#define LHEF_cxx
#include "LHEF.h"
#include <TH1.h>
#include <TStyle.h>
#include <TCanvas.h>
#include <TPad.h>

void LHEF::Loop()
{
//   In a ROOT session, you can do:
//      Root > .L LHEF.C
//      Root > LHEF t
//      Root > t.GetEntry(12); // Fill t data members with entry number 12
//      Root > t.Show();       // Show values of entry 12
//      Root > t.Show(16);     // Read and show values of entry 16
//      Root > t.Loop();       // Loop on all entries
//

//     This is the loop skeleton where:
//    jentry is the global entry number in the chain
//    ientry is the entry number in the current Tree
//  Note that the argument to GetEntry must be:
//    jentry for TChain::GetEntry
//    ientry for TTree::GetEntry and TBranch::GetEntry
//
//       To read only selected branches, Insert statements like:
// METHOD1:
//    fChain->SetBranchStatus("*",0);  // disable all branches
//    fChain->SetBranchStatus("branchname",1);  // activate branchname
// METHOD2: replace line
//    fChain->GetEntry(jentry);       //read all branches
//by  b_branchname->GetEntry(ientry); //read only this branch
   if (fChain == 0) return;

   fChain->SetBranchStatus("*", 0);  // disable all branches
   fChain->SetBranchStatus("Particle", 1);  // activate "Particle_"
   fChain->SetBranchStatus("Particle.M", 1);  // activate "Particle_M"

   TH1D *invm = new TH1D("H_invmass", "GeV", 150, 0, 150);

   Long64_t nentries = fChain->GetEntriesFast();

   Long64_t nbytes = 0, nb = 0;
   for (Long64_t jentry=0; jentry<nentries;jentry++) {
      Long64_t ientry = LoadTree(jentry);
      if (ientry < 0) break;

      nb = b_Particle_->GetEntry(ientry); nbytes += nb; // first things first
      nb = b_Particle_M->GetEntry(ientry);nbytes += nb;

      // if (Cut(ientry) < 0) continue;

      std::cout << jentry << " : " << Particle_ << " :";
      for (Int_t j = 0; j < Particle_; j++) {
	std::cout << " " << Particle_M[j];
	// if (!(Particle_M[j] > 0.0)) continue; // skip zeros
	invm->Fill(Particle_M[j]);
      }
      std::cout << std::endl;
   }

   invm->Draw();
   if (gPad) gPad->SetLogy(1);
}