The value restriction

Question

In OCaml you can\'t generalize a partially-applied curried function (the \"value restriction\").

What is the purpose of the value restriction? What unpleasant would

Answer 1

Here is the answer I gave some time ago about F#; the issue is exactly the same with OCaml. The problem is that without it, we would be able to create references that point to the wrong type of data:

let f : 'a -> 'a option =
    let r = ref None in
    fun x ->
        let old = !r in
        r := Some x;
        old

f 3           // r := Some 3; returns None : int option
f "t"         // r := Some "t"; returns Some 3 : string option!!!