人様の作品をいじっているだけです

IOSample.fs

open System

//============================================
// IOモナド
//============================================
module IO =
    type IO<'a> = IO of (unit -> 'a)

    type IOBuilder() =
        member this.Bind (IO x, f) = f (x())
        member this.Return x = x
        member this.Delay (f : unit -> 'a) = IO f
    let io = new IOBuilder()

    let run (IO i) = i()

    let read = io { return Console.ReadLine() }
    let putStr str = io { return printf "%s" str }
    let putStrn str = io { return printf "%s\n" str }
    let waitKey = io { return Console.ReadKey true |> ignore }

open IO

//============================================
// エントリポイント
//============================================
let mainIO =
    io {
        do! putStrn "Input your name."
        let! name = read
        do! putStrn ("Hello " + name)
        do! waitKey
    }

[<EntryPoint>]
let main argv = 
    run mainIO
    0