class direction(enum.Enum):
    '''Enumerate the cardinal (NEWS) and intercardinal directions.

    The enum values are vectors, and can be accessed via V.vector
    as well, for clarity.

    '''
    NORTH      = vector(-1,  0)
    NORTH_EAST = vector(-1,  1)
    EAST       = vector( 0,  1)
    SOUTH_EAST = vector( 1,  1)
    SOUTH      = vector( 1,  0)
    SOUTH_WEST = vector( 1, -1)
    WEST       = vector( 0, -1)
    NORTH_WEST = vector(-1, -1)

    @property
    def vector(self):
        return self.value

    def flip_ew(self):
        return {
            direction.NORTH_EAST: direction.NORTH_WEST,
            direction.EAST:       direction.WEST,
            direction.SOUTH_EAST: direction.SOUTH_WEST,
            direction.SOUTH_WEST: direction.SOUTH_EAST,
            direction.WEST:       direction.EAST,
            direction.NORTH_WEST: direction.NORTH_EAST,
        }.get(self, self)

    def flip_nw(self):
        return {
            direction.NORTH:      direction.SOUTH,
            direction.NORTH_EAST: direction.SOUTH_EAST,
            direction.SOUTH_EAST: direction.NORTH_EAST,
            direction.SOUTH:      direction.NORTH,
            direction.SOUTH_WEST: direction.NORTH_WEST,
            direction.NORTH_WEST: direction.SOUTH_WEST,
        }.get(self, self)