初めての関数型プログラミング

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1. ॳΊͯͷ ؔ਺ܕϓϩάϥϛϯά @petitviolet Fringe81 Co., Ltd. 

2. About Me • খࢵ ߂و(Hiroki Komurasaki) • @petitviolet • ৽ଔ1೥໨(15ଔ)

   • Fringe81͍ͬͯ͏ΞυςΫͷձࣾ • Android/iOSͷ޿ࠂSDK։ൃ 

3. ॳΊͯͷ ؔ਺ܕϓϩάϥϛϯά 

4. ॳΊͯͷ ؔ਺ܕϓϩάϥϛϯά 

5. ॳΊͯͷ Haskell 

6. What is Haskell • ७ਮؔ਺ܕϓϩάϥϛϯάݴޠ • ஗ԆධՁ • ੩తܕ෇͚/ܕਪ࿦ •

   ΋ͳͲ 

7. ७ਮؔ਺ܕʁ • ෭࡞༻͕ແ͍ • ࢀরಁաੑ • ಉ͡ೖྗʹରͯ͠͸ৗʹಉ͡ग़ྗ • ؔ਺͸ୈҰڃ •

   jsͷΑ͏ʹؔ਺ΛΦϒδΣΫτͱͯ͠ѻ͑Δ 

8. ෭࡞༻͕ͳ͍ • ༩͑ΒΕͨҾ਺ͷΈΛ࢖ͬͯ݁ՌΛฦ͢ • ΦϒδΣΫτͷঢ়ଶͱ͔جຊతʹແ͍ 

9. ؔ਺ʹ͍ͭͯ 

10. ໋ྩܗݴޠͷؔ਺͸ ίϯϐϡʔλʹରͯ͠ ԿΛ͢Δͷ͔Λ఻͑Δ 

11. ؔ਺ܕϓϩάϥϛϯάݴޠͰ͸ ίϯϐϡʔλʹରͯ͠ ԿͰ͋Δͷ͔Λ఻͑Δ 

12. ? 

13. ؔ਺͸ԿͰ͋Δ͔Λ఻͑Δ • ϑΟϘφον਺ྻ // Python def fib(n): if n <

    2: return n return fib(n - 1) + fib(n - 2) [fib(i) for i in range(1, 11)] 

14. ؔ਺͸ԿͰ͋Δ͔Λ఻͑Δ • ϑΟϘφον਺ྻ // Haskell fib :: [Int] fib =

    1 : 1 : zipWith (+) fib (tail fib) take 10 fib 1, 1, 2, 3, 5, 8, 13, … 1, 1, 2, 3, 5, 8, 13, … 1, 1, 2, 3, 5, 8, 13,21… 

15. ஗ԆධՁ • ඞཁͳ෼͚ͩΛධՁ͢Δͷ͕஗ԆධՁ • ਺ྻࣗମΛఆٛग़དྷΔ • fibؔ਺͸ແݶ௕ͷϑΟϘφον਺ྻΛฦ͢ // Haskell fib

    :: [Int] fib = 1 : 1 : zipWith (+) fib (tail fib) fib # ࢮ take 10 fib 

16. ؔ਺߹੒ • Unixత • খ͞ͳؔ਺Λ૊Έ߹Θͤͯେ͖ͳ΋ͷΛ࡞Δ Prelude> length "hello" 5 Prelude>

    show 100 "100" Prelude> (length . show) 100 3 

17. ϥϜμࣜ Prelude> let add = \x y -> x +

    y Prelude> foldr add 0 [1..10] 55 

18. \͸ࢥ͍͖ͬΓ໨ΛࡉΊΔͱ ΪϦγϟจࣈͷϥϜμλʹ ݟ͑·͢ΑͶɻ ͍͢͝Haskellֶָ͘͠΅͏ʂ p73 

19. ͳΔ΄Ͳ 

20. ܕʹ͍ͭͯ 

21. ੩తܕ෇͚ && ܕਪ࿦ Prelude> let a = 5 + 4

    Prelude> :t a a :: Num a => a Prelude> let b :: Num a => a; b = (5 :: Num a => a) + (4 :: Num a => a) Prelude> :t b b :: Num a => a 

22. • ܕͷ࣋ͭੑ࣭Λද͢ΠϯλʔϑΣʔεͬΆ͍ • Numʹଐ͢ܕ͸”਺”ͱͯ͠ͷੑ࣭Λ࣋ͭ ܕΫϥε Prelude> :t 10 10 ::

    Num a => a Prelude> :t 10 :: Int 10 :: Int :: Int Prelude> :t 10 :: Double 10 :: Double :: Double 

23. Ϟφυ 

24. Ϟφυͷલʹཧղ͍ͨ͠΍ͭ • ϑΝϯΫλʔ • ΞϓϦΧςΟϒϑΝϯΫλʔ class Functor f where fmap

    :: (a -> b) -> f a -> f b class (Functor f) => Applicative f where pure :: a -> f a (<*>) :: f (a -> b) -> f a -> f b 

25. • จ຺Λ࣋ͭܭࢉΛ࣮ݱ͢Δ࢓૊Έ • Maybe͸͋Δ͔΋͠Εͳ͍͠ɺͳ͍͔΋ • List͸ෳ਺ͷ஋͕͋Δ͔΋͠Εͳ͍ Ϟφυ Prelude> Just 10

    >>= (\x -> Just(x + 4)) Just 14 Prelude> Nothing >>= (\x -> Just(x + 4)) Nothing 

26. • จ຺Λ࣋ͭܭࢉΛ࣮ݱ͢Δ࢓૊Έ • Maybe͸͋Δ͔΋͠Εͳ͍͠ɺͳ͍͔΋ • List͸ෳ਺ͷ஋͕͋Δ͔΋͠Εͳ͍ Ϟφυ Prelude> [1, 2]

    >>= (\x -> [10, 20] >>= (\y -> [x, y])) [1,10,1,20,2,10,2,20] Prelude> [1, 2] >>= (\x -> [] >>= (\y -> [x, y])) [] 

27. class Monad m where return :: Monad m => a

    -> m a (>>=) :: Monad m => m a -> (a -> m b) -> m b … B monad  C monad  Just 10 >>= (\x -> Just(show x)) = Just “10” B monad SFUVSO
    B return 10 :: Maybe Int = Just 10  C monad B 

28. • จ຺Λ࣋ͭ஋ಉ࢜ͷܭࢉΛ៉ྷʹ΍ΔͨΊͷ࢓૊Έ • Ϟφυ஋ͱɺϞφυ஋ΛฦΓ஋ͱ͢Δؔ਺Λ ͍͍ײ͡ʹ૊Έ߹ΘͤͯϞφυ஋ΛಘΔ • ܭࢉ݁ՌΛϞφυ஋ʹ͢Δ • Just 10

    ͱ show Λ࢖ͬͯJust “10” • ࣦഊͯͨ͠ΒશମΛࣦഊͤ͞Δ • Nothing Λ show ͠Α͏ͱ͢Δͱ Nothing Ϟφυ 

29. 

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