diff -r b37052895281 -r 37b1bfcdba79 progs/lecture1.scala
--- a/progs/lecture1.scala	Fri Jan 19 14:09:08 2018 +0000
+++ b/progs/lecture1.scala	Fri Feb 23 22:26:42 2018 +0000
@@ -302,9 +302,32 @@
 time_needed(10, for (n <- list.par) yield n + 42)
 
 
-
+// mutable vs immutable factorial
+def fact_mu(n: Long): Long = {
+  var result : Long = 1
+  var i = 1
+  while (i <= n) {
+    result = result * i
+    i = i + 1
+  }
+  result
+}
 
+def fact_im(num: Long): Long = {
+  if (num == 1) num else
+    num * fact_im(num - 1)
+}
 
+def test() = {
+  for (i <- (0 to 10).par) yield {
+    val l1 = for (n <- (List.fill(100000)(20 to 21)).flatten.par) yield fact_mu(n)
+    val l2 = for (n <- (List.fill(100000)(20 to 21)).flatten.par) yield fact_im(n) 
+    l1.sum - l2.sum
+  }
+}
+
+test().sum
+println(l1.sum - l2.sum)
 
 // Webpages
 //==========
@@ -456,3 +479,67 @@
 //
 
 
+
+
+
+
+
+
+
+// advantage of case classes
+//
+case class Participant(name: String, score: Int, active: Boolean)
+
+val ps = Seq(Participant("Jack", 34, true),
+             Participant("Tom", 51, true),
+             Participant("Bob", 90, false))
+             
+ps.filter(_.score < 50).
+   filter(_.active).
+   map(_.copy(active = false))
+
+
+
+// another example why state is bad...does not work yet
+
+// for measuring time
+def time_needed[T](n: Int, code: => T) = {
+  val start = System.nanoTime()
+  for (i <- (0 to n)) code
+  val end = System.nanoTime()
+  (end - start) / 1.0e9
+}
+
+def santa_state(plan: List[Char]) : Int = {  
+
+  var floor = 0
+
+  for (i <- plan.par) {
+    if (i == '(') {
+      floor += 1
+    } else {
+      floor -= 1
+    }
+  }
+  
+  floor
+}
+
+def i(c: Char) = if (c == '(') 1 else -1
+
+def santa_imutable(plan: List[Char]) : Int =
+  plan.par.map(i(_)).reduce(_ + _)
+
+santa_state("(((((()))))".toList)
+santa_imutable("(((((()))))".toList)
+
+def randomString(length: Int) = 
+  List.fill(length)((40 + scala.util.Random.nextInt(2)).toChar)
+
+
+santa_state(randomString(100))
+
+val large_string = randomString(3000000)
+
+time_needed(10, santa_state(large_string))
+time_needed(10, santa_imutable(large_string))