重载度量​​运算符 (*) [英] Overloading measure operator (*)

问题描述

我在尝试为 Measure 类型重载 (*) 运算符时卡住了.

I am stuck attempting to overload the (*) operator for a Measure type.

我想看到的是:

> let x = 1.0<i> * 1.0<i>;;

val x : float = -1.0

以下定义似乎可以解决问题:

The following definition appears to do the trick :

> let inline (*) (v1 : float<i>) (v2 : float<i>) = float(-1) * float(v1) * float(v2);;

val inline ( * ) : float<i> -> float<i> -> float

请注意，此示例中的乘积度量正确解析为 <1>，例如在乘以复数的虚数单位时会发生这种情况.如果没有这个重载定义，默认乘积解析为 <我^2>.

Note that the product measure in this example correctly resolves to <1> as which happens for example when multiplying the imaginary unit of a complex number. Without this overloading definition the default product resolves to < i^2>.

但是上面的重载定义有一个令人讨厌的副作用:

But the overloading definition above has the nasty side effect that :

> let y = 1.0 * 1.0;;

let y = 1.0 * 1.0;;
--------^^^

stdin(11,9): error FS0001: This expression was expected to have type
float<i>    
but here has type
float

显然，我的重载定义隐藏了浮点类型的 (*) 运算符.

Apparently my overloading definition hides the (*) operator for the float type.

我做错了什么?

推荐答案

请注意，您正在重新定义 (*) 运算符，而不是重载它.

Note that you are redefining the (*) operator rather than overloading it.

让它工作的诀窍是使用中间类型编写一些东西，如下所示:

The trick to get it working is to write something using an intermediate type, like this:

type Mult = Mult with
    static member        ($) (Mult, v1: float<i>) = fun (v2: float<i>) -> 
                                 float(-1) * float(v1) * float(v2)
    static member inline ($) (Mult, v1      ) = fun v2 -> v1 * v2
    static member        ($) (Mult, v1: Mult) = fun () -> Mult //Dummy overload

let inline (*) v1 v2 = (Mult $ v1) v2

顺便说一句，使用度量单位的有趣方式.

BTW funny way to use units of measure.

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