Help. T^T Some Problems encountered when I tried to Implement Map Module

Learning
1

I tried to use AVL to write a map module myself, but an error was reported when using it.
The Make module written by myself has been introduced before,
and the example is as follows:

module Order_int_string: MyOrderType = struct
   type t = int
   let compare key1 key2 =
     key1 - key2
end

module MyMap = Make(Order_int_string)

let map_tree1 =
   let open MyMap in
   empty

let map_tree2 =
   let open MyMap in
   empty
   |> add 1 "1"

In add 1 “1” on the last line,
The error is reported as:
int
This expression has type int but an expression was expected of type key ocamllsp.

Try to compile, the error is:
File “test_tmp/bsts_test.ml”, line 156, characters 9-10:
156 | |> add 1 “1”
^
Error: This expression has type int but an expression was expected of type key
I copied the map.ml in the standard library intact, and the above example still reported the same error.

questions

May I ask how to operate to infer the type of key as int?
Why is there no problem using the standard library directly?

2

Most likely by omitting the type annotation from the module definition:

module Order_int_string = struct
   type t = int
   let compare key1 key2 =
     key1 - key2
end

Why is there no problem using the standard library directly?

Most likely because the type annotation was omitted.

2 Likes
3

ohhhhhh!!!
it works!!!
Thank you very much

1 Like