void rootForum_20899() { 


   auto x = new RooRealVar("x", "x", -1.0, 1.0);
   auto y = new RooRealVar("y", "y", -1.0, 1.0);

// Basic functions that use x,y 
      auto   P_1_x = new RooLegendre("P_1_x", "P_1_x", *x, 1, 0);
      auto    P_1_y = new RooLegendre("P_1_y", "P_1_y", *y, 1, 0);

// Some coefficient 
      auto   C_1_2 = new RooRealVar("C_1_2", "C_1_2", 2.0);

// Main function that in theory is made of several combinations of Legendre polynomials 
      auto combLeg = new RooFormulaVar("combLeg","C_1_2*P_1_x*P_1_y", RooArgList(*C_1_2, *P_1_x, *P_1_y));

// Finally, I want to project either x/y results into a histogra, e.g.:
      // project for some sensible y value (e.g. y=0.5) 
      y->setVal(0.5);

      auto pdf = combLeg->createHistogram("pdf", *x, RooFit::Binning(80));
      pdf->Draw();



}