tokiwoousaka

{-# 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

f :: Maybe Int
f = do
  x <- return 5
  y <- return 3
  return $ x + y


f' :: Maybe Int
f' = do
  x <- return 5

tokiwoousaka

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

module Main where
import Control.Monad

type Season = String
type Fruit = String
type SeasonalFruits = [(Season, Fruit)]

dt :: SeasonalFruits
dt =
  [ ("春", "いちご")

tokiwoousaka

{-# 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

{-# LANGUAGE TemplateHaskell #-}
module Main where
import Control.Monad.State
import Control.Lens

data Point = Point
  { _pointX :: Int
  , _pointY :: Int
  } deriving Show

tokiwoousaka

{-# LANGUAGE RankNTypes #-}
module Main where

type Bool' = forall a. a -> a -> a

true :: Bool'
true = const

false :: Bool'
false = const id

tokiwoousaka

{-# LANGUAGE TemplateHaskell, RankNTypes #-}
module Main where
import Control.Lens
import Control.Monad.State
import Data.List

sample :: [String]
sample =
  [ "hoge"
  , "piyo"

tokiwoousaka

モナド則： (m >>= g) >>= h == m >>= (\x -> g x >>= h)
定義： f >=> g == \x -> f x >>= g
命題：(f >=> g) >=> h == f >=> (g >=> h) 

(f >=> g) >=> h
  == (\x -> f x >>= g) >=> h         -- (>=>)の定義
  == \y -> (\x -> f x >>= g) y >>= h -- (>=>)の定義
  == \y -> (f y >>= g) >>= h
  == \y -> f y >>= (\z -> g z >>= h) -- モナド則
  == \y -> f y >>= (g >=> h)         -- (>=>)の定義

tokiwoousaka

var move_rand_pos = function (obj) {
  obj.x = rand(SCREEN_WIDTH - CHARACTER_WIDTH);
  obj.y = rand(SCREEN_HEIGHT - CHARACTER_HEIGHT);
}