pred :: Number -> Number
pred (Nr n) = Nr $ \f x -> n (\h g -> g $ h f) (\_ -> x) id
pred :: Number -> Number
pred (Nr n) = Nr $ \f x -> n (\h g -> g $ h f) (\_ -> x) id
pred (Nr n) = Nr $ \f x -> n (\h g -> g $ h f) (\_ -> x) id