F# code that simulates a lawn tennis game points

fsharp_tennis.fs

#light
open System

type Game()=

    member this.NewScore(winnersScore, othersScore)=
        match winnersScore with
        |"0"    -> "15", othersScore
        |"15"   -> "30", othersScore
        |"30"   -> "40", othersScore
        |"40"   when othersScore = "A" -> "40", "40"
        |"40"   when othersScore = "40"-> "A", "40"
        |"40"   -> "Won", othersScore
        |"A"    -> "Won", othersScore
        |_      -> failwith "Invlaide Score"; "0", "0"

    member this.ChangeScore(score, playerNumber)=
        match playerNumber, score with
        |_, ("Won", _) | _, (_, "Won") -> score
        | 1, (winner, other) -> this.NewScore(winner, other)
        | 2, (other, winner) -> this.NewScore(winner, other) |> fun(a, b) -> (b, a)
        |_  -> failwith "Invalid player"; ("0", "0")

    member this.Play()=
        let rec recPlay score=
            let playerOwn = ((new System.Random()).Next(2) + 1 )
            match score with
            |("Won", _) | (_, "Won") -> score
            |_ ->
                printfn "%A" score 
                printf "P%d\t" playerOwn
                recPlay (this.ChangeScore(score, playerOwn))
        recPlay("0", "0")
        
type Set()=
    member this.TieBreak(score)=
            match ((new System.Random()).Next(2) + 1 ), score with
            |1, (p1, p2) -> (p1 + 1, p2)
            |2, (p1, p2) -> (p1, p2+1)
            |_ -> failwith "TieBreak Error"; (0, 0)

    member this.NewGame(p1Score, p2Score)=
            let result = (new Game()).Play()
            printfn "%A" result

            match result with
            |("Won", _) -> (p1Score + 1, p2Score)
            |(_, "Won") -> (p1Score, p2Score + 1)
            |_ -> failwith "Incomplete Game!";(0,0)

    member this.Play()=
        let rec recPlay(p1Score, p2Score)=
        
            let (newP1Score, newP2Score) = this.NewGame(p1Score, p2Score)
            printfn "Set: %A" (newP1Score, newP2Score)

            if(newP1Score = 6 && newP2Score = 6) then
                this.TieBreak((newP1Score, newP2Score))

            elif (newP1Score > 5 && (newP1Score - newP2Score) >= 2) || (newP2Score > 5 && (newP2Score - newP1Score) >= 2) then
                (newP1Score, newP2Score)

            else recPlay(newP1Score, newP2Score)

        recPlay(0, 0)
             


type Match(minWins)=
    let _minWins = minWins
    member this.IsOver(sets: list<int * int>)=
        match this.WhoWon(sets) with
        |Some(_) -> true
        |None -> false
    
    member this.NewSet()=
        (new Set()).Play()


    member this.Play()=
        let rec recPlay(sets: list<int*int>)=
            let newSets = List.append sets [this.NewSet()] 
            match this.IsOver(newSets) with
            | true -> newSets
            | false -> recPlay(newSets)

        recPlay([])
        
    member this.WhoWon(sets: list<int * int>)=
        if sets.Length < minWins then None
        else
            let p1Sets = List.choose(fun(a,b) -> match (a,b) with
                                        |(x, y) when x > y -> Some(x,y)
                                        | _ -> None) sets
            if(p1Sets.Length >= _minWins) then Some(1)
            elif((sets.Length - p1Sets.Length) >= _minWins) then Some(2)
            else None 

printf "Start\t"
let m = new Match(3)
let sets = m.Play()
let winner = sets |> m.WhoWon
printfn "%A %A" winner sets

ignore(Console.ReadLine())