Add EOF token to Start rule patterns

lib/imbecile/parser.rb

@@ -3,9 +3,11 @@ class Imbecile
   class Parser
 
     def initialize(tokens, rules)
+      token_eof = Token.new("$", nil, TOKEN_EOF)
       @item_sets = []
       item_sets_set = Set.new
       start_items = rules["Start"].patterns.map do |pattern|
+        pattern.components << token_eof
         Item.new(pattern, 0)
       end
       start_item_set = ItemSet.new(start_items)

lib/imbecile/token.rb

@@ -22,9 +22,11 @@ class Imbecile
       @name = name
       @pattern = pattern
       @id = id
-      regex = Regex.new(pattern)
-      regex.nfa.end_state.accepts = self
-      @nfa = regex.nfa
+      unless pattern.nil?
+        regex = Regex.new(pattern)
+        regex.nfa.end_state.accepts = self
+        @nfa = regex.nfa
+      end
     end
 
     def c_name