Hi Christophe,
Hi Takatoshi,
this question has already been asked some time ago in a slightly different context (http://lists.boost.org/Archives/boost/2010/09/170506.php). This is unfortunately one of the points where I had to leave the compile-time world earlier than I would like (but found no better solution yet). While Event1 will not be considered for forwarding, the compiler does not know because it's only known at run-time, and it therefore complains that you cannot create Event1 from Event2.
The surprise to me is that the compiler is happy with only your second constructor, I'd expect it to require a constructor taking Event1. Should it happen, you will need to use the enable_if / disable_if workaround presented in the above thread.
I'll update the doc so that this current limitation is documented until I find a better solution.
Thanks for the reply. I understood current situation.
Or simplier:
template <class T> Event3(T const& ):val(0) {} // not used Event3(Event2 const& e):val(e.val) {} //conversion constructor
Correct. It works well. In my usecase, I think it's typical, the outer event(Event3) shouldn't know about inner event(Event2). In other words, outer event is an interface of a sub state machine. When I use the SFINAE solution, the predicate is important. If I choose the is_same, it still needs inner event information. template <class T> OuterEvent(T const& t, typename enable_if<is_same<T, InnerEvent> >::type* = 0); I considered some approaches. The first approach is the InnerEvent inherits the OuterEvent and use the is_base_of. struct InnerEvent:OuterEvent {}; is_base_of<T, OuterEvent> And next, I realized that if the InnerEvent inherits the OuterEvent, we can construct the OuterEvent from the InnerEvent automatically. It is the slicing. In my usecase, I think it works well. struct OuterEvent { int val; }; struct InnerEvent:OuterEvent {}; struct Exit:msm::front::exit_pseudo_state<OuterEvent> {}; // Start Event Next Action Guard msmf::Row < SubState1, InnerEvent, Exit, msmf::none, msmf::none > Regards, Takatoshi