Typeclass

typeclass.scala

trait Foo[T] {
  def foo(t: T): String
}

// Creates an implicit function that uses an implicit Foo[T] (evidence)
implicit def foo[T](t: T)(implicit ev: Foo[T]): String = ev.foo(t)

// Or using context bounds (choose one or the other depending on usage of the implicit evidence)
implicit def foo[T : Foo](t: T): String = implicitly[Foo[T]].foo(t)

// This is the Foo Typeclass for Int in implicit scope
implicit val FooInt = new Foo[Int] {
  def foo(i: Int) = "Foo" * i
}

5.foo
foo(3)