state-machine/disk.fsx at main · rexkizzy22/state-machine · GitHub

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namespace Disk

(*
    If the DiskType is HardDisk, has 5400 RPM and 5 Platters, return "Seeking loudly and slowly!"
    If the DiskType is HardDisk and has 7 Platters, return "Seeking loudly but quickly!"
    If the DiskType is MMC, return "Seeking quietly and slowly. This disk has %d pins!"
    If the disk is an SSD, return "Already found it!"
    Otherwise, return "Unknown disk".
*)


// Modelling a Disk using a reference type Enum
// type DiskType = HardDisk = 0 | MMC = 1 | SSD = 2

// Modelling a Disk using a value type Enum
[<Struct>]
type DiskType =
    | HardDisk = 0
    | MMC = 1
    | SSD = 2

// Modelling a Disk using a Discriminated Union
type Disk =
    | HardDisk of rpm: int * platters: int
    | MMC of pins: int
    | SSD


module DiskOption =

    type FixedDisk =
        { DiskType: DiskType
          RPM: int option
          Platters: int option
          NumberOfPins: int option }

    let seekRecord disk =
        match disk with
        | { DiskType = DiskType.HardDisk
            RPM = Some 5400
            Platters = Some 5
            NumberOfPins = _ } -> printfn "Seeking loudly and slowly!"
        | { DiskType = DiskType.HardDisk
            RPM = _
            Platters = Some 7
            NumberOfPins = _ } -> printfn "Seeking loudly but quickly!"
        | { DiskType = DiskType.MMC
            RPM = _
            Platters = _
            NumberOfPins = _ } -> printfn $"Seeking quietly and slowly. This disk has %d{disk.NumberOfPins.Value} pins!"
        | { DiskType = DiskType.SSD
            RPM = _
            Platters = _
            NumberOfPins = _ } -> printfn "Already found it!"
        | _ -> printfn "Unknown disk"

    let seek disk =
        match disk with
        | HardDisk(5400, 7) -> printfn "Seeking loudly and slowly!"
        | MMC(pins) when pins = 5 -> printfn $"Seeking quietly and slowly. This disk has %d{pins} pins!"
        | SSD -> printfn "Seeking loudly but quickly!"
        | _ -> printfn "Already found it!"

    let diskInstance = HardDisk(5400, 7)

    seek diskInstance


module DiskUnion =
    type FixedDisk =
        { DiskType: DiskType
          RPM: int
          Platters: int
          NumberOfPins: int }

    let fixedDisk =
        { DiskType = DiskType.MMC
          RPM = 30
          Platters = 45
          NumberOfPins = 23 }

    let seek (disk: DiskType, rpm: int, platters: int, numberOfPins: int) =
        match disk, rpm, platters, numberOfPins with
        | DiskType.HardDisk, 5400, _, 5 -> printfn "Seeking loudly and slowly!"
        | DiskType.HardDisk, _, 7, _ -> printfn "Seeking loudly but quickly!"
        | DiskType.MMC, _, _, _ -> printfn $"Seeking quietly and slowly. This disk has %d{numberOfPins} pins!"
        | DiskType.SSD, _, _, _ -> printfn "Already found it!"
        | _ -> printfn "Unknown disk"

    let seekRecord disk =
        match disk with
        | { DiskType = DiskType.HardDisk
            RPM = 5400
            Platters = _
            NumberOfPins = 5 } -> printfn "Seeking loudly and slowly!"
        | { DiskType = DiskType.HardDisk
            RPM = _
            Platters = 7
            NumberOfPins = 23 } -> printfn "Seeking loudly but quickly!"
        | { DiskType = DiskType.MMC
            RPM = _
            Platters = _
            NumberOfPins = _ } -> printfn $"Seeking quietly and slowly. This disk has %d{disk.NumberOfPins} pins!"
        | { DiskType = DiskType.SSD
            RPM = _
            Platters = _
            NumberOfPins = _ } -> printfn "Already found it!"
        | _ -> printfn "Unknown disk"

    seekRecord fixedDisk