jim burton
data Card = Clubs Int | Spades Int | Diamonds Int | Hearts Int | JokerA | JokerB
They aren't really Ints; better to define something like
data FaceValue = Ace | F2 | F3 | F4 | F5 | F6 | F7 | F8 | F9 | F10 | Jack | Queen | King
and possibly derive Enum (which unfortunately would give the the "wrong" values, but that can be got around).
deriving (Show, Eq) type Deck = [Card] --cardval - clubs are face value, diamonds plus 13, and so on - Jokers are both 53
I'd be inclined to define an Enum instance rather than cardval directly, but define cardval as an auxilliary function that scrunches both jokers to the same value.
isJoker :: Card -> Bool isJoker JokerA = True isJoker JokerB = True isJoker _ = False
Since you've defined an instance of Eq, you can use
isJoker c = c == JokerA || c == JokerB
--take a card to a letter card2char :: Card -> Char card2char c = case c of (Clubs i) -> int2alpha $ cardval c --can case fall through in haskell?
It's defined to, but you don't need a case clause as you can use cardval and mod.
--take a letter to int, A=1, Z=26 char2int :: Char -> Int char2int = (64 `subtract`) . (ord)
Better to use (ord 'A' - 1) if you are going to do it this way.
--take a letter to int, 1=A, Z=26 int2alpha :: Int -> Char int2alpha = (chr) . (+64)
and again
splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p
That was my mistake! Use the shorter, cleaner version I posted after that one.
in_fives l = foldr (\x y -> x++" "++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate (5 - length l `mod` 5) 'X')
Putting the spaces in at this point is a mistake! Also see what I said about length.
--get an ordered deck newdeck :: Deck newdeck = suit 'c' ++ suit 'd' ++ suit 'h' ++ suit 's' ++ JokerA : JokerB : [] where suit s = case s of 'c' -> [Clubs i | i <- [1..13]] 's' -> [Spades i | i <- [1..13]] 'd' -> [Diamonds i | i <- [1..13]] 'h' -> [Hearts i | i <- [1..13]]
That seems overly complicated. With an Enum instance, you'd just do
newdeck = [Club Ace .. JokerB]
or better, with an instance of Bounded too,
newdeck = [minBound .. maxBound]
Of course, you'd have to write toEnum to do the work, but I'd do it something like
toEnum 54 = JokerB toEnum 53 = JokerA toEnum n = [Club, Diamond, Heart, Spade]!!suit $ (toEnum (val+1)) where (suit, val) = (n-1) `divMod` 13
Comments from now on are a bit less thought through... I think there are better ways to do some of these operations, but I'm not going to present them, just nitpick a bit instead.
--key the deck ready to provide a keystream - move JokerA down one place, --JokerB down 2 places, perform a triplecut then a countcut keydeck :: Deck -> Deck keydeck = countcut. triplecut . (movedown JokerB) . (movedown JokerB) . (movedown JokerA)
--bump a card down by one place in a deck, treating the deck as circular so if the card is -- last in the deck it becomes 2nd to front not 1st movedown :: Eq a => a -> [a] -> [a] movedown c d = if c == last d
that looks like an unnecessary pass over the list
then head d : c : init (tail d) else top ++ bot!!1 : c : (tail (tail bot)) where splt = splitAt (locate c d) d top = fst splt bot = snd splt
you can write
where (top,bot) = splitAt ... But how about List.break?
And if you know that bot is going to have enough elements
where (top, card1:card2:rest) = break ...
-- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk