static function __static()
 {
     self::$plus = newinstance(__CLASS__, array(0, 'plus'), '{
     static function __static() { }
     public function evaluate($x, $y) { return $x + $y; } 
   }');
     self::$minus = newinstance(__CLASS__, array(1, 'minus'), '{
     static function __static() { }
     public function evaluate($x, $y) { return $x - $y; } 
   }');
     self::$times = newinstance(__CLASS__, array(2, 'times'), '{
     static function __static() { }
     public function evaluate($x, $y) { return $x * $y; } 
   }');
     self::$divided_by = newinstance(__CLASS__, array(3, 'divided_by'), '{
     static function __static() { }
     public function evaluate($x, $y) { return $x / $y; } 
   }');
 }