coderetreat

Program.fs

open System

type World<'a> = 'a [,]

let tryGet ar x y = 
  try Some <| Array2D.get ar x y
  with e -> None

let countAlive = List.collect Option.toList >> List.filter ((=) true) >> List.length

let getNeighborCount board x y = 
  [
    for x2 in [-1 .. 1] do
      for y2 in [-1 .. 1] do
        yield (tryGet board (x + x2) (y + y2))
  ] |> countAlive

let neighbors board = board |> Array2D.mapi (fun x y _ -> getNeighborCount board x y)

let zip ar = Array2D.mapi (fun x y cell -> (cell, Array2D.get ar x y))

let fix a = (fun _ -> a)

let action = function
        | (3, false) -> (fix true)
        | (n, true) when n >= 4 || n <= 1  -> (fix false)
        | _ -> id

let life world = 
  let fworld = zip world (neighbors world)  |> Array2D.map action
  zip world fworld |> Array2D.map (fun (f, c) -> f c)

let initWorld i = 
  let r = new Random ()
  Array2D.init i i (fun _ _ -> r.Next() % 2 = 1)

let pritty = Array2D.map (fun c -> if c then "●" else "○")

let update world =
  printfn "===================================="
  printf "%A" (world |> pritty)
  Console.ReadLine () |> ignore

let lifeGame = Seq.unfold (fun prev -> Some (life prev, life prev))

[<EntryPoint>]
let main args =
  initWorld 10 |> lifeGame |> Seq.iter update
  0