let p s n = print_string (s^string_of_int n^"\n"); flush stdout

module type AccArgT = sig
    type t and t1
    val init: t
    val f: t -> t1 -> t
end

module AccArgInt(I:sig val init:int val f:int->int->int end) = struct
    type t = int and t1 = int
    let init = I.init and f = I.f
end

(*version 1*)
module Acc(T:AccArgT) = struct
    let vR = ref T.init
    let func = T.f
    let app x =
	let newX = func !vR x in
	vR := newX;newX
end

module F1 = Acc(AccArgInt(struct let init = 0 and f = (+) end))

let _ = p "f1:" (F1.app 1)
let _ = p "f1:" (F1.app 1)
let _ = p "f1:" (F1.app 1)

(*version 2*)
module Acc1(T:AccArgT) = struct
    module A = Acc(T)
    include A
    let init x = vR:=x
end

module F2 = Acc1(AccArgInt(struct let init = 0 and f = (+) end))

let _ = p "f2:" (F2.app 1)
let _ = p "f2:" (F2.app 1)
let _ = p "f2:" (F2.app 1)
let _ = F2.init (-5)
let _ = p "f2:" (F2.app 1)
let _ = p "f2:" (F2.app 1)
let _ = p "f2:" (F2.app 1)