gistfile1.scala

// Here's a typeclass trait for types that can be sliced
trait Slicing[T] {
  def slice(o: T, from: Int, until: Int): T
}

// The companion object provides impicits for String and Vector
object Slicing {
  implicit val slicingNatureOfString: Slicing[String] =
    new Slicing[String] {
      def slice(s: String, from: Int, until: Int): String = s.substring(from, until)
    }
  implicit def slicingNatureOfVector[E]: Slicing[Vector[E]] =
    new Slicing[Vector[E]] {
      def slice(v: Vector[E], from: Int, until: Int): Vector[E] = v.slice(from, until)
    }
}

// Example has a genericSlice method that will work with any type T 
// for which an implicit Slicing[T] exists.
object Example {
  def genericSlice[T: Slicing](o: T, from: Int, until: Int): T = {
    val slicing = implicitly[Slicing[T]]
    slicing.slice(o, from, until)
  }
}

// You can, therefore, slice a String with genericSlice
scala> Example.genericSlice("one two three", 4, 7)
res1: String = two

// And a Vector
scala> Example.genericSlice("one two three".toVector, 4, 7)
res2: Vector[Char] = Vector(t, w, o)

// But not a List
scala> Example.genericSlice("one two three".toList, 4, 7)
<console>:12: error: could not find implicit value for evidence parameter of type Slicing[List[Char]]
              Example.genericSlice("one two three".toList, 4, 7)
                                  ^