+
+class Task;
+/** Smart pointer to a simgrid::s4u::Task */
+using TaskPtr = boost::intrusive_ptr<Task>;
+XBT_PUBLIC void intrusive_ptr_release(Task* o);
+XBT_PUBLIC void intrusive_ptr_add_ref(Task* o);
+class ExecTask;
+using ExecTaskPtr = boost::intrusive_ptr<ExecTask>;
+class CommTask;
+using CommTaskPtr = boost::intrusive_ptr<CommTask>;
+class IoTask;
+using IoTaskPtr = boost::intrusive_ptr<IoTask>;
+
+/**
+ * @brief Callback to dynamically change the resource's capacity
+ *
+ * Allows user to change resource's capacity depending on the number of concurrent activities
+ * running on the resource at a given instant
+ */
+using NonLinearResourceCb = std::function<double(double capacity, int n_activities)>;