diff -r c6453f3547ec -r 42d760984496 progs/lecture4.scala
--- a/progs/lecture4.scala	Fri Nov 30 07:54:49 2018 +0000
+++ b/progs/lecture4.scala	Fri Nov 30 08:46:02 2018 +0000
@@ -9,6 +9,21 @@
 // length and so on for every type of lists.
 
 
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 def length_string_list(lst: List[String]): Int = lst match {
   case Nil => 0
   case x::xs => 1 + length_string_list(xs)
@@ -333,7 +348,7 @@
 
 
 // Q: Why the kerfuffle about the polymorphic types in DFAs/NFAs?
-// A: Subset construction
+// A: Subset construction.
 
 def subset[A, C](nfa: NFA[A, C]) : DFA[Set[A], C] = {
   DFA(nfa.starts, 
@@ -405,7 +420,8 @@
   case c::Nil => CHAR(c)
   case c::s => SEQ(CHAR(c), charlist2rexp(s))
 }
-implicit def string2rexp(s: String): Rexp = charlist2rexp(s.toList)
+implicit def string2rexp(s: String): Rexp = 
+  charlist2rexp(s.toList)
 
 
 val r1 = STAR("ab")