# (in numbers.py probably, because it would otherwise be alone in its own module booleans.py)


class Boolean(metaclass=ABCMeta):
    """
    An abstract base class for booleans.
    """
    __slots__ = ()

    @abstractmethod
    def __bool__(self):
        """Return a builtin bool instance. Called for bool(self)."""

    @abstractmethod
    def __and__(self, other):
        """self & other"""

    @abstractmethod
    def __rand__(self, other):
        """other & self"""

    @abstractmethod
    def __xor__(self, other):
        """self ^ other"""

    @abstractmethod
    def __rxor__(self, other):
        """other ^ self"""

    @abstractmethod
    def __or__(self, other):
        """self | other"""

    @abstractmethod
    def __ror__(self, other):
        """other | self"""


# register bool as a virtual subclass
Boolean.register(bool)