#include "TFile.h"
#include "TTree.h"
#include "TChain.h"
#include "TTreeFormula.h"
#include <iostream>

using namespace std;

void apply_gbr(TTree *electron1_tree, const std::vector<std::string> varseb)

{
  
  Float_t target = 0.;
  
  TTree *friendtree = new TTree;
  friendtree->Branch("foo",&target,"foo/F");
  //cout << "asdfds 3" << endl;

  for (Long64_t iev=0; iev<electron1_tree->GetEntries(); ++iev) {
    electron1_tree->LoadTree(iev);
        
    friendtree->Fill();

  }

  electron1_tree->AddFriend(friendtree);
}


void solve_problem()
{
      
  TChain *chainele = new TChain("ElectronEnergyRegressionTree");
  chainele->Add("file.root");
  chainele->LoadTree(0);    
  TTree * intree = chainele;
  
  std::vector<std::string> varseb;
  TTree * electron1_tree = (TTree*)intree->Clone();

  electron1_tree->LoadTree(0);

  apply_gbr(electron1_tree, varseb);

  cout << "electron1_tree->GetEntry(0) = " << electron1_tree->GetEntry(0) << endl;
  cout << "electron1_tree->GetEntry(0) = " << electron1_tree->GetEntry(0) << endl;

}