// A stand-alone C++ program to illustrate the use of ROOT classes
// for booking, filling and storing histograms.  The program 
// displays one of the histograms.  All histograms are stored in
// a file test.root, which can be read in a further analyzed using
// the program root.  A minimal interactive root session might be:

//    > root
//    root [0] TFile f("test.root");      // read in the file
//    root [1] f->ls();                   // list the histograms
//    root [2] h1->Draw();                // draw histogram h1
//    root [3] h2->Draw();                // draw histogram h2

// For more information see the root home page:  root.cern.ch

// Glen Cowan
// RHUL Physics
// 22 November 2004

#include <iostream>
#include <cstdlib>

#include "TApplication.h"
#include "TCanvas.h"
#include "TFile.h"
#include "TH1F.h"

using namespace std;

int main(int argc, char **argv) {

  TApplication* theApp = new TApplication("App", &argc, argv);

// Set up output file, book histograms, add to list of histograms.

  TFile* outfile = new TFile("test.root", "RECREATE");
  TList* hList = new TList();      // list of histograms to store

  TH1F* h1 = new TH1F("h1", "uniform r", 100, 0.0, 1.0);
  hList->Add(h1);
  TH1F* h2 = new TH1F("h2", "r1 + r2 - 1", 100, -1.0, 1.0);
  hList->Add(h2);
 
//  Fill with some random numbers.  Uses cstdlib's rand().

  for (int i = 0; i<10000; ++i){
    float r1 = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
    float r2 = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
    h1->Fill(r1);
    h2->Fill(r1+r2-1.0);
  }

// Display a histogram.  (Alternatively, look at them with the program root.)

  TCanvas* c = new TCanvas("c", "c", 800, 600);
  h1->Draw();

// Save all histograms in the list to the output file.

  hList->Write();

// Run the TApplication (not needed if you only want to store the histograms.)

  theApp->Run();

// Close up

  outfile->Close();

  return 0;

}