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;