System.Version不会F＃中实现System.IComparable [英] System.Version doesn't implement System.IComparable in F#

问题描述

我要排序版本序列 F＃中的对象：

I want to sort a sequence of Version objects in F#:

let maxVersion =
    versions
    |> Seq.max (fun version -> version)

编译器生成以下错误消息：

The compiler produces the following error message:

类型'（SEQ - >'一）不支持比较的约束。例如，它不支持'System.IComparable'接口

The type '(seq -> 'a)' does not support the 'comparison' constraint. For example, it does not support the 'System.IComparable' interface

当我在Visual Studio中打F12来看看版本的元数据它说，版本只工具 ICloneable ，而不是 IComparable的。但是，当我去 sourceof.net 它说，它实现 IComparable的以及一些其他接口。

When I hit F12 in Visual studio to take a look at the metadata of Version it says that Version only implements ICloneable, but not IComparable. But when I go to sourceof.net it says it implements IComparable as well as some other interfaces.

难道F＃使用不同版本的.NET框架？

Does F# use a different version of the .NET framework?

推荐答案

该错误信息是告诉你，（SEQ - >'一）不执行 IComparable的，因为（SEQ - >'一）。是一个函数，而不是一个序列

The error message is telling you that (seq->'a) does not implement IComparable which is true since (seq->'a) is a function, not a sequence.

如果你看一下 Seq.max的签名只需要在序列参数。 删除的λ（FUN版 - >版本）。，它应该是正常的。

If you look at the signature of Seq.max it takes only the sequence as parameter. Remove the lambda (fun version -> version) and it should be alright.

另外，如果你想申请一个密钥生成器功能的排序，而不是使用 Seq.maxBy

Otherwise, if you want to apply a key generator function for the sort, use instead Seq.maxBy

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