Method get_bit

common/unordered_inline_set.h:19–22

    T* _ptr = nullptr;
    size_t _capacity = 0, _size = 0;
    bool get_bit(size_t i) const {
        auto c = (char*)_ptr - i / 8 - 1;
        return *c & (1 << (i % 8));
    }
    void set_bit(size_t i) {
        auto c = (char*)_ptr - i / 8 - 1;
        *c |= (1 << (i % 8));