method patt3 =
                  fun f ->
                    function
                    | Ast.PaRng (_, p1, p2) ->
                        pp f "@[<2>%a@ ..@ %a@]" o#patt3 p1 o#patt4 p2
                    | Ast.PaCom (_, p1, p2) ->
                        pp f "%a,@ %a" o#patt3 p1 o#patt3 p2
                    | p -> o#patt4 f p