anchor.diff:                                ;
   
   nameExpression
  -returns [StringBuilder text]
  -@init {
  -    StringBuilder t = new StringBuilder();
  -}
  -@after {
  -    $text = t;
  -}
                                 : ^( NAME
                                      identifier
                                    )                                
  -                              {
  -                                  t.append( getText( $identifier.text ) );
  -                              }
                                 | ^( NAME
                                      domainReference
                                      identifier
  
positive.code: 
  
  expression
  returns [StringBuilder text]
  @init {
      StringBuilder t = new StringBuilder();
  }
  @after {
      $text = t;
  }
                                : binaryExpression            
                                | unaryExpression             
                                | rangeExpression             
  
negative.code:                               | sliceExpression             
                                | primeExpression             
                                | nameExpression              
                                | literalExpression           
                                ;
  
  binaryExpression
  