16
May
10

Intermission

At the beginning of the month, I hit a wall. I have no more “saved-up” tic-tac-toe implementations, and it’s become pretty hard to contemplate taking a couple evenings a week away from my family to make new ones.

This is partly because what I’m doing with them has become less interesting, and thus motivating. The very nature of the exercise as I set it up, its pace, its limitations—a new implementation of an identical text-based game in a novel language, once a week—have been actually taking me away from the most interesting part, which is learning new ways of thinking.  Several times I’ve found myself essentially porting another implementation and in the process stripping away all the novel features of the language.  I wrote the Clojure post by modifying my scheme program.  It’s somewhat interesting that this was straightforward to do, and I tried to make the best of it.  But it felt bad, and I don’t think it was really all that enlightening to learn that you can implement the same simple program similarly in two LISP dialects.

The last one I feel I really did justice was Cobra, and that was the last one I really spent some time on.

I’ve also been avoiding or putting off languages without obvious parallels to things I already know.  This is precisely contrary to the point.  I downloaded Self the other day with the intent to use it for the week’s program, but found a) that it doesn’t seem to have a console interface at all, and b) that there’s no way to even write it outside its image-based environment and GUI.  This clearly counts as novel and interesting, but there’s no way I’m ending up with a working program after 4 hours.

So, I’m pivoting.  I’ll keep working through the list at a more measured pace, and with much more of a focus on producing end products that reflect the tool’s capabilities and intent.  I’ll write GUI programs for Visual Basic and Objective C, for example.  I’ll figure out some excuse to use goroutines in Go.

If you’ve been following along because the stunt seemed amusing, I’m sorry to disappoint.  If it’s any consolation, I still plan to do brainf*ck and Piet.  But as the man says, when you find yourself in a hole, stop digging.

It would also help me immeasurably if I knew there were people actually reading this stuff.  I don’t have stats on how many feed readers I have so some weeks it’s a bit like lecturing to an empty room.  If you’re still reading but not commenting, would you let me know?

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28
Apr
10

Tic-Tac-Toe: Scala

If Clojure is a way to have your LISP and eat your JVM too, Scala seems more like a subversive attempt to introduce the Java world to dynamic and functional programming in friendly clothing.  The whole approach is very Java: syntactically baroque and wordy, but admirably complete and well-documented.  The java integration is more seamless than it is in Clojure.  I was struggling to figure out how to read a line of input the Scala way, and finally gave up and did it like Java.  It worked, it was easy, and most importantly (ha) it didn’t look out of place.

The downside of syntactical harmony with Java is that it’s a bit ugly.  For example, if you define a method that returns Unit (void), you can stick the curl brace right next to the method name.  If you give it a return type, you have to stick an equals sign in there.  Not a big deal.  But ugly.

That said, it’s still way better than bog-standard Java, as a a language.  Type inference, pattern matching, lazy evaluation, optional duck(ish) typing.  Almost everything I like about Ruby structurally, but with relatively unobtrusive type safety.  I’d miss method_missing under some circumstances, but maybe not enough to matter.  I could definitely see myself doing my next project in Scala + JRuby.

This compiles in Scala 2.7.7.


import java.io.{BufferedReader, InputStreamReader}

object TicTacToe {
    
  private val input = new BufferedReader(new InputStreamReader(System.in))

  def main(args: Array[String]) {
  
    var result: Result = Continue(X)

    while (true) {

      println
      println(board)
      println
      print(result)

      result match {
        case Continue(player) => {
            val space = readAnswer
            if (board.spaceAvailable(space)) {
              board.place(space, player)
              result = board.checkResult(player)
            }
        }
        case _ => return
      }

    }
  }

  def readAnswer: Int = {
    try {
      input.readLine().toInt
    } catch {
      case nfe: NumberFormatException => 0
    }
  }
}

abstract class Player {
  def next: Player
}
case object X extends Player {
  override def toString() = "X"
  def next = O
}
case object O extends Player {
  override def toString() = "O"
  def next = X
}

abstract class Space
case class Empty(n: Int) extends Space { 
  override def toString() = "(" + n + ")"
}
case class Filled(player: Player) extends Space {
  override def toString() = " " + player + " "
}

abstract class Result
case class Win(player: Player) extends Result {
  override def toString() = "" + player + " Wins!\n"
}
case object Draw extends Result {
  override def toString() = "It's a Draw!\n"
}
case class Continue(player: Player) extends Result {
  override def toString() = "Select a square, " + player + ": "
}

object board {
  private val spaces = Array[Space](
    Empty(1),Empty(2),Empty(3),
    Empty(4),Empty(5),Empty(6),
    Empty(7),Empty(8),Empty(9)
  )

  def spaceAvailable(n: Int): Boolean = {
    for (space  return true
        case _ => ()
      }
    }
    return false
  }

  def full: Boolean = {
    for (space  return false
        case _ => ()
      }
    }
    return true;
  }

  def checkResult(player: Player): Result = {
    for (row  {
          return Win(p)
        }
        case _ => ()
      }
    }
    if (full) return Draw
    return Continue(player.next)
  }

  def place(n: Int, player: Player) {
    spaces(n-1) = Filled(player)
  }

  private def get(n: Int): Space = spaces(n-1)

  private def rows: Array[Array[Space]] = {
    Array[Array[Space]](
      spaces.slice(0,3),
      spaces.slice(3,6),
      spaces.slice(6,9),

      Array(get(1),get(4),get(7)),
      Array(get(2),get(5),get(8)),
      Array(get(3),get(6),get(9)),

      Array(get(1),get(5),get(9)),
      Array(get(3),get(5),get(7)))
  }

  override def toString() = {
    spaces(0) + "|" + spaces(1) + "|" + spaces(2) +
    "\n---+---+---\n" +
    spaces(3) + "|" + spaces(4) + "|" + spaces(5) +
    "\n---+---+---\n" +
    spaces(6) + "|" + spaces(7) + "|" + spaces(8)
  }
}

21
Apr
10

Tic-Tac-Toe: Clojure

Clojure, for those who don’t know, is a newish LISP implemented on top of the JVM. It’s designed to play nicely with Java libraries, which I didn’t end up exercising, and is largely lazy and functional, which I did.

If you’ve been following along, you might notice that this implementation is very similar to the one for Scheme. That’s because I cheated and just ported it over. There are some pointed differences in its API, but it was actually pretty easy to translate. No major changes in the basic logic, with the exception of one function which I had to rewrite to get around a JVM-imposed restriction on how recursive you can get inside a let.

I like scheme better on purely aesthetic grounds, but Clojure seems more useful, and is certainly more relevant lately. A few notable innovations:

  • Shortcut lambdas: #(+ %1 10) => (fn [x] (+ x 10))
  • Extensive use of vectors as syntactic distinguishers, e.g. denoting function parameters
  • Java Method calls: (.toString x)
  • Lots more that I didn’t end up using

Here’s the code:

; Defining the players -- Infinite Lazy Sequence
(def players (cycle ["X" "O"]))

; Setting up the board
(def *starting-board*
	 [[1 2 3]
	  [4 5 6]
	  [7 8 9]])

(defn space-available? [space board]
	  (some (fn [row] (some #(= %1 space) row)) board))

; Moving -- returns a transformed board
(defn move [player space board]
	  (letfn [(move-in-row
			   ([accum row]
				 (cond
				   ; if we reach the end, that's it
				   (empty? row) accum
				   ; if we have found the space, take it
				   (= space (first row)) (concat accum (cons player (rest row)))
				   ; if not, keep going
				   true (recur (concat accum (list (first row))) (rest row))))
				 ([row] (move-in-row '() row)))]
		(map move-in-row board)))

(defn space->string [space]
	  (if (number? space)
		(str "(" space ")")
		(str " " space " ")))

(defn row->string [row] (apply str (interpose "|" (map space->string row) )))

(defn board->string [board]
	  (apply str (interpose "\n---+---+---\n" (map row->string board))))

(defn third [seq] (nth seq 2))

(defn winner? [board]
	  (or
		; rows
		(apply = (first board))
		(apply = (second board))
		(apply = (third board))
		; columns
		(apply = (map first board))
		(apply = (map second board))
		(apply = (map third board))
		; diagonals
		(= (first (first board))
		   (second (second board))
		   (third (third board)))
		(= (third (first board))
		   (second (second board))
		   (first (third board)))))

(defn full? [board]
	  (not (some number? (mapcat identity board))))

(defn print-board [board]
	  (do
		(newline)
		(print (board->string board))
		(newline)
		(newline)))

(defn play [board players]
	  (do
		(print-board board)
		(let [ player (first players) ]
		  (cond
			(winner? board) (print (str (first (next players))  " Wins!\n"))
			(full? board) (print "It's a Draw!\n")
			true (do
				   (print (str "Select a square, " player ": "))
				   (flush)
				   (let 
(if (and answer (space-available? answer board)) (recur (move player answer board) (next players)) (recur board players)))))))) (play *starting-board* players)
14
Apr
10

Tic-Tac-Toe: Awk

Awk’s original intended use is as a stream processor, and in fact in its most basic form you can’t even do explicit input. My first version of this used gawk/nawk extensions for that purpose, but I figured it would be a bit more fun to use input patterns, so that’s what you see here.

Perl fans (and thus, Ruby and Python fans) might recognize an ancestor here.

#!/usr/bin/env awk -f

BEGIN {
	split("1 2 3 4 5 6 7 8 9", spaces)
	player = "X"

	print_board()
	print_prompt()
}

/[0-9]/ { place_move($1) }
/./ { print_board(); print_prompt() }

function print_board () {
	print ""
	for (i = 1; i <= 9; i++) {
		space = spaces[i]
		if (space ~ /[0-9]/)
			printf("(%d)", space);
		else
			printf(" %s ", space);

		if (i % 3 == 0) {
			if (i / 3 < 3) {
				printf "\n---+---+---\n";
			}
		} else {
			printf "|";
		}
	}

	print "\n"
}

function print_prompt () {
	printf "Select a square, %s: ", player
}

function read_move () {
	getline move
}

function place_move (move) {
	if (move && spaces[move] == move) {
		spaces[move] = player
		good_move = 0

		if (keep_playing()) {
			swap_player()
		} else {
			exit 0
		}
	}
}

function swap_player () {
	if (player == "X")
		player = "O"
	else
		player = "X"
}

function m3(i, j, k) {
	return spaces[i] == spaces[j] && spaces[j] == spaces[k]
}

function has_winner () {
	return m3(1,2,3) || 
		   m3(4,5,6) ||
		   m3(7,8,9) ||
		   m3(1,4,7) ||
		   m3(2,5,8) ||
		   m3(3,6,9) ||
		   m3(1,5,9) ||
		   m3(3,5,7);
}

function is_draw () {
	for (i = 1; i <= 9; i++) {
		space = spaces[i]
		if (space ~ /[0-9]/) 
			return 0;
	}
	return 1
}

function keep_playing() {
	if (has_winner()) {
		print_board()
		printf("%s Wins!\n", player)
		return 0;
	} else if (is_draw()) {
		print_board()
		print("It's a Draw!")
		return 0;
	} else
		return 1;
}

07
Apr
10

Tic-Tac-Toe: Haskell

Haskell is seriously packed with modern, interesting, expressive goodies.

But I have a message for the Haskell community: stop trying to “simplify” monads.  Really, just stop.  I have yet to see an “explanation” of monads that does not add to the confusion and fear a novice might feel at approaching the language.  You don’t need to know what a monad is in order to use the language effectively.  Talking about them to a beginner is about as useful as explaining loop unrolling and keyhole optimization to a beginning C programmer.  Later, yes, it’s helpful.  But it’s too much information at the start.  A beginner just needs to know that if you want to use code that does IO, it has to go inside a do, and if you want to pull out values and use them elsewhere, you need the <- operator.  It took me three nights of working on this one to learn that one, because the Gentle Introduction relegated I/O to chapter 7.

On that note, you’ve got to stop treating I/O in general as a red-headed stepchild.  I realize that isolating side effects is one of the raisons d’être for Haskell in the first place, but if you hope to win converts from the programming world at large (and I really hope you do) then you’ve got to understand that most of us mere mortals want our programs to do something, and that means input/output.  I understand, or at least I think I do, that you want to instill good habits from the start and minimize time spend in the IO monad, but honestly, the language is pretty good at doing that already.  You’ve got to go and talk to people where they already are before you can lead them somewhere else.

Once peple get used to IO and Maybe and whatever other monads are out there, then you can introduce the concept because there’s somewhere for it to land.  I remember taking CS theory in college, and talking with one of the TFs who I happened to know socially.  He is an extremely bright guy, and as is sometimes common with bright guys, can have trouble explaining a concept to someone who doesn’t get it themselves right away.  I made plea for more concrete examples to go with the theoretical explanations in the class, and his response was, “Well, we assume that you, the smart [name of school] students, can come up with the examples yourselves.”  This is exactly wrong for many many people out there, including a lot of the folks who are attracted to coding in the first place.  Some folks work well top-down — get the overarching concepts and then fill in the details themselves.  But some people learn the other way around — experience the details, and then build up the framework from there.  My impression is that the Haskell community is filled with the former type of learner.  But it’s a great language, even for the more experiential/practical and less theoretical, and I hate to see it shunned as too scary.

Ranting aside, I really enjoyed writing this.  For those of you who haven’t tried it yet, I highly recommend it.  It will make you smarter.  I stumbled on places where it differs from OCaml, and I got stuck on IO for a while, but I’m glad I persevered.

This was written against GHC 6.10.4.


import Data.List (intersperse)
import System.IO (stdout, hFlush)
import System.Exit (exitSuccess)

-- 
-- Users
--
data User = X | O
    deriving(Show, Eq)

otherUser X = O
otherUser O = X

-- 
-- Squares
--
data Square = Move User | Empty Int
    deriving(Eq)

instance Show Square where
    show (Move x)   = " " ++ show x ++ " "
    show (Empty x)  = "(" ++ show x ++ ")"

filled (Move _) = True
filled _        = False

-- 
-- Boards
--
data Board = Board [[Square]]
    deriving(Eq)

instance Show Board where
    show (Board ls) = "\n" ++ concat (intersperse "---+---+---\n" $ map showLine ls) ++ "\n"
        where
            showLine xs = concat (intersperse "|" $ map show xs) ++ "\n"

full (Board squares) = all filled (concat squares)

-- 
-- Results
--
data Result = Continue User Board | Win User Board | Draw Board

instance Show Result where
    show (Continue user board) = show board ++ "Select a square, " ++ show user ++ ": "
    show (Win user board)      = show board ++ show user ++ " Wins!\n"
    show (Draw board)          = show board ++ "It's a Draw!\n"

-- 
-- Initial Board
--
startingBoard :: Board
startingBoard = Board [[Empty 1,Empty 2,Empty 3],
                       [Empty 4,Empty 5,Empty 6],
                       [Empty 7,Empty 8,Empty 9]]

matchSquare :: User -> Int -> Square -> Square
matchSquare user position (Empty x) | x == position = Move user
matchSquare _ _ square                              = square

-- This evaluates the board and determines the result of the current user's action
outcome :: User -> Board -> Result
outcome user board =
      case board of
           (Board [[a, _, _],
                   [_, b, _],
                   [_, _, c]]) | eq a b c -> Win user board

           (Board [[_, _, a],
                   [_, b, _],
                   [c, _, _]]) | eq a b c -> Win user board

           (Board [[a, b, c],
                   [_, _, _],
                   [_, _, _]]) | eq a b c -> Win user board

           (Board [[_, _, _],
                   [a, b, c],
                   [_, _, _]]) | eq a b c -> Win user board

           (Board [[_, _, _],
                   [_, _, _],
                   [a, b, c]]) | eq a b c -> Win user board

           (Board [[a, _, _],
                   [b, _, _],
                   [c, _, _]]) | eq a b c -> Win user board

           (Board [[_, a, _],
                   [_, b, _],
                   [_, c, _]]) | eq a b c -> Win user board

           (Board [[_, _, a],
                   [_, _, b],
                   [_, _, c]]) | eq a b c -> Win user board

           _ | full board -> Draw board
             | otherwise  -> Continue (otherUser user) board
    where
        eq a b c = a == b && b == c
             

move :: User -> Int -> Board -> Result
move user pos board = result user pos board (place user pos board)
    where
        place user pos (Board lines) = Board $ map (placeInLine user pos) lines

        placeInLine user pos         = map $ matchSquare user pos

        result user pos orig board 
            | orig == board          = Continue user orig
            | otherwise              = outcome user board

main :: IO ()
main = loop (Continue X startingBoard)
    where 
        loop result = do 
            putStr $ show result
            hFlush stdout
            case result of
                 Win user board      -> exitSuccess
                 Draw board          -> exitSuccess
                 Continue user board -> getInput user board
        getInput user board = do
             pos <- readLn::IO Int 
             loop (move user pos board)
31
Mar
10

Tic-Tac-Toe: LOLCode

The clink… clink… clink sound you’ve been hearing was my IQ points sliding off onto the floor one by one as I wrote this.

This program was written against a slightly tweaked version of the the Perl-based YALI interpreter.  You can check out the original, but to run this one you will need my version, which is checked in with the rest of the code.  I also stole the array join implementation from his examples.

HAI

  OBTW
    join
    Basic array join.
  TLDR
  HOW DUZ I join YR a AN YR b
    I HAS A count ITZ ALL a
    LOL count R count NERF 1

    IZ count SMALR DEN 0 ? FOUND YR ""

    I HAS A output ITZ ""
    IM IN YR LOOP
      LOL output R count IN MAH a N output

      IZ count BIGR DEN 0 ? LOL output R b N output
      IZ count LIEK 0 ? GTFO

      LOL count R count NERF 1
    KTHX

    FOUND YR output
  IF U SAY SO

  OBTW
    cell formatting
  TLDR
  HOW DUZ I formatz YR cell
    IZ cell SORTA "\d" ? FOUND YR "(" N cell N ")"
    FOUND YR " " N cell N " "
  IF U SAY SO

  HOW DUZ I printz YR bord
    I HAS A cell
    I HAS A colsep ITZ "|"
    I HAS A rowsep ITZ "\n---+---+---\n"
    I HAS A outputz ITZ ""

    LOL cell R formatz YR 0 IN MAH bord MKAY
    LOL outputz R "\n" N cell N colsep

    LOL cell R formatz YR 1 IN MAH bord MKAY
    LOL outputz R outputz N  cell N colsep

    LOL cell R formatz YR 2 IN MAH bord MKAY
    LOL outputz R outputz N  cell N rowsep

    LOL cell R formatz YR 3 IN MAH bord MKAY
    LOL outputz R outputz N  cell N colsep

    LOL cell R formatz YR 4 IN MAH bord MKAY
    LOL outputz R outputz N  cell N colsep

    LOL cell R formatz YR 5 IN MAH bord MKAY
    LOL outputz R outputz N  cell N rowsep

    LOL cell R formatz YR 6 IN MAH bord MKAY
    LOL outputz R outputz N  cell N colsep

    LOL cell R formatz YR 7 IN MAH bord MKAY
    LOL outputz R outputz N  cell N colsep

    LOL cell R formatz YR 8 IN MAH bord MKAY
    LOL outputz R outputz N cell N "\n"

    FOUND YR outputz
  IF U SAY SO

  HOW DUZ I makezYrMove YR playr AN YR space AN YR bord
    BTW This version of LOLCode has no TROOF values, so I use NUMBRs

    IZ space SMALR DEN 1 ? FOUND YR 0
    IZ space BIGR DEN 9 ? FOUND YR 0

    I HAS A indeks ITZ space NERF 1

    IZ indeks IN MAH bord SORTA "\d" O RLY?
      YA RLY
        LOL indeks IN MAH bord R playr
        FOUND YR 1
      NO WAI
        FOUND YR 0
    KTHX
  IF U SAY SO

  HOW DUZ I canHasWinnarIn YR bord AN YR playr
    I HAS A bordMaidUvYarn ITZ join YR bord AN YR "" MKAY

    BTW rows
    IZ bordMaidUvYarn SORTA "(" N playr N ")(" N playr N ")(" N playr N ")......" ? FOUND YR 1
    IZ bordMaidUvYarn SORTA "...(" N playr N ")(" N playr N ")(" N playr N ")..." ? FOUND YR 1
    IZ bordMaidUvYarn SORTA "......(" N playr N ")(" N playr N ")(" N playr N ")" ? FOUND YR 1

    BTW columns
    IZ bordMaidUvYarn SORTA "(" N playr N ")..(" N playr N ")..(" N playr N ").." ? FOUND YR 1
    IZ bordMaidUvYarn SORTA ".(" N playr N ")..(" N playr N ")..(" N playr N ")." ? FOUND YR 1
    IZ bordMaidUvYarn SORTA "..(" N playr N ")..(" N playr N ")..(" N playr N ")" ? FOUND YR 1

    BTW diagonals
    IZ bordMaidUvYarn SORTA "(" N playr N ")...(" N playr N ")...(" N playr N ")" ? FOUND YR 1
    IZ bordMaidUvYarn SORTA "..(" N playr N ").(" N playr N ").(" N playr N ").." ? FOUND YR 1

    FOUND YR 0
  IF U SAY SO

  HOW DUZ I canHasTieIn YR fantsyBord
    IZ fantsyBord SORTA "\d" ? FOUND YR 0
    FOUND YR 1
  IF U SAY SO

  I HAS A bord
  I HAS A bord_lemf ITZ 9
  I HAS A current_lemf
  IM IN YR loop
    LOL current_lemf R ALL bord
    IZ current_lemf LIEK bord_lemf ? GTFO

    LOL current_lemf IN MAH bord R current_lemf UP 1
  KTHX

  I HAS A playr ITZ "X"
  I HAS A moovWerked ITZ 0

  IM IN YR gaimLoop
    I HAS A fantsyBord ITZ printz YR bord MKAY
    VISIBLE fantsyBord

    I HAS A winnar ITZ canHasWinnarIn YR bord AN YR playr MKAY
    IZ winnar LIEK 1 O RLY?
      YA RLY
        VISIBLE playr N " IS TEH WINNAR!1!!!"
        BTW Use this line instead if you want to run tests
        BTW VISIBLE playr N " Wins!"
        GTFO
    KTHX

    I HAS A tie ITZ canHasTieIn YR fantsyBord MKAY
    IZ tie LIEK 1 O RLY?
      YA RLY
        VISIBLE "NO MOAR WINNARZ!!!?/1!"
        BTW Use this line instead if you want to run tests
        BTW VISIBLE "It's a Draw!"
        GTFO
    KTHX

    IZ moovWerked LIEK 1 O RLY?
      YA RLY
        IZ playr LIEK "X" O RLY?
          YA RLY
            LOL playr R "O"
          NO WAI
            LOL playr R "X"
        KTHX
    KTHX

    I HAS A moov

    VISIBLE "Makez yr moov, " N playr N ": "!
    BTW Use this line instead if you want to run tests
    BTW VISIBLE "Select a square, " N playr N ": "!

    GIMMEH NUMBR moov

    LOL moovWerked R makezYrMove YR playr AN YR moov AN YR bord MKAY
  KTHX

KTHXBYE

BTW vim: ts=2 sw=2 et
24
Mar
10

Tic-Tac-Toe: Python

Lock up the women and children — a rubyist is writing python. I’m curious what the herpetophiles in the audience will think of the code, because I know the Python community spends a reasonable amount of brainpower debating “pythonicness.”

Broadly speaking, there were more places I found commonality between Ruby and Python than differences. This may have been more harmful than helpful in the short run, because it meant I kept reaching for familiar tools a finding they had been moved, or replaced. For example, you can see in several places that I do this: if type(cell) == type(1), meaning if cell is a number. Is this a common Python idiom? It seems unlikely.

Differences I liked:

  • Syntactically-significant indentation.  Makes short functions look great and longer ones look weird, thus encouraging short functions.  🙂
  • List comprehensions.  Especially with multiple lists.
  • Real named arguments.
  • Excellent documentation.
  • TIOOWTDI

Differences I didn’t like:

  • Distinction between builtins and methods.  I kept looking for any and map in all the wrong places.
  • No implicit expression value / required explicit return.
  • More difficult reflection/metaprogramming.
  • TIOOWTDI

With just a little practice, I’m sure I could be quite happy and productive in it.

What do you think, Python people?  What should I have done differently?

#!/usr/bin/env python2.6

from __future__ import print_function
import sys

X = 'X'
O = 'O'

starting_player = X
starting_board = [ [1, 2, 3],
                   [4, 5, 6],
                   [7, 8, 9] ]

# Input/Output

def format(cell):
    if type(cell) == type(1):
        return "(" + repr(cell) + ")"
    else:
        return " " + cell + " "

def print_board(board):
    print("\n" + "\n---+---+---\n".join(["|".join([format(c) for c in row]) for row in board]) + "\n")

def print_prompt(player):
    print("Select a square, " + player + ": ", end='')

def print_winner(player):
    print(player + " Wins!")

def print_draw():
    print("It's a Draw!")

def read_answer():
    str = sys.stdin.readline()
    return int(str)

# Winner Detection

def rows(board):
    return board[:] # clone

def cols(board):
    return [[row[i] for row in board] for i in [0,1,2]]

def diagonals(board):
    return [[row[i] for row, i in zip(board,[0,1,2])],
            [row[i] for row, i in zip(board,[2,1,0])]]

def lines(board):
    return rows(board) + cols(board) + diagonals(board)

def complete_line(line):
    return line[0] == line[1] and line[1] == line[2]

def winner(board):
    return any([complete_line(line) for line in lines(board)])

def full(board):
    return not any([type(row[i]) == type(1) for row in board for i in [0,1,2]])

# Game Play

def other_player(player):
    if player == X:
        return O
    else:
        return X

def legal_move(space, board):
    return any([row[i] == space for row in board for i in [0, 1, 2]])

def make_move(player, space, board):
    new_board = [row[:] for row in board]
    new_board[(space-1)/3][(space-1)%3] = player
    return new_board

# Main loop

def loop(player, board):
    print_board(board)
    if winner(board):
        print_winner(other_player(player))
        return
    elif full(board):
        print_draw()
        return
    else:
        print_prompt(player)
        space = read_answer()
        if legal_move(space, board):
            loop(other_player(player), make_move(player, space, board))
        else:
            loop(player, board)

loop(starting_player, starting_board)



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