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comparison similer.hs @ 4:66609010d477

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Define Similer example as Functor
author Yasutaka Higa <e115763@ie.u-ryukyu.ac.jp>
date Tue, 02 Sep 2014 11:01:25 +0900
parents 3c5fbce357af
children 051c663a4af2
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3:3c5fbce357af 4:66609010d477
11 eta a = Similer a id a 11 eta a = Similer a id a
12 12
13 mu :: (Eq b) => Similer a (Similer b c) -> Similer b c 13 mu :: (Eq b) => Similer a (Similer b c) -> Similer b c
14 mu (Similer a f b) = if (same (f a) b) then b else undefined 14 mu (Similer a f b) = if (same (f a) b) then b else undefined
15 15
16 instance (Eq a) => Monad (Similer a) where 16 double :: Int -> Similer Int Int
17 --return x = Similer x id x 17 double x = Similer (2 * x) id (2 * x)
18 s >>= f = mu (fmap f s) 18
19 twicePlus :: Int -> Similer Int (Similer Int Int)
20 twicePlus x = Similer x double (Similer (x + x) id $ x + x)
21
22 plusTwo :: Int -> Similer Int (Similer Int Int)
23 plusTwo x = Similer x double (Similer (x + 2) id (x + 2))
24
25 hoge :: Eq b => Similer a b -> b
26 hoge (Similer x f y) = if (f x) == y then y else undefined