Seven Languages in Seven Weeks: Scala, Day 1

ScalaReduceDocumentation.txt

def reduce [A1 >: A] (op: (A1, A1) ⇒ A1): A1

Reduces the elements of this sequence using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Note this method has a different signature than the reduceLeft and reduceRight methods of the trait Traversable. The result of reducing may only be a supertype of this parallel collection's type parameter T.

TicTacToe.scala

import collection.mutable.MutableList

object Marker extends Enumeration {
  type Marker = Value
  val EMPTY = Value("_")
  val X = Value("x")
  val O = Value("o")
}

import Marker._

class Board(boardSize: Int) {

  val board = MutableList.fill(boardSize * boardSize)(EMPTY)

  def spacer(value: String) = " " * (boardSize.toString.length() - value.length() + 2)

  override def toString = printBoard ((marker, index) => marker.toString)

  def printMoves() = printBoard ((marker, index) => if (marker == EMPTY) index.toString else EMPTY.toString)

  def printBoard(printMarker: (Marker, Int) => String): String = board.zipWithIndex.foldLeft(""){(acc, marker) =>
    val printedMarker = printMarker(marker._1, marker._2) 
    acc + (if (marker._2 > 0 && marker._2 % boardSize == 0) "\n" else "") + printedMarker + spacer(printedMarker)
  }

  def placeMarker(index: Int, marker: Marker): Boolean = {
    if (index >= 0 && index < board.length && board(index) == EMPTY) {
      board(index) = marker
      return true
    }
    
    false
  }

  def allEqual(elements: MutableList[Marker]) = !elements.contains(EMPTY) && elements.distinct.size == 1

  def anyListAllEqual(lists: TraversableOnce[MutableList[Marker]]): Boolean = lists.foldLeft(false)(_ || allEqual(_))

  def anyListAllEqual(lists: MutableList[MutableList[Marker]]): Boolean = anyListAllEqual(lists.toIterator)

  def rows() = board.grouped(boardSize)

  def cols() = board.zipWithIndex.groupBy(_._2 % boardSize).map(_._2.map(_._1))

  def diags() = MutableList(
    board.zipWithIndex.filter(_._2 % (boardSize + 1) == 0).map(_._1),
    board.zipWithIndex.filter(value => (value._2 % (boardSize - 1) == 0) && (value._2 > 0) && (value._2 < board.length - 1)).map(_._1)
  )

  def boardWon() = anyListAllEqual(rows()) || anyListAllEqual(cols()) || anyListAllEqual(diags())
  
  def boardFull() = board.count(_ == EMPTY) == 0
}

val board = new Board(3)
var currentMove = O
while (!board.boardFull() && !board.boardWon()) {
  currentMove = if (currentMove == X) O else X  
  println("\nThe board:\n")
  println(board)
  println("\nAvailable locations on the board:\n")
  println(board.printMoves())
  print("\nIt's " + currentMove + "'s turn! Enter a location: ")

  val index = Console.readInt()
  if (!board.placeMarker(index, currentMove)) {
    println("Invalid location!")    
  }
}

println()

if (board.boardWon()) {
  println("Player " + currentMove + " wins!")
} else {
  println("It's a draw!")
}

println()
println(board)

TicTacToeOutput.txt

The board:

_  _  _  
_  _  _  
_  _  _  

Available locations on the board:

0  1  2  
3  4  5  
6  7  8  

It's x's turn! Enter a location: 4

The board:

_  _  _  
_  x  _  
_  _  _  

Available locations on the board:

0  1  2  
3  _  5  
6  7  8  

It's o's turn! Enter a location: 0

The board:

o  _  _  
_  x  _  
_  _  _  

Available locations on the board:

_  1  2  
3  _  5  
6  7  8  

It's x's turn! Enter a location: 6

The board:

o  _  _  
_  x  _  
x  _  _  

Available locations on the board:

_  1  2  
3  _  5  
_  7  8  

It's o's turn! Enter a location: 2

The board:

o  _  o  
_  x  _  
x  _  _  

Available locations on the board:

_  1  _  
3  _  5  
_  7  8  

It's x's turn! Enter a location: 1

The board:

o  x  o  
_  x  _  
x  _  _  

Available locations on the board:

_  _  _  
3  _  5  
_  7  8  

It's o's turn! Enter a location: 8

The board:

o  x  o  
_  x  _  
x  _  o  

Available locations on the board:

_  _  _  
3  _  5  
_  7  _  

It's x's turn! Enter a location: 5

The board:

o  x  o  
_  x  x  
x  _  o  

Available locations on the board:

_  _  _  
3  _  _  
_  7  _  

It's o's turn! Enter a location: 3

The board:

o  x  o  
o  x  x  
x  _  o  

Available locations on the board:

_  _  _  
_  _  _  
_  7  _  

It's x's turn! Enter a location: 7

Player x wins!

o  x  o  
o  x  x  
x  x  o 

See Seven Languages in Seven Weeks: Scala, Day 1 for more info.