为什么这段 OCaml 代码不受值限制

Question

不明白函数(my_path_mapper)不受取值限制

# let rec my_map ~f l =
  match l with
    [] -> []
  | h::t -> f h::my_map f t;;
      val my_map : f:('a -> 'b) -> 'a list -> 'b list = <fun>
# let my_path_mapper =
  my_map ["/usr/sbin"; "/usr/bin"; "/sbin"; "/bin"; "/usr/games"; "/usr/local/games"];;
  val my_path_mapper : f:(string -> 'a) -> 'a list = <fun>

请教我为什么？

Answer 1

OCaml 有一个 "relaxed value restriction." 你可以在这里阅读它：

Jacques Garrigue, Relaxing the Value Restriction

这是之前关于 Whosebug 的讨论：

When does the relaxed value restriction kick in in OCaml?

为什么这段 OCaml 代码不受值限制

Why this OCaml code does not subject to the value restriction

ocaml

value-restriction