anchor.diff:  
   shift_expression
     : simple_expression
  -    ( options{greedy=true;}: shift_operator simple_expression )?
  +    ( : shift_operator simple_expression )?
     ;
   
   shift_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: // NOTE that NAND/NOR are in (...)* now (used to be in (...)?).
  // (21.1.2004, e.f.)
  expression
    : relation ( : logical_operator relation )*
    ;
  
  factor
    : primary ( : DOUBLESTAR primary )?
    | ABS primary
    | NOT primary
    ;
  