include Stdlib.Seq

let map t ~f = map f t

let filter t ~f = filter f t

let filter_map t ~f = filter_map f t

let fold_left t ~init ~f = fold_left f init t

let iter t ~f = iter f t

let return t = return t

let cons x next () = Cons (x, next)

let rec append seq1 seq2 () =
  match seq1 () with
  | Nil -> seq2 ()
  | Cons (x, next) -> Cons (x, append next seq2)
