gistfile1.scala

scala> import scalaz._
import scalaz._

scala> import Scalaz._
import Scalaz._

scala> ∅[Boolean]
res0: Boolean = false

scala> ∅[Int]
res1: Int = 0

scala> ∅[String]
res2: String = ""

scala> ∅[Seq[Int]]
res3: Seq[Int] = Vector()

scala> :paste
// Entering paste mode (ctrl-D to finish)

case class Complex(real: Double, imag: Double)

object Complex {
  implicit val Zero = zero(Complex(0.0, 0.0))
}

// Exiting paste mode, now interpreting.

defined class Complex
defined module Complex

scala> ∅[Complex]
res4: Complex = Complex(0.0,0.0)