ES6時代の関数型プログラミング

by かわばたれもん(KawabataLemon)

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ES6࣌୅ͷ ؔ਺ܕϓϩάϥϛϯάೖ໳ @Kawabata_Lemon

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,BXBCBUB-FNPO ,BXBCBUB@-FNPO !,BXBCBUB@-FNPO - Lead engineer of pairs Div. eureka, Inc. - iOS Engineer

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- pairs - couples - Subsidiary of match group / IAC

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Agenda ‣ ؔ਺ܕͱ͸ ‣ ؔ਺ܕ͕Θ͔Δͱ..? ‣ ͚ΕͲ΋෭࡞༻͸ͷ͜Δ ‣ ͚Ͳҙຯ͸͋Δ

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ؔ਺ܕݴޠͱ͸ ؔ਺ܕϓϩάϥϛϯάͰ͸ϓϩάϥϜͷߏ੒ʹؔ਺Λଟ༻͢ΔͨΊɺ΄ ͱΜͲͷؔ਺ܕݴޠͰ͸ؔ਺ΛୈҰڃΦϒδΣΫτͱͯ͠ѻ͍ɺͦͷཧ ࿦తͳܭࢉϞσϧͱͯ͠ୈҰڃΦϒδΣΫτͱͯ͠ͷؔ਺Λѻ͑ΔϥϜ μܭࢉ΍߲ॻ͖׵͑Λ࠾༻͍ͯ͠Δɻ 8JLJQFEJB

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ؔ਺ܕݴޠͱ͸ ؔ਺ܕϓϩάϥϛϯάͰ͸ϓϩάϥϜͷߏ੒ʹؔ਺Λଟ༻͢ΔͨΊɺ΄ ͱΜͲͷؔ਺ܕݴޠͰ͸ؔ਺ΛୈҰڃΦϒδΣΫτͱͯ͠ѻ͍ɺͦͷཧ ࿦తͳܭࢉϞσϧͱͯ͠ୈҰڃΦϒδΣΫτͱͯ͠ͷؔ਺Λѻ͑ΔϥϜ μܭࢉ΍߲ॻ͖׵͑Λ࠾༻͍ͯ͠Δɻ 8JLJQFEJB ม਺ʹؔ਺Λ͍ΕΒΕΔ

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ͲͷݴޠͰֶͿ͔ ECMASCRIPT2015

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ؔ਺ܕΛֶͿͱ? ‣ ෭࡞༻͕ؾʹͳΔΑ͏ʹͳΔ ɹ-> ίϯςΩετʹΑͬͯ݁Ռ͕ҟͳΔίʔυΛආ͚Δ(lexical) ‣ ࠶ར༻ੑ͕ؾʹͳΔΑ͏ʹͳΔ -> ϓϩάϥϜͱͯ͠ͷϞδϡʔϧੑ -> ςετ͠΍͢͞(Testability)

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ྫ͑͹͜Μͳίʔυ͕

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͜͏ͳΓ·͢

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ߟ͑ํΛม͑Δ ‣ ஋ʹରͯ͠Ͳ͏޲͖߹͏͔ ‣ Կճ΍ͬͯ΋ͪΌΜͱಈ͘΋ͷͳͷ͔ ‣ ୅ೖ͢Δ͜ͱ͸෭࡞༻ΛੜΉ

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ࢀরಁաੑ in out Function ͋Δೖྗʹର͢Δग़ྗ͕ৗʹಉ͡Ͱ͋Δͱ͍͏͜ͱ ෭࡞༻͕ͳ͍ 1 2 (x) => x+1 ͜ͷؔ਺͸ৗʹ౴͕͑1ର1 1 2 (x) => x+1 ͳΜ͔͍΍ͬͯ΋͓ͳ͡ ஋ͱͲ͏޲͖߹͏͔

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෭࡞༻ʁ ݺͿͨͼʹ݁Ռ͕ҟͳΔ inͱout͕ৗʹಉ͡อূ͕ͳ͍ʂ

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൚༻ੑ ‣ ࢖͍·ΘͤΔ ‣ ૊Έཱͯͯ࢖͑Δ in out Function in out Function2 Կճ΋࢖͑Δ΋ͷ͔

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࢖͍·ΘͤΔ ‣ Ϟδϡʔϧͱͯ͠ͷϓϩάϥϜ খ͍͞΋ͷΛ૊Έ߹Θͤͯେ͖ͳ΋ͷΛ࡞Δ Ϩΰͷߟ͑ํ ->

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୅ೖ͢Δ͜ͱ͸෭࡞༻ΛੜΉ ‣ ͍ͭͲ͜Ͱมߋͨ͠ͷ͔Θ͔Βͳ͘ͳΔ ‣ είʔϓ֎Ͱঢ়ଶΛ࣋ͬͨΓ….

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ECMASCRIPT2015 ࣌୅Ͱͷؔ਺ܕϓϩάϥϛϯάͰؾΛ͚ͭΔ͜ͱ ‣ ม਺ͷר্͖͛ʹࠔΒͳ͍ͨΊʹlet,constΛ࢖͓͏ let,constʹ͢Δ͜ͱͰ   ReferenceErrorΛىͤ͜Δ

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ECMASCRIPT2015 ࣌୅Ͱͷؔ਺ܕϓϩάϥϛϯάͰؾΛ͚ͭΔ͜ͱ ‣ ॻ͍ͨείʔϓ௨Γͷ࣮ߦΛͤ͞ΔͨΊʹ => Λ࢖͓͏

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ECMASCRIPT2015 ࣌୅Ͱͷؔ਺ܕϓϩάϥϛϯάͰؾΛ͚ͭΔ͜ͱ ‣ ॻ͍ͨείʔϓ௨Γͷ࣮ߦΛͤ͞ΔͨΊʹ => Λ࢖͓͏ ఆٛ࣌ͷthis ࣮ߦ࣌ͷthis

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ECMASCRIPT2015 ࣌୅Ͱͷؔ਺ܕϓϩάϥϛϯάͰؾΛ͚ͭΔ͜ͱ ‣ ॻ͍ͨείʔϓ௨Γͷ࣮ߦΛͤ͞ΔͨΊʹ => Λ࢖͓͏ ఆٛ࣌ͷthis ࣮ߦ࣌ͷthis

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ͦΕͰ΋΍ͬͺΓ෭࡞༻͸෇͖·ͱ͏ ؔ਺ܕݴޠ͸ͲͷΑ͏ʹઓ͖͔ͬͯͨ ‣ Functor, Applicative, MonadͷҙຯΛͳΜͱͳ͘ཧղ͢Δ

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x f(x) g(f(x) Applicative x f(x) Functor Functor, Applicative, Monadʁ Monad = Functor + Applicative + ػೳ(ܭࢉઓུ) ͷػೳΛ΋ͭσʔλߏ଄ ཁૉʹؔ਺ΛదԠͰ͖Δ ͦΕΛܨ͛ΒΕΔ ஋Λฦ͔͢ ࣍ͷॲཧΛΑ Ϳ͔ʜFUD

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map͸Ϟφυ Applicative(ͪΌΜͱܨ͛ΒΕΔ) Functor(஋ΛೋഒʹͰ͖Δ)

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Ϟφυ(Monad)Λ࡞ͬͯΈΔ ‣ MayBeϞφυ,IOϞφυΛ࡞ͬͯΈΔ ‣ MayBeϞφυ -> NullՄೳੑʹରͯ͠ॲཧߦ͏͔൑அ͢ΔϞφυ (ଞͷݴޠͰ͸Optionalܕͱݺ͹ΕΔΑ͏ͳ΍ͭ) ‣ IOϞφυ -> ෭࡞༻ࠐΈͷॲཧΛ಺෦Ͱॲཧͤ͞ΔϞφυ

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MaybeϞφυ -> nullՄೳੑʹରॲ͢ΔϞφυ ‣ MaybeϞφυ in out த਎͕nullͩͬͨΒॲཧ͠ͳ͍ nullͰॲཧΛ૸Βͤͳ͍࢓૊ΈΛσʔλʹ͍ΕΔ த਎͕ೖͬͯͨΒฦͯ͠ॲཧ in out

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IOϞφυ -> ֎෦͔Βͷ৘ใΠϯϓοτͷ෭࡞༻ʹର͢ΔϞφυ in out ॲཧΛ௚઀΋ͨͤͯߦ͏ σʔλ಺ʹى͜Γ͏Δ෭࡞༻΋ؚΊͯ࣋ͨͤΔ

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શવΘ͔Βͳͯ͘΋େৎ෉ ‣ ؔ਺ܕʹ͸෭࡞༻ʹରͯ͠ߦ͏΂͖ߟ͑ํ͕٧Ίࠐ·Ε͍ͯΔ ‣ ؔ਺ܕϓϩάϥϛϯάΛ௨ͯ͡਎ʹ͚ͭΑ͏ ‣ ஧࣮ʹϞφυΛ࠶ݱ͢Δඞཁ͸શ͘ͳ͍(΍ͬͯΈ͔͚ͨͬͨͩ) ‣ ͦͯࣗ͠෼΋શવΘ͔Γ͖Εͯͳ͍

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ؔ਺ܕͷߟ͑ํΛֶ΅͏ ‣ ࠶ར༻ੑɺ෭࡞༻ͷগͳ͍ίʔυͷߟ͑ํΛֶ΅͏ ‣ ण໋ͷ௕͍ɺ൚༻ੑͷߴ͍ϓϩμΫτ࣮૷ ؔ਺ܕΛֶͿՁ஋͸͋Δ

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ࢀߟϦϯΫ http://www.zsoltnagy.eu/functional-programming-with-es6/ http://moduscreate.com/monad-pattern-for-functional-programming-in-es6/ http://postd.cc/functional-programming-for-javascript-people-1/ https://github.com/KawabataLemon/MonadInJavascript ൃදͰ͔ͭͬͨίʔυ

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Thank you