“选项列表”和“列表”之间的OCaml区别

Question

将此功能输入OCaml顶级时，我得到以下结果。输入似乎与我相同，除了::运算符周围的空白。任何人都可以在这里解释'a option list和'a option之间的区别吗？

# let rec at i = function
  | [] -> None
  | h::t -> if i = 1 then Some h else at (i-1) t;;
    val at : int -> 'a option list -> 'a option = <fun>
# let rec at i = function
  | [] -> None
  | h :: t -> if i = 1 then Some h else at (i-1) t;;
    val at : int -> 'a list -> 'a option = <fun>

Answer 1

这就是我所看到的：

$ ocaml
        OCaml version 4.01.0

# let rec at i = function
  | [] -> None
  | h::t -> if i = 1 then Some h else at (i-1) t;;
val at : int -> 'a list -> 'a option = <fun>
# let rec at i = function
  | [] -> None
  | h :: t -> if i = 1 then Some h else at (i-1) t;;
val at : int -> 'a list -> 'a option = <fun>

在我看来，你的实验在某种程度上存在缺陷。 ::周围的间距不会产生任何影响。