   std::shared_ptr<ROOT::Math::IntegratorOneDim> ig; 

 FitFunction() { 
    main = std::make_shared<TF2>("main","[0]*TMath::Factorial(x)*(exp(-y)/exp([1]*pow(y,2)+[2]*pow(y,3)))");  
    f12A = std::make_shared<TF12>("f12A",main.get(),0.,"y");
                                                               
// it seems to me deno is a function of only one variable
    part = std::make_shared<TF1>("deno","exp([1]*pow(x,2)+[2]*pow(x,3))" ); 
 
    ig = std::make_shared<ROOT::Math::IntegratorOneDim>(ROOT::Math::IntegrationOneDim::kADAPTIVESINGULAR);
}

double operator() (double *x, double *p) {
   
   main->SetParameters(p[0],p[1],p[2],p[3]);
   f12A->SetXY(x[0]);
 
   ig->SetFunction(*f12A);
   double mainsum =  ig->IntegralUp(0.);

   part->SetParameters(p[1],p[2],p[3]);
   ig->SetFunction(*part);
   double deno = ig->IntegralUp(0.);
    
   return mainsum/deno;
}

};



void TestFitFunction() {

   FitFunction f;

   TF1 func("f",f,270, 340, 4);
   func.DrawClone();
}