compiler-errors - OCaml我在哪里出错？

Question

如何更正此错误？

type 'a drzewo = | Puste | Wezel of 'a * 'a drzewo * 'a drzewo

let rec inorder t =
  match t with
  | Puste -> print_int (-1)
  | Wezel (v, l, r) -> (inorder l; print_int v; inorder r)

let tree =
  (1,
   (Wezel (2, (Wezel (3, Puste, Puste)),
      (Wezel (4, (Wezel (5, Puste, Puste)), Puste)))),
   (Wezel (6, Puste, Puste)))

let _ = inorder tree

和错误日志:

let _ = inorder tree;; Error: This expression has type int * int drzewo * int drzewo but an expression was expected of type int drzewo

Answer 1

问题在这里

let tree =
  (1,
   (Wezel (2, (Wezel (3, Puste, Puste)),
      (Wezel (4, (Wezel (5, Puste, Puste)), Puste)))),
   (Wezel (6, Puste, Puste)))

您没有在前面添加 Wezel。

它应该是:

let tree =
      Wezel (1,
       (Wezel (2, (Wezel (3, Puste, Puste)),
          (Wezel (4, (Wezel (5, Puste, Puste)), Puste)))),
       (Wezel (6, Puste, Puste)))