anchor.diff:  
   floatLiteral
   	: FLOAT_WEBIDL
  -	| '-' 'Infinity'
  +	| '-Infinity'
   	| 'Infinity'
   	| 'NaN'
   ;
  
positive.code:     http://dev.w3.org/2006/webapi/WebIDL/
  
      Web IDL (Second Edition)
      W3C Editor's Draft 02 August 2013
   */
  grammar WebIDL;
  
  
negative.code: ;
  
  enumValueList
  	: STRING_WEBIDL enumValueListComma
  ;
  
  enumValueListComma
  	: ',' enumValueListString
  	| /* empty */
  ;
  
  enumValueListString
  	: STRING_WEBIDL enumValueListComma
  	| /* empty */
  ;
  
  