Generalizing over forEach operation. Smells bad. Works hard.

ForEach.scala

object ForEachExperiment extends App {

  trait ForEach[M[_]] {

    def foreach[V](m: M[V])(f: V => Unit ): Unit

  }


  object ForEachInstances {

    implicit val optionForEach: ForEach[Option] = new ForEach[Option] {
      override def foreach[V](m: Option[V])(f: (V) => Unit): Unit = m.foreach(f)
    }

    implicit val optionForList: ForEach[List] = new ForEach[List] {
      override def foreach[V](m: List[V])(f: (V) => Unit): Unit = m.foreach(f)
    }
  }

  object ForEach {

    def foreach[V, M[V]](container: M[V], f: V => Unit )(implicit impl: ForEach[M]): Unit = impl.foreach(container)(f)
  }

  object ForEachSyntax {

    implicit class ForEachOps[V, M[V]](opt: M[V]) {
      def generalForeach(f: V => Unit)(implicit impl: ForEach[M]): Unit = ForEach.foreach(opt, f)
    }

  }

  import ForEachInstances._
  import ForEachSyntax._

  val opt1: Option[Int] = Some(123)
  val opt2: Option[Int] = None

  val list1: List[Int] = Nil
  val list2: List[Int] = 1 :: 2 :: Nil

  opt1.generalForeach(v => println(s"opt1 is : $v"))
  opt2.generalForeach(v => println(s"opt2 is : $v"))
  list1.generalForeach(v => println(s"list1 is : $v"))
  list2.generalForeach(v => println(s"list2 is : $v"))
}