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def stateMonad[S]: Monad[({type L[A] = State[S, A]})#L] = {
type StateS[A] = State[S, A]
new Monad[StateS] {
override def unit[A](a: => A): StateS[A] = State(s => (a, s))
override def flatMap[A, B](f: StateS[A])(g: A => StateS[B]): StateS[B] =
State[S, B](
s1 => {
val (a, s2) = f.run(s1)
g(a).run(s2)
}
)
}
}AZ
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newtype Pred a = Pred { check :: a -> Bool }
contrmap :: (a -> b) -> (Pred b -> Pred a)
contrmap f (Pred p) = Pred (p . f)SK
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newtype Pred a = Pred { check :: a -> Bool }
contrmap :: (a -> b) -> (Pred b -> Pred a)
contrmap f (Pred p) = Pred (p . f)к
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newtype Pred a = Pred { check :: a -> Bool }
contrmap :: (a -> b) -> (Pred b -> Pred a)
contrmap f (Pred p) = Pred (p . f)AZ
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