--- a/parser.scala	Wed Oct 31 08:56:08 2012 +0000
+++ b/parser.scala	Wed Oct 31 21:46:27 2012 +0000
@@ -139,7 +139,8 @@
 
 // grammar for arithmetic expressions
 val grammar = 
-  List ("E" -> List(T_NUM),
+  List ("F" -> List(T_NUM),
+        "E" -> List(T_NUM),
         "E" -> List(NT("E"), T_OP("+"), NT("E")),
         "E" -> List(NT("E"), T_OP("-"), NT("E")),
         "E" -> List(NT("E"), T_OP("*"), NT("E")),    
@@ -165,7 +166,7 @@
   }  
 
 def parse(g: Grammar, ts: List[Token]) : Boolean = {
-  //println(ts)
+  println(ts)
   if (ts == List(NT("E"))) true
   else {
     val tss = for ((lhs, rhs) <- g) yield replace(ts, rhs, List(NT(lhs)))
@@ -180,7 +181,7 @@
   
 
 
-parser(grammar, lexing_rules, "2 + 3 * 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)")