编程 haskell 使用符号 表示加法,起到加号的作用 例如 Main> 1 2 3

instance Show (a -> b) where
show f = ""
instance Eq (a -> b) where
f == g = False
instance (Integral a, Integral b) => Num (a -> b) where
f + g = x -> f x + g x
f - g = x -> f x - g x
f * g = x -> f x * g x
fromInteger n = m -> fromIntegral m + fromIntegral n
abs f = undefined
signum f = undefined
() :: Int -> Int -> Int
() x y = x + y