--- a/progs/re1.scala	Wed Mar 15 14:34:10 2017 +0000
+++ b/progs/re1.scala	Wed Mar 22 14:10:01 2017 +0000
@@ -77,6 +77,7 @@
   (end - start)/(i * 1.0e9)
 }
 
+
 //test: (a?{n}) (a{n})
 for (i <- 1 to 20) {
   println(i + ": " + "%.5f".format(time_needed(2, matches(EVIL1(i), "a" * i))))
@@ -115,3 +116,23 @@
 size(EVIL1(3))  // 17
 size(EVIL1(5))  // 29
 size(EVIL1(7))  // 41
+
+
+// given a regular expression and building successive
+// derivatives might result into bigger and bigger
+// regular expressions...here is an example for this:
+
+val BIG_aux = STAR(ALT(CHAR('a'), CHAR('b')))
+val BIG = SEQ(BIG_aux, SEQ(CHAR('a'),SEQ(CHAR('b'), BIG_aux)))
+
+size(ders("".toList, BIG))              // 13
+size(ders("ab".toList, BIG))            // 51
+size(ders("abab".toList, BIG))          // 112
+size(ders("ababab".toList, BIG))        // 191
+size(ders("abababab".toList, BIG))      // 288
+size(ders("ababababab".toList, BIG))    // 403
+size(ders("abababababab".toList, BIG))  // 536
+
+
+size(ders(("ab" * 200).toList, BIG))    // 366808
+