尝试扩展结果类型..在F#中失败 [英] trying to extend the result type.. unsuccesfully, in F#

问题描述

现在，当我有一个Result类型时，似乎需要进行匹配以查找是否可以.

Right now, when I have a Result type, it seems like I need to do a match to find if it is ok, or not.

因此，我正在尝试简化此操作以使其能够使用，例如:

So, I am trying to simplify this to be able to use if, like that:

let a : Result<string, string> = ...
if a.IsOk then ....

这是我的尝试

[<AutoOpen>]
module ResultHelper =
    type Result with
        member this.IsOk =
            match this with
            | Ok _    -> true
            | Error _ -> false

但这不会编译.

使用:

    type Result<_, _> with

也没有帮助

我该如何实现?

推荐答案

正确的语法是为类型参数命名.另外，如果需要，您可以在代码中引用它们.

The correct syntax is to give the type parameters names. As a bonus, this will allow you to refer to them in the code if you need to.

type Result<'a, 'b> with
    member this.IsOk =
        match this with
        | Ok _    -> true
        | Error _ -> false

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P.S.为了将来，请注意，将不会编译"对问题的描述不是很好.请确保始终包含完整的错误消息.

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P.S. For the future, please note that "will not compile" is not a good description of a problem. Please make sure to always include the full error message.

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