shapeless
Encodes a coproduct type, such as a sealed family of case classes.
Each constructor from the family gets an encoding in terms of nested Inr and Inl.
Which constructor is encoded as Inl() and which as Inr(Inl()) is determined by lexical order of the subclasses. This example illustrates the encoding:
scala> sealed trait Animal defined trait Animal scala> case class Cat(name: String, livesLeft: Int) extends Animal defined class Cat scala> case class Dog(name: String, bonesBuried: Int) extends Animal defined class Dog scala> case class Koala(name: String, leavesEaten: Int) extends Animal defined class Koala scala> case class Sloth(name: String, daysToClimbDownFromCurrentTree: Int) extends Animal defined class Sloth scala> val garfield = Cat("Garfield", 9) garfield: Cat = Cat(Garfield,9) scala> val odie = Dog("Odie", 3) odie: Dog = Dog(Odie,3) scala> val koala = Koala("foo", 10) koala: Koala = Koala(foo,10) scala> val sloth = Sloth("bar", 2) sloth: Sloth = Sloth(bar,2) scala> val genAnimal = Generic[Animal] genAnimal: shapeless.Generic[Animal]{type Repr = Cat :+: Dog :+: Koala :+: Sloth} = ... scala> def showCoproduct(o: Any) : String = o match { | case Inl(a) => "Inl(" + showCoproduct(a) + ")" | case Inr(a) => "Inr(" + showCoproduct(a) + ")" | case a => a.toString | } showCoproduct: (o: Any)String scala> showCoproduct(genAnimal.to(garfield)) res5: String = Inl(Cat(Garfield,9)) scala> showCoproduct(genAnimal.to(odie)) res6: String = Inr(Inl(Dog(Odie,3))) scala> showCoproduct(genAnimal.to(koala)) res7: String = Inr(Inr(Inl(Koala(foo,10)))) scala> showCoproduct(genAnimal.to(sloth)) res8: String = Inr(Inr(Inr(Inl(Sloth(bar,2))))) scala>
Encodes a coproduct type, such as a sealed family of case classes.
Each constructor from the family gets an encoding in terms of nested Inr and Inl.
Which constructor is encoded as Inl() and which as Inr(Inl()) is determined by lexical order of the subclasses. This example illustrates the encoding: