F# 判别联合内的匿名记录类型

F#教程包括以下片段：

/// A record for a person's first and last name
type Person = {     
    First : string
    Last  : string
}

/// define a discriminated union of 3 different kinds of employees
type Employee = 
    | Engineer  of Person
    | Manager   of Person * list<Employee>            // manager has list of reports
    | Executive of Person * list<Employee> * Employee // executive also has an assistant

遗憾的是，管理者和执行者的定义现在犯了一个错误：“这个结构被弃用；考虑使用单独的记录类型。”好吧，看起来公平，我们称之为ManagerType。但是等等。。。ManagerType指的是Employee（对于报告部分），Employee指的是ManagerType（对于Manager选项）

这里有解决办法吗？两个数据结构不能相互定义吗？

如果您使用的是F#v3.1，您可以使用（并保护您的敏感度）：

---

相互递归的类型是用

type…=。。。而且：

type Employee = 
    | Engineer  of Person
    | Manager   of Manager 
    | Executive of Executive
and Manager = { Name: Person; Reports: Employee list }
and Executive = { Name: Person; Reports: Employee list; Assistant: Employee}

您可以使用
和
定义相互依赖的类型：

    type Employee = 
    | Engineer  of Person
    | Manager   of Manager            // manager has list of reports
    | Executive of Executive
    and Manager = { Name: Person; Reports: Employee list }
    and Executive = { Name: Person; Reports: Employee list; Assistant: Employee }

从FSharp 4.6开始，您可以与联合体一起使用。因此，您的示例可以这样定义：

type Person = {     
    First : string
    Last  : string
}

type Employee =
    | Engineer of Person
    | Manager of {| Name: Person; Reports: Employee list |}
    | Executive of {| Name: Person; Reports: Employee list; Assistant: Employee |}

很抱歉Lee悄悄地加快了速度：）这个解决方案不错（它确实避免了我虚弱的体质），但是如果我只想从经理那里提取报告，那么在模式匹配表达式中会是什么样子呢？使用其他解决方案，它将是：
|Manager（{Reports=rep}）->无论什么
。我没有安装v3.1，但根据我的答案中链接的MSDN页面，它将是
|Manager（Reports=rep）->……
。它看起来像这个经理（人，报告）。唯一的区别是你可以给他们命名。我们也可以使用继承吗？管理者能从经理那里得到什么？或者这只适用于记录？为了完整性：匿名记录不能进行模式匹配（）。
    type Employee = 
    | Engineer  of Person
    | Manager   of Manager            // manager has list of reports
    | Executive of Executive
    and Manager = { Name: Person; Reports: Employee list }
    and Executive = { Name: Person; Reports: Employee list; Assistant: Employee }

type Person = {     
    First : string
    Last  : string
}

type Employee =
    | Engineer of Person
    | Manager of {| Name: Person; Reports: Employee list |}
    | Executive of {| Name: Person; Reports: Employee list; Assistant: Employee |}