Refactoring Ruby with Monads
Contents Introduction Stacks Collections Abstract data types Refactoring Handling nil Multiple results Asynchronous code Monads Conclusion Introduction Hello! I’m going to tell you about monads, and how we can uncover them by refactoring our Ruby code. The ideas in this article might be unfamiliar, so before we get stuck into the details, let’s warm our brains up with something simple. People alwa
モナドトランスフォーマー・ステップ・ãƒã‚¤ãƒ»ã‚¹ãƒ†ãƒƒãƒ—(Monad Transformers Step By Step) - ã‚Šã‚“ã”ãŒã§ã¦ã„ã‚‹
著者ã®Martin Grabmülleræ°ã«è¨±å¯ã‚’ã„ãŸã ãã¾ã—ãŸã®ã§ã€ Haskellモナドトランスフォーマーã®ãƒãƒ¥ãƒ¼ãƒˆãƒªã‚¢ãƒ«ã‚’翻訳ã—ãŸã‚‚ã®ã‚’公開ã—ã¾ã™ã€‚ タイãƒã‚„誤訳ã€ãƒ—ãƒã‚°ãƒ©ãƒ ã®ãƒŸã‚¹ç‰ã‚ã‚Šã¾ã—ãŸã‚‰ã€ Twitterå®›@bicycle1885ã‹ã‚³ãƒ¡ãƒ³ãƒˆæ¬„ã¾ã§ã”é€£çµ¡é ‚ã‘ã‚‹ã¨ã‚ã‚ŠãŒãŸã„ã§ã™ã€‚ å…ƒã®ãƒ†ã‚ストやプãƒã‚°ãƒ©ãƒ ã¯ä»¥ä¸‹ã®ãƒªãƒ³ã‚¯ã‹ã‚‰å¾—られã¾ã™ã€‚ Monad Transformers Step by Step [2012/12/19] 誤りを多数訂æ£ã—ã¾ã—ãŸã€‚id:qtamakiã•ã‚“ã€ã‚ã‚ŠãŒã¨ã†ã”ã–ã„ã¾ã™ã€‚ [2014/6/19] 誤りを2点訂æ£ã—ã¾ã—ãŸã€‚id:daimatzã•ã‚“ã€id:hitotakuchanã•ã‚“ã€ã‚ã‚ŠãŒã¨ã†ã”ã–ã„ã¾ã™ã€‚ Monad Transformers Step by Step Martin Grabmüller Oct 16 2006 概è¦(Abstract) ã“ã®
Functors, Applicatives, And Monads In Pictures - adit.io
Written April 17, 2013 updated: May 20, 2013 Here's a simple value: And we know how to apply a function to this value: Simple enough. Lets extend this by saying that any value can be in a context. For now you can think of a context as a box that you can put a value in: Now when you apply a function to this value, you'll get different results depending on the context. This is the idea that Functors
Why free monads matter
Interpreters Good programmers decompose data from the interpreter that processes that data. Compilers exemplify this approach, where they will typically represent the source code as an abstract syntax tree, and then pass that tree to one of many possible interpreters. We benefit from decoupling the interpreter and the syntax tree, because then we can interpret the syntax tree in multiple ways. For
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家ã®ãªã‹ã‚’森ã«ã—ãŸã„ã€ã¨ã„ã†æ¬²æœ› 今年ã¯ãªã‚“ã ã‹è¦³è‘‰æ¤ç‰©ã®è¦³å¯ŸãŒæ¥½ã—ã„。本日ã¯æ¤ç‰©ã«ã¤ã„ã¦ã®è¨˜äº‹ã§ã™ãŒã€åœŸã‚„æ ¹ã£ã“ãªã©ã®ç”»åƒã‚‚ã‚ã‚‹ã®ã§è‹¦æ‰‹ãªæ–¹ã¯é¿ã‘ã¦ãã ã•ã„ã。 フィカス・ウンベラータ ã†ã¡ã®ãƒ¡ã‚¤ãƒ³çš„å˜åœ¨ã¯ãƒ•ã‚£ã‚«ã‚¹ãƒ»ã‚¦ãƒ³ãƒ™ãƒ©ãƒ¼ã‚¿ã€‚ウンベ殿ãŒæˆ‘ãŒå®¶ã«ã‚„ã£ã¦ããŸã®ã¯2020å¹´5月。コãƒãƒŠç¦åˆâ€¦
Programming Haskell Chapter8
The document describes how to build a parser for Backus-Naur Form (BNF) grammars in Haskell using the attoparsec parsing library. It defines types and parsers to represent BNF syntax, rules, expressions, lists and terms. The parsers use functions like spaces, string, text from attoparsec to parse individual components and combine them using operators like <*>, <|> to build up the full BNF grammar
QAã§å¦ã¶Monad - ã‚ã©ã‘ãªã„話
ã“ã®è¨˜äº‹ã¯ã€Monad ã§ã¤ã¾ã¥ã„㟠Haskeller ã®ãŸã‚ã® Monad å†å…¥é–€ã§ã™ã€‚ Monadã¨ã¯ä½•ã§ã™ã‹ï¼Ÿ Monad ã¨ã¯ã€å˜ãªã‚‹åž‹ã‚¯ãƒ©ã‚¹ã®ä¸€ã¤ã§ã™ã€‚難ã—ã„ã¨ã„ã†é¢¨è©•ã‚‚ã‚ã‚Šã¾ã™ãŒã€ãれ以上ã§ã‚‚ãれ以下ã§ã‚‚ã‚ã‚Šã¾ã›ã‚“。 ã“ã®åž‹ã‚¯ãƒ©ã‚¹ã®ãƒ¡ã‚½ãƒƒãƒ‰ã¯ã€return 㨠>>= ã§ã™ã€‚ class Monad m where (>>=) :: m a -> (a -> m b) -> m b return :: a -> m a ã¤ã¾ã‚Šã€ä»¥ä¸‹ã‚’満ãŸã™åž‹ã®é›†åˆãŒ Monad ã§ã™ã€‚ m a ã§è¡¨ç¾ã§ãるよã†ã«ä¸€ã¤ã®åž‹å¤‰æ•°ã‚’æ ¼ç´ã™ã‚‹ã‚³ãƒ³ãƒ†ãƒŠåž‹ >>= 㨠return を実装 return ã¯æ–°ã—ã„コンテナを作りã€>>= ã¯äºŒã¤ã®ã‚³ãƒ³ãƒ†ãƒŠã‚’åˆæˆã—ã¾ã™ã€‚ Monad ã®ã‚¤ãƒ³ã‚¹ã‚¿ãƒ³ã‚¹ã¯å¤±æ•—ç³»ã¨çŠ¶æ…‹ç³»ã«å¤§åˆ¥ã§ãã¾ã™ã€‚以下ã«ä»£è¡¨çš„ãªã‚¤ãƒ³ã‚¹ã‚¿ãƒ³ã‚¹ã‚’示ã—ã¾ã™ã€‚ 失敗系: Maybeã€[] (リスト)
Applicativeã®ã‚¹ã‚¹ãƒ¡ - ã‚ã©ã‘ãªã„話
ã“ã®è¨˜äº‹ã®ç›®çš„ã¯ã€Applicative 信者ã«ã‚ˆã‚‹ Applicative スタイルã®å¸ƒæ•™ã§ã™ã€‚ ç°¡æ½”ã«çµè«–ã‚’è¿°ã¹ã‚‹ã¨ã€ foo = do a <- m1 b <- m2 return (f a b) ã®ã‚ˆã†ãªã‚³ãƒ¼ãƒ‰ã‚’書ããŸããªã£ãŸã‚‰ foo = f <$> m1 <*> m2 ã¨æ›¸ãã¾ã—ょã†ã¨ã„ã†ã“ã¨ã€‚ åˆã„言葉ã¯ã€ã€Œdo 㨠return ã‚’ãªãã›ï¼ã€ã§ã™ã€‚ Functorã¨Monadã®é–“ Functor を特殊化ã—ãŸåž‹ã‚¯ãƒ©ã‚¹ãŒMonadã§ã€Monadã®æ–¹ãŒå¼·åŠ›ã§ã™ã€‚ãªãœãªã‚‰ã€ãƒ¡ã‚½ãƒƒãƒ‰ãŒå¢—ãˆã‚‹ã‹ã‚‰ã§ã™ã€‚ Functorã®ãƒ¡ã‚½ãƒƒãƒ‰ã¯fmapã§ã™ã€‚fmapã®åˆ¥åã‚’ (<$>) ã¨ã„ã„ã¾ã™ã€‚(ã“ã®è¨˜äº‹ã§ã¯ã€(<$>) 㨠liftM ã‚’åŒä¸€è¦–ã—ã¾ã™ã€‚) ãã—ã¦ã€Monadã®ãƒ¡ã‚½ãƒƒãƒ‰ã¯ã€ã”å˜çŸ¥ã®é€šã‚Š (>>=) 㨠return ã§ã™ã€‚ Functorã¨Monadã®é–“ã«Applicative
All About Monads モナドã®ã™ã¹ã¦
モナドã®ã™ã¹ã¦ Haskell ã«ãŠã‘るモナドプãƒã‚°ãƒ©ãƒŸãƒ³ã‚°ã®ç†è«–ã¨å®Ÿè·µã«é–¢ã™ã‚‹åŒ…括的ガイド Version 1.1.0 ã“ã®ãƒãƒ¥ãƒ¼ãƒˆãƒªã‚¢ãƒ«ã¯ã€ãƒ¢ãƒŠãƒ‰ã®æ¦‚念ã¨ãã®é–¢æ•°ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°ã«ãŠã‘る応用㫠ã¤ã„ã¦ã€åˆä¸ç´šã® Haskell プãƒã‚°ãƒ©ãƒžã«ã‚ã‹ã‚Šã‚„ã™ãã€åˆ©ç”¨ä¾¡å€¤ãŒã‚るよã†ãª 解説をã™ã‚‹ã“ã¨ã‚’æ—¨ã¨ã—ã¦ã„ã¾ã™ã€‚èªè€…㯠Haskell ã«ãªã‚Œã¦ã„ã‚‹ã“ã¨ã‚’å‰æ㨠ã—ã¾ã™ãŒã€ãƒ¢ãƒŠãƒ‰ã«é–¢ã™ã‚‹çµŒé¨“ã¯è¦æ±‚ã—ã¦ã„ã¾ã›ã‚“。ã“ã®ãƒãƒ¥ãƒ¼ãƒˆãƒªã‚¢ãƒ«ã¯ã€å¤š ãã®é¡Œæã‚’ã‚«ãƒãƒ¼ã—ã¦ã„ã¾ã™ã€‚後åŠã®ã‚»ã‚¯ã‚·ãƒ§ãƒ³ã§ã¯ã€å‰åŠã®é¡Œæをよãç†è§£ã— ã¦ã„ã‚‹ã“ã¨ã‚’å‰æã¨ã—ã¾ã™ã€‚é †ã‚’ãŠã£ã¦ã€ãƒ¢ãƒŠãƒ‰ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°ã‚’例示ã™ã‚‹ãŸã‚ ã®ã‚µãƒ³ãƒ—ルコードãŒãŸãã•ã‚“用æ„ã•ã‚Œã¦ã„ã¾ã™ã€‚一èªã§ã€ã™ã¹ã¦ã®é¡Œæã‚’å¸åŽã— よã†ã¨ã„ã†ã®ã¯ãŠå‹§ã‚ã§ãã¾ã›ã‚“。 ã“ã®ãƒãƒ¥ãƒ¼ãƒˆãƒªã‚¢ãƒ«ã¯ 3 ã¤ã®éƒ¨åˆ†ã§æ§‹æˆã•ã‚Œã¦ã„ã¾ã™ã€‚最åˆã®éƒ¨åˆ†ã¯ã€ 関数プãƒã‚°ãƒ©ãƒŸãƒ³ã‚°ã«ãŠã‘るモナドã®åŸºæœ¬çš„
図ã§ã‚ã‹ã‚‹(?)モナド ãŠã¾ã‘: 図ã‹ã‚‰ã‚³ãƒ¼ãƒ‰ã‚’書ã - Pixel Pedals of Tomakomai
最後ã«å‡ºã—ãŸä¾‹ã§ã™ãŒã€ module Main where main :: IO () main = getLine >>= putStrLn . reverse モナドã§æ‚Ÿã‚Šã‚’ã²ã‚‰ããŸã„ã®ãªã‚‰ - 図ã§ã‚ã‹ã‚‹(?)モナド ã•ãã»ã©ã®ã‚¨ãƒ³ãƒˆãƒªã®å›³ãŒå…¨éƒ¨ã‚ã‹ã‚Œã°ã€ä»¥ä¸‹ã®ã‚ˆã†ãªå›³ã‚‚書ã‘ã¾ã™ã。reverseã‚’fmapã§æŒã¡ä¸Šã’ã¦æ©‹ã‚’架ã‘ã€è½ã¡ã¦ã„ã‚‹putStrã®å·¦ç«¯ã‚’>>=ã§åŠã‚‹ã—上ã’ã¾ã™ã€‚ã“ã®å›³ã§ã§ãã‚‹IO Stringã‹ã‚‰IO ()ã¸ã®é–¢æ•°ã¯ã€ãƒ¢ãƒŠãƒ‰ã®æ€§è³ª(≒å¯æ›æ€§)ã‹ã‚‰ã€ã‚ã‚ŠãŒãŸã„ã“ã¨ã«æœ€åˆã®å›³ã§ã§ãる関数ã¨åŒã˜ã«ãªã‚Šã¾ã™ã€‚ ã“ã®å›³ã‹ã‚‰ã€ä»¥ä¸‹ã®ã‚³ãƒ¼ãƒ‰ãŒæ›¸ã‘ã¾ã™ã€‚ module Main where main :: IO () main = fmap reverse getLine >>= putStrLn Haskellã§ã¯é–¢æ•°é–“ã®åž‹ãŒã‚ã†ã‚ˆã†ã«ã‚³ãƒ¼ãƒ‡ã‚£ãƒ³ã‚°ã‚’ã™ã‚‹ã“ã¨ãŒå¤šã„ã¨æ€ã„ã¾ã™ãŒã€
モナドã§æ‚Ÿã‚Šã‚’ã²ã‚‰ããŸã„ã®ãªã‚‰ - 図ã§ã‚ã‹ã‚‹(?)モナド - 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 を使ãˆã°ã„ã„ã‚“ã˜ã‚ƒãªã„ã§ã—ょã†ã‹ã€‚ ダイアグラムã®æ›¸ãæ–¹ 例ãˆã°ã€ã€Œ f :: a -> b ã€ã¨ã‹ã€Œlength :: [a] -> Intã€ã¯ä»¥ä¸‹ã®ã‚ˆã†ã«æ›¸ãã¾ã™ã€‚型を点ã§ã€é–¢æ•°ã‚’矢å°ã§æ›¸ãã¾ã™ã€‚ ダイアグラムã®åˆ©ç‚¹ã¯ã€fã‚„lengthã®ä¸èº«ã‚’忘れã¦ç°¡ç•¥åŒ–ã™ã‚‹ã“ã¨ãŒã§ãã‚‹ã“ã¨ã§ã™ã€‚人間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‚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 㨠>>= ã®å›³ç¤º 今回ã®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
Stateモナドを今度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€‚ Stateモナドã«ãŠã‘ã‚‹ >>= ã®èª¬æ˜Žã¨ã€é–¢æ•°çš„ãªã‚¤ãƒ¡ãƒ¼ã‚¸ã‚’解説ã—ãŸã¤ã‚‚ã‚Šãªã®ã§ã™ãŒãƒ»ãƒ»ãƒ»ã€‚ ã†ãƒ¼ã‚“ã€ã“りゃã‚説明ã®ä»•æ–¹ãŒã¨ã¦ã‚‚よããªã„ã§ã™ã(汗。解説ã«é–¢ã—ã¦ã€ã‚‚ã£ã¨ã‚ã‹ã‚Šã‚„ã™ã„よã†ã«ãƒªãƒ™ãƒ³ã‚¸ã—ãŸæ–¹ãŒã„ã„ã‹ã‚‚ã—ã‚Œã¾ã›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€‚
Stateモナドを今度ã“ãç†è§£ã™ã‚‹(2) - Pixel Pedals of Tomakomai
å‰å›žã®ç¶šãã§ã™ã€‚２回ã§çµ‚ã‚ã‚Œã¾ã›ã‚“ã§ã—ãŸorz 今回ã¯ã€Stateモナドã®å€¤ã®èª¬æ˜Žã¨ã€returnã®å®šç¾©ã§ã™ã€‚ モナド=Stateモナドã¨ã‹ã€ãƒ¢ãƒŠãƒ‰=IOモナドãªã©ã¨æ€ã†ã®ã¯å±é™ºã§ã™ã€‚「Stateモナドã¯ã€ãƒ¢ãƒŠãƒ‰ã‚¤ãƒ³ã‚¿ãƒ•ã‚§ãƒ¼ã‚¹ã®å®Ÿè£…例ã€ãらã„ã«è§£é‡ˆã™ã‚‹ã®ãŒã„ã„ã¨æ€ã„ã¾ã™ã€‚
Stateモナドを今度ã“ãç†è§£ã™ã‚‹ - Pixel Pedals of Tomakomai
3å¹´å‰ã«ç†è§£ã—よã†ã¨ã—ã¦æƒ¨æ•—ã—ãŸ*1Haskellã®Stateモナドã®è§£èª¬ã«ã€ãƒªãƒ™ãƒ³ã‚¸ã—よã†ã¨æ€ã„ã¾ã™ã€‚åœè«–ã‚’ã¡ã‚‡ã£ã¨ã¯ã‹ã˜ã£ãŸã®ã§ã€ä»Šåº¦ã“ãã¾ã¨ã‚‚ãªè§£èª¬ãŒã§ãã‚‹ã¯ãšã€‚ ã¨è¨€ã†ã“ã¨ã§ã€ä»Šå›žã¯å‰ç·¨ã§ã™ã€‚åœè«–ã®çŸ¥è˜ã¯å‰æã¨ã¯ã—ã¦ãªã„ã§ã™ãŒã€é›†åˆã¨å†™åƒã«ã‚¢ãƒ¬ãƒ«ã‚®ãƒ¼ãŒã‚ã‚‹ã¨ãã¤ã„ã‹ã‚‚ã—ã‚Œã¾ã›ã‚“。 *1:3å¹´å‰ã®æ•—å› ã¯ã€åœã‚’Setsã ã¨æ€ã„込んã§ãŸä¸Šã«é–¢æ‰‹ã‚’「写åƒã‚’写åƒã«ç§»ã™å†™åƒã€ã ã¨èª¤è§£ã—ã¦ãŸã“ã¨ã§ã—ょã†ã‹ã€‚
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