如何在ocaml中定义序列类型 [英] How the sequence type is defined in ocaml

问题描述

type 'a node =
  | Nil
  | Cons of 'a * 'a t

and 'a t = unit -> 'a node

type 'a mappable = 'a t

'a t = unit -> 'a node在类型声明中是什么意思?我认为在ocaml的类型声明中，我们只能进行枚举或调用构造函数. 谢谢

What does 'a t = unit -> 'a node mean in a type declaration? I thought that in a type declaration in ocaml we can only do an enumeration or call a constructor. thank you

推荐答案

unit -> 'a node是不带参数并返回'a node(由'a参数化的节点)的函数的类型.例子:

unit -> 'a node is the type of a function that takes no argument and returns a 'a node (a node parameterized by 'a). Example :

let f () = Nil;;

type 'a t = unit -> 'a node是上述类型的同义词，用于您的代码中定义的第一种类型.

type 'a t = unit -> 'a node makes a synonym of the above type which is used in the first type defined in your code.

let l = Cons (4, fun () -> Cons (3, fun () -> Nil));;
let Cons(_,ll) = l;; (* ok , just for example, it returns a warning due to incomplete pattern matching *)
ll ();; (* - : int node = Cons (3, <fun>) *)

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