{

typedef boost::future<void> result_type;

result_type operator()(boost::future<void> future) const

{

assert(future.is_ready());

future.get();

return boost::make_ready_future();

}

result_type operator()(boost::future<boost::future<void> > future) const

{

assert(future.is_ready());

future.get();

return boost::make_ready_future();

}

{

#if ! defined BOOST_NO_CXX11_DECLTYPE && ! defined BOOST_NO_CXX11_AUTO_DECLARATIONS

{

boost::promise<void> test_promise;

boost::future<void> test_future(test_promise.get_future());

auto f1 = test_future.then(TestCallback());

BOOST_STATIC_ASSERT(std::is_same<decltype(f1), boost::future<boost::future<void> > >::value);

auto f2 = f1.then(TestCallback());

BOOST_STATIC_ASSERT(std::is_same<decltype(f2), boost::future<boost::future<void> > >::value);

}

{

boost::basic_thread_pool executor;

boost::promise<void> test_promise;

boost::future<void> test_future(test_promise.get_future());

auto f1 = test_future.then(executor, TestCallback());

BOOST_STATIC_ASSERT(std::is_same<decltype(f1), boost::future<boost::future<void> > >::value);

auto f2 = f1.then(executor, TestCallback());

BOOST_STATIC_ASSERT(std::is_same<decltype(f2), boost::future<boost::future<void> > >::value);

}

#endif

return 0;