> type _ t =
> | IntLit : int -> int t
> | BoolLit : bool -> bool t
> | Pair : 'a t * 'b t -> ('a * 'b) t
> | App : ('a -> 'b) t * 'a t -> 'b t
> | Abs : ('a -> 'b) -> ('a -> 'b) t
> There's something "Haskellish" about this syntax, in the sense that type
> constructors are portrayed as being like functions.
Indeed IIRC OCaml does not accept "App" as an expression (you have to
provide arguments to the construct). Maybe this is a good opportunity
to lift this restriction.
It was actually the case in Caml Light : each datatype constructor implicitly declared a constructor function with the same name. I don't exactly know why this feature was dropped in Objective Caml, but I think I remember (from a previous discussion) that people weren't sure it was worth the additional complexity.
Note that, as in Jacques's examples, the constructor function was not curryfied. (type t = A of bool * int) would generate a function (A : bool * int -> t). It doesn't help the already tricky confusion between (A of bool * int) and (A of (bool * int))...
By the way, it is unclear if
| App : ('a -> 'b) t -> 'a t -> 'b t
would be accepted in Jacques proposal. If not, I think going back to a "of ..." syntax would be wiser.