gistfile1.ml

open Prelude

type 'a accum = Acc of 'a | Done of 'a

let optMap f x = match x with None -> None | Some y -> Some (f y)

let string_of_char c = String.make 1 c
let (^.) s c = s ^ string_of_char c

module Stream =
struct
  include Stream

  let nextOpt st =
    match peek st with
      | None -> None
      | x -> (junk st; x)

  let rec foldlBreak f init st =
    match nextOpt st with
      | None -> init
      | Some x ->
        begin match f init x with
          | Acc a -> foldlBreak f a st
          | Done b -> b
        end

  let rec foldl f init st = foldlBreak (fun s i -> Acc (f s i)) init st

  let map f st = from (fun _ -> optMap f (nextOpt st))

  let remap f init st =
    from (fun _ ->
      match peek st with
        | None -> None
        | Some x -> Some (foldlBreak f init st))

  let join s st = from (fun i -> if i mod 2 = 0 then nextOpt st else Some s)

end

let lines =
  Stream.remap (fun s c -> if c = '\n' then Done s else Acc (s ^. c)) ""

let () =
  withFiles (fun ic oc ->
    let s = Stream.of_channel ic in
    let rev_lines = Stream.map srev (lines s) in
    Stream.iter (output_string oc) (Stream.join "\n" rev_lines)
  ) "src" "dst"