在F#中声明类型中的泛型变量

Question

我怎么声明我想要一些'a我没有价值的类型.

type MyType<'a> =
    let mutable something:'a = ??
    let setSomething item:'a =
        something <- a

Answer 1

你可以用Unchecked.defaultof<'a>.也就是说,对我来说更好的方法something是选择'a'.这样,"没有价值"的意图就会变得更加清晰.

type MyType<'a> =
    let mutable something:'a option = None
    let setSomething (item:'a) =
        something <- Some a