Function detach

core/ref.h:122–127

    }

    oidn_inline T* detach() noexcept
    {
      T* res = ptr;
      ptr = nullptr;
      return res;
    }

    friend oidn_inline bool operator < (const Ref<T>& a, const Ref<T>& b) noexcept { return a.ptr   <  b.ptr;   }