#include <iostream>
#include <string>
#include "TTreeReaderArray.h"
#include "TTreeReader.h"
#include "TChain.h"

struct Task {
  TTreeReaderArray<float> * f;
  std::string m_name;
  
  void init(TTreeReader& r){
    f = new TTreeReaderArray<float>(r, m_name.c_str() );
    std::cout << " inited "<< this << "  with "<< f<< std::endl;
  }
  float s=0;
  void execute(){
    if(! f->IsEmpty() ) {
      //std::cout << (*f)[0] << std::endl;
      s+=(*f)[0];
    }
  }
};


struct Loop {

  std::vector<Task*> m_tasks;

  void run(TChain *chain){

    TTreeReader reader(chain);
    std::cout << "   running with "<< chain << "  ntask= "<< m_tasks.size() << "  nevt="<< chain->GetEntries() <<std::endl;

    for(auto * t: m_tasks) t->init(reader);

    size_t n = chain->GetEntries();
    //size_t n = 10;
    for (size_t i=0;i<n;i++){
      std::cout << "event "<< i << std::endl;
      reader.SetEntry( i );
      for(auto * t: m_tasks) t->execute();
    }

  }

};