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

GoCon 2019 LT

Transcript

1. Considering the
   introduction of the
   anonymous function syntax
   sugar into Go
   !ZVSPZPSP
   (Pʹແ໊ؔ਺ͷ౶ҥߏจ͍ΕͨΒͲ͏ͳΔͷʁ
   

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

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3. ͍ΘΏΔ"SSPX'VODUJPO͕΄͍͠
   var f = (x int) int => { return x * 2 }
   

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4. ಈతܕ෇͖ͳݴޠͰ͸ʁ
   const f = (x) => { return x * 2 }
   +BWB4DSJQU
   1ZUIPO
   f = lambda x: x * 2
   3VCZ
   f = ->(x) { x * 2 }
   

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5. ੩తܕ෇͖ͳݴޠͰ͸ʁ
   const f = (x:number): number =>
   { return x * 2 }
   5ZQF4DSJQU
   +BWB
   4DBMB
   Function f =
   (Integer x) -> { return x * 2; };
   val f: (Int) => Int = (x) =>
   { x * 2 }
   

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

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

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

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9. ίϯύΠϥʹ͸ͭͷϑΣʔζ͕͋Δ
   1. Parsing
   2. Type-checking and AST transformations
   3. Generic SSA
   4. Generating machine code
   TSDDNEDPNQJMF3&"%.&NE
   

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10. ౶ҥߏจͷ௥ՃͳͷͰɺ1BSTFSΛมߋ
    1. Parsing
    2. Type-checking and AST transformations
    3. Generic SSA
    4. Generating machine code
    TSDDNEDPNQJMF3&"%.&NE
    

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11. (Pͷߏจղੳ
    LL(1)
    

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12. ͍͍ͤͥͻͱͭઌͷτʔΫϯ͔͠ઌಡΈ͠ͳ͍
    var f = ( x * 2 )
    ↑
    current: ( : _Lparen
    next : x : _Name
    

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13. ͷ࣍ʹ໊લ͕དྷͨΒɺࣜ &YQS
    ʹܾ·Δ
    var f = ( x * 2 )
    ↑
    current: ( : _Lparen
    next : x : _Name
    Expr
    

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14. "SSPX'VODUJPO͕ೖΔͱʜʜ
    var f = ( x int ) int => { … }
    ↑
    current: ( : _Lparen
    next : x : _Name
    

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15. ͷ࣍ʹ໊લ͕དྷͯ΋ɺࣜ &YQS
    ͔ؔ਺ 'VOD5ZQF
    ͔
    Θ͔Βͳ͍
    var f = ( x int ) int => { … }
    ↑
    current: ( : _Lparen
    next : x : _Name
    Expr or FuncType?
    

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16. Ͳ͏ʹ͔ͳΒͳ͍
    
    

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

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18. 3VCZͬΆ͘
    ͜ΕͳΒύʔεͰ͖Δͧ
    ->(x int) int => { return x * 2 }
    

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19. AGVODAΛAAʹม͑Δ͚ͩ
    ->(x int) int => { return x * 2 }
    func(x int) int => { return x * 2 }
    ↓
    

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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(-)
    

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21. ؔ਺ͷܕ΋Ͱ͔͚ΔΑ͏ʹ͠Α͏
    var f: ->(int) int =
    ->(x int) int { return x * 2 }
    

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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)
    }
    

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23. Ͱɺ࢖͑ͦ͏ʁ
    
    

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

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

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26. AGVODAΑΓจࣈݮͬͨ
    
    

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27. ͋Μ·ΓมΘΒͳ͍ͷͰ͸ʜʜ
    
    

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28. ͨͱ͑͹ɺ+BWBͰ͸Ҿ਺ͷܕએݴΛ
    লུͰ͖Δ
    ↓
    +BWB
    Function f =
    (Integer x) -> { return x * 2; };
    Function f =
    (x) -> { return x * 2; };
    

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29. 4DBMBͰ͸ฦΓ஋ܕΛਪ࿦ͯ͘͠ΕΔ
    ↓
    4DBMB
    val f: Int => Int = (x: Int) => { x * 2 }
    val f = (x: Int) => { x * 2 }
    

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30. SFUVSOΛলུͰ͖Δݴޠ΋ଟ͍
    ↓
    +BWB
    Function f =
    (x) -> { return x * 2; };
    Function f =
    (x) -> { x * 2; };
    

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31. ؔ਺͕࢖ΘΕΔ৔ॴͷܕ͕Θ͔͍ͬͯΔ৔߹͸
    ؔ਺ࣗମͷҾ਺΍ฦΓ஋ΛলུͰ͖Δ
    4DBMB
    val arr = Array(1, 2)
    // Array#mapͷҾ਺͸
    // (Int) => AͳͷͰҾ਺͕Intͱਪ࿦ɺ
    // ؔ਺ຊମ͔ΒฦΓ஋͕Intͱਪ࿦
    arr.map((x) => { x * 2 })
    

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

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33. ແ໊ؔ਺Λ؆ܿ໌ྎʹॻͨ͘Ίʹ͸
    ౶ҥߏจͷଞʹ֤छͷলུه๏΋
    - Argument Type Inference
    - Return Type Inference
    - implicit return statement
    - anonymous argument placeholder
    
    

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34. ͦ΋ͦ΋ͦ͜·Ͱলུ͍ͨ͠
    

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35. Α͏͢Δʹ
    Conclusion
    

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

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37. (Pʹ͋ͬͨจ๏͸ͲΜͳܗ͕Α͍͔ɺ
    Ұॹʹߟ͑ͯΈ·ͤΜ͔
    

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