anchor.diff:  
   relation
     : shift_expression
  -    ( options{greedy=true;}: relational_operator shift_expression )?
  +    ( : relational_operator shift_expression )?
     ;
   
   relational_operator
  
positive.code: // `a op -b' - use `a op (-b)' instead).
  // (3.2.2004, e.f.)
  simple_expression
    : ( PLUS | MINUS )? term ( options{greedy=true;}: adding_operator term )*
    ;
  
  simple_simultaneous_statement
  
negative.code: 
  shift_expression
    : simple_expression
      ( : shift_operator simple_expression )?
    ;
  
  shift_operator
  