>>522
それ Haskellなら

module State (State, next) where
class State s where
　next :: s -> e -> s

module StateA (StateA(), stateA) where
data StateA = StateA Integer

sateteA = StateS

instance State StateA where
next (StateA i) e = f i e
　　where
　　　f = ...


みたいにすれば良いんじゃね？