コードで遊ぼう Haskell #2.0

SampleCodes
https://bitbucket.org/BP-YooWaan/enjoycode/src/

Transcript

1. ίʔυͰ͋ͦ΅͏ # 2 HASKELL
2. ϫλγ ABOUT ME লུ
3. ݁࿦ ࢲ ͸͡Ί͔ΒΫϥΠϚοΫε
4. HEVEN ఱࠃ
5. ؔ਺ܕϓϩάϥϛϯά͸ αΠίʔʂʂϚδͰ͐ʂʂ ࢲ ༧ఆ͍ͯͨ͠ࣄ
6. HELL ஍ࠈ
7. ؔ਺ܕϓϩάϥϛϯά͸ ແཧήʔ ࢲ ݁࿦̍
8. ͏Θ͊͊͊͊͊͊ ࢲ ݁࿦̎
9. ͦͷహ຤Ͱ͢
10. લஔ͖ ϦʔϜʔͳੈք
11. Θ͔ΔϠϩʂʂͳͬʂʂ લஔ͖ ▸ ΈΜͳචऀΑΓ಄͍͍લఏͰ͢ ▸ චऀͷղऍͳͷͰɺશͯਖ਼͍͠Θ͚Ͱ͸͋Γ·ͤΜ ▸ ̍̌෼ͱ͔ແཧ͔ͩΒʂʂ
12. ߏ੒ʹ͍ͭͯ લஔ͖ ϓϩάϥϛϯάݴޠ ϓϩάϥϛϯάύϥμΠϜ ࢥ૝/࿦
 (ΞΧσϛοΫͳ࿩) ߏ଄Խ OOP ؔ਺ܕ ৘ใՊֶ ݍ࿦ τϨϯυ # 2
 લฤ # 2.1
 ޙฤ
13. ߏ੒ʹ͍ͭͯ લஔ͖ ϓϩάϥϛϯάݴޠ ϓϩάϥϛϯάύϥμΠϜ ࢥ૝/࿦ ߏ଄Խ OOP ؔ਺ܕ ৘ใՊֶ ݍ࿦ τϨϯυ ͙͎͎͎͎͠ ෼͔Γқ͍ ༏͍͠ੈք આ໌͠ʹ͘͘ ఱࠃ΁ͷ֊ஈ HEVEN HELL
14. ΑʔΘ͔ΒΜͷͰ͢Α લஔ͖ ݱ࣮ ந৅Խ Ֆ Ֆാ ந৅Խ͕ݱ࣮ʹ͍ۙ΄Ͳྑ͍ͱ͍͏લఏͰ࿩͍ͯ͠·͢ ্ه͕ਖ਼͍͔͠ʁݱ࣮͸ந৅త͔ʁͳͲ͸ผͷͱ͜ΖͰٞ࿦͍ͩ͘͞
15. CONTENTS ಺༰ ▸ ྺ࢙ ▸ ఆٛʗϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ʗؔ਺߹੒ ▸ ஗ԆධՁ ▸ Ϟφυ
 
 ݁࿦ ؔ਺ܕݴޠ ؔ਺ϓϩάϥϛϯάͬͯʂʁ Haskellͷ͞ΘΓ͚ͩ…
16. ࢀߟ·Ͱʹ ྺ࢙ ▸ 1930೥୅ɹϥϜμܭࢉ Alonzo Church
 ؔ਺ܕݴޠͷഎܠ ::ϥϜμܭࢉ
 ϥϜμܭࢉ͸ͦΕࣗମ͕νϡʔϦϯά׬શ
 ͭ·ΓɺͦΕࣗମ͕ສೳνϡʔϦϯάϚγϯ ▸ 1958೥ɹɹLISP
 Sࣜͱ͍͏γϯϓϧ͔ͭڧྗͳه๏
 ํݴɿScheme, Common Lisp, Clojure 1930೥୅ λܭࢉ 1958೥ LISP 1975೥ Scheme 1984೥ Common Lisp 1990೥ Haskell 1.0 େن໛ͳ ந৅తͳײ৮ ؔ਺ܕʹϥϜμܭࢉ ͱ͸ݴͬͯͳ͍
17. ఆ͍ٛΖ͍Ζ ఆٛɿɿຊΑΓ ▸ ؔ਺͕ୈ̍ڃͷର৅Ͱ͋Δݴޠ ▸ ؔ਺ͷϦςϥϧ͕͋Δ ▸ ؔ਺Λ࣮ߦ࣌ʹੜ੒Ͱ͖Δ ▸ ؔ਺Λม਺ʹೖΕͯѻ͑Δ ▸ ؔ਺Λखଓ͖΍ؔ਺ʹҾ਺ͱͯ͠༩͑Δ͜ͱ͕Ͱ͖Δ ▸ ؔ਺Λखଓ͖΍ؔ਺ͷ݁Ռͱͯ͠ฦ͢͜ͱ͕Ͱ͖Δ
18. ఆ͍ٛΖ͍Ζ ఆٛɿɿաڈ QCON ࢿྉΑΓ Ҿ༻ݩɿ http://qcontokyo.com/tokyo-2012/data_2012/KazuhikoYamamoto_QCon.pdf
19. ఆ͍ٛΖ͍Ζ ఆٛɿɿେਖ਼ٛ Wikipedia φϯ ͩͬͯ͐ʔ
20. ຊͱ͔WikipediaΑΓ ϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ܕ ▸ ܕ ▸ ७ਮ ▸ ධՁઓུ ▸ ϞδϡϥϦςΟ ▸ ෭࡞༻ ▸ OOP ▸ ΦϒδΣΫτ͕૬ޓ ʹϝοηʔδͷ΍Γ औΓ ▸ ΧϓηϧԽ ▸ ܧঝ ▸ ϙϦϞϑΟζϜ ▸ ߏ଄Խ ▸ ػೳΛந৅Խͨ͠Ծ ૝ػց ▸ ֊૚Խͨ͠ந৅Խ ▸ ࣮૷Өڹ͸ಉҰ֊૚
21. ༨ஊ ϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ܕ ▸ ܕ ▸ ७ਮ ▸ ධՁઓུ ▸ ϞδϡϥϦςΟ ▸ ෭࡞༻ ▸ OOP
 
 
 
 
 
 
 
 ▸ ߏ଄Խ ݪଇ͸͋Δ͚Ͳ ΦϒδΣΫτͷൣғͬͯʁ ֊૚ͬͯͲΜͳ͘͘Γʁ
22. ༨ஊ ϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ܕ ▸ ܕ ▸ ७ਮ ▸ ධՁઓུ ▸ ϞδϡϥϦςΟ ▸ ෭࡞༻ ▸ OOP
 
 
 
 
 
 
 
 ▸ ߏ଄Խ ݁ہɺࣗ༝͗ͯ͢ɾɾɾ ʰෆ७ʱͰʰϞδϡϥϦςΟແ͘ʱͯʰ෭࡞༻ͩΒ͚ʱͳ ੈքΛߏங
23. ༨ஊ ̤̤̥ɺߏ଄Խ ͰਐΊΔͱ
24. ༨ஊ ͜͏ͳ͍͖ͬͯ·͢ΑͶ ▸ ࠷ॳ͸ΈΜͳ
 ʮ७ਮʯͰ
 ʮϞδϡϥϦςΟʯ͋ͬͯ
 ʮ෭࡞༻ʯͳ͍
 
 ΋ͷΛ໨ࢦͯͨ͠ͷʹɾɾɾ ▸ ࠞಱͱͨ͠ੈքʹɾɾɾ
25. ͦΖͦΖhaskellʹϑΥʔΧεͯ͠ Haskellʹ͍ͭͯ ܕ෇͖ ɹܕͳ͠ͷ৔߹͸۠ผͳ͘ܭࢉՄೳ ੩తܕ෇͚ ɹܕݕࠪΛίϯύΠϧ࣌ʹ࣮ߦ ڧ͍ܕ෇͚ ɹܕݕࠪʹ੒ޭͨ͠৔߹ʹ҆શੑΛอূ ७ਮ ɹࢀরಁաੑʢಉ͡৭͸ಉ݁͡Ռʣ ܕݕࠪ͋Γ ɹʮܕʯͷ੔߹ੑνΣοΫ ܕਪ࿦ ɹϓϩάϥϚ͕༩͑ͨܕͷ৘ใ͔Βྨਪ ஗ԆධՁ ɹࣜΛධՁ͢Δॱ൪
26. CONTENTS ಺༰ ▸ ྺ࢙ ▸ ఆٛʗϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ʗؔ਺߹੒ ▸ ஗ԆධՁ ▸ Ϟφυ
 
 ݁࿦
27. ϓϩάϥϛϯάαΠυ ؔ਺ ▸ ؔ਺ͷ࡞Γํ ▸ ؔ਺ద༻ʢ෦෼ద༻ʣ ▸ ؔ਺߹੒ ▸ ͦͷଞ ▸ ຊεϥΠυͰ͸লུ ͜͜Ͱѻ͏ؔ਺ʹ͍ͭͯ int y = 0; int func(int x) { y = y + 1; // ঢ়ଶมԽ return y + x // yʹґଘͯ݁͠Ռ͕มΘΔ } ʮ७ਮʯͰͳ͍ ʮϞδϡϥϦςΟʯͰͳ͍ ʮ෭࡞༻ʯ͕͋Δ ɹؔ਺Ͱ͸ͳ͍
28. FUNCTION APPLICATION ؔ਺ద༻ ▸ ؔ਺ద༻ ▸ ؔ਺ͷҾ਺ʹ஋Λ༩͑Δ͜ͱ ▸ ෦෼ద༻ ▸ ؔ਺ͷҰ෦͚ͩʹҾ਺Λ༩͑Δ ▸ ηΫγϣϯΛར༻ͯ͠Ұ෦Ҿ਺
 Λ༩͑Δ countChar :: String -> Char -> Int countChar str c = length $ filter (== c) str countA :: String -> Int countA str = countChar str ‘a' main = do printf "num %d\n" (countChar "a characters" 'a') printf "apply %d\n" (countA "a characters") printf "calc %d\n" ((2 ^) 4 :: Int) ؔ਺ʹҰ෦Ҿ਺Λ༩͑Δʢ෦෼ద༻ʣ ηΫγϣϯΛར༻ ؔ਺ద༻
29. FUNCTION COMPOSITION ؔ਺߹੒ ▸ ఆٛҬ X ͔Β஋Ҭ Y ΁ͷ
 ͋Δؔ਺ g ͱɺఆٛҬ Y ͔Β஋Ҭ
 Z ΁ͷ͋Δؔ਺ f ͕͋Δͱ͖
 ҎԼͷ౳ࣜΛຬͨ͢ఆٛҬ X ͔Β
 ஋Ҭ Z ΁ͷؔ਺ h ͕ଘࡏ͠·͢
 h (x) = f ( g ( x ) )
 
 
 h Λ f ◦ g ͱॻ͖fͱgͷؔ਺߹੒ʹ
 ΑΔ߹੒ؔ਺ͱݴ͍·͢
 (f ◦ g)( x ) = f( g ( x ) ) countChar :: String -> String -> Char -> String countChar fmt str c = printf fmt $ length $ filter (== c) str main = do putStrLn (countChar "a num %d" "a characters" 'a') putStrLn (countChar "c num %d" "a characters" 'c') X Y Z g f f ° g h ؔ਺߹੒
30. CONTENTS ಺༰ ▸ ྺ࢙ ▸ ఆٛʗϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ʗؔ਺߹੒ ▸ ஗ԆධՁ ▸ Ϟφυ
 
 ݁࿦
31. ϓϩάϥϛϯάαΠυ ஗ԆධՁ ▸ ධՁઓུͷҰछͰ༩͑ΒΕͨࣜΛܭࢉ݁͠ՌΛಘΔɻ
 ධՁΛߦ͏ͱ͖ͷܭࢉॱংͷܾΊํͰ͢ɻ
 ࣮ࡍʹධՁ͕ඞཁͱ͞ΕΔ·ͰධՁΛߦΘͳ͍ઓུͰ͢ɻ emptyList :: Bool emptyList = let x = undefined : x in null x nullTake :: Int nullTake = let x = undefined : x in length (take 10 x) main = do print (take 10 [0..]) -- ແݶͷ഑ྻΛѻ͏ print (length [ undefined, undefined, undefined ]) -- ະఆٛͳ஋ͷ഑ྻ΋ѻ͑Δ print emptyList -- ۭϦετνΣοΫʹະఆٛΛ౉͢ print nullTake -- ະఆٛͳ஋Λ10ճऔಘ ஗ԆධՁͳͷͰແݶΛѻ͏͜ͱ΋Մೳ
32. ϓϩάϥϛϯάαΠυ ஗ԆධՁ —- Haskell import System.Environment (getArgs) tarai :: Int -> Int -> Int -> Int tarai x y z | x <= y = y | otherwise = tarai (tarai (x - 1) y z) (tarai (y - 1) z x) (tarai (z - 1) x y) main = do args <- getArgs let nums = map cv args where cv str = read str :: Int if length nums >= 3 then print (tarai (nums !! 0) (nums !! 1) (nums !! 2)) else print "illegal argument !!" // C #include <iostream> #include <cstdlib> int tarai(int x, int y, int z) { return x <= y ? y :tarai(tarai(x - 1, y, z), tarai(y - 1, z, x), tarai(z - 1, x, y) ); } int main(int argc, char* argv[]) { if (argc < 4) return 1; int x = std::atoi(argv[1]); int y = std::atoi(argv[2]); int z = std::atoi(argv[3]); std::cout << tarai(x, y, z) << std::endl; return 0; } ./tarai 20 10 0 # ऴΘΒͳ͍ ./tarai 20 10 0 # ऴΘΔ
33. CONTENTS ಺༰ ▸ ྺ࢙ ▸ ఆٛʗϓϩάϥϛϯάύϥμΠϜ ▸ ؔ਺ʗؔ਺߹੒ ▸ ஗ԆධՁ ▸ Ϟφυ
 
 ݁࿦
34. Ϟφυʁ
35. ෆ७͍͍ͬͯΑͶ ͬ͘͟Γͱͨ͠Ϟφυ ෭࡞༻Λѻ͑ͳ͍ͱ࣮༻ʹ଱͑͏ΔͷͰ ෭࡞༻Λѻ͑ΔΑ͏ʹͨ͠࢓૊ΈͷҰछ
36. Ϟφυ Ϟφυͷ͍Ζ͍Ζ ▸ Identity จ຺Λ࣋ͨͳ͍ ▸ Maybe ࣦഊͷՄೳੑΛ͍࣋ͬͯΔ ▸ List ෳ਺ͷՄೳੑΛ͍࣋ͬͯΔ ▸ Reader ࢀরͰ͖Δ؀ڥΛڞ༗͢Δ ▸ Writer ओཁͳܭࢉͷԣͰɺผͷ஋΋Ұ௚ઢʹ߹੒͢Δ ▸ State ঢ়ଶͷҾ͖ܧ͗ ▸ IO ෭࡞༻Λ൐͏
37. ͱ͍͏ͷΛ౿·͑ͯ ݍ࿦ͱབྷΊͯΈ·͢ ؔ਺߹੒ɹϞφυ
38. υϯυϯऴΘ͍ͬͯ͘ දࣔతҙຯ࿦ͷcompositionality ▸ ϓϩάϥϜP,QΛ૊Έ߹Θͤͯ৽͍͠ϓϩάϥϜRΛ࡞ͬͨ࣌
 P,Qͷੑ࣭͕Θ͔͍ͬͯΔ৔߹ʹ߹੒ͯ͠࡞ͬͨRͷੑ࣭Λɺ
 PͱQͷੑ࣭͚͔ͩΒಋ͚Δ͔ʁ 
 
 
 Yes → ͦΕͧΕͷ෦඼ͷੑ࣭͔ΒશମͷϓϩάϥϜͷੑ࣭Λಋ͘͜ͱ͕Մೳ
 
 
 ͦͷΑ͏ͳੑ࣭͸ɺcompositional(߹੒త)ͱ͍͍·͢ P Q + = R
39. ऴΘΓͷ࢝·Γ ݍ࿦ͱ͸ ‣ WikipediaΑΓ
 ݍ࿦ʢ͚ΜΖΜɺcategory theoryʣ͸ɺ਺ֶతߏ଄ͱͦͷؒͷؔ܎Λந৅తʹѻ͏਺ֶཧ࿦ͷ 1 ͭͰ͋Δɻ ߟ͍͑ͯΔछྨͷʮߏ଄ʯΛ࣋ͬͨର৅ͱͦͷߏ଄Λ൓ө͢ΔΑ͏ͳର৅ؒͷࣹͷू ·Γ͔ΒͳΔݍ͕جຊతͳߟ࡯ͷର৅ʹͳΔɻ ‣ ຊΑΓ
 ۙࣅͱͯ͠ɺݍ࿦ͱ͸ࣸ৅ͷͳ͢ʢந৅ʣ୅਺
 ΤΞϥϯήϯɾϓϩάϥϜ(Erlangen Program)ͷ఻౷ΛҾ͖ܧ͍ͰߟҊ͞ΕͨɺҰൠతͳ֓೦͸
 ”ߏ଄Λอͭม׵”ͷ֓೦ͷಛ௃͚ͮΛ༩͑ɺ͜ͷΑ͏ͳม׵Λڐ༰͢Δߏ଄ͷɺ͋Δछͷಛ௃ͮ ͚Λ༩͑Δ
40. Φϫλ ݍͱ͸ ▸ Category(ݍ) = (O, A, ◦, id)
 ɾO͸ର৅
 ɾX,Y∈O ʹରͯ͠A(X,Y)͸ɺର৅X͔Βର৅Y΁ͷࣹͷू߹
 ɾ߃౳ࣹ X∈Oʹରͯ͠ idxɿX → X ͕ఆ·͍ͬͯΔ
 ɾ߹੒ɹ݁߹཯ɿ೚ҙͷࣹʹରͯ͠ h◦(g◦f) = (h◦g)◦f
 ɹ୯Ґ཯ɿ೚ҙͷࣹ X→Yʹରͯ͠ id y ◦ f = f = f ◦ id x X Y Z f g f ◦ g ʁʁʁ ʁʁʁ
41. R ʘ(^O^)ʗ ·ͱΊΔͱ ݍ X (ෆมྔ) ݍ Y (ෆมྔ) P (ੑ࣭) Q (ੑ࣭) ؔख (ࣹ) ※ ద੾ͳߏ଄Λอͭؔखʹج͍ͮͯ
 දࣔతҙຯ࿦Λ༩͑ΒΕΕ͹ = දࣔతҙຯ࿦ ݍ࿦ ந৅౓͕ߴ͍=
42. FUNC_R ʘ(^O^)ʗ ແཧ΍Γ·ͱΊΔͱ ݍ X (ෆมྔ) ݍ Y (ෆมྔ) FUNC_P FUNC_Q ؔख (ࣹ) ※ ద੾ͳߏ଄Λอͭؔखʹج͍ͮͯ
 දࣔతҙຯ࿦Λ༩͑ΒΕΕ͹ = Haskell ݍ࿦ ந৅౓͕ߴ͍= ◦
43. ਃ͠༁ఔ౓ʹ Ϟφυ දࣔతҙຯ࿦ͰͷɺܭࢉޮՌͷ໽հ͝ͱΛแׅతʹѻ͏ΞΠσΞ
 ʢܭࢉޮՌɿܭࢉ͕ऴΘΒͳ͍ɺϝϞϦ΁ͷಡΈॻ͖ɺ૷ஔ΁ͷೖग़ྗʣ
 ݍCʹ͓͚ΔϞφυ(monad)ͱ͸ɼࣗݾവखT:C→Cͱ
 ࣗવม׵ η:1C→T, μ:T2→T ͔ΒͳΓ౳ࣜ μ∘μT=μ∘T(μ)μ∘ηT=μ∘T(η)=1T ͕੒Γཱͭ΋ͷͰ͋ΔɻηΛϞφυͷ୯ҐݩɼμΛϞφυͷੵͳͲͱݺͿ
44. ʁʁʁ ɾɾɾ
45. ݁࿦࠶ͼ ݁࿦
46. ཪ੾Γͷੈք ༧ఆ͍ͯͨ݁͠࿦ ίʔυ؆ૉԽ ؔ਺ܕಛ௃ ਺ֶతͳந৅Խ ඒ͍͠ந৅Խ αΠίʔ × ×
47. ຊ౰ͷੈք ݱ࣮తͳ݁࿦ ίʔυ؆ૉԽ ؔ਺ܕಛ௃ ਺ֶతͳந৅Խ ϦʔϜʔ × × ஌ͬͯΔΑͶʁ ॻ͚ΔΑͶʁ ཧղͯ͠ΔΑͶʁ
48. զʑͷݩʹ໭͓͍ͬͯͰ OOP ߏ଄Խ
49. # 2.1 TO BE CONTINUED