Code snippets from "Generics of Higher Kinds" paper

gistfile1.scala

// First-order parametric polymorphism - abstract over types (simple types or proper types)
// Higher-order parametric polymorphism - abstract over type constructors (type functions)

// Other names for Higher-order polymorphism
// - Type constructor polymorphism
// - Higher-kinded types

// Higher-kinded types enables us to use type constructor as type parameters and abstract type members
// Higher-kinded types is a type that abstract over types that abstract over types

trait Iterable[T] {
  def filter(p: T => Boolean): Iterable[T]
  def remove(p: T => Boolean): Iterable[T] = filter{ x => !p(x) }
}

trait List[T] {
  def filter(p: T => Boolean): List[T]
  def remove(p: T => Boolean): List[T] = filter{ x => !p(x) }
}