public function isEqual($a=null, $b=null) {
    list($a, $b) = self::_wrapArgs(func_get_args(), 2);
    
    if(isset($this) && isset($this->_chained) && $this->_chained) $a =& $this;
    
    if($a === $b) return self::_wrap(true);
    if(gettype($a) !== gettype($b)) return self::_wrap(false);
    if(is_callable($a) !== is_callable($b)) return self::_wrap(false);
    
    if($a == $b) return self::_wrap(true);
    
    // Objects and arrays compared by values
    if(is_object($a) || is_array($a)) {
      
      // Do either implement isEqual()?
      if(is_object($a) && isset($a->isEqual)) return self::_wrap($a->isEqual($b));
      if(is_object($b) && isset($b->isEqual)) return self::_wrap($b->isEqual($a));
      if(is_array($a) && array_key_exists('isEqual', $a)) return self::_wrap($a['isEqual']($b));
      if(is_array($b) && array_key_exists('isEqual', $b)) return self::_wrap($b['isEqual']($a));
      
      if(count($a) !== count($b)) return self::_wrap(false);
      
      $__ = new self;
      $keys_equal = $__->isEqual($__->keys($a), $__->keys($b));
      $values_equal = $__->isEqual($__->values($a), $__->values($b));
      return self::_wrap($keys_equal && $values_equal);
    }
    
    return self::_wrap(false);
  }