nwtgck / othello-scala

Type-safe Othello written in Scala

othello

Type-safe Othello written in Scala

Play

sbt "runMain io.github.nwtgck.othello.Main"

(In the future, this may be changed.)

AI

This game has three types of AI for now.

• RandomPlayer - moves randomly
• MonteCarloPlayer - moves by Monte Carlo method
• UguisuEvaluationTablePlayer - moves by a evalutation table found in http://uguisu.skr.jp/othello/5-1.html
• MinimaxPlayer - moves by minimax method with alpha-beta pruning

Type-safety

For example, Disk and Cell are not the same. Disk is a subset of Cell, mathematically, Disk ⊂ Cell. Because of this definition, Player has Disk, not Cell since Player should not have Empty, which is a state of a cell.

/**
  * Cell
  */
sealed trait Cell

/**
  * Disk (Disk is a subset of Cell)
  */
sealed trait Disk extends Cell{
...
}
case object Black extends Disk
case object White extends Disk
case object Empty extends Cell

If union types are available like TypeScript, the type definition will be more clear like the following. This project will be written in Dotty when Dotty get more stable.

// NOTE: TypeScript
type Cell = "Black" | "White" | "Empty"
type Disk = "Black" | "White"

For another example, the parameters of Game class ensure to have valid players like the following.

class Game(player1: Player[Black.type], player2: Player[White.type]) {
 ...
}

(The player1's disk is always Black and the player2's disk is always white.)

Definition of Player abstract class is like the following.

abstract class Player[+D <: Disk] (val disk: D) {
  ...
}

Game Tree

Game tree is represented as lazy tree. So you can get entire game tree by the following.

// The entire game tree of Othello!
GameTree.create(GamePosition(
  board = Board.initial,
  disk  = Black,
  previousMoveOpt = None
))

Here is a visualization of the game tree where depth limit = 3.