ExploreIntersectionTypes

ExploreIntersectionTypes.scala

object ExploreIntersectionTypes {

  trait Mapper[A, B] {
    def map(l: List[A])(f: A => B): List[B] = l.map(f)
  }

  trait Reducer[A, B >: A] {
    def reduce(l: List[A])(f: (B, B) => B): B = l.reduce(f)
  }

  def mapAndReduce[A, B, C >: B](mR: Mapper[A, B] & Reducer[B, C], l: List[A])(
      mapFuncf: A => B
  )(reduceFuncf: (C, C) => C): C = {
    mR.reduce(mR.map(l)(mapFuncf))(reduceFuncf)
  }

  val multBy2: Int => Int = (e: Int) => e * 2
  val reduceToSum: (Int, Int) => Int = (a: Int, b: Int) => (a + b)

  case class MapperAndReducer[A, B, C >: B]()
      extends Mapper[A, B]
      with Reducer[B, C]

  @main
  def m: Unit = {
    println(
      mapAndReduce(MapperAndReducer[Int, Int, Int](), List(1, 2, 3))(multBy2)(
        reduceToSum
      )
    )
  }
}