我正在尝试将 Cantor Pairing Function 实现为通用 Pair 类型类的实例,如下所示:
module Pair (Pair, CantorPair) where
-- Pair interface
class Pair p where
pi :: a -> a -> p a
k :: p a -> a
l :: p a -> a
-- Wrapper for typing
newtype CantorPair a = P { unP :: a }
-- Assume two functions with signatures:
cantorPair :: Integral a => a -> a -> CantorPair a
cantorUnpair :: Integral a => CantorPair a -> (a, a)
-- I need to somehow add an Integral a constraint to this instance,
-- but I can't work out how to do it.
instance Pair CantorPair where
pi = cantorPair
k = fst . cantorUnpair
l = snd . cantorUnpair
如何向实例添加适当的积分约束?我有一种模糊的感觉,我可能需要修改 Pair 接口本身,但不知道如何去做。