BikeRuleEngine.fs

// Determine the next command given a current state
let (|SpeedUp|SlowDown|DoNothing|Jump|) bikeState =
    match bikeState, bikeState.Speed with
    | OnTheRunway, TooSlow -> SpeedUp
    | OnTheRunway, TooFast -> SlowDown
    | OnTheRunway, TargetSpeed | InFlight, _ -> DoNothing
    | JustBeforeGap, _ -> Jump
    | AfterGap, _ -> SlowDown

// translate our domain model into a format for the interpreter
match bikeState with
| SpeedUp -> "SPEED"
| SlowDown -> "SLOW"
| DoNothing -> "WAIT"
| Jump -> "JUMP"