gistfile1.scala

object funsets {

  type Set = Int => Boolean
  
  def contains(s: Set, elem: Int): Boolean = s(elem)
                                                  //> contains: (s: Int => Boolean, elem: Int)Boolean
  def singletonSet(elem: Int): Set = Set(elem)    //> singletonSet: (elem: Int)Int => Boolean
  
  def union(s: Set, t: Set): Set = i => s(i) || t(i)
                                                  //> union: (s: Int => Boolean, t: Int => Boolean)Int => Boolean
   
}