Functor.C

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//Example to create class Functor
//Author: Omar Zapata
#include<TRInterface.h>
#include<TMath.h>
 
typedef Double_t (*Function)(Double_t);
 
//Functor class with the function inside
class MyFunctor{
public:
  MyFunctor(){
    status=false;
    f=TMath::BesselY1;
  }
  void setFunction(Function fun)
  {
    f=fun;
    status=true;
  }
  Bool_t getStatus(){return status;}
  Double_t doEval(Double_t x) {
    return f(x);
  }
private:
   Function f;
   Bool_t status;
};
//this macro exposes the class into R's enviornment
// and lets you pass objects directly.
ROOTR_EXPOSED_CLASS(MyFunctor)

//Macro to create a module
ROOTR_MODULE(MyFunctorModule) {
    ROOT::R::class_<MyFunctor>( "MyFunctor" )
    //creating a default constructor
    .constructor()
    //adding the method doEval to evaluate the internal function
    .method( "doEval", &MyFunctor::doEval )
    .method( "getStatus", &MyFunctor::getStatus)
    ;
}
 
void Functor()
{
   ROOT::R::TRInterface &r=ROOT::R::TRInterface::Instance();
   //////////////////////////////////////////////////////////
   //Creating functor with deafult function TMath::BesselY1//
   // and status false from R's environment                //             
   //////////////////////////////////////////////////////////
   //Loading module into R's enviornment
   r["MyFunctorModule"]<<LOAD_ROOTR_MODULE(MyFunctorModule);
   
   //creating a class variable from module
   r<<"MyFunctor <- MyFunctorModule$MyFunctor";
   //creating a MyFunctor's object
   r<<"u <- new(MyFunctor)";

   //printing status
   r<<"print(u$getStatus())";
   
   //printing values from Functor and Function
   r<<"print(sprintf('value in R = %f',u$doEval( 1 )))";
   std::cout<<"value in ROOT = "<<TMath::BesselY1(1)<<std::endl;
   
   ////////////////////////////////////////////////////////////
   //creating a MyFunctor's object and passing objects to R's //
   //enviornment, the status should be true because it is not   //
   //using the default function                              //
   ////////////////////////////////////////////////////////////
   MyFunctor functor;
   functor.setFunction(TMath::Erf);
   r["functor"]<<functor;
   //printing the status that should be true
   r<<"print(functor$getStatus())";
   r<<"print(sprintf('value in R = %f',functor$doEval( 1 )))";
   std::cout<<"value in ROOT = "<<TMath::Erf(1)<<std::endl;
}