rich-mans-type-classes.scala

trait Isomorphism[A, B] {
  def fw: A => B
  def bw: B => A
}
 
object Isomorphism {
  implicit def anyIso[A](a: A) = new {
    def as[B](implicit ev: Isomorphism[A, B]) = ev fw a
  }
 
  implicit def isoX[A] = new Isomorphism[(Unit, A), A] {
    def fw = _._2
    def bw = ((), _)
  }
}
 
trait Storable[A] {
  def size: Int
}
 
object Storable {
  implicit object IntIsStorable extends Storable[Int] {
    def size = 4
  }
 
  def size[A](implicit s: Storable[A]) = s.size
}
 
object Main {
  import Storable._
  import Isomorphism._
 
  def main(args: Array[String]): Unit = {
    println(size[Int])
    println(((), 'hello).as[Symbol])
  }
}

/* Output:
4
'hello
*/