Swift Functional Programming

Swift Functional Programming Hirofumi Wakasugi (@5T111111)

4XJGUؔ਺ܕϓϩάϥϛϯά let list: List = .cons("pork", .cons("beef", .cons("chicken", .null))) //
=> (pork . (beef . (chicken . ()))) car(list) // => pork cdr(list) // => (beef . (chicken . ())) car(cdr(list)) // => beef cdr(cdr(list)) // => (chicken . ())

!)JSPGVNJ8BLBTVHJ !U 4XJGUษڧத ؔ਺ܕϓϩάϥϛϯάษڧத ࣗݾ঺հ

8IZ4XJGU ͳͥ4XJGUͷ࿩Λ͢Δͷ͔ͷઆ໌ 4XJGUͰؔ਺ܕϓϩάϥϛϯάͷ࣮ફ * ίʔυͷ࣮ྫɺέʔεελσΟ ** ؔ਺ܕϓϩάϥϛϯάͷͨΊͷϥΠϒϥϦͷ঺հ ***
4%, $PDPB ʹΑΔ੍ݶͱͦͷXPSLBSPVOE ؔ਺ܕϓϩάϥϛϯάελΠϧͰͷ8FCϓϩάϥϛϯά * 7BQPSͱ͍͏8"'Λ࢖ͬͯؔ਺ܕϓϩάϥϛϯάΛద༻ͯ͠ΈΔ ΞδΣϯμ

8IZ4XJGU ͳͥ4XJGUͷ࿩Λ͢Δͷ͔ͷઆ໌ 4XJGUͰؔ਺ܕϓϩάϥϛϯάͷ࣮ફ * ίʔυͷ࣮ྫɺέʔεελσΟ ** ؔ਺ܕϓϩάϥϛϯάͷͨΊͷϥΠϒϥϦͷ঺հ ***
4%, $PDPB ʹΑΔ੍ݶͱͦͷXPSLBSPVOE ؔ਺ϓϩάϥϛϯάελΠϧͰͷ8FCϓϩάϥϛϯά * 7BQPSͱ͍͏8"'Λ࢖ͬͯؔ਺ܕϓϩάϥϛϯάΛద༻ͯ͠ΈΔ ΞδΣϯμ ࠓ೔࿩͢ͷ͸͜Ε͚ͩʂ

8):48*'5

w੩తͳܕνΣοΫͱܕ҆શੑΛඋ͑ͨܕγεςϜ͕͋Δ wωΠςΟϒίʔυʹίϯύΠϧ͞ΕΔ wαʔόʔαΠυͷ8FCϓϩάϥϛϯάͰ࢖͑ΔՄೳੑ͕͋Δ ݸਓతͳझຯ ❤

w੩తͳܕνΣοΫͱܕ҆શੑΛඋ͑ͨܕγεςϜ͕͋Δ wωΠςΟϒίʔυʹίϯύΠϧ͞ΕΔ wαʔόʔαΠυͷ8FCϓϩάϥϛϯάͰ࢖͑ΔՄೳੑ͕͋Δ ݸਓతͳझຯ (PͰ͠ΐ

w੩తͳܕνΣοΫͱܕ҆શੑΛඋ͑ͨܕγεςϜ͕͋Δ wωΠςΟϒίʔυʹίϯύΠϧ͞ΕΔ wαʔόʔαΠυͷ8FCϓϩάϥϛϯάͰ࢖͑ΔՄೳੑ͕͋Δ ݸਓతͳझຯ Swift

8):48*'5

ؔ਺ܕϓϩάϥϛϯάͱ4XJGU

ͦ΋ͦ΋

4XJGUͰ ؔ਺ܕϓϩάϥϛϯά ͱ͍͏ωλ͕

શ͘໨৽͍͠΋ͷͰ͸ͳ͍

͘Β͍͸࿩͞Ε͖ͯͨ ͨͿΜ

ͳΜͰ·ͨ͋͑ͯ ͦΜͳ࿩Λ͍ͨ͠ͷ͔

"QQMF88%$ 4XJGUൃද

ؔ਺͕ϑΝʔετΫϥεʁ

pMUFSSFEVDFNBQqBU.BQ

0QUJPOBM

ͥΜͿ 0CKFDUJWF$ʹ͸ ͳ͔ͬͨͧʁ

ؔ਺ܕͷಛ௃Λඋ͑ͨݴޠ͕ "QQMFެࣜͰ ʮJ04NBD04։ൃʯ ͱ͍͏ڊେϚʔέοτʹݱΕͨ

ྑ͘΋ѱ͘΋ ؔ਺ܕʹରͯ͠ ஫໨͕ू·Δ ͭͷ͖͔͚ͬʹͳͬͨ

͡Ό͋

4XJGU͸ؔ਺ܕϓϩ άϥϛϯάݴޠͳ ͷ͔ʁ

4XJGUͰؔ਺ܕϓϩ άϥϛϯά͸Մೳ ͔ʁ

*%0/`55)*/,40 ؔ਺ܕϓϩάϥϛϯά͸ίʔσΟϯάελΠϧʹա͗ͳ ͍ͱ͍͏ݟํ΋͋Δ͕ɺ ؔ਺ܕͬΆ͍ػೳ΍ख๏ΛҰ෦औΓೖΕͯ΋ ͦΕ͚ͩͰ͸ؔ਺ܕϓϩάϥϛϯάʹ͸ͳΒͳ͍ͱࢥ͏ FH+BWB4DSJQU+BWB3VCZ$ -JOR FUD

ͦ͏ࢥͬͯͨ࣌ظ͕Ӡʑ

͋Εʁ Α͘ݟͯΈΔͱʜ 4XJGU͸ࢥͬͨҎ্ʹ ؔ਺ܕϓϩάϥϛϯά͕ ΍Γ΍ͦ͢͏ʹݟ͑·ͧ͢ʁʁ

4XJGUͰ͸ʜ w ؔ਺Λ஋ͱͯ͠ѻ͑Δ w ؔ਺͸ϑΝʔετΫϥε w typealiasͰؔ਺ͷܕఆٛ΋Մೳ MJLFtypeJO)BTLFMM

4XJGUͰ͸ʜ w .PEVMBCMFͳσβΠϯ΍એݴతͳهड़Λ΍Γ΍͘͢͢Δ࢓૊Έ͕͋Δ w 0QUJPOBM "SSBZͳͲ͕'VODUPS.POBEͱ࣮ͯ͠૷͞Ε͍ͯΔ  ϝιουνΣʔϯͰ͖Δ w 1SPUPDPM1SPUPDPM&YUFOTJPOͰܕΛ֦ு MJLFUZQFDMBTTUZQF
DMBTTJOTUBODJBUJPO w ԋࢉࢠͷఆ͕ٛՄೳ <*> <^>)

w ෭࡞༻Λൃੜͤ͞ʹ͍͘ ࢀরಁաʹ͠΍͍͢ w σʔλܕ͕جຊJNNVUBCMFͳ஋ܕ w letʹΑΔଋറΛଅਐ͢Δݴޠ࢓༷ w *NNVUBCMFͳ஋͸ίϯύΠϥʹΑͬͯ࠷దԽ͞ΕΔ
4XJGUͰ͸ʜ

w౰ͨΓલͷΑ͏ʹΫϩʔδϟ͕͋Δ w౰ͨΓલͷΑ͏ʹύλʔϯϚον͕͋Δ w౰ͨΓલͷΑ͏ʹHVBSEจ͕͋Δ w౰ͨΓલͷΑ͏ʹ຤ඌ࠶ؼ͕࠷దԽ͞ΕΔ w౰ͨΓલͷΑ͏ʹΧϦʔԽʹઐ༻ͷߏจ͕͋Δ 4XJGUͰফ͑·ͨ͠ʂ 4XJGUͰ͸ʜ

ެࣜͳݟղ w"QQMFࣗ਎͸4XJGU͕ؔ਺ܕͩͱ͸શ͘ݴͬͯͳ͍

ެࣜͳݟղ w"QQMFࣗ਎͸4XJGU͕ؔ਺ܕͩͱ͸શ͘ݴͬͯͳ͍ ͕ɺ101701ͳϓϩάϥϛϯάΛڧ͘ਪ঑ (WWDC 2015 - Building Better Apps with
Value Types in Swift) (WWDC 2016 - Protocol and Value Oriented Programming in UIKit Apps) 001͔ΒͷύϥμΠϜγϑτ͸Ψν

ެࣜͳݟղ “Objective-C without the C” implies something subtractive, but Swift
dramatically expands the design space through the introduction of generics and functional programming concepts. - Chris Lattner

'VDOUJPOBM4XJGU$PNNVOJUZ w'VODUJPOBM4XJGU$POGFSFODF  IUUQGVOTXJGUDPOGDPN wUZQFMJGU4XJGU[ wUIPVHIUCPU3VOFT

ઐ໳Ͱॻ੶΋ग़͍ͯΔ

͜Ε͸΋͏ ؔ਺ܕϓϩάϥϛϯά͕Ͱ͖Δͱ ݴ͍͍ͬͯΜ͡Όͳ͍Ͱ͔͢Ͷʜ

͋Εʁ

ͳΜͰ·ͨ͋͑ͯࠓߋ ʮ4XJGUͰؔ਺ܕΆΑΆΑʙʯ Έ͍ͨͳ࿩Λ͍ͨ͠ͷ͔ શવ͜ͷཧ༝ʹͳͬͯͳ͘ͳ͍ʁ

8):48*'5

4XJGU1SPHSBNNJOH-BOHVBHF&WPMVUJPO IUUQTHJUIVCDPNBQQMFTXJGUFWPMVUJPO 4XJGUJTFWPMWJOH UPP GBTU

&OVNͰ࠶ؼతͳσʔλߏ଄Λ࡞Εͳ͍

4XJGUͰ࣮૷ࡁ enum List<T> { case null indirect case cons(T, List<T>)
} ˢ๯಄ͷϦετͷ࣮૷Ͱ΋࠶ؼ&OVNΛ࢖͍ͬͯΔ

UZQFBMJBTʹHFOFSJDT͕࢖͑ͳ͍

UZQFBMJBTʹHFOFSJDT͕࢖͑ͳ͍ 4XJGUͰ࢖͑ΔΑ͏ʹͳͬͨ

ଞʹ΋ʜ wFYQFSJNFOUBMͰ͸͋Δ͕ؔ਺߹੒ԋࢉࢠ͕ຊମʹ࣮૷  IUUQTHJUIVCDPNBQQMFTXJGUCMPCECDDCEGEEFTUEMJC JOUFSOBM4XJGU&YQFSJNFOUBM4XJGU&YQFSJNFOUBMTXJGU- w(FOFSJDT.BOJGFTUPͷதͰߴ֊ܕͷ࣮૷ܭը͋Γ  IUUQTHJUIVCDPNBQQMFTXJGUCMPCECDDCEGEEFEPDT (FOFSJDT.BOJGFTUPNEIJHIFSLJOEFEUZQFT   protocol Functor
{ associatedtype A func fmap<FB where FB ~= Self>(f: A -> FB.A) -> FB }

ׂͱΨϯΨϯมΘͬͯΔ wωοτͷ࣍৘ใ͸ݹ͘ͳ͍ͬͯΔ΋ͷ΋ଟ͍ wؔ਺ܕϓϩάϥϛϯάͷจ຺Ͱͷมߋ΋ؚ·ΕΔ 4XJGUJTFWPMWJOH UPP GBTU ʮ4XJGUͰؔ਺ܕϓϩάϥϛϯάແཧʯ ͬͯࢥͬͨਓ΋࠷৽৘ใʹ৮ΕΔͱ໘ന͍͔΋ʁ

Swift Functional Programming

Swift Functional Programming

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