Dear list,
Consider the following OCaml session.
Objective Caml version 3.12.0
# let f : 'v . 'v -> 'v = fun x -> x;;
val f : 'a -> 'a = <fun>
# let g : 'v . 'v -> 'v = (fun x -> x) (fun x -> x);;
Error: This definition has type 'a -> 'a which is less general than
'b. 'b -> 'b
#
Why doesn't OCaml generalize the type 'a -> 'a? According to the typing rules
in "Principal type-schemes for functional programs" (
http://portal.acm.org/citation.cfm?id=582176 ), the type 'a -> 'a can be
generalized.
Something similar happens in the following OCaml session.
Objective Caml version 3.12.0
# let f : 'v . 'v -> 'v = fun x -> x;;
val f : 'a -> 'a = <fun>
# let h = f f;;
val h : '_a -> '_a = <fun>
# h 1;;
- : int = 1
# h h;;
Error: This expression has type int -> int
but an expression was expected of type int
#
I want the type of h to be \forall 'a . 'a -> 'a. :'(
Best regards,
Ruslán.
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