Scala Magic, Alexander Podhaliusin
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Talk given by Alexander Podhaliusin at scaladev'12 (scaladev.ru)
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Scala Magic, Alexander Podhaliusin
- 1. Scala magic 仍亠从舒仆亟 仂亟舒仍ﾐ経湖 19 仄舒 2012 亞. 1 / 19
- 2. Syntactic sugar For comprehensions By-name parameters Non local return Local functions Lazy values Generated ByteCode Binary Syntactic sugar compatibility Questions? 2 / 19
- 3. For comprehensions Syntactic sugar For Scala for 磦仍磳 亳仆舒从亳亠从亳仄 舒舒仂仄, 亠仄 仆亠 comprehensions By-name 仄亠仆亠亠 仗舒于亳仍舒 仗亠仂弍舒亰仂于舒仆亳 亟仂于仂仍仆仂 仍仂亢仆 parameters Non local return 亟亳仆 亞亠仆亠舒仂 yield 仂亢亠, 仂 于亰仂于 仄亠仂亟舒 map Local functions Lazy values 亟亳仆 亞亠仆亠舒仂 弍亠亰 yield 仂亢亠, 仂 foreach Generated 亠从仂仍从仂 亞亠仆亠舒仂仂于 舒仆仍亳ﾑ 于仂 flatMap ByteCode Binary compatibility Questions? f o r ( i < 1 t o 5) (1 to 5) . map { i = i > i } yield i i (1 to 5) . f o r e a c h { f o r ( i < 1 t o println ( i ) 5) 油 } i = println ( i ) > f o r { i < 1 t o 5 (1 to 5) . f l a t M a p { j < 1 t o 5} i = (1 to 5) . map { j = i + j } > > yield i + j } 仂亟仂弍仆亠亠 仄仂亢仆仂 仗仂亳舒 于 仗亠亳亳从舒亳亳. 3 / 19
- 4. By-name parameters Syntactic sugar For 仂亰仄仂亢仆仂 于 于亰仂于 仄亠仂亟舒 仗亠亠亟舒于舒 于舒亢亠仆亳 comprehensions By-name 仍亠仆亳于仂 仂 亟亞仂亶 仗亳仄亠 仂亞仂, 亞亟亠 仆亠磦仆仂 仄仂亞 弍 parameters Non local return 亰舒亳 closures. 弌仍亠亟ﾑ亳亠 亟于舒 仗亳仄亠舒 亳亟亠仆亳仆: Local functions Lazy values d e f foo ( x : => Int ) { d e f foo ( x : ( ) => Int ) { Generated ByteCode println ( x ) println ( x ( ) ) } } Binary compatibility foo ( 1 ) foo ( ( ) => 1 ) Questions? 丼仂 亳亰亠亟从舒 仄仂亢亠 仗亳于仂亟亳 从 仂亳弍从亠 (仗舒舒仄亠 弍亟亠 于亳仍 从舒亢亟亶 舒亰, 从仂亞亟舒 从 仆亠仄 弍亟亠 仗仂亳亰于仂亟亳 仂弍舒亠仆亳亠). 4 / 19
- 5. Non local return Syntactic sugar For Return statement 于仆亳 closure 仆舒 亟亠仍亠 从仂仄仗亳仍亳亠 于 comprehensions By-name 从仂亟, 从仂仂亶 弍仂舒亠 NonLocalReturnControl. parameters Non local return 弍仂仍亳仆于亠 仍舒亠于 仂 亟仂弍仆仂, 仆仂 仆亢仆仂 亳于舒 Local functions 仍亠亟ﾑ亠亠 Lazy values Generated 从亳亳仆 仗仂 仗仂亳亰于仂亟亳亠仍仆仂亳 从从舒 从仂亟舒 仂 ByteCode Binary exception 仍亠亟亠 亳亰弍亠亞舒 compatibility 亠仍亰 仍仂于亳 Throwable 于 仂仄 仄亠亠, 亞亟亠 仂 Questions? exception 弍仂舒亠 亳仍 亳仆舒从亳亠从仂亞仂 舒舒舒 仂仗亳舒仆仆仂亞仂 舒仆亠亠, 于亠 仂 仄仂亢亠 仗仂亳仂亟亳 仆亠磦仆仂 (for-comprehensions 亳 by-name parameters) 5 / 19
- 6. Local functions Syntactic sugar For Java 仍ﾐ頴笑 于仗仂仄仂亞舒亠仍仆亶 从仂亟 仂仂仄仍磳 于 于亳亟亠 comprehensions By-name private 仄亠仂亟仂于 仆舒 仂于仆亠 从仍舒舒. Scala 仂 仄仂亢仆仂 parameters Non local return 亟亠仍舒 弍仂仍亠亠 从亳仂于舒仆仆仄, 亠仍亳 亳仗仂仍亰仂于舒 Local functions 仍仂从舒仍仆亠 仄亠仂亟, 仂 仆舒 仂于仆亠 bytecode 仗仂仍舒亠 Lazy values Generated 仗亳仄亠仆仂 仂亢亠 舒仄仂亠: ByteCode Binary compatibility import scala . runtime . IntRef ; public class LocalFunctions { Questions? class LocalFunctions { p u b l i c void foo () { def foo { I n t R e f i $ 1 = new I n t R e f ( 1 ) ; var i = 1 i n t j$1 = 2; val j = 2 l o c a l $ 1 ( i$1 , j$1 ) ; def local { i += j 油 l o c a l $ 1 ( i$1 , j$1 ) ; } } p r i v a t e f i n a l void local$1 ( local IntRef intref , i n t i ) { local i n t r e f . e l e m += i ; } } } p u b l i c L o c a l F u n c t i o n s ( ) {} } 6 / 19
- 7. Lazy values Syntactic sugar For 亅仂 仂亢亠 亳仆舒从亳亠从亳亶 舒舒, 从仂仂亶 仆舒亟仂 comprehensions By-name 亳仗仂仍亰仂于舒 舒从从舒仆仂 (舒从 从舒从 于仂亰仄仂亢仆 deadlock 亳 parameters Non local return 仗仂弍仍亠仄 仗仂亳亰于仂亟亳亠仍仆仂亳). 亠亰舒于亳亳仄仂 仂 Local functions 舒仗仂仍仂亢亠仆亳 lazy val, 从仂仄仗亳仍亳亠 仂仆 舒从亳仄 仂弍舒亰仂仄 Lazy values Generated ByteCode import scala . runtime . BoxedUnit ; Binary p u b l i c c l a s s Lazy { compatibility public int x () { i f ( ( b i t m a p $ 0 & 2 ) == 0 ) Questions? synchronized ( this ) { i f ( ( b i t m a p $ 0 & 2 ) == 0 ) { x = 1; bitmap$0 = bitmap$0 | 2; c l a s s Lazy { lazy val x = 1 油 } BoxedUnit _tmp = } BoxedUnit . UNIT ; } return x ; } p u b l i c L a z y ( ) {} private int x ; public v o l a t i l e i n t bitmap$0 ; } 7 / 19
- 8. Syntactic sugar Generated ByteCode Classes and names Objects Traits Trait subclasses Linearization Initialisation order Binary Generated ByteCode compatibility Questions? 8 / 19
- 9. Classes and names Syntactic sugar 仍 从仍舒仂于 仆亳亠亞仂 仄舒亞亳亠从仂亞仂 仆亠 仗仂亳仂亟亳. Generated ByteCode 舒从 仗亠仂弍舒亰ﾑ 亳仄亠仆舒. 仍 弍仂仍亳仆于舒 亳仄于仂仍仂于 Classes and names Objects 亠 亠亞仂 亠从仂于亶 从于亳于舒仍亠仆 Traits Trait subclasses : 油 $colon Linearization Initialisation order + 油 $plus Binary 息 油 $u00A9 compatibility Questions? 仆亳 Scala 从仂亟舒 仄仂亢仆仂 亳仗仂仍亰仂于舒 仂弍舒 于舒亳舒仆舒 仗仂亟仂弍仆 亳亟亠仆亳亳从舒仂仂于 仂亟仂弍仆亠亠 仄仂亢仆仂 亳亰亳 仗亠仂弍舒亰仂于舒仆亳 仗仂仄仂 仄亠仂亟仂于 NameTransfomer.encode/decode 亳亰 scala-compiler.jar. 9 / 19
- 10. Objects Syntactic sugar 弍亠从 于亠亞亟舒 从仂仄仗亳仍亳亠 于 亟于舒 从仍舒舒. Generated ByteCode Classes and names Object$ 仂亟亠亢亳 于 亠弍亠 舒亳亠从仂亠 仗仂仍亠 MODULE$, Objects 舒 舒从亢亠 从仂亟 于亠 仄亠仂亟仂于 Traits Trait subclasses Object 仂亟亠亢亳 于 亠弍亠 于亠 舒亳亠从亳亠 仄亠仂亟 Linearization Initialisation order 仂弍亠从舒, 亠仍仂仄 于亳亟舒 Object$.MODULE$.foo() Binary compatibility 舒亢仆仂 仗仂仆亳仄舒, 仂 舒亳亠从亳亠 仄亠仂亟 亟仂弍舒于仍亠仆 亟仍 Questions? 亟仂弍于舒 于亰仂于舒 亳亰 Java. 丐亠仄 仆亠 仄亠仆亠亠 仂仆亳 亟仂弍舒于仍ﾑ 仆亠 于亠亞亟舒. Companion Trait 仆亠 亟仂弍舒于仍磳 仆亳亠亞仂. Companion Class 仆亠 亟仂弍舒于仍ﾑ 仄亠仂亟 舒从亳仄 亳仄亠仆亠仄, 从仂仂仂亠 亢亠 亠 于 仂仄 从仍舒亠 亠仂亟 从仍舒舒 java.lang.Object 10 / 19
- 11. Traits Syntactic sugar 仍亳 trait 仂仍亳舒亠 仂 仂弍仆仂亞仂 亳仆亠亠亶舒 于 Java Generated ByteCode 仆舒仍亳亳亠仄 从仂仆从亠仆 仄亠仂亟仂于, 仂 从 仂仂于亠于ﾑ亠仄 Classes and names Objects 亳仆亠亠亶 弍亟亠 仂亰亟舒仆 从仍舒 Trait$class Traits Trait subclasses 亳仄仗仍亠仄亠仆舒亳亠亶 亳 仄亠仂亟仂于. Linearization Initialisation order Binary public abstract class A$class { compatibility public static int foo ( A $this , int x) { Questions? return 2; trait A { } val x = 1 油 public s t a t i c void $init$ ( A $this def foo ( x : Int ) = 2 ) { } $this . test$A$_setter_$x_$eq (1) ; } } 11 / 19
- 12. Trait subclasses Syntactic sugar 仍亳 于 Java 仗仂仗舒 亠舒仍亳亰仂于舒 Trait, 于 从仂仂仂仄 亠 Generated ByteCode 亢亠 亳仄仗仍亠仄亠仆亳仂于舒仆亠 仄亠仂亟, 仂 亳 于亠 舒于仆仂 Classes and names Objects 仗亳仍仂 弍 亠舒仍亳亰仂于于舒. 亞仂亶 于仂仗仂, 仂 仂 Traits Trait subclasses 仄仂亢仆仂 亟亠仍舒 仗亠亟亠仍仆仂 仍亠亞从仂: Linearization Initialisation order Binary i n t foo ( ) { r e t u r n Trait$class . foo ( t h i s ) ; } compatibility Questions? 仍舒亠 仆舒仍亠亟仆亳从仂于 仆舒仗亳舒仆仆 仆舒 Scala, 仂 亢亠 舒仄仂亠 亟亠仍舒亠 从仂仄仗亳仍仂. 12 / 19
- 13. Linearization Syntactic sugar 亅仂 舒仍亞仂亳仄 亠弍亠 从仂仄仗亳仍仂, 仂弍 仂仗亠亟亠仍亳, Generated ByteCode 于 从舒从仂仄 仗仂磲从亠 仆舒亟仂 亳从舒 仄亠仂亟 于 弍舒亰仂于 从仍舒舒. Classes and names Objects Traits Trait subclasses trait A extends B Linearization trait B Initialisation order class C extends B Binary class D extends C with A compatibility Questions? 亟亠 仗仂磲仂从 D, A, C, B. 仍亳 亟于舒 仄亠仂亟舒 仂亟亳仆舒从仂于仂亶 亳亞仆舒仂亶 弍亠亰 仄仂亟亳亳从舒仂舒 override 仗亳仂亟 于 从仍舒 仆舒仍亠亟仆亳从 亳亰 仗亠亠亶仂于, 仂 仂亳弍从亳 仆亠 弍亟亠, 舒从 从舒从 仂弍磶舒亠仍仆仂 仆舒亟仂 弍亟亠 仗亠亠仂仗亠亟亠仍亳 亳亞仆舒. 仍亳 亢亠 从仂亞仂-仂 亠 仄仂亟亳亳从舒仂 override, 仄仂亢亠 仍亳 仆亠磦仆亶 override 仂亞仍舒仆仂 仗舒于亳仍舒仄 仍亳仆亠舒亳亰舒亳亳. 13 / 19
- 14. Initialisation order Syntactic sugar 仆亳亳舒仍亳亰舒亳 仗仂亳仂亟亳 于 仗仂磲从亠, 仂弍舒仆仂仄 Generated ByteCode 仍亳仆亠舒亳亰舒亳亳. 仍亳 从 仗亠亠仄亠仆仆仂亶 仂弍舒亳 亟仂 仂亞仂, 从舒从 Classes and names Objects 仂仆舒 仗仂亳仆亳亳舒仍亳亰亳仂于舒仆舒, 仄仂亢仆仂 仗仂仍亳 NPE. Traits Trait subclasses 亟于舒 仗仂仂弍舒 亳亰弍舒于亳 仂 仗仂亟仂弍仆 仗仂弍仍亠仄: Linearization Initialisation order 仗仂仍亰仂于舒 lazy val Binary compatibility 仗仂仍亰仂于舒 early definitions Questions? 14 / 19
- 15. Syntactic sugar Generated ByteCode Binary compatibility Methods Values Lazy values Questions? Binary compatibility 15 / 19
- 16. Methods Syntactic sugar 亟亠 于亠 仂亠仆 仗仂仂亢亠 仆舒 Java. 丼舒亠 于亠亞仂 仗仂弍仍亠仄 仆亠 Generated ByteCode 弍亟亠. Binary compatibility 仂弍舒于仍 仄亠仂亟 仄仂亢仆仂 亟舒亢亠 于 Trait, 仆仂 仂仍从仂 亠仍亳 Methods Values 舒亠 仄亠仂亟 仆亠 仍舒ﾑ 仆舒 仆仂于亠, 舒从 从舒从 Lazy values 亳仄仗仍亠仄亠仆舒亳亳 于 从仍舒 仆舒仍亠亟仆亳从亳 亟仂弍舒于仍亠仆 仆亠 Questions? 弍亟. 从仍舒 仂仗舒仆仂 亟仂弍舒于仍 仄亠仂亟, 亳仄亠仆舒 从仂仂 仂于仗舒亟舒ﾑ 亳仄亠仆亠仄 仄亠仂亟仂于 亳亰 Companion Object, 舒从 从舒从 舒亳亠从亳亠 亠舒仍亳亰舒亳亳 弍亟 亟舒仍亠仆 从仂仄仗亳仍仂仂仄, 仂 仄仂亢亠 于亰于舒 仗仂弍仍亠仄 从仂亟仂仄 仆舒仗亳舒仆仆仄 仆亠 仆舒 Scala. 16 / 19
- 17. Values Syntactic sugar 仍亳 仗亠亠仄亠仆仆舒 仆舒仂亟亳 于 从仍舒亠 亳仍亳 仂弍亠从亠, 仂 Generated ByteCode 仗亠亠仄亠仆仆舒 从仂仄仗亳仍亳亠 于 getter, setter (亟仍 variables) 亳 Binary compatibility field, 从仂仂亶 亳仆亳舒仍亳亰亳亠 于 从仂仆从仂亠 从仍舒舒. Methods 亰仆舒亳 于亠 弍亟亠 舒从亢亠 仂仂仂 从舒从 亳 仄亠仂亟舒仄亳. Values Lazy values 仍亳 仗亠亠仄亠仆仆舒 仆舒仂亟亳 于 Trait, 仂 仂仆舒 从仂仄仗亳仍亳亠 Questions? 于 getter 亳 setter (于亠亞亟舒). 仆亳亳舒仍亳亰舒亳 仗仂亳仂亟亳 于 仄亠仂亟亠 Trait$class.$init$ 亠亠亰 于亰仂于 setter. 仆舒亳 亟仂弍舒于仍 仗亠亠仄亠仆仆 于 亠亶 仆亠仍亰. 丐舒从 从舒从 弍亟亠 于亰于舒仆 舒弍舒从仆亶 setter. 仂 舒仆舒仍仂亞亳仆仄 仗亳亳仆舒仄 仆亠仍亰 亳亰仄亠仆 def 仆舒 val 丐亠仄 仆亠 仄亠仆亠亠 val 仆舒 def 舒从亢亠 亳亰仄亠仆 仆亠仍亰, 舒从 从舒从 仂亞亟舒 于 从仍舒舒 仆舒仍亠亟仆亳从舒, 亞亟亠 从舒从 舒亰 亳 舒仆亳 field, 仗亠亠仄亠仆仆舒 仆亠 弍亟亠 仗仂亳仆亳亳舒仍亳亰亳仂于舒仆舒. 17 / 19
- 18. Lazy values Syntactic sugar 仗仂亟从仍舒舒 仆亠 亞亠仆亠亳亠 field bitmap, 亠仍亳 仂仆 亠 于 Generated ByteCode 弍舒亰仂于仂仄 从仍舒亠. Binary compatibility 仂仂仄 于 亳 仍舒 亟仂弍舒于仍 lazy value 于 从仍舒 Methods Values 仆亠仍亰 Lazy values Trait 亟仂弍舒于仍 仄仂亢仆仂, 亠仍亳 舒 仗亠亠仄亠仆仆舒 仆亠 Questions? 弍亟亠 亳仗仂仍亰仂于舒仆舒 于 舒仂仄 从仂亟亠 丐舒从 从舒从 从仂仄仗亳仍亳 lazy val 于 Trait 仂 从仂仄仗亳仍亳亳 仄亠仂亟舒 仆亠 仂仍亳舒亠 仂于亠仄, 仂 亳 仄仂亢仆仂 亰舒仄亠仆 亟亞 仆舒 亟亞舒, 亳于舒 仂仍从仂, 仂 于 仆舒仍亠亟仆亳从舒 仗仂亟仂弍仆舒 亠仄舒仆亳从舒 仆亠 亳亰仄亠仆亳 18 / 19
- 19. Syntactic sugar Generated ByteCode Binary compatibility Questions? Questions? 19 / 19