迷彩变体类型 [英] Ocaml Variant Types

问题描述

OCaml类型始终使我感到困惑，无论我阅读了什么教程/手册.我需要定义一个类型，比如说test，它确实包含以下形式:

OCaml types have always really confused me no matter what tutorials/manuals I read. I need to define a type, let's say test, that does contains the following forms:

具有以下形式之一的类型('a，'b)测试: 空，T t，N n，Seq [x1 ... xn]

a type ('a, 'b) test that has one of the forms: Empty, T t, N n, Seq [x1...xn]

我知道怎么做前3个，但是我绝对不知道如何定义最后一个形式.这就是我所拥有的:

I know how to do the first 3, but I have absolutely no idea how to define the last form. This is what I have:

type ('nonterm, 'term) test =
   | Empty
   | T of 'term
   | N of 'nonterm
   | ????

对于seq，我需要将子表达式x1的实例匹配为xn.如果x = 0，则为空.有人可以帮我吗?预先感谢.

For seq, I need to match the instances of subexpressions x1 to xn. If x = 0, then this is empty. Can anybody please help me? Thanks in advance.

推荐答案

Seq的子表达式是否也在测试?如果是这样，您可以使用一个列表:

Are the subexpressions of Seq also tests? If so, you can use a list:

type ('nonterm, 'term) test =
  | Empty
  | T of 'term
  | N of 'nonterm
  | Seq of ('nonterm, 'term) test list

列表当然可以为空.

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