{

std::string ans("forty two");

#if defined EXAMPLE_1

//! Compiles and produces correct result.

{

boost::packaged_task<int()> example(int_no_params);

boost::future<int> f = example.get_future();

boost::thread task(boost::move(example));

int answer = f.get();

std::cout << "Answer to life and whatnot, in English: " << answer << std::endl;

task.join();

}

#endif

#if defined EXAMPLE_2

//! Compiles and produces correct result.

{

boost::packaged_task<std::string()> example(string_no_params);

boost::future<std::string> f = example.get_future();

boost::thread task(boost::move(example));

std::string answer = f.get();

std::cout << "string_no_params: " << answer << std::endl;

task.join();

}

#endif

#if defined EXAMPLE_3

//! Doesn't compile in C++03.

//! error: variable âboost::packaged_task<std::basic_string<char>(std::basic_string<char>&)> exampleâ has initializer but incomplete type

{

boost::packaged_task<std::string(std::string&)> example(string_with_params);

boost::future<std::string> f = example.get_future();

example(ans);

std::string answer = f.get();

std::cout << "string_with_params: " << answer << std::endl;

}

#endif

#if defined EXAMPLE_4

//! Doesn't compile in C++11

{

boost::packaged_task<std::string(std::string&)> example(string_with_params);

boost::future<std::string> f = example.get_future();

boost::thread task(boost::move(example), boost::ref(ans));

std::string answer = f.get();

std::cout << "string_with_params: " << answer << std::endl;

task.join();

}

#endif

#if defined EXAMPLE_5

//! Doesn't compile in C++03, C++11 only.

//! error: extended initializer lists only available with -std=c++11 or -std=gnu++11 [-Werror]

{

boost::packaged_task<std::string(std::string&)> example

{ boost::bind(&string_with_params, ans) };

boost::future<std::string> f = example.get_future();

boost::thread task(boost::move(example), boost::ref(ans));

std::string answer = f.get();

std::cout << "string_with_params: " << answer << std::endl;

task.join();

}

#endif

#if defined EXAMPLE_6

//! Doesn't compile in C++03, C++11 only.

// packagedTestTest.cpp:94:43: error: invalid use of incomplete type ‘class boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>’

// packagedTestTest.cpp:95:37: error: incomplete type ‘task_t {aka boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>}’ used in nested name specifier

// boost/thread/future.hpp:1320:11: error: declaration of ‘class boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>’

{

//typedef boost::packaged_task<std::string(std::string&)> task_t;

typedef boost::packaged_task<std::string()> task_t;

boost::shared_ptr<task_t> example = boost::make_shared<task_t>(boost::bind(&string_with_params, boost::ref(ans)));

boost::future<std::string> f = example->get_future();

boost::thread task(boost::bind(&task_t::operator(), example));

std::string answer = f.get();

std::cout << "string_with_params: " << answer << std::endl;

task.join();

}

#endif

#if defined EXAMPLE_7

//! Doesn't compile in C++03, C++11 only.

// packagedTestTest.cpp:94:43: error: invalid use of incomplete type ‘class boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>’

// packagedTestTest.cpp:95:37: error: incomplete type ‘task_t {aka boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>}’ used in nested name specifier

// boost/thread/future.hpp:1320:11: error: declaration of ‘class boost::packaged_task<std::basic_string<char>(std::basic_string<char>&)>’

{

boost::asio::io_service io_service;

boost::thread_group threads;

boost::asio::io_service::work work(io_service);

for (int i = 0; i < 3; ++i)

{

threads.create_thread(boost::bind(&boost::asio::io_service::run,

&io_service));

}

typedef boost::packaged_task<std::string()> task_t;

boost::shared_ptr<task_t> example = boost::make_shared<task_t>(boost::bind(&string_with_params, ans));

boost::future<std::string> f = example->get_future();

io_service.post(boost::bind(&task_t::operator(), example));

std::string answer = f.get();

std::cout << "string_with_params: " << answer << std::endl;

threads.join_all();

}

#endif

return 0;