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Boost Graph Library documentation unclear
by Lindley M French 26 Apr '09

26 Apr '09

I've been trying to use the Boost Graph Library. For the most part I'm working it out. However, I'm finding the documentation annoyingly decentralized....it isn't interlinked enough, at the very least. Too hard to go from "how do I use X" to "oh, here's the documentation on X." Took me half an hour just to find *something* on the add_edge function (turns out it's on the Concepts page?), and what's there *barely* qualifies as a prototype, much less a proper man page. My current question is regarding properties. Some of the algorithms specify the "edge_weight" property as if it's something all edges have, and the vertex_index property as if it's something all vecS-specified graphs have. Yet I can't find any documentation explicitly confirming this, and my compiler seems to disagree in any case. http://www.boost.org/doc/libs/1_38_0/libs/graph/doc/kruskal_min_spanning_tr… Can something be done about the state of the documentation, and is there a comprehensive list of default properties available somewhere (together with how those are replaced or supplemented when user properties are introduced)?

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initializing intrusive_ptrs through library calls
by Zachary Turner 26 Apr '09

26 Apr '09

I frequently use COM, and I've written an add_ref() and release() so that I can use my COM objects with boost::intrusive_ptr. However, one generally obtains these pointers through a library call that accepts a T** or a void**, and returns a pointer that's already been AddRef'd the first time. Normally it would go something like this: template<typename T> d3d_ptr<T> take_ptr(T* t) { return d3d_ptr<T>(t, false); } ID3DXFont* pFont = NULL; D3DXCreateFontIndirect(m_pDeviceObject, &fontDesc, &pFont); m_spFont = take_ptr(pFont); To remove these extra 2 lines I wrote the following class / function: template<typename T> class recv_by_addr_t { public: recv_by_addr_t(d3d_ptr<T>& r) : m_auto(r), m_raw(NULL) {} ~recv_by_addr_t() {m_auto = take_ptr(m_raw);} operator T**() { return &m_raw; } private: T* m_raw; d3d_ptr<T>& m_auto; }; template<typename T> recv_by_addr_t<T> recv_by_addr(d3d_ptr<T>& rptr) { return recv_by_addr_t<T>(rptr); } And I can now call the function like this: D3DXCreateFontIndirect(m_pDeviceObject, &fontDesc, recv_by_addr(m_spFont)); I feel like this is pretty solid, but figured I should ask the gurus :) Even in the case where the function errors out and sets the thing to NULL, the original pointer should still get correctly released. Anything wrong with this approach?

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Boost 1.39.0 beta 1 is available for download
by Beman Dawes 26 Apr '09

26 Apr '09

Boost 1.39.0 beta 1 is available for download from SourceForge. See http://sourceforge.net/project/showfiles.php?group_id=7586&package_id=8041&… New Libraries: Signals2. Updated Libraries: Asio, Flyweight, Foreach, Hash, Interprocess, Intrusive, Program.Options, Proto, PtrContainer, Range, Unordered, Xpressive. Updated Tools: Boostbook, Quickbook. Plus the usual bug fixes to numerous libraries. Please report any problems to the Boost users or developers mailing list. Thanks, --Beman Dawes, Daniel James, and all the other Boosters who help get releases out

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Examples....
by Campagne 26 Apr '09

26 Apr '09

Dear all I am a quite new in Boost... Although I have experienced successfuly the smart_ptr library. Now, I would like to use IOSTREAM library. Even if the tutorial and User Guide are fine, they describe mostly how-to-write-xyz but very rarely how-to-use in practice. For instance I despearate to see an exmple on how-to-use the "line_wrapping_input_filter" example... Does someone can 1) tell me if there is somewhere example of how-to-use for end-user IOSTREAM features? 2) if someone as used the example and how... Best. JE -- +++++++++++++++++++++++++++++++++++++++ Jean-Eric Campagne Laboratoire de l'Accélérateur Linéaire d'Orsay IN2P3/CNRS et Université Paris XI LAL Orsay - B.P 34 91898 Orsay Cedex Tél: 0164468429 from abroad +3316.. Fax: 0164468397 +++++++++++++++++++++++++++++++++++++++

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ASIO, boost::function in VC7.1
by Kimon Simons 26 Apr '09

26 Apr '09

Hi all, I started playing with ASIO timers and after scanning through the relevant docs, I set up a small case. Please find below the code snippet. The IntervalEvent class is supposed to fire the event provided on the construction at a frequency equal to the durationInterval. Somehow the code below fails to compile on VC7.1. I am getting several warnings and the error: c:\program files\boost\boost_1_38\boost\mem_fn.hpp(343) : error C4716: 'boost::_mfi::dm<void __thiscall IntervalEvent::(boost::system::error_code &),IntervalEvent>::operator()' : must return a value I have not tried yet gcc. Probably I am doing something stupid. Any ideas? Further to that, I am wondering, in principle should I cancel the deadline_timer on the destructor of the IntervalEvent class? Does the io_service class know when any of the deadline_timers that is being registered goes out of scope? Thank you very much in advance. Any help would be highly appreciated. Kimon #include <boost/function.hpp> #include <iostream> #include <boost/asio.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <boost/date_time/posix_time/posix_time.hpp> class Counter { public: Counter():m_value(0) { } void onIncrement() { ++m_value; std::cout<<"Counter is "<<m_value<<std::endl; } protected: int m_value; }; class IntervalEvent { public: IntervalEvent(boost::asio::io_service &io, long durationSeconds, boost::function<void(void)> event): m_intervalDuration(durationSeconds), m_timer(io,boost::posix_time::seconds(m_intervalDuration)), m_event(event) { //io_service::run is running in only one thread m_timer.async_wait(boost::bind(&IntervalEvent::handler, this)); } ~IntervalEvent() { //should I call m_timer.cancel to notify the io_service? } void handler(boost::system::error_code& error) { if(error!= boost::asio::error::operation_aborted) { m_event(); reset(m_intervalDuration); } } void reset(long duration) { if (m_timer.expires_from_now(boost::posix_time::seconds(duration)) > 0) { m_intervalDuration = duration; //reset the async wait m_timer.async_wait(boost::bind(&IntervalEvent::handler, this)); } else { //Timer already canceled } } void cancel() { m_timer.cancel(); } size_t getCurrentInterval() const { return m_intervalDuration; } protected: long m_intervalDuration; boost::asio::deadline_timer m_timer; boost::function<void(void)> m_event; }; int main() { boost::asio::io_service io; boost::shared_ptr<boost::asio::io_service::work> work(new boost::asio::io_service::work(io)); boost::thread ioservice_thread(boost::bind(&boost::asio::io_service::run, &io)); std::vector<boost::shared_ptr<IntervalEvent> > events; Counter count; long duration = 1; boost::shared_ptr<IntervalEvent> firstEvent(new IntervalEvent(io, duration, boost::bind(&Counter::onIncrement,boost::ref(count) )) ); events.push_back(firstEvent); char response = 'N'; while(response == 'N') { std::cout<<"Create a new interval event? [Y/N]"<<std::endl; std::cin>>response; if(response == 'Y') { boost::shared_ptr<IntervalEvent> test(new IntervalEvent(io, duration, boost::bind(&Counter::onIncrement,boost::ref(count) )) ); events.push_back(test); } } //cancel interval events for(std::vector<boost::shared_ptr<IntervalEvent> >::iterator it = events.begin(), itEnd = events.end(); it!=itEnd; ++it) { (*it)->cancel(); } //reset ioservice_work work.reset(); ioservice_thread.join(); return 0; }

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Boost 1.38.0 and gcc 4.3.2
by Brian Webb 26 Apr '09

26 Apr '09

I'm trying to build the boost libraries on Ubuntu 8.10 with gcc-4.3.2, and it's a mess! I think there are more failed compiles than there are successes. Is there something that I'm missing, or is this currently unsupported? This is the compile command that I'm using: bjam --toolset=gcc --prefix=$PREFIX --layout=system --user-config=`pwd`/user-config.jam stage This is user-config.jam: using gcc : : g++ : <compileflags>-I/swl/ix86-linux/include <linkflags>-L/swl/ix86-linux/lib ; using mpi ; Any pointers would be appreciated. Thanks, Brian

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How to detect the presence of a particular type of constructor?
by Siegfried Kettlitz 25 Apr '09

25 Apr '09

Hello, what i like to do, is to detect the presence of a particular type of constructor for a class in a template. It is possible to use template overloading to detect the presence of members or member functions (like with::some_func(int) ), but since it is not possible(?) to take a pointer to a constructor ( like with::with(int) ), this method does not work to detect the present types of the templated class T. Consider this pseudocode: struct with { with( int ); } struct without { without( void ); } template<typename T> T* do_construct() { a) return new T(int) if T::T(int) present; b) return new T() if T::T(int) not present; } int main( void ) { do_construct<with>(); do_construct<without>(); } So far i did not find anything useful in type_traits to make the do_construct-function work without modifying the classes (adding inheritance or some static member). Does anyone know another possibility to do this, or is it not possible using the current standard of c++? Regards, Siegfried Kettlitz

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undefined reference to `__sync_fetch_and_add_4'
by Birju Prajapati 24 Apr '09

24 Apr '09

Hi, I built boost 1.38 as so: bjam architecture=x86 address-model=32 --stagedir=stage32 --with-filesystem --with-thread --with-signals --with-serialization --with-system --with-program_options --with-date_time stage Copied the files over to /usr/local/lib32: sudo cp stage32/lib/* /usr/local/lib32/ Compiled object files, eg: g++ -m32 -c -g -D_LINUX -I. -I/opt/sts_vendor/onix-eurex/include -I/usr/local/include/boost-1_38 -MMD -MP -MF build/Debug/GNU-Linux-x86/reference/ReferenceData.o.d -o build/Debug/GNU-Linux-x86/reference/ReferenceData.o reference/ReferenceData.cpp Then linking does not work: g++ -m32 -o dist/Debug/GNU-Linux-x86/spreadx build/Debug/GNU-Linux-x86/multicast/MulticastChannel.o build/Debug/GNU-Linux-x86/reference/ReferenceData.o build/Debug/GNU-Linux-x86/reference/Strategy.o build/Debug/GNU-Linux-x86/executor/MessageExecutor.o build/Debug/GNU-Linux-x86/multicast/MulticastSelector.o build/Debug/GNU-Linux-x86/fast/FIXStreamSubscriber.o build/Debug/GNU-Linux-x86/reference/Product.o build/Debug/GNU-Linux-x86/spreadx.o build/Debug/GNU-Linux-x86/fast/FIXMessage.o build/Debug/GNU-Linux-x86/multicast/Message.o build/Debug/GNU-Linux-x86/fast/FastDecoder.o build/Debug/GNU-Linux-x86/reference/Outright.o -L/opt/sts_vendor/onix-eurex/lib -L/usr/tibco/tibrv/lib -L/usr/local/lib32 -lffCppFixEngine -lACE -lcrypto -lboost_serialization-gcc43-mt -lboost_system-gcc43-mt -lboost_thread-gcc43-mt /usr/local/lib32/libboost_serialization-gcc43-mt.so: undefined reference to `__sync_fetch_and_add_4' I've tried #define BOOST_SP_USE_PTHREADS in user.hpp, I've tried -march=i486, but neither works. What gives? My platform details: birju@xx:~$ g++ --version g++ (Ubuntu 4.3.2-1ubuntu12) 4.3.2 Copyright (C) 2008 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. birju@xx:~$ uname -a Linux xx 2.6.27-11-generic #1 SMP Wed Apr 1 20:53:41 UTC 2009 x86_64 GNU/Linux birju@xx:~$ Cheers, Birju Schneider Trading 4th Floor, 25 Copthall Avenue London EC2R 7BP -------------------------------------------------------- Message from: Birju.Prajapati(a)schneidertrading.com Message to: boost-users(a)lists.boost.org Attached files: 0 This e-mail and any files transmitted with it are confidential, may be legally privileged, and are for the sole use of the intended recipient. Copyright in this e-mail and any accompanying document created by us is owned by us. If you are not the intended recipient of this e-mail or any part of it please telephone our IT Department at the number shown above or by e-mail at info(a)schneidertrading.com. You should not use or disclose to any other person the contents of this e-mail or its attachments (if any), nor take copies. This e-mail is not a representation or warranty and is not intended nor should it be taken to create any legal relations, contractual or otherwise. Schneider Trading Associates Ltd (Registration No. 3692131) is incorporated in England and Wales and the registered office is at 25 Copthall Avenue, London EC2R 7BP. The company is authorised and regulated by the Financial Services Authority

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BoostCon 2009 Registrar's Report
by Kim Scheibel 24 Apr '09

24 Apr '09

I'm very happy to report that, despite the current economic climate, we currently have a very solid number of confirmed registrations for BoostCon 2009. 84 registrations to be precise, of which 6 were registered in the last two days alone. You still have time to register at the discounted price of USD599 at http://www.boostcon.com/registration, on or before Apr. 26th. After that, the fee is USD699. Best regards, Kim Scheibel BoostCon 2009 Registrar

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[signals] maximum combiner example calls slot twice
by Dominique Devienne 24 Apr '09

24 Apr '09

In http://www.boost.org/doc/libs/1_38_0/doc/html/signals/tutorial.html, once I read: "The input iterators passed to the combiner transform dereference operations into slot calls" I realized that the maximum<T> combiner introduced earlier is implemented using: if (max_value < *first) max_value = *first; Which ends up calling the slot twice. In this case it's harmless since the slot has no side effect, but it may not be a good example to follow, or maybe it should be pointed out a little later when the combiner deref statement quoted above is made. Just my $0.02. Thanks, --DD

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