Roger,

Without writing any code, and still learning Haskell I personally don't see anything intrinsically wrong with using a String, it's simple, it works and what more can you ask from code than that!

I would go so far as to add "\n" after each line so that you can print the status of the game to the console in one go, then checking for a winning line would be as simple as writing a function that takes as its input the String and a list of string offsets which make up a line, with the assumption that [0] is the first board position, [2] is the end of the first line and [3] contains the first "\n" character I would (pseudo-code / made up from keyboard, pebcak may apply) go for this approach:

topLineWin = checkLine myBoard "O" [0,1,2]   -- did O win ?
topleftDiagWin = checkLine myBoard "X" [0,5,10] -- did X win ?
botLineWin     = checkLine my Board "X" [8,9,10] -- did X win ?

and so on. The implementation of checkLine is left as an exercise for the reader as they say but by using partial application you can make the code very readbable. I might even try this myself and post it back for a laugh. It's surprising sometime the difference between what you think you know and what you actually know!

Some coding hints and thinking as I go...

topLine = [0,1,2]
topleftDiagWin = [0,5,10]
etc.

winnerO = checkLine myString "O"
winnerX = checkLine myString "X"

checkLine topLine playerCode -- did the top line win?
...

By making the checkLine return a Bool then you can have a list of functions that you could then pass through the Data.List.all and make it something like this:

all [ winnerO topLine, winnerO botLine, ... etc]

Just to make the array number clear, here is the complete board:

         "\n"
0 1   2 3
4 5   6 7
8 9 10 10

All the best, that's no coding and pure thought for that so YMMV!

Sean Charles.

On 18 March 2013 15:54, Costello, Roger L. <costello@mitre.org> wrote:

Hi Folks,

Currently I am representing a tic-tac-toe board as a string, with 'X' denoting player 1 and 'O' denoting player 2. For example, I represent this 2x2 game board:

'X' |
-----------------------
| 'O'

with this string: "X O"

The nice thing about that representation is that it is each to identify which cells are filled or empty, and it is easy to mark a cell with an 'X' or 'O'.

The problem with the representation is that it is difficult to determine when a player has won.

Can you recommend a representation that makes it easy to:

1. determine when a player has won
2. identify cells that are filled or empty
3. mark an empty cell

/Roger

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