gistfile1.ml

(* vim: ts=2 sts=2 sw=2:
*)
#directory "+extlib"
#load "extLib.cma"
type mark = X | O

type space = 
    Empty
  | Full of mark

type result = 
    Continue
  | Draw 
  | Win of mark

exception Space_is_full
exception Game_is_over
exception Out_of_turn

let string_of_mark m =
  match m with
    X -> "X"
  | O -> "O"

let string_of_space s = 
  match s with
    Full(m) -> string_of_mark m
  | Empty   -> " "

let string_of_result r =
  match r with
    Win(m)   -> "Win(" ^ (string_of_mark m) ^ ")"
  | Draw     -> "Draw"
  | Continue -> "Continue"

class board = object (self)
  val b = Array.make 9 Empty
  val mutable result = Continue
  val mutable last_mark = ref O

  val winners = List.flatten [
    List.map (fun i -> Array.init 3 (fun j -> i + j)) [ 0; 3; 6 ];
    List.map (fun i -> Array.init 3 (fun j -> i + 3 * j)) [ 0; 1; 2 ];
    List.map (fun i -> Array.init 3 (fun j -> i * (j - 1) + 1 + 3 * j)) [ 1; -1 ];
  ]

  method calculate_result = 
    let find_win w = 
      match Array.map (fun i -> b.(i)) w with
        [| Full(x); Full(y); Full(z) |] when x == y && y == z -> Win(x)
      | _ -> Continue
    in
    try  List.find (fun w -> w != Continue) (List.map find_win winners)
    with Not_found ->
      if   List.exists (fun s -> s == Empty) (Array.to_list b)
      then Continue
      else Draw

  method make_move i m = 
    if m == !last_mark
    then raise Out_of_turn
    else match b.(i) with
        Full(_) -> raise Space_is_full
      | Empty   -> last_mark := m; b.(i) <- Full(m)

  method move i m =
    if self#calculate_result == Continue
    then self#make_move i m
    else raise Game_is_over

  method display =
    let rec grouped a n = 
      match a with 
        [||] -> []
      | a -> Array.sub a 0 n :: grouped (Array.sub a n (Array.length a - n)) n
    in
    let string_of_row a = 
      "[" ^ String.concat "" (List.map string_of_space (Array.to_list a)) ^ "]"
    in
    String.concat "\n" (List.map string_of_row (grouped b 3)) ^ "\n"
end

let play_game ms =
  let b = new board in
  List.iter (fun (i, m) -> b#move i m) ms;
  print_string b#display;
  print_string (string_of_result b#calculate_result ^ "\n");;

let main () =
  play_game [(0, X); (4, O); (8, X); (2, O); (6, X); (3, O); (7, X)];
  play_game [(0, X); (4, O); (8, X); (2, O); (6, X); (7, O); (3, X)];
  play_game [(0, X); (3, O); (4, X); (2, O); (8, X)];
  play_game [(0, X); (4, O); (8, X); (3, O); (5, X); (2, O); (6, X); (7, O); (1, X)];
  exit 0;;

main ()