--- a/progs/lecture5.scala	Fri Dec 07 03:15:46 2018 +0000
+++ b/progs/lecture5.scala	Fri Dec 07 07:57:54 2018 +0000
@@ -6,9 +6,9 @@
 // Laziness with style
 //=====================
 
-// The concept of lazy evaluation doesn’t really exist in 
-// non-functional languages, but it is pretty easy to grasp. 
-// Consider first 
+// The concept of lazy evaluation doesn’t really 
+// exist in non-functional languages, but it is 
+// pretty easy to grasp. Consider first 
 
 def square(x: Int) = x * x
 
@@ -16,8 +16,9 @@
 
 // this is called strict evaluation
 
-// pretty expensive operation
+// say we have a pretty expensive operation
 def peop(n: BigInt): Boolean = peop(n + 1) 
+
 val a = "foo"
 val b = "foo"
 
@@ -43,25 +44,24 @@
 def generatePrimes (s: Stream[Int]): Stream[Int] =
   s.head #:: generatePrimes(s.tail.filter(_ % s.head != 0))
 
-val primes: Stream[Int] = generatePrimes(Stream.from(2))
+val primes = generatePrimes(Stream.from(2))
 
 // the first 10 primes
 primes.take(10).toList
 
-//primes.filter(_ > 100).take(2000).toList
-
 time_needed(1, primes.filter(_ > 100).take(3000).toList)
 time_needed(1, primes.filter(_ > 100).take(3000).toList)
 
+// a stream of successive numbers
+Stream.from(2)
 
-Stream.from(2)
 Stream.from(2).take(10)
 Stream.from(2).take(10).print
 Stream.from(10).take(10).print
 
 Stream.from(2).take(10).force
 
-// itterative version of the Fibonacci numbers
+// iterative version of the Fibonacci numbers
 def fibIter(a: BigInt, b: BigInt): Stream[BigInt] =
   a #:: fibIter(b, a + b)
 
@@ -88,12 +88,6 @@
 case class STAR(r: Rexp) extends Rexp             // star         r*
 
 
-
-// writing (ab)* in the format above is 
-// tedious
-val r0 = STAR(SEQ(CHAR('a'), CHAR('b')))
-
-
 // some convenience for typing in regular expressions
 import scala.language.implicitConversions    
 import scala.language.reflectiveCalls 
@@ -107,17 +101,12 @@
   charlist2rexp(s.toList)
 
 
-val r1 = STAR("ab")
-val r2 = STAR(ALT("ab", "baa baa black sheep"))
-val r3 = STAR(SEQ("ab", ALT("a", "b")))
-
 implicit def RexpOps (r: Rexp) = new {
   def | (s: Rexp) = ALT(r, s)
   def % = STAR(r)
   def ~ (s: Rexp) = SEQ(r, s)
 }
 
-
 implicit def stringOps (s: String) = new {
   def | (r: Rexp) = ALT(s, r)
   def | (r: String) = ALT(s, r)
@@ -144,7 +133,8 @@
 // task: enumerate exhaustively regular expression
 // starting from small ones towards bigger ones.
 
-// 1st idea: enumerate them up to a level
+// 1st idea: enumerate them all in a Set
+// up to a level
 
 def enuml(l: Int, s: String) : Set[Rexp] = l match {
   case 0 => Set(ZERO, ONE) ++ s.map(CHAR).toSet
@@ -156,9 +146,11 @@
     (for (r1 <- rs) yield STAR(r1))
 }
 
+enuml(1, "a")
 enuml(1, "a").size
 enuml(2, "a").size
-enuml(3, "a").size // out of heap space
+enuml(3, "a").size 
+enuml(4, "a").size // out of heap space
 
 
 def enum(rs: Stream[Rexp]) : Stream[Rexp] = 
@@ -168,7 +160,7 @@
 
 
 enum(ZERO #:: ONE #:: "ab".toStream.map(CHAR)).take(200).force
-enum(ZERO #:: ONE #:: "ab".toStream.map(CHAR)).take(200000).force
+enum(ZERO #:: ONE #:: "ab".toStream.map(CHAR)).take(5000000)
 
 
 val is = 
@@ -325,7 +317,7 @@
 
 
 
-// The End ... Almost Christimas
+// The End ... Almost Christmas
 //===============================
 
 // I hope you had fun!
@@ -336,7 +328,8 @@
 // reason not to.
 
 // I did it, but this is actually not a good reason:
-// generating new labels
+// generating new labels:
+
 var counter = -1
 
 def Fresh(x: String) = {

--- a/slides/slides05.tex	Fri Dec 07 03:15:46 2018 +0000
+++ b/slides/slides05.tex	Fri Dec 07 07:57:54 2018 +0000
@@ -99,6 +99,29 @@
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
+
+\begin{frame}[c]
+\frametitle{Marks for CW7 (Part 1 +  2)}
+
+Raw marks (234 submissions):
+
+\begin{itemize}
+\item 6\%: \hspace{4mm}192 students
+\item 5\%: \hspace{4mm}16
+\item 4\%: \hspace{4mm}7
+\item 3\%: \hspace{4mm}2
+\item 2\%: \hspace{4mm}6
+\item 1\%: \hspace{4mm}1
+\item 0\%: \hspace{4mm}9 
+\end{itemize}  
+\end{frame}
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c,fragile]
 \small