view tests/functor.ur @ 1505:8c851e5508a7

Tutorial: up to First-Class Polymorphism
author Adam Chlipala <adam@chlipala.net>
date Sun, 17 Jul 2011 11:00:04 -0400
parents 71bafe66dbe1
children
line wrap: on
line source
signature S = sig
        type t
        val z : t
        val s : t -> t
end

signature T = sig
        type t
        val three : t
end

functor F (M : S) : T where type t = M.t = struct
        type t = M.t
        val three = M.s (M.s (M.s M.z))
end


structure O = F (struct
        type t = int
        val z = 0
        val s = fn x : t => x
end)
val three : int = O.three

structure S = struct
        type t = int
        val z = 0
        val s = fn x : t => x
end
structure SO = F (S)
val three : int = SO.three

structure SS : S = S
structure SSO = F (SS)
val three : SS.t = SSO.three

val main = three