nextWord

        inline fn nextWord(self: *Self, comptime is_first_word: bool) void {
            var word = switch (direction) {
                .forward => self.words_remain[0],
                .reverse => self.words_remain[self.words_remain.len - 1],
            };
            switch (kind) {
                .set => {},
                .unset => {
                    word = ~word;
                    if ((direction == .reverse and is_first_word) or
                        (direction == .forward and self.words_remain.len == 1))
                    {
                        word &= self.last_word_mask;
                    }
                },
            }
            switch (direction) {
                .forward => self.words_remain = self.words_remain[1..],
                .reverse => self.words_remain.len -= 1,
            }
            self.bits_remain = word;
        }