具有F#函数类型的扩展方法 [英] Extension method with F# function type

问题描述

有关类型扩展的MSDN文档指出:在F#3.1之前，F#编译器不支持使用具有通用类型变量，数组类型，元组类型或F#函数类型作为C#样式的扩展方法.此"参数."( http://msdn.microsoft.com/en-us/library/dd233211.aspx )如何在F#函数类型上使用类型扩展?在什么情况下，此功能有用?

The MSDN doc on Type Extensions states that "Before F# 3.1, the F# compiler didn't support the use of C#-style extension methods with a generic type variable, array type, tuple type, or an F# function type as the "this" parameter." (http://msdn.microsoft.com/en-us/library/dd233211.aspx) How can be a Type Extension used on F# function type? In what situations would such a feature be useful?

推荐答案

以下是您的操作方法:

[<Extension>]
type FunctionExtension() =
    [<Extension>]
    static member inline Twice(f: 'a -> 'a, x: 'a) = f (f x)

// Example use
let increment x = x + 1
let y = increment.Twice 5  // val y : int = 7

现在对于在某种情况下该功能有用吗?"，我实在不知道，我认为这样做可能是个坏主意.函数调用方法感觉太像JavaScript了，在F#中根本不是习惯用法.

Now for "In what situations would such a feature be useful?", I honestly don't know and I think it's probably a bad idea to ever do this. Calling methods on a function feels way too JavaScript-ey, not idiomatic at all in F#.

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