misterspeedy

    /// A card suit.
    type Suit = 
        | Club  | Diamond | Heart | Spade
        static member FromChar c =
            match c with
            | '♣' -> Club | '♦' -> Diamond | '♥' -> Heart | '♠' -> Spade
            | _ -> raise (ArgumentException(sprintf "Invalid suit character: %c" c))

misterspeedy

    /// A card rank.
    type Rank = 
        | Ace | King | Queen | Jack | Value of int
        static member FromString s =
            match s with
            | "A" -> Ace | "K" -> King | "Q" -> Queen | "J" -> Jack 
            | "10" -> Value(10)
            | _ when s.Length = 1 && s.[0] >= '2' && s.[0] <= '9' -> Value(int(s.[0]) - int('0'))
            | _ -> raise (ArgumentException(sprintf "Invalid rank string: %s" s))
        /// The value of the rank for comparison purposes.

misterspeedy

    /// A hand of exactly five cards.
    type Hand(cards : Card[]) =
        do
            if cards.Length <> 5 then
                raise (ArgumentException("Invalid number of cards"))
        /// The cards in the hand, sorted in descending order of rank.
        member h.Cards = cards |> Array.sortBy (fun card -> 0 - card.Rank.SortValue)
        static member FromString (s : string) =
            let cards = 
                s.Split([|' '|])

misterspeedy

    /// True if all cards in the sequence are the same suit.
    let SameSuit cards =
        ( cards |> Seq.distinctBy (fun card -> card.Suit) |> Seq.length ) = 1

    /// True if all the cards in the sequence are consecutive by value.
    /// Includes both the high-Ace and the low-Ace cases.
    let Consecutive cards =
        cards
        |> Array.map (fun card -> card.Rank)
        |> Array.sortBy (fun rank -> 0 - rank.SortValue)

misterspeedy

    let (|RoyalFlush|_|) (hand : Hand) =
        if (hand.Cards.[0].Rank) = Ace && (Consecutive hand.Cards) && (SameSuit hand.Cards) then
            RoyalFlush |> Some
        else
            None

misterspeedy

    let (|StraightFlush|_|) (hand : Hand) =
        if (SameSuit hand.Cards) && (Consecutive hand.Cards) then
            StraightFlush |> Some
        else
            None

misterspeedy

    let (|FourOfAKind|_|) (hand : Hand) =
        if (RankCounts hand.Cards).[0] = 4 then
            FourOfAKind |> Some
        else
            None

misterspeedy

   /// The possible outcomes when comparing two Poker hands.
    type Outcome = Win | Draw | Lose
        with 
        static member FromRanks (rank1 : Rank) (rank2 : Rank) =
            let sortValue1, sortValue2 = rank1.SortValue, rank2.SortValue
            if sortValue1 > sortValue2 then
                Win
            elif sortValue1 < sortValue2 then
                Lose
            else

misterspeedy

    /// Compare two hands, the first of which can Win, Draw or Lose against the second.
    let CompareHands (hand1 : Hand) (hand2 : Hand) =
        match hand1, hand2 with

        | RoyalFlush, RoyalFlush ->
            raise (ArgumentException("Impossible combination: two Royal Flushes"))
        | RoyalFlush, _ -> Win
        | _, RoyalFlush -> Lose

        | StraightFlush, StraightFlush ->

misterspeedy

           let rank1, rank2 = hand1.Cards.[0].Rank, hand2.Cards.[0].Rank