标签:control instance 类型 map class flip 学习 应用 ica
class Bifunctor p => Biapplicative p where
bipure :: a -> b -> p a b
(<<*>>) :: p (a -> b) (c -> d) -> p a c -> p b d
(*>>) :: p a b -> p c d -> p c d
a *>> b = bimap (const id) (const id) <<$>> a <<*>> b
(<<*) :: p a b -> p c d -> p a b
a <<* b = bimap const const <<$>> a <<*>> b
(<<$>>) :: (a -> b) -> a -> b
(<<$>>) = id
Biapplicative 是个类型类。主要用于在二元数据结构上应用 Applicative。
instance Biapplicative (,) where
bipure = (,)
(f, g) <<*>> (a, b) = (f a, g b)
instance Biapplicative Const where
bipure a _ = Const a
Const f <<*>> Const x = Const (f x)
Prelude Data.Biapplicative> ((+2),(*3)) <<*>> (3,4)
(5,12)
Prelude Data.Biapplicative Control.Applicative> Const (+2) <<*>> Const 3
Const 5
Prelude Data.Biapplicative> bimap (+) (*) <<$>> (2,3) <<*>> (3,4)
(5,12)
Prelude Data.Biapplicative Control.Applicative> bimap (+) (*) <<$>> Const 2 <<*>> Const 3
Const 5
(<<**>>) :: Biapplicative p => p a c -> p (a -> b) (c -> d) -> p b d
(<<**>>) = biliftA2 (flip id) (flip id)
biliftA2 :: Biapplicative w => (a -> b -> c) -> (d -> e -> f) -> w a d -> w b e -> w c f
biliftA2 f g a b = bimap f g <<$>> a <<*>> b
biliftA3 :: Biapplicative w => (a -> b -> c -> d) -> (e -> f -> g -> h) -> w a e -> w b f -> w c g -> w d h
biliftA3 f g a b c = bimap f g <<$>> a <<*>> b <<*>> c
Prelude Data.Biapplicative> (2,3) <<**>> ((2^), (3*))
(4,9)
Prelude Data.Biapplicative> biliftA2 (+) (*) (2,3) (4,5)
(6,15)
Prelude Data.Biapplicative Control.Applicative> biliftA2 (+) (*) (Const 2) (Const 3)
Const 5
Haskell语言学习笔记(60)Biapplicative
标签:control instance 类型 map class flip 学习 应用 ica
原文地址:http://www.cnblogs.com/zwvista/p/8016556.html