F# 我可以为构建器（如DSL）创建嵌套计算表达式吗？

这就是我想做的：

type DirectionBuilder() =
    member self.Yield(()) = []

    [<CustomOperation("left")>]
    member self.Left (acc, degree) = None

    [<CustomOperation("right")>]
    member self.Right (acc, degree) = None 

    [<CustomOperation("velocity")>]
    member self.Velocity (acc, ()) = new VelocityBuilder()


and VelocityBuilder() = 
    member self.Yield(()) = []

    [<CustomOperation("accelerate")>]
    member self.Accesslarate (acc, v) = None

    [<CustomOperation("decelerate")>]
    member self.Decelerate (acc, v) = None


let direction () = new DirectionBuilder()

direction() {
    right 90
    left 30
    velocity() {
        accelerate 1
    }
}

---

有没有办法向F#解释一下，这个自定义操作确实应该接受一个计算表达式？

我想有一种方法几乎可以得到您想要的语法。您使

velocity

操作接受VelocityBuilder生成的类型-在您的情况下，它似乎是一个

选项

。然后创建一个单独的计算并传入

你会得到这样的结果：

type DirectionBuilder() =
    member self.Yield(()) = []

    [<CustomOperation("left")>]
    member self.Left (acc, degree) = None

    [<CustomOperation("right")>]
    member self.Right (acc, degree) = None 

    [<CustomOperation("velocity")>]
    member self.Velocity (acc, odd: 'a option) = None


type VelocityBuilder() = 
    member self.Yield(()) = []

    [<CustomOperation("accelerate")>]
    member self.Accelerate (acc, v) = None

    [<CustomOperation("decelerate")>]
    member self.Decelerate (acc, v) = None

let dir = new DirectionBuilder()
let vel = new VelocityBuilder()

dir {
    right 90
    left 30
    velocity (vel {
        accelerate 1
    })
}

type DirectionBuilder（）=
成员自身收益率（（））=[]
[]
左侧成员自身（acc，学位）=无
[]
成员自身权利（acc，学位）=无
[]
成员自身速度（acc，奇数：'a选项）=无
键入VelocityBuilder（）=
成员自身收益率（（））=[]
[]
成员自加速（acc，v）=无
[]
构件自身减速（acc，v）=无
let dir=new DirectionBuilder（）
设vel=new VelocityBuilder（）
迪尔{
对90
左30
速度（vel）{
加速1
})
}

这就是说，如果您开始编写计算工作流，那么您可能应该首先设计一个类型来表示您的计算状态。现在你有糖，但没有肉；）

一旦你有了一个类型，如果它被证明是有用的，那么一个工作流就可以从中产生

type DirectionBuilder() =
    member self.Yield(()) = []

    [<CustomOperation("left")>]
    member self.Left (acc, degree) = None

    [<CustomOperation("right")>]
    member self.Right (acc, degree) = None 

    [<CustomOperation("velocity")>]
    member self.Velocity (acc, odd: 'a option) = None


type VelocityBuilder() = 
    member self.Yield(()) = []

    [<CustomOperation("accelerate")>]
    member self.Accelerate (acc, v) = None

    [<CustomOperation("decelerate")>]
    member self.Decelerate (acc, v) = None

let dir = new DirectionBuilder()
let vel = new VelocityBuilder()

dir {
    right 90
    left 30
    velocity (vel {
        accelerate 1
    })
}