Slide 1
Slide 1 text
Ծؔςʔϒϧͱ
ܕΫϥεΛݟൺΔ
ҏಸ ྛଠ
id:tarao @tarao @oarat
2024-01-26
ୈޒճؔܕϓϩάϥϛϯά (Ծ) ͷձ
Slide 2
Slide 2 text
ࣗݾհ
໊લ ɹ
͍ ͳ
ҏಸ
ɹ ɹ
ΓΜͨΖ͏
ྛଠ
ɹ ( id:tarao @tarao @oarat)
2021-02 ∼ ͯͳ ΤϯδχΞϦϯάϚωʔδϟ
2013-04 ∼ ͯͳ ΤϯδχΞ
2010-04 ∼ ژେֶ ใֶݚڀՊ (ࠤ౻ɾޒेཛྷݚ)
ത࢜ޙظ՝ఔ / ຊֶज़ৼڵձ ಛผݚڀһ (DC1)
࠷ۙ
▶ record4s: extensible records for Scala
▶ ͋ΒΏΔϓϩάϥϛϯάݴޠͷ࠷ઌΛߦ
͘ Scala 3 ͷϚΫϩ
ੲ
▶ L. Ina and A. Igarashi.
Gradual Typing for Generics.
In Proc. of OOPSLA 2011.
▶ “gradual typing” Λʮਐతܕ͚ʯͱ༁
ͨ͠ऀͷ 1 ਓ
Slide 3
Slide 3 text
ܕΫϥεͱOOP
SPJ ᐌ͘
“ ▶ A bit like OOP, except that method suite passed separately?
▶ No!! Type classes implement type-based dispatch, not
value-based dispatch
▶ S. P. Jones.
Classes, Jim, but not as we know them — Type classes in Haskell.
In ECOOP 2009.
Slide 4
Slide 4 text
͋ʔ ͦʔΏʔ͜ͱͶ
શʹཧղͨ͠
Slide 5
Slide 5 text
͋ʔ ͦʔΏʔ͜ͱͶ
શʹཧղͨ͠
. . . ͬͯࢥͬͨͷ tarao ͚͔ͩ͠Εͳ͍͔Β
͜ͷΛ͢Δ͜ͱʹ͠·ͨ͠
(tarao ʹͱͬͯͨΓલͷ͔͠͠·ͤΜ)
Slide 6
Slide 6 text
OOPͱܕΫϥεͷҙຯΛൺֱ
Slide 7
Slide 7 text
ݴޠػೳͷҙຯ
ݴޠ L ͷػೳ F
▶ L ⇝ (L − F) ͷมͰఆٛ͢Δ
(࣮ࡍͷॲཧܥʹ͓͚Δҥߏจͷ desugar ʹ૬)
ྫ
▶ ݴޠ L : Haskell
▶ ػೳ F : ܕΫϥε
▶ ม : ܕΫϥε͋Γͷ Haskell ⇝ ܕΫϥεͳ͠ͷ Haskell
(Wadler ’89 ͷจͰ࣮ࡍͦ͏ͬͯҙຯΛ༩͍͑ͯΔ)
Slide 8
Slide 8 text
OOP
Slide 9
Slide 9 text
OOP (෦ܕଟ૬ + ಈతσΟεύον)
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
listen(new Cat)
// "Meow"
listen(new Dog)
// "Woof"
Slide 10
Slide 10 text
OOP (෦ܕଟ૬ + ಈతσΟεύον)
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
listen(new Cat)
// "Meow"
listen(new Dog)
// "Woof"
▶ ҟͳΔܕΛ౷Ұతʹѻ͍͍ͨ
Slide 11
Slide 11 text
OOP (෦ܕଟ૬ + ಈతσΟεύον)
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
listen(new Cat)
// "Meow"
listen(new Dog)
// "Woof"
▶ ڞ௨ͷ্ҐܕΛࢦఆ (෦ܕଟ૬)
Slide 12
Slide 12 text
OOP (෦ܕଟ૬ + ಈతσΟεύον)
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
listen(new Cat)
// "Meow"
listen(new Dog)
// "Woof"
▶ ಉ໊ϝιουΛ෦ܕ͝ͱʹ࣮
Slide 13
Slide 13 text
OOP (෦ܕଟ૬ + ಈతσΟεύον)
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
listen(new Cat)
// "Meow"
listen(new Dog)
// "Woof"
▶ ݺΕΔͷ෦ܕͷϝιου࣮ (ಈతσΟεύον)
Slide 14
Slide 14 text
OOPͷҙຯ
(Ծؔςʔϒϧ (vtable))
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
abstract class Pet( val vtable: PetMethods )
class PetMethods(val speak: Pet => String)
class Cat extends Pet( CatIsPet ):
def speak(): String = "Meow"
val CatIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Cat].speak() )
class Dog extends Pet( DogIsPet ):
def speak(): String = "Woof"
val DogIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Dog].speak() )
def listen(pet: Pet): String =
pet.vtable .speak(pet)
˞ ࣮ࡍͷॲཧܥͷ࣮ͱҟͳΔ (͋͘·Ͱ֓೦্ͷઆ໌)
Slide 15
Slide 15 text
OOPͷҙຯ
(Ծؔςʔϒϧ (vtable))
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
abstract class Pet( val vtable: PetMethods )
class PetMethods(val speak: Pet => String)
class Cat extends Pet( CatIsPet ):
def speak(): String = "Meow"
val CatIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Cat].speak() )
class Dog extends Pet( DogIsPet ):
def speak(): String = "Woof"
val DogIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Dog].speak() )
def listen(pet: Pet): String =
pet.vtable .speak(pet)
▶ override ͳ͠Ͱॻ͘
Slide 16
Slide 16 text
OOPͷҙຯ
(Ծؔςʔϒϧ (vtable))
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
abstract class Pet( val vtable: PetMethods )
class PetMethods(val speak: Pet => String)
class Cat extends Pet( CatIsPet ):
def speak(): String = "Meow"
val CatIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Cat].speak() )
class Dog extends Pet( DogIsPet ):
def speak(): String = "Woof"
val DogIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Dog].speak() )
def listen(pet: Pet): String =
pet.vtable .speak(pet)
▶ ڞ௨ͷϝιουͷശ (ࣙॻ) Λ༻ҙ͓ͯ͘͠
Slide 17
Slide 17 text
OOPͷҙຯ
(Ծؔςʔϒϧ (vtable))
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
abstract class Pet( val vtable: PetMethods )
class PetMethods(val speak: Pet => String)
class Cat extends Pet( CatIsPet ):
def speak(): String = "Meow"
val CatIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Cat].speak() )
class Dog extends Pet( DogIsPet ):
def speak(): String = "Woof"
val DogIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Dog].speak() )
def listen(pet: Pet): String =
pet.vtable .speak(pet)
▶ ෦ܕ͝ͱʹผʑͷϝιουΛ٧Ί͓ͯ͘
Slide 18
Slide 18 text
OOPͷҙຯ
(Ծؔςʔϒϧ (vtable))
abstract class Pet:
def speak(): String
class Cat extends Pet:
override def speak(): String =
"Meow"
class Dog extends Pet:
override def speak(): String =
"Woof"
def listen(pet: Pet): String =
pet.speak()
abstract class Pet( val vtable: PetMethods )
class PetMethods(val speak: Pet => String)
class Cat extends Pet( CatIsPet ):
def speak(): String = "Meow"
val CatIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Cat].speak() )
class Dog extends Pet( DogIsPet ):
def speak(): String = "Woof"
val DogIsPet =
PetMethods((pet: Pet) =>
pet.asInstanceOf[Dog].speak() )
def listen(pet: Pet): String =
pet.vtable .speak(pet)
▶ vtable Λܦ༝ͯ͠ϝιουΛݺͿ
Slide 19
Slide 19 text
ܕΫϥε
Slide 20
Slide 20 text
ܕΫϥε
(ύϥϝʔλଟ૬ + ΞυϗοΫଟ૬)
trait Pet[P] :
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet ](pet: P ): String =
pet.speak()
listen( new Cat )
// "Meow"
listen( new Dog )
// "Woof"
Slide 21
Slide 21 text
ܕΫϥε
(ύϥϝʔλଟ૬ + ΞυϗοΫଟ૬)
trait Pet[P] :
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet ](pet: P ): String =
pet.speak()
listen( new Cat )
// "Meow"
listen( new Dog )
// "Woof"
▶ ҟͳΔܕΛ౷Ұతʹѻ͍͍ͨ
Slide 22
Slide 22 text
ܕΫϥε
(ύϥϝʔλଟ૬ + ΞυϗοΫଟ૬)
trait Pet[P] :
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet ](pet: P ): String =
pet.speak()
listen( new Cat )
// "Meow"
listen( new Dog )
// "Woof"
▶ ಛఆͷΠϯλϑΣʔεΛཁٻ
(͜Ε͕ܕΫϥε)
Slide 23
Slide 23 text
ܕΫϥε
(ύϥϝʔλଟ૬ + ΞυϗοΫଟ૬)
trait Pet[P] :
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet ](pet: P ): String =
pet.speak()
listen( new Cat )
// "Meow"
listen( new Dog )
// "Woof"
▶ ΠϯλϑΣʔεΛຬͨ͢ূڌ
(ܕΫϥεͷΠϯελϯε)
Slide 24
Slide 24 text
ܕΫϥε
(ύϥϝʔλଟ૬ + ΞυϗοΫଟ૬)
trait Pet[P] :
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet ](pet: P ): String =
pet.speak()
listen( new Cat )
// "Meow"
listen( new Dog )
// "Woof"
▶ ূڌʹج͍ͮͯݺͼ͚
Slide 25
Slide 25 text
ܕΫϥεͷҙຯ
trait Pet[P]:
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P): String =
pet.speak()
class Pet[P](val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat]((cat: Cat) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog]((dog: Dog) => dog.speak())
def listen[P](pet: P) (dict: Pet[P]) : String =
dict .speak(pet)
Slide 26
Slide 26 text
ܕΫϥεͷҙຯ
trait Pet[P]:
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P): String =
pet.speak()
class Pet[P](val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat]((cat: Cat) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog]((dog: Dog) => dog.speak())
def listen[P](pet: P) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ܕΫϥεͷ࣮ମϝιουͷࣙॻ
Slide 27
Slide 27 text
ܕΫϥεͷҙຯ
trait Pet[P]:
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P): String =
pet.speak()
class Pet[P](val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat]((cat: Cat) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog]((dog: Dog) => dog.speak())
def listen[P](pet: P) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ΠϯλϑΣʔεͷূڌࣙॻΠϯελϯε
Slide 28
Slide 28 text
ܕΫϥεͷҙຯ
trait Pet[P]:
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P): String =
pet.speak()
class Pet[P](val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat]((cat: Cat) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog]((dog: Dog) => dog.speak())
def listen[P](pet: P) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ܕΫϥεΛ͏ϝιουࣙॻΛऔΔܗʹม
Slide 29
Slide 29 text
ܕΫϥεͷҙຯ
trait Pet[P]:
extension (p: P) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[Cat] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[Dog] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P): String =
pet.speak()
listen(new Cat)
listen(new Dog)
class Pet[P](val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat]((cat: Cat) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog]((dog: Dog) => dog.speak())
def listen[P](pet: P) (dict: Pet[P]) : String =
dict .speak(pet)
listen(new Cat) (CatIsPet)
listen(new Dog) (DogIsPet)
Slide 30
Slide 30 text
ൺֱ
Slide 31
Slide 31 text
දΛݟൺΔ
OOP
abstract class Pet :
def speak(): String
class Cat extends Pet :
override def speak(): String =
"Meow"
class Dog extends Pet :
override def speak(): String =
"Woof"
def listen(pet: Pet ): String =
pet.speak()
ܕΫϥε
trait Pet[ P ]:
extension (p: P ) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[ Cat ] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[ Dog ] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P ): String =
pet.speak()
Slide 32
Slide 32 text
දΛݟൺΔ
OOP
abstract class Pet :
def speak(): String
class Cat extends Pet :
override def speak(): String =
"Meow"
class Dog extends Pet :
override def speak(): String =
"Woof"
def listen(pet: Pet ): String =
pet.speak()
ܕΫϥε
trait Pet[ P ]:
extension (p: P ) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[ Cat ] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[ Dog ] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P ): String =
pet.speak()
▶ ෦ܕଟ૬ vs. ύϥϝʔλଟ૬
Slide 33
Slide 33 text
දΛݟൺΔ
OOP
abstract class Pet :
def speak(): String
class Cat extends Pet :
override def speak(): String =
"Meow"
class Dog extends Pet :
override def speak(): String =
"Woof"
def listen(pet: Pet ): String =
pet.speak()
ܕΫϥε
trait Pet[ P ]:
extension (p: P ) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[ Cat ] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[ Dog ] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P ): String =
pet.speak()
▶ ͕ؔܕͷఆٛͱີ݁߹ vs. ͕ؔޙ͚
Slide 34
Slide 34 text
දΛݟൺΔ
OOP
abstract class Pet :
def speak(): String
class Cat extends Pet :
override def speak(): String =
"Meow"
class Dog extends Pet :
override def speak(): String =
"Woof"
def listen(pet: Pet ): String =
pet.speak()
ܕΫϥε
trait Pet[ P ]:
extension (p: P ) def speak(): String
class Cat:
def speak(): String = "Meow"
given Pet[ Cat ] with
extension (cat: Cat)
def speak(): String = cat.speak()
class Dog:
def speak(): String = "Woof"
given Pet[ Dog ] with
extension (dog: Dog)
def speak(): String = dog.speak()
def listen[P: Pet](pet: P ): String =
pet.speak()
▶ ಉ໊ͰΦʔόʔϥΠυ vs. όϥόϥʹ࣮ (ผ໊ͰՄ)
Slide 35
Slide 35 text
ҙຯΛݟൺΔ
OOP
abstract class Pet ( val vtable: PetMethods )
class PetMethods (val speak: Pet => String)
class Cat extends Pet(CatIsPet) :
def speak(): String = "Meow"
val CatIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Cat] .speak())
class Dog extends Pet(DogIsPet) :
def speak(): String = "Woof"
val DogIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Dog] .speak())
def listen(pet: Pet ): String =
pet.vtable .speak(pet)
ܕΫϥε
class Pet[P] (val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat] ((cat: Cat ) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog] ((dog: Dog ) => dog.speak())
def listen [P] (pet: P ) (dict: Pet[P]) : String =
dict .speak(pet)
Slide 36
Slide 36 text
ҙຯΛݟൺΔ
OOP
abstract class Pet ( val vtable: PetMethods )
class PetMethods (val speak: Pet => String)
class Cat extends Pet(CatIsPet) :
def speak(): String = "Meow"
val CatIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Cat] .speak())
class Dog extends Pet(DogIsPet) :
def speak(): String = "Woof"
val DogIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Dog] .speak())
def listen(pet: Pet ): String =
pet.vtable .speak(pet)
ܕΫϥε
class Pet[P] (val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat] ((cat: Cat ) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog] ((dog: Dog ) => dog.speak())
def listen [P] (pet: P ) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ෦ܕଟ૬ vs. ύϥϝʔλଟ૬
Slide 37
Slide 37 text
ҙຯΛݟൺΔ
OOP
abstract class Pet ( val vtable: PetMethods )
class PetMethods (val speak: Pet => String)
class Cat extends Pet(CatIsPet) :
def speak(): String = "Meow"
val CatIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Cat] .speak())
class Dog extends Pet(DogIsPet) :
def speak(): String = "Woof"
val DogIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Dog] .speak())
def listen(pet: Pet ): String =
pet.vtable .speak(pet)
ܕΫϥε
class Pet[P] (val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat] ((cat: Cat ) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog] ((dog: Dog ) => dog.speak())
def listen [P] (pet: P ) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ໊લ͕ҧ͏͚ͩ
Slide 38
Slide 38 text
ҙຯΛݟൺΔ
OOP
abstract class Pet ( val vtable: PetMethods )
class PetMethods (val speak: Pet => String)
class Cat extends Pet(CatIsPet) :
def speak(): String = "Meow"
val CatIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Cat] .speak())
class Dog extends Pet(DogIsPet) :
def speak(): String = "Woof"
val DogIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Dog] .speak())
def listen(pet: Pet ): String =
pet.vtable .speak(pet)
ܕΫϥε
class Pet[P] (val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat] ((cat: Cat ) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog] ((dog: Dog ) => dog.speak())
def listen [P] (pet: P ) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ͔ΒऔΓग़͢ vs. ҾͰ͢
Slide 39
Slide 39 text
ҙຯΛݟൺΔ
OOP
abstract class Pet ( val vtable: PetMethods )
class PetMethods (val speak: Pet => String)
class Cat extends Pet(CatIsPet) :
def speak(): String = "Meow"
val CatIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Cat] .speak())
class Dog extends Pet(DogIsPet) :
def speak(): String = "Woof"
val DogIsPet =
PetMethods ((pet: Pet ) =>
pet .asInstanceOf[Dog] .speak())
def listen(pet: Pet ): String =
pet.vtable .speak(pet)
ܕΫϥε
class Pet[P] (val speak: P => String)
class Cat:
def speak(): String = "Meow"
val CatIsPet =
Pet[Cat] ((cat: Cat ) => cat.speak())
class Dog:
def speak(): String = "Woof"
val DogIsPet =
Pet[Dog] ((dog: Dog ) => dog.speak())
def listen [P] (pet: P ) (dict: Pet[P]) : String =
dict .speak(pet)
▶ ͋ͱಉ͡!!
Slide 40
Slide 40 text
·ͱΊ
Slide 41
Slide 41 text
ࣅ͍ͯΔͱ͜Ζ
▶ ҟͳΔܕΛ౷Ұతʹѻ͏͘͠Έ
▶ ϝιουͷࣙॻΛͬͯݺͼ͚Δ
Slide 42
Slide 42 text
ҧ͏ͱ͜Ζ
OOP ܕΫϥε
ଟ૬ ෦ܕଟ૬ ύϥϝʔλଟ૬
ܕͷؔ ີ݁߹ ޙ͚Մ ˞
ϝιου࣮ ಉ໊ͰΦʔόʔϥΠυ ໌ࣔతʹࢦఆ
ࣙॻͷ͠ํ ʹೖΕΔ ҾͰ͢
ࣙॻͷղܾ ಈత ੩త
˞ ͜ͷͨΊʹܕΫϥεͷΠϯελϯεղܾͷΈ͕ඞཁ
▶ ཧܕϓϩάϥϛϯάΈ͍ͨʹͳΔ
Slide 43
Slide 43 text
͓ΘΓ