void twohist2()
{
   TCanvas *c1 = new TCanvas("c1");
   TH1F *h1 = new TH1F("h1","h1",10,-3,3);
   h1->FillRandom("gaus",10000);
   c1->DrawFrame(h1->GetXaxis()->GetXmin(), h1->GetMinimum(),
                 h1->GetXaxis()->GetXmax(), h1->GetMaximum());
   TExec* ex1 = new TExec("ex1","gStyle->SetErrorX(0.0);");
   ex1->Draw();
   h1->Draw("PE SAME");

   TCanvas *c2 = new TCanvas("c2");
   Double_t x[] = {-3,-2,0,2,3};
   TH1F *h2 = new TH1F("h2","h2",4,x);
   h2->FillRandom("gaus",10000);
   c2->DrawFrame(h2->GetXaxis()->GetXmin(), h2->GetMinimum(),
                 h2->GetXaxis()->GetXmax(), h2->GetMaximum());
   TExec* ex2 = new TExec("ex2","gStyle->SetErrorX(0.5);");
   ex2->Draw();
   //h2->GetListOfFunctions()->Add(ex2);
   h2->Draw("PE");
   
}