double uni( double* x, double* par ) {
  double val = x[0];
  double a = par[0];
  double b = par[1];
  if( val < a || val > b ) return 0;
  else return ( 1./(b-a) );
}


void uniform_exponential() 
{
  TF1* funi1 = new TF1( "funi1", uni, -1, 10, 2);
  funi1->SetParameters( 1, 2 );
  funi1->SetNpx( 1000 );
  funi1->Draw();
  funi1->SetTitle( "Uniform PDF: x #in [1,2]" );
  funi1->GetXaxis()->SetTitle( "x" );
  funi1->GetYaxis()->SetTitle( "f(x;a,b)" );
  funi1->SetMaximum( 1.1 );
  gPad->SaveAs( "uniform1.pdf" );

  TF1* funi2 = new TF1( "funi2", uni, -1, 10, 2);
  funi2->SetParameters( 0, 7 );
  funi2->SetNpx( 1000 );
  funi2->Draw();
  funi2->SetTitle( "Uniform PDF: x #in [0,7]" );
  funi2->GetXaxis()->SetTitle( "x" );
  funi2->GetYaxis()->SetTitle( "f(x;a,b)" );
  funi2->SetMaximum( 1.1 );
  gPad->SaveAs( "uniform2.pdf" );

  TF1* fexp1 = new TF1( "fexp1", "[0]*TMath::Exp(-[0]*x)", 0, 10 );
  fexp1->SetParameter( 0, 1 );
  fexp1->SetNpx( 1000 );
  fexp1->Draw();
  fexp1->SetTitle( "Exponential PDF: #lambda = 1.0" );
  fexp1->GetXaxis()->SetTitle( "x" );
  fexp1->GetYaxis()->SetTitle( "f(x;#lambda)" );
//  fexp1->SetMaximum( 1.1 );
  gPad->SaveAs( "expo1.pdf" );

  TF1* fexp2 = new TF1( "fexp2", "[0]*TMath::Exp(-[0]*x)", 0, 10 );
  fexp2->SetParameter( 0, 0.2 );
  fexp2->SetNpx( 1000 );
  fexp2->Draw();
  fexp2->SetTitle( "Exponential PDF: #lambda = 0.2" );
  fexp2->GetXaxis()->SetTitle( "x" );
  fexp2->GetYaxis()->SetTitle( "f(x;#lambda)" );
//  fexp1->SetMaximum( 1.1 );
  gPad->SaveAs( "expo2.pdf" );
}