]>
>I thought I could fix this by saying type 'a t = T of int | Tl of 'a t list, but that seems to constrain (@->) to be 'a t -> 'a t -> 'a t and I lose the cruicial ('a -> 'b) t combinator (not sure if I'm using that word correctly) and I get a type error. Any idea how I could get it to nest?
Okay, I fixed this by introducing another type that didn't need to be parameterized (see below). I guess I should have thought of that earlier. Now my only problem is that I collapse int_t -> (int_t -> int_t) to int_t -> int_t -> int_t, which is correct for languages with currying, but C doesn't curry, so I need to keep those parens around to generate the right type. Not sure how to do this, but I might be able to pull something fancy...gotta think about it. Or, maybe I should left associate, which will make the return type last always, rather than first, and any time I come across a list on the right I should preserve it...
Chris
(* handles nested function types *)
module C:
sig
type 'a t
val int_t : int t
val float_t : float t
(* Begins with @ so it's right-associative :-) *)
val (@->) : 'a t -> 'b t -> ('a -> 'b) t
val get_function : string -> 'a t -> 'a
val print : 'a t -> unit
end =
struct
type tt = T of int | Tl of tt list
type 'a t = tt
let int_t = T 1
let float_t = T 2
let (@->) a b = match a,b with
((T _ as a),(T _ as b)) -> Tl [a;b]
| ((T _ as a),Tl b) -> Tl (a :: b)
| (((Tl _) as a),((Tl _) as b)) -> Tl [a;b]
| (((Tl _) as a),(T _ as b)) -> Tl [a;b]
let get_function s l = Obj.magic s (* just get it to compile *)
let print el =
let rec doprn el =
match el with
T a -> Printf.printf " %d " a
| Tl a -> begin print_string " [ "; List.iter ~f:doprn a; print_string " ] " end
in doprn el
end
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