anchor.diff:  prefix_arg :
        pow_arg
     |  t_NOT t_FILLER? prefix_arg
  -  |  t_PLUS t_FILLER? prefix_arg
  -  |  t_MINUS t_FILLER? prefix_arg
  +  |  (t_PLUS | t_MINUS) t_FILLER? prefix_arg //NB: plus_arg may break if this is written as two rules
     ;
   
   pow_arg :
  
positive.code: 
  t_ASSIGN : ASSIGN { offsetTracker.advanceInLine(1); };
  
  t_LPAREN : LPAREN { offsetTracker.advanceInLine(1); };
  t_RPAREN : RPAREN { offsetTracker.advanceInLine(1); };
  t_LCURLY : LCURLY { offsetTracker.advanceInLine(1); };
  t_RCURLY : RCURLY { offsetTracker.advanceInLine(1); };
  t_LSQUARE : LSQUARE { offsetTracker.advanceInLine(1); };
  t_RSQUARE : RSQUARE { offsetTracker.advanceInLine(1); };
  
  t_IDENTIFIER : IDENTIFIER { offsetTracker.advanceByTextSize($text); };
  t_NUMBER : NUMBER { offsetTracker.advanceByTextSize($text); };
  
negative.code: prefix_expr :
       pow_expr
    |  t_NOT t_FILLER? prefix_expr
    |  (t_PLUS | t_MINUS) t_FILLER? prefix_expr //NB: plus_expr breaks if this is written as two rules
    ;
  
  pow_expr :
  