在F#中的列表上键入扩展名 [英] type extension on a list in F#

问题描述

假设我有一个类型:

let MyType =
    some info
    ...

但是，它通常用于列表中:MyType列表

but, it is commonly used in a list: MyType list

所以我可以定义:

let MyTypeList =
    MyType list

是否可以在MyTypeList上定义类型扩充?

is there a way to define a type augmentation on MyTypeList?

我的实际情况是该类型返回某些工作的结果，它是分批处理的，并且我有一些代码告诉我整个批处理是否正常，部分是否正常或是否出错.如果我可以将扩展名添加到列表类型，则语法会更简单.

my practical case is that the type returns results of some work, it is handled in batches and I have some code that tell me if the whole batch is ok, if it is partially ok, or if everything went wrong. If I could add extensions to the list type, the syntax would be simpler.

 let a : MyTypeList = ...

 if a.IsAllOk() then ...

但是我找不到如何用列表来做到这一点.

but I can't find how to make this with a list.

推荐答案

有在F#中定义类型扩展的两种不同方式.一种选择是通过F#类型扩展，另一种是(与C#兼容)扩展方法.

There are two different ways of definining type extensions in F#. One option is via an F# type augmentation and the other is (C#-compatible) extension method.

扩展方法使您可以为特定类型的实例定义扩展，包括例如 list< MyType> :

The extension method approach lets you define extensions for a specific type instantiation, including for example list<MyType>:

type MyType = { N : int }
type MyTypeList = int list

[<System.Runtime.CompilerServices.Extension()>]
type MyTypeListExtensions() = 
  [<System.Runtime.CompilerServices.Extension()>]
  static member AllOk(l:MyTypeList) = false

let foo (a:MyTypeList) = 
  a.AllOk()

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