在类型中定义选项的正确方法

Question

我正在学习 F# 并尝试创建一个名为 Person 的类型，它具有 4 个属性。其中 2 个（母亲和父亲）是可选的，但不知何故我收到编译器错误。

type Person = {
    name : string;
    age : int;
    mother: Person option -> Person option;
    father: Person option -> Person option;
}

let defaultPerson = {
    name = ""; 
    age = 0; 
    mother = fun person -> person; 
    father = fun person -> person }

let displayPerson person =
    printfn "Name: %s, Age: %d" person.name person.age

let setName person name = 
    { person with Person.name = name }

let setAge person name = 
    { person with Person.name = name }

let setMother person mother = 
    { person with Person.mother = mother }

let setFather person father = 
    { person with Person.father = father }

但是当我尝试下面的代码时，它抛出一个编译器错误：

let mother1 = { 
    Person.name = "Angelica"; 
    age = 47; 
    mother = Option<Person>.None; //mother = None doesn't work 
    father = Option<Person>.None }

Answer 1

我不清楚为什么 mother 和 father 被定义为函数，但您可以使用 fun 关键字设置它们，正如您似乎已经发现的那样：

let mother1 = { 
    Person.name = "Angelica"; 
    age = 47; 
    mother = fun _ -> None;
    father = fun _ -> None }

以下是 Person 更合理的定义吗？

type Person' = {
    Name : string;
    Age : int;
    Mother: Person' option;
    Father: Person' option;
}

这样您就可以定义这样的值：

let mother2 = { 
    Name = "Angelica"; 
    Age = 47; 
    Mother = None;
    Father = None }

在类型中定义选项的正确方法

Correct way of defining option in a type

f#

f#-interactive

f#-3.0