anchor.diff:  
   start
   :	( expr 
  -	| exprGroup EOF 
  -	| relation EOF ) 
  +	| exprGroup 
  +	| relation  ) 
   ;
positive.code: | regex
  ;
  
  /*	
  andGroup
  : 	(((LRB exprGroup RRB)|expr) AND)+ ((LRB exprGroup RRB)|expr)
  ;
  
  orGroup
  : 	(((LRB exprGroup RRB)|expr) OR)+ ((LRB exprGroup RRB)|expr)
  ;
  */
  
  relation
  :	(expr|exprGroup) conj (expr|exprGroup|relation)
  ; 
  
  exprGroup
  
negative.code: 
  expr
  :	(value operator)? field operator value
  //|	LRB expr RRB
  ;
  	
  field
  