lazily recurse files in a root directory

gistfile1.scala

import java.io.File

/**
 * Iterate all files in the given directory recursively.
 * @param root the root directory to traverse
 * @return an Iterator[File] of traversed files
 */
def listFiles(root: File): Iterator[File] = {
  def rec(files: List[File]): Stream[File] = {
    files match {
      case h :: rest =>
        if (h.isFile) h #:: rec(rest)
        else rec(h.listFiles.toList) #::: rec(rest)
      case Nil => Stream.empty
    }
  }
  rec(root.listFiles.toList).iterator
}