如何使用重载的显式转换运算符? [英] How to use overloaded explicit conversion operators?

问题描述

我在C#中定义了这样的类型:

I have a type defined in C# like this:

struct F {
    public static explicit operator F(long value) {}
    public static explicit operator long(F value) {}
    public static explicit operator F(double value) {}
    public static explicit operator double(F value) {}
    // more conversion operators
}

在F#中，如果我想长时间创建它，我发现的唯一方法是:

In F# if I want to create it from a long, the only way I found is:

let l = F.op_Explicit 3L

我尝试创建一个内联函数以使其变得更好:

I tried creating an inline function to make this nicer:

let inline f a = F.op_Explicit a

但这无法编译.我还尝试了成员约束:

But this doesn't compile. I also tried with a member constraint:

let inline f (x:^a) = (F: (static member op_Explicit : ^a -> F) x) 

那也不会编译.

是否可以定义一个函数或运算符来选择正确的重载?

Is it possible to define a function or operator to choose the right overload?

顺便说一句，它确实可以在相反的方向上很好地工作:

On a side note, it does work nicely in the opposite direction:

let f = someF |> int64 // calls the right conversion operator

推荐答案

在单个具体类型上具有成员约束是无效的.但是，这可能对您有用:

It's not valid to have a member constraint on a single concrete type; however, this might work for you:

let inline f (x:^a) : F =
    let inline g x = ((^b or ^c):(static member op_Explicit : ^b -> ^c) x)
    g x

具有更通用的类型f : ^a -> F when ( ^a or F) : (static member op_Explicit : ^a -> F)，该类型无法使用手动注释任何值！

This has the more general type f : ^a -> F when ( ^a or F) : (static member op_Explicit : ^a -> F), which is a type that is impossible to manually annotate any value with!

这篇关于如何使用重载的显式转换运算符?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！