pp (lazy ("lunghezza xs = " ^ string_of_int (List.length xs)));
let ls, rs = HExtlib.split_nth leftno xs in
pp (lazy ("lunghezza ls = " ^ string_of_int (List.length ls)));
pp (lazy ("lunghezza rs = " ^ string_of_int (List.length rs)));
pp (lazy ("lunghezza xs = " ^ string_of_int (List.length xs)));
let ls, rs = HExtlib.split_nth leftno xs in
pp (lazy ("lunghezza ls = " ^ string_of_int (List.length ls)));
pp (lazy ("lunghezza rs = " ^ string_of_int (List.length rs)));