//
//
// This file is for Assignment 4, BU CAS CS 520, Fall, 2008
//
//

(* ****** ****** *)

// An implementation of random-access list based on nested datatypes

(* ****** ****** *)

staload "ralist.sats"

(* ****** ****** *)

// this is just an example
fun{a:t@ype} ralist_last {n:pos} .<n>. (xs: ralist (a, n)):<> a =
  case+ xs of
  | RAone x => x
  | RAevn xxs => let
      val xx = ralist_last<P a a> xxs in xx.1
    end // end of [RAevn]
  | RAodd (_, xxs) => let
      val xx = ralist_last<P a a> xxs in xx.1
    end // end of [RAodd]
// end of [ralist_last]

(* ****** ****** *)

//
// please put your code here
//

(* ****** ****** *)

//
// please do not change any of the following code; it is to
// be used for testing when your implementation is finished.
//
//
// How to compile:
//
// atscc -O3 -o ralist_test ralist.sats ralist.dats
//
// How to test:
//
// ./ralist_test

fun ralist_gen {n:nat} (n: int n): ralist (int, n) = let
  fun loop {i,j:nat | i+j == n}
    (i: int i, xs: ralist (int, j)): ralist (int, n) =
    if i > 0 then loop (i - 1, ralist_cons (i, xs)) else xs
in
  loop (n, RAnil ())
end // end of [ralist_gen]

(* ****** ****** *)

fn{a:t@ype} ralist_foreach {n:nat}
  (xs: ralist (a, n), f: a -<cloref1> void): void = let
  var x: a // uninitialized
  fun loop {n:nat} {l:addr}
    (pf: !a? @ l | xs: ralist (a, n), p: ptr l, f: a -<cloref1> void): void =
    case+ xs of
    | RAnil () => ()
    | _ =>> let
        val xs = ralist_uncons<a> (xs, !p); val () = f (!p)
      in
        loop (pf | xs, p, f)
      end
  // end of [loop]
in
  loop (view@ x | xs, &x, f)
end // end of [ralist_foreach]

(* ****** ****** *)

implement main () = let
  val xs = ralist_gen (100)
  val () = ralist_foreach (xs, lam x => (print x; print_newline ()))
  val n = ralist_length<int> (xs)
  val () = begin
    print "n(100) = "; print n; print_newline ()
  end
  val x = ralist_lookup<int> (xs, 50)
  val () = begin
    print "x(51) = "; print x; print_newline ()
  end
  val xs = ralist_update<int> (xs, 50, ~51)
  val x = ralist_lookup<int> (xs, 50)
  val () = begin
    print "x(-51) = "; print x; print_newline ()
  end
in
  // empty
end // end [main]

(* ****** ****** *)

(* end of [ralist.dats] *)