ROOT opening a tbranch of a ttree from a tfile, doing a calculation, writing a histogram

ROOT open, calculate, write out 1

#include "TFile.h"
#include "TTree.h"
#include "TH1D.h"

#include <iostream>

void histo2()
{
std::cout << "fetch file\n" ;

// runs 349, 357, 365
//TFile *f = TFile::Open("run357_quartic.root");
//TTreeReader myReader("tdc", f);
TFile *f = new TFile("run365_quartic.root","READ");


std::cout << "fetch tree\n" ;
TTree *tree = (TTree*)f->Get("tdc");
tree->Print();

std::cout << "fetch branch\n" ;
Double_t leading_edge = 0.0;
tree->SetBranchAddress("leading_edge", &leading_edge);

std::cout << "start calculation\n" ;

Int_t entries = tree->GetEntries();

std::cout << entries << "\n" ;

for (Int_t i = 0; i<entries; i++) {
   tree->GetEntry(i);
   cout << leading_edge << "\n";
}
std::cout << "calculation ended\n" ;

f->Close();

}