replace "get_scheduler" with "this_task" example using more syntax sugar (#63)

* replace get_scheduler with this_task example

* fix format

Author: m-fila

examples/CMakeLists.txt

@@ -36,8 +36,8 @@ add_executable(alien_counting_scope alien_counting_scope.cpp)
 target_link_libraries(alien_counting_scope PRIVATE CoroutineTests)
 add_executable(alien_schedule_on alien_schedule_on.cpp)
 target_link_libraries(alien_schedule_on PRIVATE CoroutineTests)
-add_executable(alien_get_scheduler alien_get_scheduler.cpp)
-target_link_libraries(alien_get_scheduler PRIVATE CoroutineTests)
+add_executable(alien_this_task alien_this_task.cpp)
+target_link_libraries(alien_this_task PRIVATE CoroutineTests)
 
 if(BUILD_STDEXEC)
   add_executable(exec_task_stdexec exec_task.cpp)

examples/README.md

@@ -150,11 +150,11 @@ Link: [alien_schedule_on.cpp](alien_schedule_on.cpp)
 
 This example demonstrates changing scheduler used by part of a chain of coroutines following the semantics from ["Alien" example](#alien). The `schedule_on` algorithm can be used to adapt a coroutine to use a different scheduler than its parent. Starting the coroutine suspends its parent and reschedule work on the new scheduler, finishing the coroutine reschedules continuation of its parent using parent's scheduler.
 
-## Alien get_scheduler
+## Alien this_task
 
-Link: [alien_get_scheduler.cpp](alien_get_scheduler.cpp)
+Link: [alien_this_task.cpp](alien_this_task.cpp)
 
-This example shows how the contents of promise type can be extracted from within a coroutine. The `GetScheduler` awaitable when co_awaited accessed the promise type and returns the currently used coroutine. The example uses then `schedule_on` algorithm from ["alien schedule_on" example](#alien-schedule_on) to alternate between used schedulers in each nested coroutine.
+This example shows how the contents of promise type can be extracted from within a coroutine. The `this_task::scheduler` uses custom `operator co_await` that returns a helper awaitable which returns the scheduler used by the current coroutine. The example uses then `schedule_on` algorithm from ["alien schedule_on" example](#alien-schedule_on) to alternate between used schedulers in each nested coroutine.
 
 ## Capy task
 

examples/alien_get_scheduler.cpp examples/alien_this_task.cppexamples/alien_get_scheduler.cpp renamed to examples/alien_this_task.cpp

@@ -1,14 +1,15 @@
 #include <format>
 #include <string_view>
 
-#include "CoroutineTests/alien/get_scheduler.hpp"
 #include "CoroutineTests/alien/schedule_on.hpp"
 #include "CoroutineTests/alien/sync_wait.hpp"
+#include "CoroutineTests/alien/this_task.hpp"
 #include "CoroutineTests/alien/tool.hpp"
 #include "CoroutineTests/threadpool.hpp"
 #include "logging_utils.hpp"
 
 using namespace CoroutineTests::alien;
+
 using scheduler_t = std::function<void(std::coroutine_handle<>)>;
 tool::Task<void> innermost_task(std::string_view parent) {
     const auto self = format_name(parent, "innermost_task");
@@ -31,7 +32,7 @@ tool::Task<void> outer_task(scheduler_t inner_scheduler,
                             std::string_view parent) {
     const auto self = format_name(parent, "outer_task");
     log(self) << "Running outer task" << std::endl;
-    auto current_scheduler = co_await GetScheduler{};
+    auto current_scheduler = co_await this_task::scheduler;
     log(self) << "Got current scheduler in outer task, scheduling inner task "
                  "on inner scheduler"
               << std::endl;

…e/CoroutineTests/alien/get_scheduler.hpp …clude/CoroutineTests/alien/this_task.hppinclude/CoroutineTests/alien/get_scheduler.hpp renamed to include/CoroutineTests/alien/this_task.hpp include/CoroutineTests/alien/get_scheduler.hpp renamed to include/CoroutineTests/alien/this_task.hpp

@@ -1,7 +1,9 @@
 #include <coroutine>
 #include <functional>
 
-namespace CoroutineTests::alien {
+namespace CoroutineTests::alien::this_task {
+
+namespace detail {
 
 class GetScheduler {
     public:
@@ -24,4 +26,14 @@ class GetScheduler {
     std::function<void(std::coroutine_handle<>)> m_scheduler;
 };
 
-}  // namespace CoroutineTests::alien
+}  // namespace detail
+
+struct scheduler_tag {};
+
+constexpr scheduler_tag scheduler;
+
+// Custom operator to produce a helper awaitable which will be actually awaited.
+inline auto operator co_await(scheduler_tag) noexcept {
+    return detail::GetScheduler{};
+}
+}  // namespace CoroutineTests::alien::this_task