#include "TROOT.h"
#include "TFile.h"
#include "TTree.h"
#include "TBrowser.h"
#include "TH2.h"
#include "TRandom.h"

void tree1w( bool getndata )
{
  gRandom->SetSeed( 123456 );
   
  //create the Tree and a few branches

  TTree t1("t1","a simple Tree with simple variables");
  
  Float_t px, py, pz;
  t1.Branch("px",&px,"px/F");
  t1.Branch("py",&py,"py/F");
  t1.Branch("pz",&pz,"pz/F");

  vector<float> vecp;
  t1.Branch("vecp",&vecp);
   
  // create tree formulas
  
  TTreeFormula ttfFloat("ttfFloat","py",&t1);               // evaluates a float == py
  TTreeFormula ttfVector("ttfVector","vecp[1]",&t1);        // evaluates a vector<float> element ==py

  // event loop

  for (Int_t i=0;i<10;i++) {

    // reset
    
    vecp.clear();

    // generate event
    
    gRandom->Rannor(px,py);
    pz = px*px + py*py;
    
    vecp.push_back(px);
    vecp.push_back(py);
    vecp.push_back(pz);

    // evaluate formulas
    
    if( getndata )
      ttfVector.GetNdata();
    
    cout << "     ttfFloat  : py = " << py << " / " << ttfFloat.EvalInstance()  
	 << "     ttfVector : py = " << vecp[1] << " / " << ttfVector.EvalInstance() << endl;

    // fill

    t1.Fill();    
  }
}

void tree1() {
 
  cout << endl;
  cout << "Printout : py variable (double) / same from formula; py as vector element / same from formula" << endl;
  cout << endl;

  cout.setf(ios::showpos); 
  cout.setf(ios::fixed,ios::floatfield);
  cout.precision(5);

  cout << "No call to GetNdata : looks ok ?!" << endl;
  cout << endl;
  tree1w( false );
  cout << endl;
  cout << "With call to GetNdata : vector gets stuck at first event" << endl;
  cout << endl;
  tree1w( true );
}