diff -r 7a777d9cc343 -r 6fe4facb56a6 parser.scala
--- a/parser.scala	Wed Oct 31 02:05:12 2012 +0000
+++ b/parser.scala	Wed Oct 31 08:35:00 2012 +0000
@@ -86,7 +86,7 @@
 case class T_OP(s: String) extends Token
 case object T_LPAREN extends Token
 case object T_RPAREN extends Token
-case class T_NT(s: String) extends Token
+case class NT(s: String) extends Token
 
 type Rule = (Rexp, List[Char] => Token)
 
@@ -140,10 +140,10 @@
 // grammar for arithmetic expressions
 val grammar = 
   List ("E" -> List(T_NUM),
-        "E" -> List(T_NT("E"), T_OP("+"), T_NT("E")),
-        "E" -> List(T_NT("E"), T_OP("-"), T_NT("E")),
-        "E" -> List(T_NT("E"), T_OP("*"), T_NT("E")),    
-        "E" -> List(T_LPAREN, T_NT("E"), T_RPAREN))
+        "E" -> List(NT("E"), T_OP("+"), NT("E")),
+        "E" -> List(NT("E"), T_OP("-"), NT("E")),
+        "E" -> List(NT("E"), T_OP("*"), NT("E")),    
+        "E" -> List(T_LPAREN, NT("E"), T_RPAREN))
 
 
 def chop[A](ts1: List[A], prefix: List[A], ts2: List[A]) : Option[(List[A], List[A])] = 
@@ -164,19 +164,25 @@
     case Some((before, after)) => Some(before ::: in ::: after)
   }  
 
-def parse1(g: Grammar, ts: List[Token]) : Boolean = {
+def parse(g: Grammar, ts: List[Token]) : Boolean = {
   //println(ts)
-  if (ts == List(T_NT("E"))) true
+  if (ts == List(NT("E"))) true
   else {
-    val tss = for ((lhs, rhs) <- g) yield replace(ts, rhs, List(T_NT(lhs)))
-    tss.flatten.exists(parse1(g, _))
+    val tss = for ((lhs, rhs) <- g) yield replace(ts, rhs, List(NT(lhs)))
+    tss.flatten.exists(parse(g, _))
   }
 }
  
+def parser(g: Grammar, rs: List[Rule], s: String) = {
+  println("\n")
+  parse(g, tokenizer(rs, s))
+}
+  
 
-println() ; parse1(grammar, tokenizer(lexing_rules, "2 + 3 * 4 + 1"))
-println() ; parse1(grammar, tokenizer(lexing_rules, "(2 + 3) * (4 + 1)"))
-println() ; parse1(grammar, tokenizer(lexing_rules, "(2 + 3) * 4 (4 + 1)"))
+
+parser(grammar, lexing_rules, "2 + 3 * 4 + 1")
+parser(grammar, lexing_rules, "(2 + 3) * (4 + 1)")
+parser(grammar, lexing_rules, "(2 + 3) * 4 (4 + 1)")