sig
class virtual ['i, 'o] start :
object ('a)
method private virtual guard : ('a, 'i, 'o, unit) Cf_state_gadget.guard
method start : ('s, 'i, 'o, unit) Cf_state_gadget.t
end
class virtual ['i, 'o] next :
object ('b)
method private virtual guard : ('b, 'i, 'o, unit) Cf_state_gadget.guard
method next : ('b, 'i, 'o, 'a) Cf_state_gadget.t
end
end