anchor.diff:      ;
   
   unaryExpression
  -    : op=NEGATION primaryExpression -> ^(UNARY_NOT[$op] primaryExpression)
  -    | op=PLUS primaryExpression -> ^(UNARY_PLUS[$op] primaryExpression)
  -    | op=MINUS primaryExpression -> ^(UNARY_MINUS[$op] primaryExpression)
  +    : op=NEGATION primaryExpression -> ^(UNARY NEGATION primaryExpression)
  +    | op=PLUS primaryExpression -> ^(UNARY PLUS primaryExpression)
  +    | op=MINUS primaryExpression -> ^(UNARY MINUS primaryExpression)
       | primaryExpression -> ^(UNARY primaryExpression)
       ;
   
  
positive.code:     ;
  
  brackettedExpression
      : OPEN_BRACE expression CLOSE_BRACE -> expression
      ;
  
  builtInCall
  
negative.code: PATH_SEQUENCE;
  PATH_PRIMARY;
  PATH_NEGATED;
  BRACKETTED_EXPRESSION;
  UNARY_NOT;
  UNARY_PLUS;
  UNARY_MINUS;
  