diff -r 53f08d873e09 -r 7af2eea19646 solutions/cw3/lexer.sc
--- a/solutions/cw3/lexer.sc	Sun Sep 17 19:12:57 2023 +0100
+++ b/solutions/cw3/lexer.sc	Tue Sep 19 09:54:41 2023 +0100
@@ -1,5 +1,6 @@
-import scala.language.implicitConversions    
-import scala.language.reflectiveCalls
+// Lexer from CW2
+//================
+
 
 // Rexp
 abstract class Rexp
@@ -27,7 +28,7 @@
 case class Rec(x: String, v: Val) extends Val
 
 
-// Convenience typing
+// Convenience for typing
 def charlist2rexp(s : List[Char]): Rexp = s match {
   case Nil => ONE
   case c::Nil => CHAR(c)
@@ -136,7 +137,7 @@
 
   case (RANGE(_), Empty) => Chr(c)
   case (PLUS(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
-  case (OPTIONAL(r), Left(v1)) => Stars(List(inj(r, c, v1)))
+  case (OPTIONAL(r), v1) => Stars(List(inj(r, c, v1)))
   case (NTIMES(r, n), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)
 }