March 2014 - Boost-users - lists.preview.boost.org

[BOOST Users] serialize a pointer
by Andy Sardina 29 Mar '14

29 Mar '14

Hello, I would like to just serialize a pointer value. I have understood that boost save the pointer value, and serialize the object it points. How can I do?

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[serialization] serialization of an ifstream/ofstream class member
by Pablo Madoery 28 Mar '14

28 Mar '14

Hi. Do You know if there is a way to serialize an ifstream/ofstream class member. I have this class for example class Object { public: Object(); Object(string name); virtual ~Object(); string getName() const; private: string name_; ifstream file_; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & name_; ar & file_; } }; when I try to serialize it throw compilation error : error: 'struct std::basic_ifstream<char>' has no member named 'serialize'. Is there a specific header i must include ?

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[serialization] of nested stl containers
by Pablo Madoery 27 Mar '14

27 Mar '14

I have the following code: #include <list> #include <utility> #include <vector> #include <string> #include <fstream> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/access.hpp> #include <boost/serialization/string.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/utility.hpp> #include <boost/serialization/map.hpp> #include <boost/serialization/base_object.hpp> using namespace std; int main() { list< pair<string, string> > stlStr; pair<string, string> par1("aaa", "bbb"); stlStr.push_back(make_pair("key", par1)); std::ofstream ofs("filename"); { boost::archive::text_oarchive serial(ofs); serial << stlStr; } std::ifstream ifs("filename"); boost::archive::text_iarchive serial2(ifs); list<pair<string, string> > lst; serial2 >> lst; return 0; } that throw the following compilation error: error: 'class std::list<std::pair<std::basic_string<char>, std::basic_string<char> > >' has no member named 'serialize'. I'd like to know if I have to manually implement the serialization of this nested list. Because for example I haven't problems with maps that have inside a pair : map<string, pair<string, string> >. Thanks !

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boost::future and when_all => compile error "call to deleted constructor"
by Tobias Oberstein 26 Mar '14

26 Mar '14

Hello, I am trying to use boost::future with continuations, in particular when_all/when_any. I am using Boost trunk from GitHub (since only that has when_all etc). This is what I want to compile: === #include <iostream> #define BOOST_THREAD_PROVIDES_FUTURE #define BOOST_THREAD_PROVIDES_FUTURE_CONTINUATION #define BOOST_THREAD_PROVIDES_FUTURE_WHEN_ALL_WHEN_ANY #include <boost/thread/future.hpp> using namespace boost; int main() { future<int> f1 = async([]() { return 1; }); future<int> f2 = async([]() { return 2; }); auto f3 = when_all(f1, f2); f3.then([](decltype(f3)) { std::cout << "done" << std::endl; }); f3.get(); } === https://gist.github.com/oberstet/9783359 This bails out with /usr/include/c++/v1/memory:1685:31: error: call to deleted constructor of 'boost::future<int>' https://gist.github.com/oberstet/9783364 Am I doing it wrong? Thanks! /Tobias

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[msm] handle errors and no_transition
by Sam Fisher 25 Mar '14

25 Mar '14

Hi, I have root fsm which has a sub-fsm. In the sub-fsm there are some useful actions that can throw exceptions. For that case any fsm has its own exception handler that translates exception into a generic error event: template <typename Event, typename OtherFSM> void exception_caught(Event&, OtherFSM& fsm, std::exception& e) { fsm.process_event(error()); } I faced a strange problem: if an exception occurs, the sub successfully goes to Error state, the root has no_transition I use boost 1.55 and VS2013 there are transition tables: Sub: Error & Finish - exit points A_Exception action generates exception typedef ::boost::mpl::vector<Empty, AllOk> initial_state; struct /*sub*/ transition_table : public ::boost::mpl::vector < // Start Event Next Action Guard // +----------------+---------------+------------------+----------------------+--------------------------+ Row < Empty , none , Waiting , none , none >, Row < Waiting , process , Process , A_Exception , none >, Row < Process , none , Finish , none , none >, // +----------------+---------------+------------------+----------------------+--------------------------+ Row < AllOk , error , Error , none , none > // +----------------+---------------+------------------+----------------------+--------------------------+ > {}; Root: struct S { typedef SubFsm::exit_pt<SubFsm_::Error> Error; typedef SubFsm::exit_pt<SubFsm_::Finish> Finish; }; struct /*root*/ transition_table : public ::boost::mpl::vector < // Start Event Next Action Guard // +----------------+---------------+------------------+----------------------+--------------------------+ Row < Empty , init , Initial , none , none >, Row < Initial , sub , SubFsm , none , none >, // +----------------+---------------+------------------+----------------------+--------------------------+ Row < S::Error , error , Error , none , none >, Row < S::Finish , none , Initial , none , none > // +----------------+---------------+------------------+----------------------+--------------------------+ > {}; the control flow: Root root; root.start(); root.process_event(init()); root.process_event(sub()); root.process_event(process()); output log: =============> start Root_::InitEvent: Enter to Root_ state. Root_::InitEvent: Enter to Root_::Empty state. =============> init Exit from Root_::Empty state. init: Enter to Root_::Initial state. =============> sub Exit from Root_::Initial state. sub: Enter to Root_::SubFsm_ state. sub: Enter to SubFsm_::Empty state. sub: Enter to SubFsm_::AllOk state. Exit from SubFsm_::Empty state. front::none: Enter to SubFsm_::Waiting state. =============> process Exit from SubFsm_::Waiting state. SubFsm_::A_Exception() State machine produces an exception on event process Current state: SubFsm_::Waiting Message: A_Process exception Exit from SubFsm_::AllOk state. error: Enter to SubFsm_::Error state. No transition from state Root_::SubFsm_ on event process Exit from SubFsm_::Waiting state. Exit from SubFsm_::Error state. Exit from Root_::SubFsm_ state. error: Enter to Root_::Error state. A I understood, after exception comes, the "process" event now in kind of "unhandled" state. So it rises up to the root fsm that doesn't have any suitable transition How to make the root or sub to "forget" about unhandled event?

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'Hashable' concept for type erasure
by Samuel Christie 25 Mar '14

25 Mar '14

Hello, I've been trying to add a 'hashable' concept to one of my type erasure requirements, but I haven't been getting anywhere and I still don't understand the voluminous error messages enough to make any progress. Here's approximately what I tried so far: namespace mpl = boost::mpl; namespace te = boost::type_erasure; template<class T> struct hashable { static size_t apply(const T& obj) { return std::hash<T>()(obj); } }; namespace std { template<> class hash<t>{ public : size_t operator()(const test &t ) const { return te::call(hashable<test>(), t); } }; }; typedef mpl::vector< ... hashable<te::_self>, ... > requirements typedef any<requirements> test; namespace std { template<> class hash<test>{ public : size_t operator()(const test&h ) const { return te::call(hashable<test>(), h); } }; }; I also tried something else, similar to the following: template<class C> struct hashable { static std::size_t apply(const C& c) { return c.hash(); } }; namespace boost { namespace type_erasure { template<class C, class Base> struct concept_interface<hashable<C>, Base, C> : Base { std::size_t hash() const { return call(hashable<C>(), *this); } }; } } // ... similar requirements / typedef as above namespace std { template<> class hash<test>{ public : size_t operator()(const test &t ) const { return t.hash(); } }; }; The first one is probably just wrong, and for the second one I'm getting some failed assertions when I try to use it with an implementation of hash that is: size_t hash() const { //coord is a member std::vector<int> return boost::hash_range(coord.begin(), coord.end()); } Any help would be most useful. -sc

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[ANN] CppCon 2014 Call for Submissions
by Boris Kolpackov 25 Mar '14

25 Mar '14

Hi, CppCon is the annual, week-long face-to-face gathering for the entire C++ community. The conference is organized by the C++ community for the community and so we invite you to present. Have you learned something interesting about C++, maybe a new technique possible in C++11? Or perhaps you have implemented something cool related to C++, maybe a new C++ library? If so, consider sharing it with other C++ enthusiasts by giving a talk at CppCon 2014. Submissions deadline is May 15 with decisions sent by June 13. For topic ideas, possible formats, and submission instructions, see the Submissions page: http://cppcon.org/submissions/ Hope to hear you speak! Boris

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[GSoC 14] Request community to rank proposals
by Niall Douglas 24 Mar '14

24 Mar '14

Dear Boost Community, The Google Summer of Code 2014 proposals for Boost are in, and we would deeply appreciate the community's help in ranking the proposals according to merit before the 1st of April. To vote, the process is easy: 1. Go to this page https://www.google-melange.com/gsoc/homepage/google/gsoc2014 and click the "Log in" button under Mentors and Administrators. 2. Now click "Create Profile" on the same page. Note that even if you registered last year, you must register again in 2014. Fill in the form. Note that after submitting it drops you at "Edit Profile", which is confusing. 3. Click "My Dashboard", then "Connect with organisations". 4. Choose "Boost C++ Libraries". 5. In the message box, write this: "I am a member of the Boost community and the email(s) I normally post to boost mailing lists with is <email>" filling in the email address(es) you normally use to post to boost mailing lists. This lets us verify that you are indeed a long standing member of the Boost community. 6. Once we approve your request, you will get an email with the subject "Welcome as organisation member". You can now return to the Dashboard on the GSoC website where there will be a new item "Proposals". 7. Work your way through as many of the 42 proposals as you can. You can score them using the stars at the bottom of each proposal page, taking care to read any comments by the mentors and students if present. PLEASE try to rank some of the lowest scored proposals, every year we get a lot of people who only rank the top five and don't bother with the rest. Try to score on the basis of (i) proposal quality and your best estimate of the student's capability (ii) if the student came early to the mailing lists to ask for help writing the proposal (the mentors who helped them with their proposals have usually indicated this in the private comments) (iii) usefulness/appropriateness of the feature or work being proposed. Remember a good GSoC is more about getting promising new engineers into Boost and C++ than necessarily getting code to pass Boost peer review in a single summer. 8. Optional: If a proposal looks especially great to you and you feel able to mentor a student this year, please slide the "wish to mentor" button. Just because a proposal already has willing mentors does NOT mean you should not add yourself - we have at least two mentors with many attached very highly ranked proposals and we really don't want to have to reject an outstanding proposal just because we can't find the mentors for it as no mentor can realistically mentor more than two projects simultaneously. As you know, Google Summer of Code is usually worth $35,000 - $50,000 to Boost each year, and a successful GSoC raises our visibility and reputation in the wider open source community. Our thanks to you in advance for taking the time to vote. Niall Douglas Boris Schäling --- Boost C++ Libraries Google Summer of Code 2014 admin https://svn.boost.org/trac/boost/wiki/SoC2014

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[boost-build] building dependencies that use makefiles
by Mauricio Carneiro 24 Mar '14

24 Mar '14

I am using boost-build to build my project, but I have added a static library as a dependency that is built using GNU make. If I build this library manually, I can link it to my project in boost build using this simple Jamfile: lib hts : : <link>static <file>lib/lib.a : : <include>lib_headers ; Is there a way to tell boost-build to run make on the directory if the lib/lib.a is not present there? Thank you, Mauricio Carneiro, Ph.D. http://www.broadinstitute.org/~carneiro/

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lexical_cast between double and string slow in Visual Studio 2013
by David Roberts 24 Mar '14

24 Mar '14

In Boost 1.54 I have noticed that lexical_cast from double to string and back is much slower in Visual Studio 2013 (Visual C++ 12) than it was in Visual Studio 2010 (Visual C++ 10). The following test program demonstrates the problem: #include <boost/lexical_cast.hpp> #include <string> int main (int, char **) { for (double count = 0.0; count < 1000000.0; count += 1.41) { std::string result(boost::lexical_cast<std::string>(count)); count = boost::lexical_cast<double>(result); } return 0; } It can be built at the Visual Studio command prompt using: cl /O2 /EHsc /DNDEBUG /I\some\path\boost-1_54 lexcast.cpp to give the program lexcast.exe. When built with Visual Studio 2013 this program takes about 10 seconds to run on my machine. When built with Visual Studio 2010 it takes about 3 seconds. Is this already a known issue? If not I can do a bit more investigation to narrow down why it's so much slower, but I don't want to waste my time if this has already been done. Thanks, David

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