ryanlecompte

import scala.collection.generic.CanBuildFrom
import scala.collection.immutable.MapLike
import scala.collection.mutable

/**
 * Immutable version of the PrefixMap demonstrated in the Scala collections
 * guide here: http://www.scala-lang.org/docu/files/collections-api/collections-impl_6.html
 * 
 * This version also has a smarter remove method (doesn't leave behind dead nodes with empty values)
 */