--- a/progs/app4.scala	Tue Sep 24 01:12:36 2013 +0100
+++ b/progs/app4.scala	Tue Sep 24 01:56:53 2013 +0100
@@ -6,7 +6,7 @@
 def crawl(url: String, n: Int) : Unit = {
   if (n == 0) ()
   else {
-    println("Visiting: " + n + " " + url)
+    println(s"Visiting: $n $url")
     val page = get_page(url)
     println(email_pattern.findAllIn(page).mkString("\n"))
     for (u <- get_all_URLs(page)) crawl(u, n - 1)