gistfile1.txt

 // Determine if a value is the product of any two numbers in a vector
 // Converts the array to a stream so it can be consumed lazily
 // the helper function is recursive but subject to tail call optimization
 
 def prod(in: Array[Int], v: Int): Boolean = {
    def helper(in: Stream[Int], v: Int, found: Map[Int, Int]): Boolean = in match {
      case x #:: xs => {
      	val r = v / x
      	if(r * x != v) helper(xs, v, found)
      	else if(found.contains(x)) true
      	else helper(xs, v, found + (r -> x))
      }
      case _ => false
    }

    helper(in.toStream, v, Map())
  } 
  
  //	(1 to 10).map(n => prod(sample, n))       //> res3: scala.collection.immutable.IndexedSeq[Boolean] = Vector(false, false, 
                                                  //| false, false, false, true, false, true, false, true)