September 2013 - Boost-users - lists.preview.boost.org

[units] Convert from Degree Minutes to Degrees
by Ryan 21 Sep '13

21 Sep '13

Angles have their own system that define both radians and degrees. I would like to create the necessary type for minutes (this is 1/60 of a degree). My first thought was to create a scale unit with degrees as the base type. I couldn't determine how to enter the scale of 1/60. The other option is to define a new base unit. I would think using the degrees base unit would be a good reference, but it uses an "INTERNAL ONLY" macro call "BOOST_UNITS_DEFINE_BASE_UNIT_WITH_CONVERSIONS". What should I use to create a unit type that will convert from degree minutes to just degrees? Ryan

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tcp::socket::is_open() is true after socket is closed
by niXman 20 Sep '13

20 Sep '13

Hi, In the following simple code: tcp::socket socket(ios); ... const bool iso1 = socket.is_open(); socket.close(); const bool iso2 = socket.is_open(); I get: iso1 == iso2 == true Why? Thanks. -- Regards, niXman ___________________________________________________ Dual-target(32 & 64-bit) MinGW compilers for 32 and 64-bit Windows: http://sourceforge.net/projects/mingwbuilds/ ___________________________________________________ Another online IDE: http://liveworkspace.org/

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Getting ASIO application to link (undefined reference to `boost::system::generic_category())
by Ulf Samuelsson 20 Sep '13

20 Sep '13

Hi, Trying to get an ASIO example (udp_echo_client) to build on an Ubuntu 12.04 machine. It looks like both 1.46 and 1.48 can be installed. (I have installed 1.48). The libboost*.so all are linked vs 1.48, and the /usr/include/boost/version.hpp contains #define BOOST_LIB_VERSION "1_48" so I think that there should not be a version mismatch, I can build some really simple examples but, as soon as I add "asio" with the statement below, the build fails. using boost::asio::ip::udp; Fiirst problem is that `boost::system::generic_category()' is missing. When I grep the libboost libraries, they are only found in "libboost_[file]system[-mt].so" but these files are included in the link. Searching on Internet, also tells me to link with those libraries, which is not a help. Tried with "-mt" version as well. Added #include <boost/system/error_code.hpp> #include <boost/system/linux_error.hpp> without any change. What is going on? Running out of ideas... Thanks for any advice. /Ulf Samuelsson ---------------------------------------------------------- g++ -I/usr/include -Iinclude -L/usr/lib -lboost_filesystem -lboost_system -lpthread -std=c++0x -o udp_echo_client udp_echo_client.cpp /tmp/ccu20iRA.o: In function `__static_initialization_and_destruction_0(int, int)': udp_echo_client.cpp:(.text+0x58d): undefined reference to `boost::system::generic_category()' udp_echo_client.cpp:(.text+0x597): undefined reference to `boost::system::generic_category()' udp_echo_client.cpp:(.text+0x5a1): undefined reference to `boost::system::system_category()' /tmp/ccu20iRA.o: In function `boost::system::error_code::error_code()': udp_echo_client.cpp:(.text._ZN5boost6system10error_codeC2Ev[_ZN5boost6system10error_codeC5Ev]+0x10): undefined reference to `boost::system::system_category()' /tmp/ccu20iRA.o: In function `boost::asio::error::get_system_category()': udp_echo_client.cpp:(.text._ZN5boost4asio5error19get_system_categoryEv[boost::asio::error::get_system_category()]+0x7): undefined reference to `boost::system::system_category()' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_tss_ptr_create(unsigned int&)': udp_echo_client.cpp:(.text._ZN5boost4asio6detail20posix_tss_ptr_createERj[boost::asio::detail::posix_tss_ptr_create(unsigned int&)]+0x15): undefined reference to `pthread_key_create' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_thread::~posix_thread()': udp_echo_client.cpp:(.text._ZN5boost4asio6detail12posix_threadD2Ev[_ZN5boost4asio6detail12posix_threadD5Ev]+0x1d): undefined reference to `pthread_detach' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_thread::join()': udp_echo_client.cpp:(.text._ZN5boost4asio6detail12posix_thread4joinEv[boost::asio::detail::posix_thread::join()]+0x25): undefined reference to `pthread_join' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_thread::start_thread(boost::asio::detail::posix_thread::func_base*)': udp_echo_client.cpp:(.text._ZN5boost4asio6detail12posix_thread12start_threadEPNS2_9func_baseE[boost::asio::detail::posix_thread::start_thread(boost::asio::detail::posix_thread::func_base*)]+0x24): undefined reference to `pthread_create' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context>::~posix_tss_ptr()': udp_echo_client.cpp:(.text._ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceENS4_11thread_infoEE7contextEED2Ev[_ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceENS4_11thread_infoEE7contextEED5Ev]+0xf): undefined reference to `pthread_key_delete' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context>::operator boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context*() const': udp_echo_client.cpp:(.text._ZNK5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceENS4_11thread_infoEE7contextEEcvPS7_Ev[boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context>::operator boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context*() const]+0xf): undefined reference to `pthread_getspecific' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::strand_service::strand_impl, unsigned char>::context>::~posix_tss_ptr()': udp_echo_client.cpp:(.text._ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_14strand_service11strand_implEhE7contextEED2Ev[_ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_14strand_service11strand_implEhE7contextEED5Ev]+0xf): undefined reference to `pthread_key_delete' /tmp/ccu20iRA.o: In function `boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context>::operator=(boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context*)': udp_echo_client.cpp:(.text._ZN5boost4asio6detail13posix_tss_ptrINS1_10call_stackINS1_15task_io_serviceENS4_11thread_infoEE7contextEEaSEPS7_[boost::asio::detail::posix_tss_ptr<boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context>::operator=(boost::asio::detail::call_stack<boost::asio::detail::task_io_service, boost::asio::detail::task_io_service::thread_info>::context*)]+0x16): undefined reference to `pthread_setspecific' collect2: ld returnerade avslutningsstatus 1 make: *** [udp_echo_client] Fel 1 -------------------------------------------------------------- Makefile: ------------------------------------------------------ # Using 1.48.0 in Ubuntu 12.04 BOOST=/usr INCLUDES += -I$(BOOST)/include -Iinclude LIBS +=-L$(BOOST)/lib -lboost_filesystem -lboost_system -lpthread CFLAGS=$(INCLUDES) $(LIBS) -std=c++0x all: udp_echo_client udp_echo_client: udp_echo_client.cpp g++ $(CFLAGS) -o $@ udp_echo_client.cpp clean: rm -f udp_echo_client rm -f *~ -------------------------------------------------------- Code from example: -------------------------------------------------------- // // blocking_udp_echo_client.cpp // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2013 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #include <cstdlib> #include <cstring> #include <iostream> #include <boost/asio.hpp> using boost::asio::ip::udp; enum { max_length = 1024 }; int main(int argc, char* argv[]) { try { if (argc != 3) { std::cerr << "Usage: blocking_udp_echo_client <host> <port>\n"; return 1; } boost::asio::io_service io_service; udp::socket s(io_service, udp::endpoint(udp::v4(), 0)); udp::resolver resolver(io_service); udp::endpoint endpoint = *resolver.resolve({udp::v4(), argv[1], argv[2]}); std::cout << "Enter message: "; char request[max_length]; std::cin.getline(request, max_length); size_t request_length = std::strlen(request); s.send_to(boost::asio::buffer(request, request_length), endpoint); char reply[max_length]; udp::endpoint sender_endpoint; size_t reply_length = s.receive_from( boost::asio::buffer(reply, max_length), sender_endpoint); std::cout << "Reply is: "; std::cout.write(reply, reply_length); std::cout << "\n"; } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; }

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Re: [Boost-users] cross-compilation x86_64-w64-ming32: undefined reference to `InterlockedIncrement'
by Frédéric Bron 19 Sep '13

19 Sep '13

> Solved this by adding define=BOOST_USE_WINDOWS_H and that forces the include > of windows.h and as such the different types of InterlockedIncrement. I tried that and it worked until I realized that including windows.h causes me lots of troubles in another library (wxWidgets) so that I cannot use this solution. What is in windows.h that should be copied in interlocked.hpp? I start to be desperate to build a 64 bit version of my program with mingw-w64... also, it is difficult because I have absolutly no idea of what these interlocked... mean. Regards, Frédéric

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Variadic versions of all the vector200 map50 stuff
by Michael Steinberg 19 Sep '13

19 Sep '13

Hello, I'm currently tracking down all the slowdowns I encounter when using boost in my Visual Studio solutions. Much of the slowdowns seem to happen, because there's a wide inclusion-usage of <boost/typeof/vector.hpp> throughout boost. This seems to be a replicate of <boost/mpl/vector.hpp>, which is not as much used, but equally evil. Inclusion of any of these headers leads to a 20MB increase in Visual Studio IntelliSense database size. I tested to comment out the inclusion of all the generated <vectorXXX.hpp>. This indeed works fine and is a real relief in Visual Studio responsiveness, because although these headers seem to be included from everywhere, they dont seem to be actually used. Tracking down the inclusion paths proves difficult to me, because the Visual-Studio tool doesn't seem to be able to handle the Preprocessor-generated include directives that boost uses extensively (and I'm just a newbie). With the advent of variadic-enabled compilers (Visual Studio 2013RC just arrived), is anybody working on making this mpl-stuff variadic? That would be a major help for almost anybody using tools like IntelliSense or VisualAssist (the vector200.hpp is a wopping 2mb of totally redundant template goodness...). I think I could make the appropriate changes to my local copy, however I have no idea how to write proper boost-worthy code or even how to file it for inclusion. Also I'm not too sure why the different sized vectors have different names and if the client code relies on that, etc., but I could probably find out. Are there any "template-instantiation-coverage"-tests included, so I could check that my variadics are compatible in the use-cases? Any help would be appreciated! With Kind Regards Michael

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[boost-regex] 1.47.0 regexp_search with match_partial does not return 'what'
by Frank Bergemann 18 Sep '13

18 Sep '13

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Static map like array or range?
by Duane Murphy 18 Sep '13

18 Sep '13

I find myself often building lookup tables for conversion or mapping of one piece of data to another. Common conversions include * converting from one string to a different string (e.g. text translation), * converting from an enum to a descriptive string * converting from a string to an enum * converting from a string to a function or functor The key aspect of these lookup tables is that they are static. If the table is reasonably large, say 7-10 items, I ensure that the table is presorted and use lower_bounds() to search the table. Some uses have started using map_list_of() to initialize the map. My inner optimizer finds this disturbing as inherently static information is being allocated dynamically in order to due to the lookup. I believe it would be more intuitive if there was a map like interface to the lookup table. The implementation would use the static nature of the data to its advantage. In particular the implementation would not require the data to be copied, re-allocated, etc. I've been searching the boost libraries, but have not been able to find something like this. Thank you for your suggestions. …Duane

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Copy fusion::vector -> {std,boost}::array
by Rodrigo Madera 17 Sep '13

17 Sep '13

Checking the archives, I see that a *lot* was discussed on [1], and there was a mention (waaay after much debate and proposed solutions) on having a copy and copy_if to do such copies. Mr. Steven Watanabe mentioned a copy impl was lying around his computer [2]. Did it actually make it into Boost? Thanks for any input, Rodrigo [1] http://lists.boost.org/boost-users/2010/10/63168.php [2] http://lists.boost.org/boost-users/2010/10/63343.php

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Generic “Observable” mixin based on Boost
by Павел Фролов 17 Sep '13

17 Sep '13

I find Observer pattern a very useful tool to decrease coupling between modules of a system. Boost provides Signals2 which can be used for that purpose. But adding Signal2 objects to arbitrary classes is not very convenient, because your must manually implement RegisterEvent/FireEvent functions. What I was looking for is a reusable mixin which could add “Observable” behavior to arbitrary class with minimal hassle. Ideally, the user of mixing must only provide event table which contains event tags and handler signatures, e.g. (in pseudocode): EventTable { EventA: void(), EventB: int(bool), ... } I came up with working proof of concept which uses CRTP-based mixin and traits class for event table declaration. I'm new to template meta-programming, so I'm looking forward to comments about possible improvements. In particular, I'm not very satisfied with syntax boost::fusion::pair<Show, boost::optional<boost::signals2::signal<void()>>> (see attachement). I think, I can do better by allowing user to specify just boost::fusion::pair<Show, void()> and then generate proper type with mpl::transform and/or fusion::transform. This way is shorter and implementation details (optional, signals2) are hidden from the user. The mixin code (full code with example usage in attachment): #include <utility> #include <boost/fusion/container/map.hpp> #include <boost/fusion/sequence/intrinsic/at_key.hpp> #include <boost/fusion/sequence/intrinsic/value_at_key.hpp> #include <boost/optional.hpp> #include <boost/signals2.hpp> #include <boost/utility/in_place_factory.hpp> //***************************************************************************** // EventSource mixin //***************************************************************************** // event source traits base (concrete event source must create specialization) template<typename ConcreteEventSource> struct Events; // event source mixin (using CRTP) template<typename ConcreteEventSource> class EventSource { public: typedef ::Events<ConcreteEventSource> Events; private: typedef typename Events::EventTable EventTable; // helper type generator template<typename Event> struct GetType { // boost::optional type typedef typename boost::fusion::result_of:: value_at_key<EventTable, Event>::type SignalWrapper; // boost::signal type for particular boost::optional type typedef typename SignalWrapper::value_type Signal; // slot return type for particular boost::signal type typedef typename Signal::result_type SignalReturnType; }; public: // connect event handler template<typename Event, typename Handler> void Connect(Handler&& handler) { GetSignal<Event>()->connect(std::move(handler)); } protected: // generate nullary signal template<typename Event> typename GetType<Event>::SignalReturnType FireEvent() { return GetSignal<Event>()->operator()(); } // generate unary signal template<typename Event, typename Arg1> typename GetType<Event>::SignalReturnType FireEvent(Arg1 arg1) { return GetSignal<Event>()->operator()(arg1); } // ... more overloads (MSVC does not support variadic templates) private: // creates signal if not exists, returns reference to it template<typename Event> typename GetType<Event>::SignalWrapper& GetSignal() { auto& signal = boost::fusion::at_key<Event>(signals_); if (!signal) signal = boost::in_place(); return signal; } EventTable signals_; };

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[units]
by Robert Ramey 16 Sep '13

16 Sep '13

I have an urgent and definite need for the functionality which boost.units is meant to provide. The concept is quite simple so I had expected it to be relatively easy to use. I had anticipated spending a few hours perusing the documentation and examples, adding code to my application and moving on. T'was not to be. I'm now on day 3 (or 4?) trying to figure this thing out. The main hurdle is that the documentation is indecipherable. There are a number of templated classes defined which depend upon each other. I expect to find a page for each of the templates along with a description of what the template arguments should be. (Ideally these should be backed up with concept checking classes). Ideally there would be a small example showing how one would use these templates. It seems that the library is layered from low level ideas to higher level ones. The documentation touches on this - but its not really formalized. Theres a reference section which includes scores of things like base_units types for wide variety of units - but no where is there any indication how these should be used - not even in the examples are they used. There is a concept of "system" (of dimensions?) and the idea of mixing units from different systems and the idea that the same dimension (eg length) have multiple renderings in the system (nautical vs metric). I realize I've likely got this wrong and I'm not asking for anyone to explain this to me here - my point is that what should be very simple is incredibly confusing. I still haven't figured out whether it's only the documentation which is incomplete or if it is the actual logical design of the library itself is what's flawed. I'm still working on this. I don't remember much traffic on this list regarding this library and if I google information on boost C++ units library I don't get a whole lot of hits. This could mean that that the library is so easy to use no one ever needs to ask about it or it could be that almost no one every uses it. In Boost we don't gather statistics on usage by library so I don't which of these it might be. So my question is: Has anyone had good success with this library? How much effort did it take? What did you have to do to make it work. I would be curious about any other user feed back in these questions. Robert Ramey

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