F# 的血继限界（2）

open System

 

let changeColor clr =

    let orig = Console.ForegroundColor

    Console.ForegroundColor <- clr

 

    // 用对象表达式返回一个实现了 IDisposable 接口的对象

    { new IDisposable with

        member x.Dispose () =

            Console.ForegroundColor <- orig

    }

    

 

[<EntryPoint>]

let main argv =

    Console.WriteLine "原来的颜色"

    do  use clr = changeColor ConsoleColor.Red

        Console.WriteLine "变成红色"

    Console.WriteLine "好贱，又变回来了"

    Console.ReadLine () |> ignore

    0