Goに無名関数の糖衣構文いれたらどうなるの？ / Considering the introduction of the anonymous function syntax sugar into Go

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1. Considering the introduction of the anonymous function syntax sugar into

   Go !ZVSPZPSP (Pʹແ໊ؔ਺ͷ౶ҥߏจ͍ΕͨΒͲ͏ͳΔͷʁ

2. (Pͷແ໊ؔ਺ var f = func(x int) int { return x

   * 2 }

3. ͍ΘΏΔ"SSPX
   'VODUJPO͕΄͍͠ var f = (x int) int => { return

   x * 2 }

4. ಈతܕ෇͖ͳݴޠͰ͸ʁ const f = (x) => { return x *

   2 } +BWB4DSJQU 1ZUIPO f = lambda x: x * 2 3VCZ f = ->(x) { x * 2 }

5. ੩తܕ෇͖ͳݴޠͰ͸ʁ const f = (x:number): number => { return x

   * 2 } 5ZQF4DSJQU +BWB 4DBMB Function<Integer, Integer> f = (Integer x) -> { return x * 2; }; val f: (Int) => Int = (x) => { x * 2 }

6. (PͰ͸͜ΜͳܗͷߏจʹͳΓͦ͏ (name type, …) type => { function body }

7. ྫ͑͹͜Μͳ;͏ʹ (x int) int => { return x * 2

   }

8. (PίϯύΠϥΛվ଄͠Α͏ʂ src/cmd/compile/ https://github.com/golang/go

9. ίϯύΠϥʹ͸ͭͷϑΣʔζ͕͋Δ 1. Parsing 2. Type-checking and AST transformations 3. Generic

   SSA 4. Generating machine code TSDDNEDPNQJMF3&"%.&NE

10. ౶ҥߏจͷ௥ՃͳͷͰɺ1BSTFSΛมߋ 1. Parsing 2. Type-checking and AST transformations 3. Generic

    SSA 4. Generating machine code TSDDNEDPNQJMF3&"%.&NE

11. (Pͷߏจղੳ LL(1)

12. ͍͍ͤͥͻͱͭઌͷτʔΫϯ͔͠ઌಡΈ͠ͳ͍ var f = ( x * 2 ) ↑

    current: ( : _Lparen next : x : _Name

13. ͷ࣍ʹ໊લ͕དྷͨΒɺࣜ &YQS ʹܾ·Δ var f = ( x * 2

    ) ↑ current: ( : _Lparen next : x : _Name Expr

14. "SSPX
    'VODUJPO͕ೖΔͱʜʜ var f = ( x int ) int =>

    { … } ↑ current: ( : _Lparen next : x : _Name

15. ͷ࣍ʹ໊લ͕དྷͯ΋ɺࣜ &YQS ͔ؔ਺ 'VOD5ZQF ͔
    Θ͔Βͳ͍ var f = (

    x int ) int => { … } ↑ current: ( : _Lparen next : x : _Name Expr or FuncType?

16. Ͳ͏ʹ͔ͳΒͳ͍

17. ߏจΛม͑ͯΈΑ͏ ->(name type, …) type { function body }

18. 3VCZͬΆ͘
    ͜ΕͳΒύʔεͰ͖Δͧ ->(x int) int => { return x *

    2 }

19. AGVODA
    Λ
    AA
    ʹม͑Δ͚ͩ ->(x int) int => { return x * 2

    } func(x int) int => { return x * 2 } ↓

20. ॻ͍ͯΈͨ src/cmd/compile/internal/syntax/parser.go | 2 +- src/cmd/compile/internal/syntax/scanner.go | 7 ++++++- src/cmd/compile/internal/syntax/token_string.go

    | 4 ++-- src/cmd/compile/internal/syntax/tokens.go | 1 + 4 files changed, 10 insertions(+), 4 deletions(-)

21. ؔ਺ͷܕ΋Ͱ͔͚ΔΑ͏ʹ͠Α͏ var f: ->(int) int = ->(x int) int {

    return x * 2 }

22. %FNP package main import "fmt" func main() { f :=

    ->(x int, y int) int { return x + y } fmt.Printf("%d\n", f(3, 4)) fmt.Printf("%d", higherFunc(f)) } func higherFunc(f ->(x int, y int) int) int { return f(1, 2) }

23. Ͱɺ࢖͑ͦ͏ʁ

24. ΈΜͳେ޷͖IUUQ4FSWFS http.HandleFunc("/", ->(w http.ResponseWriter, r *http.Request) { ... })

25. ΋͠(Pʹ(FOFSJDT͕ೖͬͨΒ var arr = [1, 2, 3] arr.map( ->(x int)

    int { return x * 2 })

26. AGVODA
    ΑΓจࣈݮͬͨ

27. ͋Μ·ΓมΘΒͳ͍ͷͰ͸ʜʜ

28. ͨͱ͑͹ɺ+BWBͰ͸Ҿ਺ͷܕએݴΛ
    লུͰ͖Δ ↓ +BWB Function<Integer, Integer> f = (Integer x)

    -> { return x * 2; }; Function<Integer, Integer> f = (x) -> { return x * 2; };

29. 4DBMBͰ͸ฦΓ஋ܕΛਪ࿦ͯ͘͠ΕΔ ↓ 4DBMB val f: Int => Int = (x:

    Int) => { x * 2 } val f = (x: Int) => { x * 2 }

30. SFUVSOΛলུͰ͖Δݴޠ΋ଟ͍ ↓ +BWB Function<Integer, Integer> f = (x) -> {

    return x * 2; }; Function<Integer, Integer> f = (x) -> { x * 2; };

31. ؔ਺͕࢖ΘΕΔ৔ॴͷܕ͕Θ͔͍ͬͯΔ৔߹͸
    ؔ਺ࣗମͷҾ਺΍ฦΓ஋ΛলུͰ͖Δ 4DBMB val arr = Array(1, 2) // Array<Int>#mapͷҾ਺͸

    // (Int) => AͳͷͰҾ਺͕Intͱਪ࿦ɺ // ؔ਺ຊମ͔ΒฦΓ஋͕Intͱਪ࿦ arr.map((x) => { x * 2 })

32. ແ໊Ҿ਺1MBDFIPMEFSͳͲɺ
    ΋ͬͱলུͰ͖Δ࢓ֻ͚΋ʜ 4DBMB val arr = Array(1, 2) // ແ໊ؔ਺ͷҾ਺Λ

    _ Ͱड͚Δ arr.map(_ * 2)

33. ແ໊ؔ਺Λ؆ܿ໌ྎʹॻͨ͘Ίʹ͸
    ౶ҥߏจͷଞʹ֤छͷলུه๏΋ - Argument Type Inference - Return Type Inference

    - implicit return statement - anonymous argument placeholder

34. ͦ΋ͦ΋ͦ͜·Ͱলུ͍ͨ͠

35. Α͏͢Δʹ Conclusion

36. ؾ࣋ͪΑ͘ແ໊ؔ਺Λॻͨ͘Ίʹ͸
    ߟ͑Δ͜ͱ͕ଟ͍ - Syntax - Type Inference - etc

37. (Pʹ͋ͬͨจ๏͸ͲΜͳܗ͕Α͍͔ɺ
    Ұॹʹߟ͑ͯΈ·ͤΜ͔