CODEWITHSUNDEEP
compiler-errorsocaml
user3077133
user3077133

Reputation: 219

OCaml Where did I make an error?

How to correct this error ?

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

And the log of error:

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

Upvotes: 0

Views: 74

Answers (2)

Jackson Tale
Jackson Tale

Reputation: 25812

The problem is here

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

You didn't add Wezel in front.

It should be:

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

Upvotes: 1

rafix
rafix

Reputation: 1749

Your error message is already very informative, just carefully re-read it again. The type of 'tree' is 'int * int drzewo * int drzewo' (a triple), but it must be 'int drzewo' (because inorder has type 'int drzewo -> unit').

So just correct it:

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

Upvotes: 0

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