F# in social gaming (CodeMash 15)

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F# in SocialGamingF# in Social Gaming Yan Cui (@theburningmonk)

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agenda

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Hi, my nameis Yan Cui.

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1MILLION USERS ACTIVE DAILY

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250MILLION DAY PER REQUEST

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why F#?

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time to market

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correctness

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efficient

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tame complexity

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Implementing a slots engine

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Collectables Wager Size Special Symbol AvgWager Size Web Server call

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• Line Win! –X number of matching symbols on adjacent columns! – Positions have to be a ‘line’! – Wild symbols substitute for other symbols! ! • Scatter Win! – X number of matching symbols anywhere! – Triggers bonus game

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What symbols shouldland?! Any special symbol wins?! Did the player win anything?

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What the player’snew average wager?

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Should the playerreceive collectables?

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type Symbol =Standard! of string! ! ! ! | Wild

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type Symbol =Standard! of string! ! ! ! | Wild e.g.! Standard “hat”! ! Standard “shoe”! ! Standard “bonus”! ! …

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type Symbol =Standard! of string! ! ! ! | Wild i.e.! Wild

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! ! ! type Win =LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int

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! ! ! type Win =LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int e.g.! LineWin (5, Standard “shoe”, 4)

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! ! ! type Win =LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int e.g.! ScatterWin (Standard “bonus”, 3)

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type LineNum =int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count

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type LineNum =int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count e.g.! LineWin (5, Standard “shoe”, 4)

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type LineNum =int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count e.g.! ScatterWin (Standard “bonus”, 3)

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make invalid states unrepresentable

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NASA orbiter crashed becauseone engineer accidentally used miles instead of kilometres

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you’re never toosmart to make mistakes

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[<Measure>]! type Pence e.g.! 42<Pence>! !153<Pence>! ! …

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10<Meter> / 2<Second>! = 5<Meter/Second>! 10<Meter> * 2<Second> ! = 20<Meter Second> ! 10<Meter> + 10<Meter> ! = 20<Meter>! 10<Meter> * 10! ! ! = 100<Meter>! 10<Meter> * 10<Meter> ! = 100<Meter2>! 10<Meter> + 2<Second> ! // error! 10<Meter> + 2 ! ! ! // error

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10<Meter> / 2<Second>! = 5<Meter/Second>! 10<Meter> * 2<Second> ! = 20<Meter Second> ! 10<Meter> + 10<Meter> ! = 20<Meter>! 10<Meter> * 10! ! ! = 100<Meter>! 10<Meter> * 10<Meter> ! = 100<Meter2>! 10<Meter> + 2<Second> ! // error! 10<Meter> + 2 ! ! ! // error

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type Wager =int64<Pence>! type Multiplier = int! ! type Payout = Coins! of Wager! ! ! | MultipliedCoins of Multiplier * Wager! ! ! | Multi! of Payout list! ! ! | BonusGame

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type State =! {! AvgWager! : Wager! SpecialSymbol : Symbol! Collectables : Map<Collectable, Count>! }

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New avg wagerGot a Collectable! A pay line win!

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Betting small reducesavg wager! Bonus Game!

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[<Measure>]! type Position! ! type MonopolyBoard=! {! Spaces : MonopolyBoardSpace [ ]! }! member this.Item with ! get (pos : int<Position>) =! this.Spaces.[int pos]

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[<Measure>]! type Position! ! type MonopolyBoard=! {! Spaces : MonopolyBoardSpace [ ]! }! member this.Item with ! get (pos : int<Position>) = ! this.Spaces.[int pos]

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And a payline win! Coin size brought over from main game Houses = multiplier on wins GAME OVER Collected in the bonus game. Gives player extra ‘lives’.

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type BonusGameState =! {! Board! : MonopolyBoard! Position ! : int<Position>! Lives ! : int<Life>! Doubles! : int<Double>! CoinSize! : Wager! TotalWin! : Wager! }

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Coin size broughtover from main game

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And a payline win! Houses = multiplier on wins

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Collected in thebonus game. Gives player extra ‘lives’.

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0<Position>

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let jail =6<Position>

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let rec movenewPos state =! match state.Board.[newPos] with! …! | GotoJail when state.Lives = 0<Life> -> ! ! move jail state |> gameOver! | GotoJail ! ! -> move jail state! …

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let rec movenewPos state =! match state.Board.[newPos] with! …! | RailRoad true ! -> awardRailRoadMultiplier state! | Property n when n > 0 -> awardPropertyMultiplier n state! | ElectricityCompany true! | WaterCompany true -> awardUtilityMultiplier state! …

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let rec movenewPos state =! match state.Board.[newPos] with! …! | CommunityChest! -> playCommunityChestCard state! | Chance ! ! -> playChanceCard state! …

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Recap

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lightweight syntax to createtypes and hierarchies

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great for domain modelling

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make invalid states unrepresentable

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clear, concise wayto handle branching

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better correctness

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order of magnitude increasein productivity

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Stateful Server

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player states arebig

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Stateless Server DatabaseClient

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1:1 read-write ratio

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stateless = ! Inefficient& Expensive

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ServerClient Session 1 Session 2

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ServerClient Database

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Elastic Load Balancer S3 Autoscaling Group Server A Server B ... EC2 CloudFront Stateful Server

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The Actor Model Anactor is the fundamental unit of computation which embodies the 3 things! • Processing! • Storage! • Communication! that are essential to computation.! ! -Carl Hewitt* * http://bit.ly/HoNHbG

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The Actor Model •Everything is an actor! • An actor has a mailbox! • When an actor receives a message it can:! – Create new actors! – Send messages to actors! – Designate how to handle the next message

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Stateful Server • Gatekeeper! –Manages the local list of active workers! – Spawns new workers! ! • Worker! – Manages the states for a player! – Optimistic locking! – Persist state after period of inactivity

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Stateful Server Game Server PlayerA Player B S3 Worker C Worker B Gatekeeper RequestHandlers Asynchronous

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Stateful Server Game Server WorkerC Worker B Gatekeeper Worker A ok RequestHandlers Player A Player B Asynchronous S3

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Stateful Server Game Server S3 WorkerC Worker B Gatekeeper Worker A RequestHandlers Player A Player B Asynchronous

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Stateful Server Game Server S3 WorkerC Gatekeeper Worker A RequestHandlers Player A Player B Asynchronous

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Stateful Server Game Server WorkerC Worker A Gatekeeper error RequestHandlers Player A Player B S3 Asynchronous

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type Agent<‘T> =MailboxProcessor<‘T>! ! ! !

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type Agent<‘T> =MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<…>! | Put of State * Version * AsyncReplyChannel<…>

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type Agent<‘T> =MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<…>! | Put of State * Version * AsyncReplyChannel<…>

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type Result<‘T> =! |Success! of ’T! | Failure! of Exception! ! ! !

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type Result<‘T> =! |Success! of ’T! | Failure! of Exception! ! type GetResult = Result<State * Version>! type PutResult = Result<unit>!

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type Agent<‘T> =MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<GetResult>! | Put of State * Version * AsyncReplyChannel<PutResult>

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type Agent<‘T> =MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<GetResult>! | Put of State * Version * AsyncReplyChannel<PutResult>

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type Worker (playerId)=! let agent = Agent<Message>.Start(fun inbox ->! let state = getCurrentState playerId! ! let rec workingState (state, version) = ! async { … }! and closedState () =! async { … }! ! workingState (state, 1))

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let rec workingState(state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! | None -> ! do! persist state! return! closedState()! …! }!

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non-blocking I/O

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let rec workingState(state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Get(reply)) ->! reply.Reply <| Success(state, version)! return! workingState(state, version)! …! }!

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let rec workingState(state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Put(newState, v, reply)) when version = v ->! reply.Reply <| Success()! return! workingState(newState, version+1)! …! }

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let rec workingState(state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Put(_, v, reply)) ->! reply.Reply <| Failure(VersionMismatch(version, v))! return! workingState(state, version)! }

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let rec workingState(state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! | None ! ! ! ! ! ! ! -> …! | Some(Get(reply)) ! ! ! ! ! -> …! | Some(Put(newState, v, reply)) when version = v ! -> …! | Some(Put(_, v, reply)) ! ! ! ! -> …! }

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and closedState ()= ! async { ! let! msg = inbox.Receive()! match msg with! | Get(reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! | Put(_, _, reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! }

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and closedState ()= ! async { ! let! msg = inbox.Receive()! match msg with! | Get(reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! | Put(_, _, reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! }

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5x efficient improvement

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60% latency drop

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no databases

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need to ensure serveraffinity

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need to balanceload

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need to avoid hotspots

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• Persist playerstate after short inactivity! • Move player to another server after persistence

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need to gracefully scaledown

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Recap

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Agents! • no locks! •async message passing! !

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Agents! • no locks! •async message passing! • self-contained! • easy to reason with

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Agents! • low level! •exceptions kills agents! • primitive error monitoring! • no supervision! • no distribution

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MS Orleans Cricket akka.Net

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Async Workflow! • non-blockingI/O! • no callbacks

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Pattern Matching! • clear& concise

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Replacing a large class hierarchy

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Caught a Gnome

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EXP Item Gold QuestProgress Caught a Gnome

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Level Up Quest Progress EXPItem Gold Caught a Gnome Quest Complete

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Level Up Quest Progress EXPItem Gold Caught a Gnome New Quest Quest Complete

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Quest Progress EXP ItemGold Caught a Gnome Quest Complete New Quest Level Up

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Quest Progress New Quest Achievement Progress EXPItem Gold Quest Complete Level Up Caught a Gnome

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Level Up Quest Progress EXPItem Gold Caught a Gnome Quest Complete New Quest Achievement Progress Achievement Complete

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Level Up Quest Progress EXPItem Gold Caught a Gnome Quest Complete New Quest Achievement Progress Achievement Complete

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100+ actions

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triggered by different abstractionlayers

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non-functional requirements

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message-broker pattern

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting Ignore Process Process Process Process Ignore

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold Process Ignore Ignore Ignore Process Ignore

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold LevelUp

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Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold LevelUp

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need lots offacts

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type Reward =! |GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! ! type StateChange =! | LevelUp! ! of OldLevel * NewLevel! …

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type Fact =! |StateChange! of StateChange! | Reward! ! of Reward! | Trapping! ! of Trapping! | Fishing! ! of Fishing! …

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let process fact=! match fact with! | StateChange(stateChange)! -> …! | Reward(reward)! ! ! -> …! | Trapping(trapping)! ! -> …! …

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C# interop

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…! var fact =Fact.NewStateChange(! ! StateChange.NewLevelUp(oldLvl, newLvl));! …

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type IFact =interface end! ! type Reward =! | GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! interface IFact

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type IFact =interface end! ! type Reward =! | GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! interface IFact

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simple

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flexible

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extensible

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saver

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April 2015

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Fri 8.30am, SalonH @theburningmonk / theburningmonk.com

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Fri 8.30am, SalonH Fri 2.45pm, Guava + Tamarind @theburningmonk / theburningmonk.com

F# in social gaming (CodeMash 15)

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