anchor.diff:  primary
    : Name=NAME
    | Literal=literal
  - | True=TRUE
  - | False=FALSE
  - | Nil=NIL
  + | True=KEY_TRUE
  + | False=KEY_FALSE
  + | Nil=KEY_NIL
    | '(' Expression=expression ')' 
    ;
   
  
positive.code:  * The above copyright notice and this permission notice shall be
   * included in all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
   * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
   * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
   * OTHER DEALINGS IN THE SOFTWARE.
   *
   */
  
  grammar Lury;
  
  tokens { INDENT, DEDENT }
  
  @lexer::header {
  using System;
  
negative.code: 
  suite
   : simple_statement
   | NEWLINE KEY_INDENT Statements=statement+ DEDENT
   ;
  
  expression
  