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(* Some more cases of polymorphism conversion. *)
(* This changes the polymorphism at some level. *)
structure S: sig type 'a t val x: 'a t val f : 'a t -> int val g: int -> 'a t end =
struct
type 'a t = int
val x: 'a t = 1
fun f (n: int): 'a t = n (* int -> 'a t*)
fun g (x :'a t): int = x (* 'a t -> int *)
end;
if S.x = 1 then () else raise Fail "Error";
if S.f S.x = 1 then () else raise Fail "Error";
(* Slightly different version that completely hides the relationship with int. *)
structure S:> sig type 'a t val x: 'a t val f : 'a t -> int val g: int -> 'a t end =
struct
type 'a t = int
val x: 'a t = 1
fun f (n: int): 'a t = n (* int -> 'a t*)
fun g (x :'a t): int = x (* 'a t -> int *)
end;
val x = S.x;
if S.f x = 1 then () else raise Fail "Error";
if S.f S.x = 1 then () else raise Fail "Error";
(* The signature adds polymorphism to a monomorphic function. *)
structure Dispatch:
sig
type 'a union
val Char : word -> 'a union;
end =
struct
type 'a union = word
fun Char (x:word) : 'a union = x;
end;
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