auto operator()() const noexcept {

using namespace sml;

// clang-format off

return make_transition_table(

*"idle"_s + event<e3> / [] { std::cout << "in sub sm" << std::endl; } = "s1"_s

, "s1"_s + event<e4> / [] { std::cout << "finish sub sm" << std::endl; } = X

);

// clang-format on

}

auto operator()() const noexcept {

using namespace sml;

// clang-format off

return make_transition_table(

*"idle"_s + event<e1> = "s1"_s

, "s1"_s + event<e2> / [] { std::cout << "enter sub sm" << std::endl; } = state<sub>

, state<sub> + event<e5> / [] { std::cout << "exit sub sm" << std::endl; } = X

);

// clang-format on

}

sml::sm<composite> sm;

using namespace sml;

assert(sm.is("idle"_s));

assert(sm.is<decltype(state<sub>)>("idle"_s));

sm.process_event(e1{});

assert(sm.is("s1"_s));

assert(sm.is<decltype(state<sub>)>("idle"_s));

sm.process_event(e2{}); // enter sub sm

assert(sm.is(state<sub>));

assert(sm.is<decltype(state<sub>)>("idle"_s));

sm.process_event(e3{}); // in sub sm

assert(sm.is(state<sub>));

assert(sm.is<decltype(state<sub>)>("s1"_s));

sm.process_event(e4{}); // finish sub sm

assert(sm.is(state<sub>));

assert(sm.is<decltype(state<sub>)>(X));

sm.process_event(e5{}); // exit sub sm

assert(sm.is(X));

assert(sm.is<decltype(state<sub>)>(X));