Both explicit polymorphic annotations and the polymorphic syntax of locally
abstract types are extensions.
http://caml.inria.fr/pub/docs/manual-ocaml/extn.html
See subsections 7.12 and 7.13.

Jacques Garrigue
2013/10/26 10:09 "Norman Hardy" <norm@cap-lore.com>:

>
> On 2013 Oct 25, at 13:44 , Jacques Le Normand <rathereasy@gmail.com>
> wrote:
>
> I'm surprised noone has pointed out the new type annotation syntax:
>
> let id : type s. s -> s = fun x -> x
>
>
> I like that syntax, I think.
> I suppose that "id : type s. s -> s = fun x -> x" is a let-binding
> and that "id : type s. s -> s" is a pattern,
> but I cannot get the syntax at
> http://caml.inria.fr/pub/docs/manual-ocaml/patterns.html
> to produce "id : type s. s -> s”.
>