Double_t myfunc(Double_t *x, Double_t *par) {
  
  Float_t xx = x[0];
  
  Double_t f = TMath::Abs(par[0]*sin(par[1]*xx)/xx);
  cout << "xx = " << xx << "\tmyfunc value = " << f << endl;
  return f;

}

void TF1_test() {
  
  cout << endl << "Creating testFunc..." << endl;
  TF1* testFunc = new TF1("testFunc", myfunc, 1, 9, 2);
  testFunc->SetNpx(8);
  testFunc->SetParameters(2,1);

  cout << endl << "Creating testHist..." << endl;
  TH1D* testHist = new TH1D();
  testHist = (TH1D*) testFunc->GetHistogram();
  testHist->SetName("testHist");
  testHist->SetTitle("testHist");
  testHist->SetMarkerStyle(20);
  cout << endl << "Printing testHist..." << endl;
  testHist->Print("all");

  TFile* f = new TFile("TF1.root", "recreate");
  cout << endl << "Saving testFunc..." << endl;
  testFunc->Write();
  testHist->Write();
  f->Close();
  f->Delete();

  return;

}