Monoids, Functors, Applicatives, and Monads: 10 Main Ideas
I’m making this post because after spending months learning about all the different properties of monoids, functors, applicatives, and monads, I thought it would be nice to collect everything I’ve learned from different tutorials, StackOverflow questions, and reddit posts into a neat beginner’s introduction to these topics. I’ll break up this post into a few Main Ideas and say a little about each.
第52å›žã€€ãƒ‡ãƒ¼ã‚¿æ§‹é€ ã‚’èµ°æŸ»ã™ã‚‹ãŸã‚ã®Traversableクラス
ãƒ‡ãƒ¼ã‚¿æ§‹é€ ã«å¯¾ã™ã‚‹å‡¦ç†ã‚’抽象化ã™ã‚‹ãŸã‚ã®åž‹ã‚¯ãƒ©ã‚¹ã¨ã—ã¦ï¼Œç¬¬3回ã§ã¯Functorクラス，第34回ã§ã¯Foldableクラスを説明ã—ã¾ã—ãŸã€‚FunctorクラスやFoldableクラスã§ã¯ï¼Œã€Œãƒ‡ãƒ¼ã‚¿æ§‹é€ ã®èµ°æŸ»ï¼ˆtraverse）ã€ã¨ã€Œãƒ‡ãƒ¼ã‚¿æ§‹é€ を走査ã—ãŸéš›ã«è¡Œã†å‡¦ç†ã€ã‚’セットã«ã—ãŸfmapã‚„fold*ã¨ã„ã†å‡¦ç†ãŒç›´æŽ¥æä¾›ã•ã‚Œã¦ã„ã¾ã™ã€‚ Haskell以外ã®è¨€èªžãŒæŒã¤ã‚¤ãƒ†ãƒ¬ãƒ¼ã‚¿ãªã©ã®æ©Ÿèƒ½ã§ã¯ã€Œãƒ‡ãƒ¼ã‚¿æ§‹é€ ã®èµ°æŸ»ã€ã¨ã€Œãƒ‡ãƒ¼ã‚¿æ§‹é€ を走査ã—ãŸéš›ã«è¡Œã†å‡¦ç†ã€ã‚’切り離ã™ã“ã¨ã§ï¼Œã‚ˆã‚Šä¸€èˆ¬çš„ãªå‡¦ç†ã‚’è¡Œãˆã¾ã™ã€‚Haskellã§ã¯ãã®ã‚ˆã†ãªæž 組ã¿ã¨ã—ã¦ï¼ŒData.Traversableモジュールã§TraversableクラスãŒæä¾›ã•ã‚Œã¦ã„ã¾ã™ã€‚ mapM関数やsequence関数を一般化 ã¾ãšï¼ŒTraversableクラスãŒã©ã®ã‚ˆã†ãªã‚‚ã®ã‹ã‚’ç°¡å˜ã«è¦‹ã¦ã¿ã¾ã—ょã†ã€‚ Prelude Data.Traversable
Functor-Applicative-Monad Proposal - HaskellWiki
Haskell calls a couple of historical accidents its own. While some of them, such as the "number classes" hierarchy, can be justified by pragmatism or lack of a strictly better suggestion, there is one thing that stood out as, well, not that: Applicative not being a superclass of Monad. The topic has been discussed multiple times in the past (cf. link section at the very end). This article describe
Applicative Functors | pbrisbin dot com
Every time I read Learn You a Haskell, I get something new out of it. This most recent time through, I think I’ve finally gained some insight into the Applicative type class. I’ve been writing Haskell for some time and have developed an intuition and explanation for Monad. This is probably because monads are so prevalent in Haskell code that you can’t help but get used to them. I knew that Applica
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
Play2.1ã®functional packageã®Applicativeを使ㆠ- xuwei-k's blog
Play2.1内部ã«ã€ç‹¬è‡ªã® Functor URL ã¨ã‹ Applicative URL ã¨ã‹ Monoid URL ãŒè¿½åŠ ã•ã‚Œã¦ã„ã¦å‘³ã‚ã„æ·±ã„ã§ã™ã・・・ 2012-11-18 01:16:51 via web ã¨ã„ã†ã‚ã‘ã§ã€Play2.1ã‹ã‚‰ç‹¬è‡ªã®Functorã¨ã‹Applicativeã¨ã‹Alternative(ApplicativePlus)ãŒã‚ã‚‹ã®ã§ç°¡å˜ã«Optionã®Applicativeã®ä½¿ã„æ–¹ã ã‘紹介。 https://github.com/playframework/Play20/blob/2.1.0/framework/src/play/src/main/scala/play/api/libs/functional/Util.scala Scalazã§ãã®è¾ºã‚ŠçŸ¥ã£ã¦ã‚‹äººã¯ã€ç°¡å˜ã«ç†è§£ã§ãã‚‹ã¯ãšã§ã™ã€‚ã¨ã“ã‚ã§ã€ãªãœã‹Monadã®typeclassã¯ãªã„ã‚“ã§ã™ã・・・。
jaspervdj - Monads and Arrows: modelling a build system
An success story of Arrows Published on January 14, 2012 under the tag haskell This is a recap of an older blogpost of mine. I decided to rewrite it after I wanted to refer a friend to it, and I saw the blogpost clearly failed a bit in getting the point across. In this blogpost, I hope to correct that. It’s about a situation in which Monads fall short, but Arrows (and Applicative) prove to be very
Parsing context-sensitive languages with Applicative
Many parser combinator libraries in Haskell (such as parsec) have both a Monad interface as well as an Applicative interface. (Actually, to be really useful, you also need MonadPlus along with Monad, or Alternative along with Applicative, in order to encode choice; from now on when I talk about Monad and Applicative note that I really have MonadPlus or Alternative in mind as well.) The Applicative
Typeclassopedia - HaskellWiki
By Brent Yorgey, byorgey@gmail.com Originally published 12 March 2009 in issue 13 of the Monad.Reader. Ported to the Haskell wiki in November 2011 by Geheimdienst. This is now the official version of the Typeclassopedia and supersedes the version published in the Monad.Reader. Please help update and extend it by editing it yourself or by leaving comments, suggestions, and questions on the talk pag
The Strathclyde Haskell Enhancement
please won't you tell me who is she? The Strathclyde Haskell Enhancement is an experimental preprocessor for the Glasgow Haskell Compiler, concocted hastily by Conor McBride at the University of Strathclyde. Its current functionality includes types indexed by data pi types pattern synonyms — definitions you can use on left and right support for a crude kind of aspect-oriented programming idiom bra
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)
Haskellã§ã®ã‚¨ãƒ©ãƒ¼ã®æ‰±ã„方。ã‚ã‚‹ã„ã¯Applicative, Monadç‰ã¨liftãŒå¤šããªã‚‹ã“ã¨ã«ã¤ã„ã¦ã®è€ƒãˆã€‚
@tanakh 師㨠@nushio ã«ã‚ˆã‚‹ä¼šè©±ã‚’横ã‹ã‚‰ãƒ¡ãƒ¢ã—ãŸã‚‚ã®ã€‚ - Haskellã§ã¯ã‚¨ãƒ©ãƒ¼ã¯åž‹ã«è¿½ã„出ã™ã®ãŒæ£æ”»æ³•ã€‚Pureãªè¨ˆç®—ã‹ã‚‰ErrorãŒé£›ã³å‡ºã¦ãã‚‹ã®ã¯å¯¾å‡¦ã—よã†ãŒãªã„ã®ã§é¿ã‘ã‚‹ã¹ã。 - åž‹ã«è¿½ã„ã ã™ã¨æœ€çµ‚çš„ã«ã™ã¹ã¦ã®æ“作ãŒä¾‹ãˆã°Monadã®ä¸ã§è¡Œã‚れるã“ã¨ã«ãªã‚‹ã€‚ãれをã©ã†è€ƒãˆã‚‹ã‹ã€‚ 続ãã‚’èªã‚€
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
HIMA
HIMA(Haskell Internet Meeting Anytime) ã¯ã€Haskell 好ããŒã‚¤ãƒ³ã‚¿ãƒ¼ãƒãƒƒãƒˆã§ã¨ã‚ã©ãªããŠå–‹ã‚Šã™ã‚‹ä¼šã§ã™ã€‚ 第4回 2010/01/23 FRP @ google wave by sakai (ãƒã‚°) 第3回 2009/12/12 副作用 @ chaton by nobsun (ãƒã‚°) 第2回 2009/11/14 Typeclassopedia @ IRC by kazu (ãƒã‚°) 第1回 2009/10/03 Cabal @ IRC by nwn (ã¾ã¨ã‚)
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GitHub - foxnewsnetwork/arrows: ruby lambda proc tools for functional programming and arrows
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