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tokiwoousaka / gist:744595f076137b1402e3
Created December 20, 2014 10:29
{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes #-}
module Main where
----
-- Coyoneda
data CoYoneda f x = forall b. CoYoneda (b -> x) (f b)
instance Functor (CoYoneda f) where
@tokiwoousaka
tokiwoousaka / gist:1a06887f58e7465ef6e9
Last active August 29, 2015 14:10
SeasonalFruitsを「SeasonとFruitのタプル」のリストと定義、即ち、季節と果物の直積の部分集合を表す。SeasonalFruits -> [Season] という型から、query関数はSeasonalFruitsから季節の部分集合への写像であると読める。
module Main where
import Control.Monad
type Season = String
type Fruit = String
type SeasonalFruits = [(Season, Fruit)]
dt :: SeasonalFruits
dt =
[ ("春", "いちご")
@tokiwoousaka
tokiwoousaka / gist:7c7fd14dca71a5da0e2e
Last active August 29, 2015 14:10
import Control.Monad.State
main :: IO ()
main = print $ runState f 1000 --状態の初期値を1000にしてfを実行
f :: State Int ()
f = do
x <- sub1
sub2 x
@tokiwoousaka
tokiwoousaka / gist:c9a073ddb7b64b65495a
Created November 20, 2014 13:48
f :: Maybe Int
f = do
x <- return 5
y <- return 3
return $ x + y
f' :: Maybe Int
f' = do
x <- return 5
@tokiwoousaka
tokiwoousaka / gist:ace99e3a5dcb81c6b67e
Last active August 29, 2015 14:09
Stateにたいして色んな処理が書けるようになったよー https://github.com/tokiwoousaka/reasonable-lens
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Control.Monad.State
import Control.Lens
type StateIO s a = StateT s IO a
data Hoge a = Hoge
{ _foo :: a
, _bar :: String
@tokiwoousaka
tokiwoousaka / gist:d76abdfc1f98d6a8eba8
Last active August 29, 2015 14:08
今度こそ多相型に対応 https://github.com/tokiwoousaka/reasonable-lens
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Control.Lens
import Control.Monad.State
data Hoge = Hoge
{ _Foo :: Int
, _Bar :: String
} deriving (Show, Read, Eq, Ord)
@tokiwoousaka
tokiwoousaka / gist:1a8b72044f6e3a7b5b93
Created October 1, 2014 06:51
Eff.Choose + Eff.State + Lens
{-# LANGUAGE FlexibleContexts, ScopedTypeVariables #-}
{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, UndecidableInstances #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Data.Typeable
import Control.Eff
import Control.Eff.State.Lazy as EST
import Control.Eff.Choose
@tokiwoousaka
tokiwoousaka / gist:944425424107f0f578a3
Created October 1, 2014 05:44
Eff.StateをMonadStateのインスタンスにすればLensが使える
{-# LANGUAGE FlexibleContexts, ScopedTypeVariables #-}
{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, UndecidableInstances #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Data.Typeable
import Control.Eff
import Control.Eff.State.Lazy as EST
import Control.Monad.State.Class (MonadState(..))
@tokiwoousaka
tokiwoousaka / gist:852d512d8ab57ecd5b3d
Last active August 29, 2015 14:02
今更QuickCheckの練習してた
{-# LANGUAGE DeriveFunctor #-}
module Main where
import Test.QuickCheck
import Prelude (($), (.), id)
import Prelude (Integer, Bool)
import Prelude (IO(..), putStrLn)
import Prelude (Show(..), Read(..), Eq(..))
import Prelude (Functor(..), Monad(..))
import Control.Monad
import Control.Applicative
@tokiwoousaka
tokiwoousaka / gist:5875c4a3bf2d0ebcc1a3
Last active August 29, 2015 14:02
無限リストはComonadだってじっちゃが言ってたもんだから・・・
{-# LANGUAGE DeriveFunctor #-}
module Main where
import Control.Applicative
import Test.QuickCheck
import Data.Maybe (fromJust)
class Functor w => Comonad w where
extract :: w a -> a
duplicate :: w a -> w (w a)
extend :: (w a -> b) -> w a -> w b