May 2011 - Boost-users - lists.preview.boost.org

[fusion] result_of
by Robert Ramey 08 May '11

08 May '11

I'm very interested in fusion and have been experimenting with it. There is one thing that is currently confusing me. (OK more than one thing). The documentation a typical function at .../fusion/sequence/concepts/associative_sequence.html shows valid expression has_key<K>(s) returning type result_of::has_key<S, K>::type which is OK by me. But why doesn't fusion use: #include <boost/result_of.hpp> then use boost::result_of<has_key<K>(S)>::type which would seem to me to reduce the size of fusion (and the docs) by around 50%. What am I missing here? Robert Ramey

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[asio] Pending handlers not invoked in boost.asio?
by Germán Diago 08 May '11

08 May '11

Hello. I'm writing a little game which keeps four players connected. At first, my protocol does something like the following: -Server waits for 3 incoming connections. io_service::run is running in another thread (and the code I'll show you server side is executed after that). -Clients connect and send its data (name and team). When everything's done, the server continues and shows the received data from the clients. I have a loop like this on the Server side (with the great coroutine implementation from the examples): for (; num_players_connected_ !=3; ++num_players_connected_) { //Create context connection_contexts_.at(num_players_connected_) = std::make_shared<ConnectionContext>(service_); yield acceptor_.async_accept(*connection_contexts_.at(num_players_connected_)->socket(), std::ref(*this)); std::cout << "Servidor: Incoming connection" << std::endl; connection_contexts_.at(num_players_connected_)->start(); //This calls ClientContext::operator() //Start connection processing std::cout << "Servidor: Players connected: " << num_players_connected_ << std::endl; } //Here every connection is already done but must wait for data available in every context. std::cout << "Server: All " << num_players_connected_ << " players are connected" << std::endl; for (std::size_t i = 0; i < 3; i++) { //Wait for each player to have its data available server-side connection_contexts_.at(i)->playerDataReady().get(); std::cout << "Player info:\n"; std::cout << "\tPlayer name " << connection_contexts_.at(i)->playerName() << std::endl; std::cout << "\tPlayer team " << connection_contexts_.at(i)->playerTeam() << std::endl; } /////////////////////////////////// The Context for each client in the server side looks something like this: void ClientContext::operator()() { using namespace boost; const MsjDatosJugador * player_data = 0; MensajeRed msg; reenter (coro_opcall_state_) { yield asyncReadMessageFromSocketIntoQueue(std::ref(*this)); msg = getNextMessage(); std::cout << "Message has been read\n" << std::endl; if (msg.getTipo() == typeid(MsjDatosJugador)) { player_data = &(msg.getInfo<MsjDatosJugador>()); player_name_ = std::move(player_data->name_); player_team_ = player_data->team_; player_ready_ = true; } else { message_received_handler_(getNextMessage()); } } } void ClientContext::asyncReadMessageFromSocketIntoQueue( std::function<void ()> handler, const boost::system::error_code & ec, std::size_t bytes) { using namespace boost; if (!ec) { reenter (coro_read_state_) { message_size_ = std::make_shared<boost::int64_t>(); yield asio::async_read(*socket_, asio::buffer(message_size_.get(), sizeof(boost::int64_t)), std::bind(&GuinyoteClientContext::asyncReadMessageFromSocketIntoQueue, this, handler, std::placeholders::_1, std::placeholders::_2)); message_buffer_ = std::make_shared<std::vector<char> >(*message_size_); yield asio::async_read(*socket_, asio::buffer(message_buffer_->data(), *message_size_), std::bind(&GuinyoteClientContext::asyncReadMessageFromSocketIntoQueue, this, handler, std::placeholders::_1, std::placeholders::_2)); std::istringstream stream(std::string(message_buffer_->begin(), message_buffer_->end()), std::ios::binary); boost::archive::binary_iarchive archive(stream); MensajeRed msg; archive >> msg; std::cout << "GuinyoteClientContext: Pushing message into the message queue.\n"; messages_.push(msg); handler(); } } else { BOOST_THROW_EXCEPTION(std::runtime_error("GuinyoteContext: Error reading from client socket: " + ec.message())); } } My EXACT problem is that when the THIRD client connects, after invoking ClientContext::asyncReadMessageFromSocketIntoQueue once and reaching the first yield, it is never invoked again, even if I passed the handler function. Am I missing something? Must I flush the io_service handler execution in some way? Thanks in advance.

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Query on proposed Boost.Move library
by Leo Carreon 07 May '11

07 May '11

Hi, I’m new to this mailing list and I haven’t figured out how to search the archives yet. At this stage, all I wanted to find out is whatever happened to the proposed Boost.Move library? Regards, Leo

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Boost Install on Mac OS X using GCC
by Andrew 07 May '11

07 May '11

Hello, I'm trying to install boost on mac using the gcc compiler. I encounter these errors during installation for all libraries: "g++" -Wl,-R -Wl,"/System/Library/Frameworks/Python.framework/Versions/2.6/lib" -Wl,-R -Wl,"/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/config" -o "stage/lib/libboost_prg_exec_monitor.dylib" -Wl,-h -Wl,libboost_prg_exec_monitor.dylib -shared -Wl,--start-group "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/execution_monitor.o" "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/debug.o" "/Users/andrew/boost/boost/bin.v2/libs/test/build/gcc-4.2.1/release/threading-multi/cpp_main.o" -Wl,-Bstatic -Wl,-Bdynamic -Wl,--end-group ...failed gcc.link.dll stage/lib/libboost_prg_exec_monitor.dylib... gcc.link.dll stage/lib/libboost_unit_test_framework.dylib ld: unknown option: -R collect2: ld returned 1 exit status I have no experience at all using boost in mac, and it is necessary that I use gcc. I am wondering if anyone could point me to a solution regarding this. Thanks, Andrew

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[iterator] Problems with iterator_facade and const-qualification
by Evan Driscoll 07 May '11

07 May '11

I'm trying to use the iterator_facade and am running into trouble. It's not really caused by the iterator_facade, but I figured I'd ask anyway. This takes some explanation, so if anyone reads this, know that I *do* appreciate it. :-) TLDR version: I'm getting a compiler error about converting between pointers of iterator_facade<> instantiations with different const qualifications on the value_type. The code's attached, in addition to mostly appearing (with a few minor formatting changes) inline below. Please help me figure out what to do to fix it. What I'm doing is a bit roundabout, but here goes. One fault with C++ iterators (at least from some point of view) is that if you want to operate on different kinds of iterators you have to care about too much -- you need to know more than just the type that op* returns (which is all you care about most of the time, iterator_traits notwithstanding), but what the underlying iterator type is. This means that if you want to write code that operates on multiple kinds of iterators, it must be a template. Templates don't suit my needs at this time, so I'm trying to write a couple wrapper classes that will do dynamic dispatch to different iterator types. Think of this as writing a C++ version of Java's Iterator interface. Thus I define a base class for my iterators: template<typename ValueType, typename ReferenceType> class iterator_base : public iterator_facade<iterator_base<ValueType, ReferenceType>, ValueType, boost::forward_traversal_tag, ReferenceType> { friend class boost::iterator_core_access; protected: virtual void increment() = 0; virtual ReferenceType dereference() const = 0; virtual bool equal(iterator_base const & other) const = 0; public: virtual iterator_base* clone() const = 0; }; (I'm only worrying about forward iterators at this time. I'm also ignoring ptrdiff_t) The first three functions are straight from the iterator_facade class, and the fourth is your typical clone() method. Now, I define a template that wraps any iterator that doesn't implement my iterator_base; it just stores an instance of the backing iterator type and does the corresponding thing (I'm removing some 'typenames' in there to avoid line wraps): template<typename BackingIter> class cplusplus_iterator_adaptor : public iterator_base<iterator_traits<BackingIter>::value_type, iterator_traits<BackingIter>::reference> { private: BackingIter backing; typedef typename iterator_traits<BackingIter>::value_type ValueType; typedef typename iterator_traits<BackingIter>::reference Reference; public: cplusplus_iterator_adaptor() {} cplusplus_iterator_adaptor(cplusplus_iterator_adaptor const & other) : backing(other.backing) {} explicit cplusplus_iterator_adaptor(BackingIter iter) : backing(iter) {} cplusplus_iterator_adaptor* clone() const { return new cplusplus_iterator_adaptor(*this); } // Actual iterator functions void increment() { ++backing; } bool equal(iterator_base<ValueType, Reference> const& other) const { const cplusplus_iterator_adaptor * p = dynamic_cast<cplusplus_iterator_adaptor const*>(&other); return p && backing == p->backing; } Reference dereference() const { return *backing; } }; Okay, now we have something that we can use like cplusplus_iterator_adaptor<vector<int>::iterator> my_itr(vec.begin()); *my_itr; ++my_itr; and it will work the same as vector<int>::iterator, except that you can treat it polymorphically from an iterator_base<int> reference or pointer, thus freeing you from caring that it wraps a vector iterator instead of just caring that it gives you an int&. There's one problem with this however, which is that if I <i>actually</i> want to deal with it polymorphically, I have to use a reference or pointer; but (1) this kinda sucks and (2) lots of code is written that operates on iterators by value (like, say, the STL). To solve this problem, I implemented a wrapper class that gives value semantics to a iterator_base<> pointer. This wrapper class also implements the elements required of the iterator concept, and additionally behaves like a cloning smart pointer. template<typename ValueType, typename ReferenceType = ValueType &> class iterator_base_wrapper : public iterator_facade<iterator_base_wrapper<ValueType, ReferenceType>, ValueType, boost::forward_traversal_tag, ReferenceType> { private: iterator_base<ValueType, ReferenceType> * backing; public: iterator_base_wrapper() : backing(0) {} iterator_base_wrapper(iterator_base_wrapper const & other) : backing(other.backing->clone()) {} explicit iterator_base_wrapper(iterator_base const & base) : backing(base.clone()) {} private: void swap(iterator_base_wrapper & other) const { std::swap(backing, other.backing); } public: iterator_base_wrapper& operator=(iterator_base_wrapper const&other) { iterator_base_wrapper copy(other); swap(copy); return *this; } ~iterator_base_wrapper() { delete backing; } private: friend class boost::iterator_core_access; virtual void increment() { ++(*backing); } virtual bool equal(iterator_base_wrapper const & other) const { return backing->equal(*other.backing); } ReferenceType dereference() const { return **backing; } }; OK, goal achieved! Somewhat. It's now possible to use the iterator_base_wrapper like you would a normal iterator: int run() { const int arr[] = {0,1,2,3,4,5,6,7,8,9,10}; const int size_arr = sizeof(arr)/sizeof(arr[0]); vector<int> v(arr, arr+size_arr); cplusplus_iterator_adaptor<vector<int>::iterator> a_beg(v.begin()); cplusplus_iterator_adaptor<vector<int>::iterator> a_end(v.end()); iterator_base_wrapper<int> ii(a_beg); iterator_base_wrapper<int> ii_end(a_end); vector<int>::const_iterator vi = v.begin(); while(ii != ii_end) { assert( *vi == *ii ); ++vi; ++ii; } assert( vi == v.end() ); return 0; } (BY the way, I totally intend on writing a couple make_* functions, a la make_pair.) OK, but now, what happens if we change things to be const_iterators? I can still make the cplusplus_iterator_adaptor: cplusplus_iterator_adaptor<vector<int>::const_iterator> a_beg(v.begin()); But I *can't* make my wrapper, using either iterator_base_wrapper<const int, const int &> ii(a_beg); or iterator_base_wrapper<int, const int &> ii(a_begin); because of this error: cannot convert from 'iterator_base<int, const int&>*' to 'iterator_base<const int, const int&>*'. The reason for *this* is that the cplusplus_iterator_adaptor uses the iterator_traits<>::value_type of the underlying iterator -- vector's const_iterator -- which isn't const-qualified when it subclasses iterator_facade. This means that the iterator_facade base class in both cases are different types. What's the best way to fix this? The best I can come up with is to add like a clone_const() function that returns a const-qualified version of the value type. But that seems ugly. Is there something elegant I'm missing? Evan Driscoll

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cgal python compilation with boost
by Ferdi Zoet 07 May '11

07 May '11

dear boost user, there seems to be an error when I am trying to compile cgal-python. ============================================================================ 103-99:cgal-python-0.9.4-beta1 2 FerdiZoet$ make ======================================================= Compiling of CGAL package Be patient this may take a while ======================================================= Compiling All_files_at_once.cpp In file included from All_files_at_once.cpp:30: /opt/local/include/boost/python/detail/invoke.hpp: In function ‘PyObject* boost::python::detail::invoke(boost::python::detail::invoke_tag_<false, true>, const RC&, F&, TC&, AC0&) [with RC = boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<const CGAL::Point_3<CGAL::Epeck>&>, F = const CGAL::Point_3<CGAL::Epeck>& (CGAL::Triangle_3<CGAL::Epeck>::*)(int)const, TC = boost::python::arg_from_python<CGAL::Triangle_3<CGAL::Epeck>&>, AC0 = boost::python::arg_from_python<int>]’: /opt/local/include/boost/python/detail/caller.hpp:223: instantiated from ‘PyObject* boost::python::detail::caller_arity<2u>::impl<F, Policies, Sig>::operator()(PyObject*, PyObject*) [with F = const CGAL::Point_3<CGAL::Epeck>& (CGAL::Triangle_3<CGAL::Epeck>::*)(int)const, Policies = boost::python::default_call_policies, Sig = boost::mpl::vector3<const CGAL::Point_3<CGAL::Epeck>&, CGAL::Triangle_3<CGAL::Epeck>&, int>]’ /opt/local/include/boost/python/object/py_function.hpp:38: instantiated from ‘PyObject* boost::python::objects::caller_py_function_impl<Caller>::operator()(PyObject*, PyObject*) [with Caller = boost::python::detail::caller<const CGAL::Point_3<CGAL::Epeck>& (CGAL::Triangle_3<CGAL::Epeck>::*)(int)const, boost::python::default_call_policies, boost::mpl::vector3<const CGAL::Point_3<CGAL::Epeck>&, CGAL::Triangle_3<CGAL::Epeck>&, int> >]’ Py_global_functions_2.cpp:171: instantiated from here /opt/local/include/boost/python/detail/invoke.hpp:88: error: no match for call to ‘(const boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<const CGAL::Point_3<CGAL::Epeck>&>) (const CGAL::Point_3<CGAL::Epeck>&)’ /opt/local/include/boost/python/detail/caller.hpp: In static member function ‘static const PyTypeObject* boost::python::detail::converter_target_type<ResultConverter>::get_pytype() [with ResultConverter = boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<const CGAL::Point_3<CGAL::Epeck>&>]’: /opt/local/include/boost/python/detail/caller.hpp:242: instantiated from ‘static boost::python::detail::py_func_sig_info boost::python::detail::caller_arity<2u>::impl<F, Policies, Sig>::signature() [with F = const CGAL::Point_3<CGAL::Epeck>& (CGAL::Triangle_3<CGAL::Epeck>::*)(int)const, Policies = boost::python::default_call_policies, Sig = boost::mpl::vector3<const CGAL::Point_3<CGAL::Epeck>&, CGAL::Triangle_3<CGAL::Epeck>&, int>]’ /opt/local/include/boost/python/object/py_function.hpp:48: instantiated from ‘boost::python::detail::py_func_sig_info boost::python::objects::caller_py_function_impl<Caller>::signature() const [with Caller = boost::python::detail::caller<const CGAL::Point_3<CGAL::Epeck>& (CGAL::Triangle_3<CGAL::Epeck>::*)(int)const, boost::python::default_call_policies, boost::mpl::vector3<const CGAL::Point_3<CGAL::Epeck>&, CGAL::Triangle_3<CGAL::Epeck>&, int> >]’ Py_global_functions_2.cpp:171: instantiated from here /opt/local/include/boost/python/detail/caller.hpp:102: error: ‘struct boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<const CGAL::Point_3<CGAL::Epeck>&>’ has no member named ‘get_pytype’ make[1]: *** [All_files_at_once.o] Error 1 make: *** [all] Error 2 ============================================================================ anybody an idea? thanks. kind regards, Ferdi

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[filesystem] boost::filesystem::file_size fails on Solaris 11
by Red Taza 07 May '11

07 May '11

Hi, I have been trying to get filesystem::file_size() on boost_1_46_1 to work but am getting the following error: $ ./tut1 tut1.cpp boost::filesystem::file_size: Not owner: "tut1.cpp" Note: To avoid core file I modified tut1.cpp so that it catches exceptions. The permissions and ownership of tut1.cpp seem fine: -rw-r--r-- 1 redtaza staff 760 2011-05-07 10:40 tut1.cpp $ uname -a SunOS lunar 5.11 snv_151a i86pc i386 i86pc Solaris $ CC -V CC: Sun C++ 5.11 SunOS_i386 2010/08/13 usage: CC [ options ] files. Use 'CC -flags' for details $ CC -g -library=stlport4 -I/usr/local/boost_1_46_1/include tut1.cpp -o tut1 /usr/local/boost_1_46_1/lib/libboost_system.a /usr/local/boost_1_46_1/lib/libboost_filesystem.a Boost was built with the toolset sun and no other options. Also if I compile and run the following code (which I believe is similar to the code that file_size()) I get expected results: #include <iostream> #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #include <cstdio> int main(int argc, char* argv[]) { if (argc < 2) { std::cout << "Usage: tut1 path\n"; return 1; } struct stat path_stat; if(::stat(argv[1], &path_stat)!= 0) { std::perror("stat() error: "); return -1; } if(!S_ISREG(path_stat.st_mode)) { std::cerr << argv[1] << " is not a regular file\n"; return -1; } std::cout << path_stat.st_size << '\n'; return 0; } $ CC -g -library=stlport4 -I/usr/local/boost_1_46_1/include getFilesize.cpp -o getFilesize /usr/local/boost_1_46_1/lib/libboost_system.a /usr/local/boost_1_46_1/lib/libboost_filesystem.a $ ./getFilesize tut1.cpp 760 Thanks

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Invitation to connect on LinkedIn
by Ted McCormack via LinkedIn 07 May '11

07 May '11

LinkedIn ------------Ted McCormack requested to add you as a connection on LinkedIn: ------------------------------------------ Hermann, I'd like to add you to my professional network on LinkedIn. - Ted Accept invitation from Ted McCormack http://www.linkedin.com/e/9m2kgu-gne8wkqz-0/vyhGWmEqB2IKeRN9DMTel5y44rvJcs9… View invitation from Ted McCormack http://www.linkedin.com/e/9m2kgu-gne8wkqz-0/vyhGWmEqB2IKeRN9DMTel5y44rvJcs9… ------------------------------------------ DID YOU KNOW you can conduct a more credible and powerful reference check using LinkedIn? Enter the company name and years of employment or the prospective employee to find their colleagues that are also in your network. This provides you with a more balanced set of feedback to evaluate that new hire. http://www.linkedin.com/e/9m2kgu-gne8wkqz-0/rsr/inv-27/ -- (c) 2011, LinkedIn Corporation

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[pool] singleton_pool crash in multithreaded mode
by Phil Bouchard 07 May '11

07 May '11

Hi, I have a strange bug here. I am using singleton_pool and it crashes at a call to singleton_pool::ordered_malloc in multithreaded mode. The funny thing is I am locking a mutex before the call and it still crashes. The test file can be found here: https://svn.boost.org/svn/boost/sandbox/block_ptr/libs/smart_ptr/example/th… And the calls to the pool (allocate & deallocate) a made from class "pool" of the following file: https://svn.boost.org/svn/boost/sandbox/block_ptr/boost/detail/block_base.h… The backtrace I get is: #0 0x0000000000407842 in boost::simple_segregated_storage<unsigned long>::try_malloc_n (start=@0x42e7ddc0, n=10, partition_size=8) at /home/vnmr1/phil/boost_1_46_1/boost/pool/simple_segregated_storage.hpp:236 #1 0x00000000004078f7 in boost::simple_segregated_storage<unsigned long>::malloc_n (this=0x614d88, n=11, partition_size=8) at /home/vnmr1/phil/boost_1_46_1/boost/pool/simple_segregated_storage.hpp:260 #2 0x000000000040c2ab in boost::pool<boost::default_user_allocator_new_delete>::ordered_malloc (this=0x614d88, n=88) at /home/vnmr1/phil/boost_1_46_1/boost/pool/pool.hpp:527 #3 0x000000000040c9b8 in boost::singleton_pool<boost::detail::sh::pool, 1u, boost::default_user_allocator_new_delete, boost::details::pool::pthread_mutex, 32u, 0u>::ordered_malloc (n=88) at /home/vnmr1/phil/boost_1_46_1/boost/pool/singleton_pool.hpp:72 #4 0x000000000040d937 in boost::detail::sh::pool::allocate (s=88) at ../../../boost/detail/block_base.hpp:150 #5 0x000000000040d9cd in boost::detail::sh::block<std::pair<int, int> >::operator new (s=88) at ../../../boost/detail/block_base.hpp:301 #6 0x000000000040d9f1 in boost::detail::sh::make_block<std::pair<int, int>, std::pair<int, int> > (t0=@0x42e7e030) at ../../../boost/block_ptr.hpp:492 #7 0x0000000000405fd3 in worker (id=1) at thread_test.cpp:17 #8 0x0000000000408b5c in boost::_bi::list1<boost::_bi::value<int> >::operator()<void (*)(int), boost::_bi::list0> (this=0x1776e660, f=@0x1776e658, a=@0x42e7e0cf) at /home/vnmr1/phil/boost_1_46_1/boost/bind/bind.hpp:253 #9 0x0000000000408b9a in boost::_bi::bind_t<void, void (*)(int), boost::_bi::list1<boost::_bi::value<int> > >::operator() (this=0x1776e658) at /home/vnmr1/phil/boost_1_46_1/boost/bind/bind_template.hpp:20 #10 0x0000000000408bb8 in boost::detail::thread_data<boost::_bi::bind_t<void, void (*)(int), boost::_bi::list1<boost::_bi::value<int> > > >::run ( this=0x1776e4d0) at /home/vnmr1/phil/boost_1_46_1/boost/thread/detail/thread.hpp:61 #11 0x00002b6910e0a914 in thread_proxy () from /home/vnmr1/phil/lib/libboost_thread.so.1.46.1 #12 0x0000003906a06367 in start_thread () from /lib64/libpthread.so.0 #13 0x0000003905ed30ad in clone () from /lib64/libc.so.6 Anybody has any idea? Thanks, -Phil

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Re: [Boost-users] [iostreams] Flushing problems with :filtering_ostream
by eg 06 May '11

06 May '11

On Wed, May 4, 2011 at 2:31 PM, Bo Jensen <jensen.bo(a)gmail.com> wrote: > > > In the interest of closure, can you confirm (from the comment you made in > > another thread), that this now works for you after changing the stream > open > > call to be: > > > > std::ofstream strm("test.gz", std::ios_base::out | > std::ios_base::binary); > > > > I know that it works for me when I tried it. > > > Thanks for your interest in this, much appreciated. The problem > persists, the written file can not be decompressed, I have worked my > way around the problem, so it's not a issue for me anymore, but I > would be happy to help track it down. I think it's very strange you > can run without problems. > > To clarify, when I built and ran it with VS 2008 and boost 1.35 it worked. When I just re-tried using VS 2008 and boost 1.45 or boost 1.46.1, it seems to produce invalid .gz files. Perhaps you can create a New Ticket and enter this as a bug at: https://svn.boost.org/trac/boost/newticket

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