function Search var aL TDList const aData TData integer var PElem TPEl

function Search(var aL : TDList; const aData : TData ):integer;
var
  PElem: TPElem;
  position:integer;
begin
   position:=1;
   PElem:=aL.PFirst;
   while PElem<>nil do
   begin
     if PElem.Data = aData then
      begin
      Search:=position;
      Exit();
      end
     else
        position:=position+1;
     PElem:=PElem^.PNext;
   end;
   Search:=0;
end;