Invert meaning of operator bool for CUDA stream and event

include/ghex/device/cuda/event.hpp

@@ -40,15 +40,7 @@ struct cuda_event
         if (!m_moved) { GHEX_CHECK_CUDA_RESULT_NO_THROW(cudaEventDestroy(m_event)) }
     }
 
-    /**
-     * @brief	Returns `true` if `*this` has been moved, i.e. can no longer be used.
-     *
-     * @todo  The semantic of this function is a bit confusing as a valid object returns
-     *   `false`. It should be changed such that a valid object returns `true` and an
-     *   invalid one returns `false`. This is the behaviour for `GHEX_C_STRUCT` and
-     *   `GHEX_C_MANAGED_STRUCT` but not for `stream` and `cuda_event`.
-     */
-    operator bool() const noexcept { return m_moved; }
+    operator bool() const noexcept { return !m_moved; }
 
     cudaEvent_t& get() noexcept
     {

include/ghex/device/cuda/event_pool.hpp

@@ -70,7 +70,7 @@ struct event_pool
         while (!(m_next_event < m_events.size())) { m_events.emplace_back(cuda_event()); }
 
         const std::size_t event_to_use = m_next_event;
-        assert(!bool(m_events[event_to_use]));
+        assert(bool(m_events[event_to_use]));
         m_next_event += 1;
         return m_events[event_to_use];
     }

include/ghex/device/cuda/stream.hpp

@@ -39,15 +39,7 @@ struct stream
         if (!m_moved) { GHEX_CHECK_CUDA_RESULT_NO_THROW(cudaStreamDestroy(m_stream)) }
     }
 
-    /**
-     * @brief	Returns `true` if `*this` has been moved, i.e. can no longer be used.
-     *
-     * @todo  The semantic of this function is a bit confusing as a valid object returns
-     *   `false`. It should be changed such that a valid object returns `true` and an
-     *   invalid one returns `false`. This is the behaviour for `GHEX_C_STRUCT` and
-     *   `GHEX_C_MANAGED_STRUCT` but not for `stream` and `cuda_event`.
-     */
-    operator bool() const noexcept { return m_moved; }
+    operator bool() const noexcept { return !m_moved; }
 
     operator cudaStream_t() const noexcept
     {