--- a/progs/token.scala	Tue Oct 16 08:29:49 2018 +0100
+++ b/progs/token.scala	Tue Oct 16 14:40:30 2018 +0100
@@ -1,3 +1,5 @@
+// Simple Tokenizer according to Sulzmann & Lu
+
 import scala.language.implicitConversions    
 import scala.language.reflectiveCalls
 
@@ -9,7 +11,7 @@
 case class SEQ(r1: Rexp, r2: Rexp) extends Rexp 
 case class STAR(r: Rexp) extends Rexp 
 case class RECD(x: String, r: Rexp) extends Rexp
-
+   
 abstract class Val
 case object Empty extends Val
 case class Chr(c: Char) extends Val
@@ -25,7 +27,8 @@
   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)
 
 implicit def RexpOps(r: Rexp) = new {
   def | (s: Rexp) = ALT(r, s)
@@ -42,6 +45,9 @@
   def $ (r: Rexp) = RECD(s, r)
 }
 
+// A test for more conveninet syntax
+val re : Rexp = ("ab" | "a") ~ ("b" | ONE)
+
 // nullable function: tests whether the regular 
 // expression can recognise the empty string
 def nullable (r: Rexp) : Boolean = r match {
@@ -85,6 +91,7 @@
 }
 
 // extracts an environment from a value
+// used for tokenise a string
 def env(v: Val) : List[(String, String)] = v match {
   case Empty => Nil
   case Chr(c) => Nil
@@ -126,8 +133,9 @@
 
 def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)
 
-
-lexing(("ab" | "a") ~ ("b" | ONE), "ab")
+// a simple test for extracting an environment
+val re1 : Rexp = ("first" $ ("a" | "ab")) ~ ("second" $ ("b" | ONE))
+env(lexing(re1, "ab"))
 
 // some "rectification" functions for simplification
 def F_ID(v: Val): Val = v
@@ -243,7 +251,7 @@
 //========================
 println("prog0 test")
 
-val prog0 = """read n"""
+val prog0 = """read if"""
 println(env(lexing_simp(WHILE_REGS, prog0)))
 
 println("prog1 test")

Binary file slides/slides04.pdf has changed

--- a/slides/slides04.tex	Tue Oct 16 08:29:49 2018 +0100
+++ b/slides/slides04.tex	Tue Oct 16 14:40:30 2018 +0100
@@ -665,7 +665,7 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
-\frametitle{Sulzmann Matcher}
+\frametitle{Sulzmann \& Lu Matcher}
 
 We want to match the string \bl{$abc$} using \bl{$r_1$}: