anchor.diff:  //
  -// Grammer for path expressions
  +// Grammar for path expressions
   //
   
   header {
  
positive.code: orExpr
      : andExpr ( "or"^ andExpr )*
      ;
      
  andExpr
      : atom ( "and"^ atom )*
      ;
  
negative.code:     : IDENTIFIER
      | bracketedExpr
      ;
  
  bracketedExpr
      : OPEN_PAREN! orExpr CLOSE_PAREN!
      ;
  