[B! monad] kanbayashiã®ãƒ–ãƒƒã‚¯ãƒžãƒ¼ã‚¯

kanbayashi id:kanbayashi

monadã«é–¢ã™ã‚‹kanbayashiã®ãƒ–ãƒƒã‚¯ãƒžãƒ¼ã‚¯ (11)

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æªœå±±æ£å¹¸ã®ã‚ãƒžã‚¤ãƒ©é£¼è‚²è¨˜ - ä¸–ç•Œã§ä¸€ç•ªã‹äºŒç•ªãã‚‰ã„ã«ã‚„ã•ã—ã„ã€Œãƒ¢ãƒŠãƒ‰å…¥é–€ã€
æ°—ã¾ãã‚Œã¨å¶ç„¶ã¨ãªã‚Šã‚†ãã§ã€ã“ã“2,3å›žã¯ãƒ¢ãƒŠãƒ‰ã‚’è©±é¡Œã«ã—ã¾ã—ãŸã€‚googleã§ã€Œãƒ¢ãƒŠãƒ‰ã€ã‚’å¼•ã„ã¦ã‚¶ãƒƒã¨çœºã‚ã‚‹ã¨ã€ã€Œãƒ¢ãƒŠãƒ‰ã¯ã‚€ãšã‹ã—ã„ãƒ¼ã€ã¨ã‹ã€Œãƒ¢ãƒŠãƒ‰ã§æŒ«æŠ˜ã—ãŸã€ã¿ãŸã„ãªé›°å›²æ°—ãŒæ„Ÿã˜ã‚‰ã‚Œã¦ã€èª¬æ˜ŽèŠ¸äººã®è¡€ãŒå°‘ã—é¨’ãŽã¾ã—ãŸãã€‚ã€Œãªã‚‰ã€äºˆå‚™çŸ¥è˜ã‚¼ãƒã§ãƒ¢ãƒŠãƒ‰ã®èª¬æ˜Žã‚’ã—ã¦ã‚„ã‚ã†ã˜ã‚ƒããƒ¼ã‹ã€ã¨ã€‚ ã‚¿ã‚¤ãƒˆãƒ«ã¯ã ã„ã¶ç…½ã£ã¡ã‚ƒã£ãŸâ€¦â€¦ ã‘ã©ã€ãƒãƒƒã‚¿ãƒªã˜ã‚ƒãªã„ã¤ã‚‚ã‚Šâ€¦â€¦ ã‘ã©ã€å®Ÿéš›ã¯ã©ã†ã‹ãªï¼Ÿ â€»å°åˆ·ã®ã¨ãã¯ã‚µã‚¤ãƒ‰ãƒãƒ¼ãŒæ¶ˆãˆã¾ã™ã€‚ å†…å®¹ï¼š ã¨ã‚Šã‚ãˆãšã€ã‚ãŸã‚Šã•ã‚ã‚Šãªããƒ¢ãƒŠãƒ‰ã®æ¥æ´ã‚’ç´¹ä»‹ã™ã‚‹ ã“ã‚“ãªèª²é¡Œã‚’è€ƒãˆã¦ã¿ã‚ˆã†ï¼šå‰¯ä½œç”¨ä»˜ãè¨ˆç®— ã‚«ã‚¦ãƒ³ãƒˆã‚¢ãƒƒãƒ—ã™ã‚‹é–¢æ•°é” ã‚«ã‚¦ãƒ³ãƒˆã‚¢ãƒƒãƒ—ã—ãŸã„æ„å¿—ã‚’æˆ»ã‚Šå€¤ã§ä¼ãˆã‚‹ ãã‚Œã§ã¯ã€ã„ã£ãŸã„èª°ãŒã‚«ã‚¦ãƒ³ãƒˆã‚¢ãƒƒãƒ—ã‚’ã™ã‚‹ã®ã é–¢æ•°ã®å¼•æ•°ã®åž‹ã‚’Countupåž‹ã«ã¾ã§æ‹¡å¼µã™ã‚‹ ãã—ã¦ã€ã“ã‚ŒãŒãƒ¢ãƒŠãƒ‰ã ã¨ã‚Šã‚ãˆãšã€ã‚ãŸã‚Šã•ã‚ã‚Šãªããƒ¢ãƒŠãƒ‰ã®æ¥æ´ã‚’ç´¹ä»‹ã™ã‚‹ ä»Šã‹ã‚‰ã“ã“ã§èª¬æ˜Žã™ã‚‹ã€Œãƒ¢ãƒŠãƒ‰ï¼ˆmonadï¼‰
kanbayashi 2011/12/18
fmfm

haskell

monad

introduction
ãƒªãƒ³ã‚¯
ãƒ¢ãƒŠãƒ‰ã§æ‚Ÿã‚Šã‚’ã²ã‚‰ããŸã„ã®ãªã‚‰ - å›³ã§ã‚ã‹ã‚‹(?)ãƒ¢ãƒŠãƒ‰ - Pixel Pedals of Tomakomai
åœè«–ã®æœ€å¤§ã®æ¦å™¨ã¯ãƒ€ã‚¤ã‚¢ã‚°ãƒ©ãƒ ãªã®ã§ã€ãƒ¢ãƒŠãƒ‰ã§æ‚Ÿã‚Šã‚’ã²ã‚‰ããŸã„ã®ãªã‚‰ãƒ€ã‚¤ã‚¢ã‚°ãƒ©ãƒ ã‚’ä½¿ãˆã°ã„ã„ã‚“ã˜ã‚ƒãªã„ã§ã—ã‚‡ã†ã‹ã€‚ ãƒ€ã‚¤ã‚¢ã‚°ãƒ©ãƒ ã®æ›¸ãæ–¹ ä¾‹ãˆã°ã€ã€Œ f :: a -> b ã€ã¨ã‹ã€Œlength :: [a] -> Intã€ã¯ä»¥ä¸‹ã®ã‚ˆã†ã«æ›¸ãã¾ã™ã€‚åž‹ã‚’ç‚¹ã§ã€é–¢æ•°ã‚’çŸ¢å°ã§æ›¸ãã¾ã™ã€‚ ãƒ€ã‚¤ã‚¢ã‚°ãƒ©ãƒ ã®åˆ©ç‚¹ã¯ã€fã‚„lengthã®ä¸èº«ã‚’å¿˜ã‚Œã¦ç°¡ç•¥åŒ–ã™ã‚‹ã“ã¨ãŒã§ãã‚‹ã“ã¨ã§ã™ã€‚äººé–“ã®è„³ãŒã§ãã‚‹ã“ã¨ã«ã¯é™ã‚ŠãŒã‚ã‚‹ã®ã§ã€æ³¨ç›®ã™ã‚‹æƒ…å ±ãŒå°‘ãªã„æ–¹ãŒç†è§£ã—ã‚„ã™ããªã‚‹ã£ã¦ã‚¹ãƒ³ãƒãƒ¼ã§ã™ã€‚ ãªãŠã€ åˆæˆ g . f ã¯å›³ç¤ºã™ã‚‹æ™‚ã«é †ãŒé€†ã«ãªã‚‹ã®ã§æ°—ã‚’ã¤ã‘ã¦ä¸‹ã•ã„ã€‚ã“ã‚Œã¯ã€åˆæˆé–¢æ•°ã®é©ç”¨ãŒ g ( f x ) ã¨æ›¸ã‘ã‚‹ã“ã¨ã«ç”±æ¥ã—ã¦ã¾ã™ã€‚ã¾ãšfã‚’é©ç”¨ã—ã€æ¬¡ã«gã‚’é©ç”¨ã™ã‚‹ã¨ã„ã†ã“ã¨ã§ã™ã€‚ return ã¨ >>= ã®å›³ç¤º ä»Šå›žã®ãƒ€ã‚¤ã‚¢ã‚°ãƒ©ãƒ ã®ç´„æŸã¨ã—ã¦ã€å…ƒã¨ãªã‚‹åž‹(Bool, Char, Int ç‰)ã¯æœ€ä¸‹æ®µã«æ›¸ãã¾ã™ã€‚ã
kanbayashi 2011/12/18
illustration

å›³ç¤º

haskell

monad

è‹«å°ç‰§
ãƒªãƒ³ã‚¯
Readerãƒ¢ãƒŠãƒ‰ã‚’è©¦ã—ã¦ã¿ã‚‹ - ã¿ãšã´ãƒ¼æ—¥è¨˜
30åˆ†ãƒ—ãƒã‚°ãƒ©ãƒ ã€ãã®663ã€‚Readerãƒ¢ãƒŠãƒ‰ã‚’è©¦ã—ã¦ã¿ã¾ã—ãŸã€‚ The Reader monadã‚’èªã‚“ã§ãŸã‚‰ã€ç’°å¢ƒãŒã©ã†ã®ã“ã†ã®æ›¸ã„ã¦ã‚ã£ãŸã®ã§ã€ç°¡å˜ãªãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°è¨€èªžã‚’ä½œã£ã¦ã¿ã¾ã—ãŸã€‚ç’°å¢ƒãŒä½¿ã„ãŸã‹ã£ãŸã ã‘ãªã®ã§ã€å¤‰æ•°æŸç¸›ã¨å¤‰æ•°å‚ç…§ã®ã»ã‹ã«ã¯ã€æ•´æ•°ãƒªãƒ†ãƒ©ãƒ«ã¨åŠ ç®—æ¼”ç®—åãã‚‰ã„ã—ã‹ã‚ã‚Šã¾ã›ã‚“ã€‚ å‰ã«èªã‚“ã Haskellã®å…¥é–€æ›¸ã«ã¯ã€Œè¤‡æ•°ã®é–¢æ•°ã§å¼•æ•°ã‚’å…±æœ‰ã—ãŸã„ã¨ãã¯Readerãƒ¢ãƒŠãƒ‰ã‚’ä½¿ã†ã¨ã„ã„ã‚ˆãƒ¼ã€ã¨æ›¸ã„ã¦ã‚ã£ãŸã‘ã©ã€å¾®å¦™ã«é•ã†æ°—ãŒã™ã‚‹ã€‚å…±æœ‰ã§ãã‚‹ã®ã¯å¼•æ•°ä¸€å€‹ã ã‘ã ã—ã€å…±æœ‰ã—ã¦ã‚‹å¤‰æ•°ã‚’æ›¸ãæ›ãˆã‚‹ã“ã¨ã‚‚ã§ãã‚‹ã—ã€‚ ä½¿ã„æ–¹ *Main> runEval $ Int 40 `Add` Int 2 42 *Main> runEval $ Let ("x",Int 1) $ Int 4 `Add` Var "x" 5 ã‚½ãƒ¼ã‚¹ã‚³ãƒ¼ãƒ‰ import Control.Monad.Reader dat
kanbayashi 2011/12/18
monad

reader monad

haskell

mzp
ãƒªãƒ³ã‚¯
Writerãƒ¢ãƒŠãƒ‰ã‚’è©¦ã—ã¦ã¿ãŸ - ã¿ãšã´ãƒ¼æ—¥è¨˜
30åˆ†ãƒ—ãƒã‚°ãƒ©ãƒ ã€ãã®670ã€‚Writerãƒ¢ãƒŠãƒ‰ã‚’è©¦ã—ã¦ã¿ã¾ã—ãŸã€‚ å‰å›žãŒReaderãƒ¢ãƒŠãƒ‰ã ã£ãŸã®ã§ã€ä»Šå›žã¯Writerãƒ¢ãƒŠãƒ‰ã‚’è©¦ã—ã¦ã¿ã¾ã—ãŸã€‚ The Writer monadã«ã¯ã€Writerãƒ¢ãƒŠãƒ‰ã¯è£ã§ãƒã‚°ã‚’ã¨ã£ãŸã‚Šã™ã‚‹ã®ã«ä¾¿åˆ©ã ã¨æ›¸ã„ã¦ã‚ã£ãŸã®ã§ã€é–¢æ•°ã®å‘¼ã³å‡ºã—ã‚’è¨˜éŒ²ã—ã¦ã¿ã¾ã—ãŸã€‚ ä½¿ã„æ–¹ *Main> runWriter $ fib 10 (55,["fib(10)", "fib(9)", "fib(8)", "fib(7)", "fib(6)", "fib(5)", "fib(4)", "fib(3)", "fib(2)", "fib(2)", "fib(3)", "fib(2)", ....]) ã¨ã‚„ã£ã¦ã€æ™®é€šã®ãƒ•ã‚£ãƒœãƒŠãƒƒãƒæ•°ã®å®šç¾©ãŒã€ã„ã‹ã«éžåŠ¹çŽ‡ã‹ã«é©šãã€‚ ãã®ã‚ã¨ã€ *Main> runWriter $ fibi (1,0) 10 (55,["fibi(10)","fi
kanbayashi 2011/12/18
monad

haskell

writer monad
ãƒªãƒ³ã‚¯
Inemuri nezumi diary(2009-01-08) - _ unsafePerformIO ã®ä½¿ç”¨ã¯é™å®šã•ã‚Œã¦ã„ã¾ã™ã€‚ã”åˆ©ç”¨ã¯è¨ˆç”»çš„ã«ã€‚
_ unsafePerformIO ã®ä½¿ç”¨ã¯é™å®šã•ã‚Œã¦ã„ã¾ã™ã€‚ã”åˆ©ç”¨ã¯è¨ˆç”»çš„ã«ã€‚ ã„ãŸã‚‹ã¨ã“ã‚ã§ã€ unsafePerformIO ã‚’è¦‹ã‹ã‘ã‚‹ã‚ˆã†ã«ãªã£ãŸã®ã§ã²ã¨ã“ã¨è¨€ã†ã¨ã„ãŸã‚‹ã‚ã€‚ã€ŒUnsafe ã‚„ã£ã¦æ›¸ã„ã¦ã‚ã‚‹ã€ã‚„ã‚ã€‚ãŠã£ã¨ã€åœ°ãŒå‡ºã¦ã—ã‚‚ãŸã€‚ unsafePeformIO ã¯ã‚‚ã¨ã‚‚ã¨ Haskell ã®è¦æ ¼ Haskell98 ã«ã¯ã‚ã‚Šã¾ã›ã‚“ã€‚åˆã‚ã¦ç¾ã‚ŒãŸã®ã¯ã€ "The Haskell 98 Foreign Function Interface 1.0 An Addendum to the Haskell 98 Report" ã® 5ç¯€ Marshalling ã«ã¤ã„ã¦ã®ã€5.1 ç¯€ Foreign ãƒ¢ã‚¸ãƒ¥ãƒ¼ãƒ«ãŒæä¾›ã™ã‚‹ã‚¤ãƒ³ã‚¿ãƒ¼ãƒ•ã‚§ãƒ¼ã‚¹ã«ã¤ã„ã¦ã§ã™ã€‚ unsafePerformIO :: IO a -> a Return the value resulting from execut
kanbayashi 2011/12/18
monad

haskell

unsafeperformio

st monad

reader monad

writer monad

state monad
ãƒªãƒ³ã‚¯
Data.IORefã‚’ä½¿ã£ã¦ã¿ã‚ˆã† - ã¿ãšã´ãƒ¼æ—¥è¨˜
30åˆ†ãƒ—ãƒã‚°ãƒ©ãƒ ã€ãã®513ã€‚Haskellã§mutableãªå¤‰æ•°ãŒä½¿ãˆã‚‹ã¨è©•åˆ¤ã®Data.IORefã‚’ä½¿ã£ã¦ã¿ãŸã€‚ ã§ã€ã„ã–æ›¸ãæ›ãˆå¯èƒ½ãªå¤‰æ•°ãŒã‚ã‚‹ã¨ãªã‚‹ã¨ã€ãªã‹ãªã‹ã„ã„ã‚µãƒ³ãƒ—ãƒ«ãŒæ€ã„ã¤ã‹ãªã„ã€‚ã—ã‚‡ã†ãŒãªã„ã®ã§ã€ãƒ•ã‚£ãƒœãƒŠãƒƒãƒæ•°ã§é–¢æ•°ãŒä½•å›žå‘¼ã³å‡ºã•ã‚Œã‚‹ã‹ã‚«ã‚¦ãƒ³ãƒˆã™ã‚‹ã‚„ã¤ã‚’ä½œã£ã¦ã¿ãŸã€‚ ã‚ã‚Šã¨Stateãƒ¢ãƒŠãƒ‰ã¨ã®é•ã„ãŒåˆ†ã‹ã‚‰ãªã„ã€‚ ä½¿ã„æ–¹ *Main> fibWithCount 10 (55,177) ã‚½ãƒ¼ã‚¹ã‚³ãƒ¼ãƒ‰ import Data.IORef incr ref = do modifyIORef ref (+1) fib :: IORef Int -> Int -> IO Int fib ref n = do incr ref if n <= 1 then return n else do x <- fib ref (n-1) y <- fib ref (n-2) return $ x
kanbayashi 2011/12/18
haskell

monad

ioref

fibonacci
ãƒªãƒ³ã‚¯
ST ã§ç ´å£Šçš„ãªãƒ’ãƒ¼ãƒ—ã‚½ãƒ¼ãƒˆ - ã‚ã©ã‘ãªã„è©±
ST ãƒ¢ãƒŠãƒ‰ã®ä¸ã§ã¯ã€é…åˆ—ã«å¯¾ã—ã¦ç ´å£Šçš„ãªæ“ä½œãŒã§ãã‚‹ã®ã§ã€è©¦ã—ã«ãƒ’ãƒ¼ãƒ—ã‚½ãƒ¼ãƒˆã‚’ä½œã£ã¦ã¿ã¾ã—ãŸã€‚ãƒ’ãƒ¼ãƒ—ã‚½ãƒ¼ãƒˆã®ã‚¢ãƒ«ã‚´ãƒªã‚ºãƒ ã¯ã€ã€Œç çŽ‰ã®ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°ã€ã‚’å‚è€ƒã«ã—ã¾ã—ãŸã€‚ > x <- randomArray 10 100 > x array (1,10) [(1,71),(2,27),(3,85),(4,6),(5,79),(6,8),(7,58),(8,97),(9,25),(10,89)] > heapSort x array (1,10) [(1,6),(2,8),(3,25),(4,27),(5,58),(6,71),(7,79),(8,85),(9,89),(10,97)] ä»¥ä¸‹ãŒãã®ã‚³ãƒ¼ãƒ‰ã§ã™ã€‚(UArray ã«æŒ‡å®šã™ã‚‹ã‚¤ãƒ³ãƒ‡ãƒƒã‚¯ã‚¹ã‚„å€¤ã®åž‹åˆ¶ç´„ã¯ã†ã¾ãæ›¸ã‘ãªã„ã¿ãŸã„ãªã®ã§ã€åž‹ã‚’æ±ºã‚ã†ã¡ã«ã—ã¦ã„ã¾ã™ã€‚) import Control.Applicative import Cont
kanbayashi 2011/12/18
monad

haskell

st monad

sort

heap sort
ãƒªãƒ³ã‚¯
Stateãƒ¢ãƒŠãƒ‰ã‚’ä»Šåº¦ã“ãç†è§£ã™ã‚‹(3) - Pixel Pedals of Tomakomai
ã•ã‚‰ã«å‰å›žã®ç¶šãã§ã™ã€‚ã“ã‚Œã§æœ€å¾Œã€‚ Stateãƒ¢ãƒŠãƒ‰ã«ãŠã‘ã‚‹ >>= ã®èª¬æ˜Žã¨ã€é–¢æ•°çš„ãªã‚¤ãƒ¡ãƒ¼ã‚¸ã‚’è§£èª¬ã—ãŸã¤ã‚‚ã‚Šãªã®ã§ã™ãŒãƒ»ãƒ»ãƒ»ã€‚ ã†ãƒ¼ã‚“ã€ã“ã‚Šã‚ƒã‚èª¬æ˜Žã®ä»•æ–¹ãŒã¨ã¦ã‚‚ã‚ˆããªã„ã§ã™ã(æ±—ã€‚è§£èª¬ã«é–¢ã—ã¦ã€ã‚‚ã£ã¨ã‚ã‹ã‚Šã‚„ã™ã„ã‚ˆã†ã«ãƒªãƒ™ãƒ³ã‚¸ã—ãŸæ–¹ãŒã„ã„ã‹ã‚‚ã—ã‚Œã¾ã›ã‚“ã€‚ ã¨ã‚Šã‚ãˆãšã€è‡ªåˆ†ã®å‹‰å¼·ã¨ã—ã¦ã¯ãƒ¢ãƒŠãƒ‰ã®çµµçš„ãªã‚¤ãƒ¡ãƒ¼ã‚¸ãŒæŽ´ã‚ãŸã®ã§ã‚ˆã‹ã£ãŸã§ã™ã€‚
kanbayashi 2011/12/16
ç¬¬1å›ž=> http://bit.ly/tHT0wt / ç¬¬2å›ž=>http://bit.ly/uIBGHa

monad

state monad

haskell
ãƒªãƒ³ã‚¯
Subject: [haskell-jp:157] Re: Stateãƒ¢ãƒŠãƒ‰ã‚’ä½¿ã£ãŸå®Ÿä¾‹ã‚³ãƒ¼ãƒ‡ã‚£ãƒ³ã‚°ã¯ï¼Ÿ
From: Jun Mukai <mukai@j...> Date: Wed, 23 Jan 2008 22:27:22 -0800 Subject: [haskell-jp:157] Re: Stateãƒ¢ãƒŠãƒ‰ã‚’ä½¿ã£ãŸå®Ÿä¾‹ã‚³ãƒ¼ãƒ‡ã‚£ãƒ³ã‚°ã¯ï¼Ÿ å‘äº•ã¨ã„ã„ã¾ã™ã€‚ State ãƒ¢ãƒŠãƒ‰ã¯åå‰ãŒæ··ä¹±ã®åŽŸå› ã ã¨æ€ã„ã¾ã™ã€‚ ã“ã‚Œã¯ç§è¦‹ã§ã™ãŒã€ã¾ãšã¯ Writer ãƒ¢ãƒŠãƒ‰ã¨ Reader ãƒ¢ãƒŠãƒ‰ã‚’ç†è§£ã™ã‚‹ã¨ State ãƒ¢ãƒŠãƒ‰ã¯ç†è§£ã—ã‚„ã™ã„ã¨æ€ã£ã¦ã„ã¾ã™ã€‚ã•ã‚‰ã«ã€ãã®å‰æ®µéšŽã¨ã—ã¦ Identity ãƒ¢ãƒŠãƒ‰ã‚‚è¸ã¾ãˆã¦ã„ã‚‹ã¨è¦‹é€šã—ãŒã¯ã£ãã‚Šã—ã¾ã™ã€‚ ä»¥ä¸‹ã€ã¡ã‚‡ã£ã¨é•·ããªã‚Šã¾ã™ãŒã€ã©ã†ã„ã†æ„å‘³ã‹èª¬æ˜Žã—ã¦ã¿ã¾ã™(ã‚ã‹ã‚Šã«ãã‹ã£ ãŸã‚‰ã”ã‚ã‚“ãªã•ã„)ã€‚ Identity ãƒ¢ãƒŠãƒ‰ã¨ã„ã†ã®ã¯ã€é–¢æ•°åˆæˆã®ã“ã¨ã ã¨æ€ã†ã“ã¨ãŒã§ãã¾ã™ã€‚ç´°ã‹ã„ åž‹ã‚’æ°—ã«ã—ãªã‘ã‚Œã°ã€ return x >>= f >>= g ã¯ g (f x
kanbayashi 2011/12/16
ãªã‚‹ã»ã©

monad

state monad

haskell
ãƒªãƒ³ã‚¯
Route 477 - gemcutterã®ä½¿ã„æ–¹ã¾ã¨ã‚ (2009å¹´ç§‹)
â– [haskell] ãƒ¢ãƒŠãƒ‰ã£ã¦çµå±€ãªã‚“ãªã® ç¤¾å†…å‹‰å¼·ä¼šã§ãƒ¢ãƒŠãƒ‰ã«ã¤ã„ã¦ç™ºè¡¨ã—ã¾ã—ãŸã€‚åˆ†ã‹ã£ãŸæ°—ãŒã™ã‚‹ãŸã³ã«ã™ãã«æ‰‹ã‹ã‚‰ã™ã‚Šã¬ã‘ã¦ã—ã¾ã†ã€ãã‚ŒãŒãƒ¢ãƒŠãƒ‰â€¦ï¼ è¿½è¨˜ï¼š ãƒ¢ãƒŠãƒ‰ãã®ã‚‚ã®ãŒä½•ãªã®ã‹ã¨ã‹è€ƒãˆãªã„ã»ã†ãŒã„ã„ã‚“ã˜ã‚ƒãªã„ã§ã™ã‹ãï¼ [Twitter / ã„ãƒ¼ãã‚‹ã¨ã¾ã¨ã‚ˆã‚Šå¼•ç”¨] ã¾ã•ã«ãã®é€šã‚Šã ã¨æ€ã„ã¾ã™(ç¬‘)ã€‚IOã®ä½¿ã„æ–¹ã€Maybeã®ä½¿ã„æ–¹ã€Stateã®ä½¿ã„æ–¹ãªã©ã‚’æŠ¼ã•ãˆã¦ãŠã‘ã°ã€ ä¸ãŒã©ã†ãªã£ã¦ã‚‹ã‹ãªã‚“ã¦çŸ¥ã‚‰ãªãã¦ã‚‚å¤§ä¸ˆå¤«ã€‚ ã§ã‚‚ã€ãƒ¢ãƒŠãƒ‰ã®æŒã¤ã€Œãªã‚“ã‹ç§˜æŠ€ãŒã‚ã‚Šãã†ãªæ„Ÿã˜ã€ãŒã€ä¸ã‚’è¦—ã„ã¦ã¿ãŸãã•ã›ã‚‹ã‚“ã§ã™ã‚ˆãã€‚ ã“ã®ã€ã©ã“ã¾ã§æŽ˜ã£ã¦ã‚‚è‡ªåˆ†ã®çŸ¥ã‚‰ãªã„ã“ã¨ãŒå‡ºã¦ãã‚‹æ„Ÿã˜ãŒHaskellã®é…åŠ›ãªã®ã‹ã‚‚ã€‚ Haskell ã®æœ¬å½“ã«ã™ã”ã„ã¨ã“ã‚ã¯ã€ã€Œãªãœãªã«ã€ã‚’å•ã„ã‹ã‘ã‚‹ã“ã¨ã§ã„ã¤ã¾ã§ã‚‚ãƒ—ãƒã‚°ãƒ©ãƒžãŒæˆé•·ã§ãã‚‹ã¨ã“ã‚ã«ã‚ã‚‹ã€‚ [ãµãã¼ã£ãŸãƒ¼ / ikegami__ã‚ˆã‚Šå¼•ç”¨] ä¸€å•ä¸€ç” Q. ãƒ¢
kanbayashi 2011/12/16
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haskell

monad

state monad
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Stateãƒ¢ãƒŠãƒ‰ - ãŠã£ã±ã„å¤§é”ç¥žã®æ—¥è¨˜
http://itpro.nikkeibp.co.jp/article/COLUMN/20070109/258229/ ã‚ˆã‚Šï¼Ž newtype State s a = State { runState :: s -> (a, s) } instance Monad (State s) where return a = State $ \s -> (a, s) m >>= k = State $ \s -> let (a, s') = runState m s in runState (k a) s' State ãƒ¢ãƒŠãƒ‰å†…ã®å€¤ã¯ã€ã‚ã‚‹åˆæœŸå€¤ã‹ã‚‰ã€(value,newState) ã®ãƒšã‚¢ã¸ã®é·ç§»é–¢æ•°ã¨ã—ã¦è¡¨ç¾ã•ã‚Œã‚‹ï¼Ž Stateã¯s -> (a, s)ã¨ã„ã†åž‹ã‚’æŒã¤é–¢æ•°ã‚’æ ¼ç´ã™ã‚‹ã‚³ãƒ³ãƒ†ãƒŠã§ã™ã€‚ Stateãƒ¢ãƒŠãƒ‰ã®returnã¯ï¼Œaã¨ã„ã†å€¤ã‹ã‚‰\s -> (a, s)ã¨ã„ã†ãƒ©ãƒ ãƒ€æŠ½è±¡ã‚’ä½œã‚Šå‡ºã—ï¼Œ
kanbayashi 2011/12/16
haskell

state monad

monad
ãƒªãƒ³ã‚¯
1