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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Considering the
introduction of the
anonymous function syntax
sugar into Go
!ZVSPZPSP
(Pʹແ໊ؔͷҥߏจ͍ΕͨΒͲ͏ͳΔͷʁ
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(Pͷແ໊ؔ
var f = func(x int) int { return x * 2 }
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͍ΘΏΔ"SSPX'VODUJPO͕΄͍͠
var f = (x int) int => { return x * 2 }
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ಈతܕ͖ͳݴޠͰʁ
const f = (x) => { return x * 2 }
+BWB4DSJQU
1ZUIPO
f = lambda x: x * 2
3VCZ
f = ->(x) { x * 2 }
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੩తܕ͖ͳݴޠͰʁ
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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(PͰ͜ΜͳܗͷߏจʹͳΓͦ͏
(name type, …) type => { function body }
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ྫ͑͜Μͳ;͏ʹ
(x int) int => { return x * 2 }
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(PίϯύΠϥΛվ͠Α͏ʂ
src/cmd/compile/
https://github.com/golang/go
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ίϯύΠϥʹͭͷϑΣʔζ͕͋Δ
1. Parsing
2. Type-checking and AST transformations
3. Generic SSA
4. Generating machine code
TSDDNEDPNQJMF3&"%.&NE
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ҥߏจͷՃͳͷͰɺ1BSTFSΛมߋ
1. Parsing
2. Type-checking and AST transformations
3. Generic SSA
4. Generating machine code
TSDDNEDPNQJMF3&"%.&NE
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(Pͷߏจղੳ
LL(1)
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͍͍ͤͥͻͱͭઌͷτʔΫϯ͔͠ઌಡΈ͠ͳ͍
var f = ( x * 2 )
↑
current: ( : _Lparen
next : x : _Name
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ͷ࣍ʹ໊લ͕དྷͨΒɺࣜ &YQS
ʹܾ·Δ
var f = ( x * 2 )
↑
current: ( : _Lparen
next : x : _Name
Expr
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"SSPX'VODUJPO͕ೖΔͱʜʜ
var f = ( x int ) int => { … }
↑
current: ( : _Lparen
next : x : _Name
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ͷ࣍ʹ໊લ͕དྷͯɺࣜ &YQS
͔ؔ 'VOD5ZQF
͔
Θ͔Βͳ͍
var f = ( x int ) int => { … }
↑
current: ( : _Lparen
next : x : _Name
Expr or FuncType?
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Ͳ͏ʹ͔ͳΒͳ͍
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ߏจΛม͑ͯΈΑ͏
->(name type, …) type { function body }
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3VCZͬΆ͘
͜ΕͳΒύʔεͰ͖Δͧ
->(x int) int => { return x * 2 }
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AGVODAΛAAʹม͑Δ͚ͩ
->(x int) int => { return x * 2 }
func(x int) int => { return x * 2 }
↓
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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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ؔͷܕͰ͔͚ΔΑ͏ʹ͠Α͏
var f: ->(int) int =
->(x int) int { return x * 2 }
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%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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Ͱɺ͑ͦ͏ʁ
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ΈΜͳେ͖IUUQ4FSWFS
http.HandleFunc("/",
->(w http.ResponseWriter, r *http.Request) { ... })
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͠(Pʹ(FOFSJDT͕ೖͬͨΒ
var arr = [1, 2, 3]
arr.map( ->(x int) int { return x * 2 })
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AGVODAΑΓจࣈݮͬͨ
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͋Μ·ΓมΘΒͳ͍ͷͰʜʜ
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ͨͱ͑ɺ+BWBͰҾͷܕએݴΛ
লུͰ͖Δ
↓
+BWB
Function f =
(Integer x) -> { return x * 2; };
Function f =
(x) -> { return x * 2; };
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4DBMBͰฦΓܕΛਪͯ͘͠ΕΔ
↓
4DBMB
val f: Int => Int = (x: Int) => { x * 2 }
val f = (x: Int) => { x * 2 }
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SFUVSOΛলུͰ͖Δݴޠଟ͍
↓
+BWB
Function f =
(x) -> { return x * 2; };
Function f =
(x) -> { x * 2; };
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͕ؔΘΕΔॴͷܕ͕Θ͔͍ͬͯΔ߹
ؔࣗମͷҾฦΓΛলུͰ͖Δ
4DBMB
val arr = Array(1, 2)
// Array#mapͷҾ
// (Int) => AͳͷͰҾ͕Intͱਪɺ
// ؔຊମ͔ΒฦΓ͕Intͱਪ
arr.map((x) => { x * 2 })
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ແ໊Ҿ1MBDFIPMEFSͳͲɺ
ͬͱলུͰ͖Δֻ͚ʜ
4DBMB
val arr = Array(1, 2)
// ແ໊ؔͷҾΛ _ Ͱड͚Δ
arr.map(_ * 2)
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ແ໊ؔΛ؆ܿ໌ྎʹॻͨ͘Ίʹ
ҥߏจͷଞʹ֤छͷলུه๏
- Argument Type Inference
- Return Type Inference
- implicit return statement
- anonymous argument placeholder
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ͦͦͦ͜·Ͱলུ͍ͨ͠
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Α͏͢Δʹ
Conclusion
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ؾ࣋ͪΑ͘ແ໊ؔΛॻͨ͘Ίʹ
ߟ͑Δ͜ͱ͕ଟ͍
- Syntax
- Type Inference
- etc
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(Pʹ͋ͬͨจ๏ͲΜͳܗ͕Α͍͔ɺ
Ұॹʹߟ͑ͯΈ·ͤΜ͔