anchor.diff:  
       rule rule_name: VAR
   
  -    rule rule_predicate: expression
  +    rule rule_predicate: "\\(" expression "\\)"
   
       rule rule_satements: "RULESST"
   
  
positive.code: globalvars = {}       # We will store the calculator's variables here
  def lookup(map, name):
      print "lookup", map, name
      for x, v in map:
          if x == name: return v
      if not globalvars.has_key(name):
          print 'Undefined (defaulting to 0):', name
      return globalvars.get(name, 0)
  
  %%
  
negative.code:     rule variable_declaration:
          Type_item VAR [ "=" expression ] ';'
  
      rule variable_declaration_and_initializations:
          variable_declaration
          | let_statement
  
      rule rules_statement:
          "rules" [ ":"  rules_name]
          rule_satements
          (variable_declaration | variable_assignment)*
          #variable_declaration
          "endrules" [ ":"  rules_name]
  
      rule action_statement:
          "action" [ ":"  action_name] [ ';' ]
          action_statements
          "endaction" [ ":" action_name]
  
  