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beginner boost::statechart questions
by Bedeho Mender 20 Nov '16

20 Nov '16

Hi, I have a few questions about the statechart library. 1) I would like to pass around a representation of the current configuration of a machine, to allow inspection of local variables and active states. The easiest approach would be to just pass around a copy of the machine, but this is not possible since the state_machine class is noncopyable. An alternative could have been to pass around a constant ref/ptr to the machine, but this is also not workable because the inspection will happen in another thread, and synchronisation is not feasible. Any suggestions? One alternative is to create a new snapshot representation, but it will be a headache to keep in synch with the primary machine. 2) A related question is whether there is a good way to start a machine in a given configuration? Using a sequence of events works in principle, but its a very impractical way to do so. For example if one wishes to restore a configuration from a prior session, then the client code has to log the full event history, and it may have a very hard time determining how many events need to be logged to reconstruct the given configuration. Logging and storing *all* events from the prior session will in many cases be wasteful, or even infeasible. 3) Suppose a machine makes a certain callback to client code in a set of different reactions. It would be nice if the client could inspect the currently active state, from which the given reaction is originating. However, my understanding is that the machine is unstable when processing a reaction, hence this is not possible. Is there a way around this? Best Bedeho Mender ᐧ

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[geometry] Cannot compile boost::geometry::intersection
by Stanley Friesen 17 Nov '16

17 Nov '16

I am using boost library version 1.54 with gcc --std=c++11. I am trying a simple use of geometry::intersection as follows: #include <boost/geometry.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/geometries/adapted/boost_polygon.hpp> using namespace boost::geometry; ...... typedef model::d2::point_xy<double> point_xy; model::polygon<point_xy> clipBounds; // add points to clipBounds model::polygon<point_xy> area; // add points to area model::polygon<point_xy> result; if(boost::geometry::intersection(area, clipBounds, result)) { std::cout << std::endl << "Boost intersection, size = " << num_points(result) << std::endl; } If I comment out the call to intersection, everything compiles. With it I get: In file included from /usr/include/boost/serialization/level.hpp:28:0, from /usr/include/boost/serialization/nvp.hpp:31, from ...: /usr/include/boost/mpl/eval_if.hpp: In instantiation of ‘struct boost::mpl::eval_if_c<false, boost::range_const_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > >, boost::range_mutable_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > > >’: /usr/include/boost/range/iterator.hpp:63:63: required from ‘struct boost::range_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > >’ /usr/include/boost/range/value_type.hpp:30:12: required from ‘struct boost::range_value<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > >’ /usr/include/boost/geometry/algorithms/intersection.hpp:97:64: required from ‘static bool boost::geometry::dispatch::intersection<Geometry1, Geometry2, Tag1, Tag2, Reverse>::apply(const Geometry1&, const Geometry2&, GeometryOut&, const Strategy&) [with GeometryOut = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >; Strategy = boost::geometry::strategy_intersection<boost::geometry::cartesian_tag, boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >, boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >, boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian>, void>; Geometry1 = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >; Geometry2 = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >; Tag1 = boost::geometry::polygon_tag; Tag2 = boost::geometry::polygon_tag; bool Reverse = false]’ /usr/include/boost/geometry/algorithms/intersection.hpp:201:67: required from ‘bool boost::geometry::intersection(const Geometry1&, const Geometry2&, GeometryOut&) [with Geometry1 = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >; Geometry2 = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >; GeometryOut = boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> >]’ /home/stanley/workspace/worldmodel/metric/map/GISCache.cpp:2492:62: required from here /usr/include/boost/mpl/eval_if.hpp:60:31: error: no type named ‘type’ in ‘boost::mpl::eval_if_c<false, boost::range_const_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > >, boost::range_mutable_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > > >::f_ {aka struct boost::range_mutable_iterator<boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double, boost::geometry::cs::cartesian> > >}’ typedef typename f_::type type; Since my code is virtually identical to the sample code in the documentation, I am very puzzled by this. What have I missed? How do I get this to compile? (I do find it odd that this error refers to boost/serialization rather than boost/geometry, but I suppose that has to do with the order of inclusion). -- View this message in context: http://boost.2283326.n4.nabble.com/geometry-Cannot-compile-boost-geometry-i… Sent from the Boost - Users mailing list archive at Nabble.com.

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[statechart] Pass event data to state constructor using triggering_event
by ramonpadilla1＠yahoo.co.uk 16 Nov '16

16 Nov '16

I would like to be able to communicate the data from an event to a state that gets constructed as a result of a transition. From this post in 2009 and this one in 2010 the use of triggering_event() is suggested. However, I can't find an example anywhere that demonstrates how to use it. Can anyone help? Links in the message | Google Groups | | | | Boost - Users - [statechart] Passing pa... | |

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[statechart] Passing parameters from event to State Local Storage
by Christophe Bourez 16 Nov '16

16 Nov '16

I need to maintain a parameter into the state local storage. This parameter is initially contained in the event that causes the transition to the target state. I give hereafter a small illustrative example. typename sc = boost::statechart; class EvTest : public sc::event<EvTest> { public: EvTest(std::size_t val) : value(val) {} std::size_t getValue() const { return this->value; } private: std::size_t value; }; class MyStateMachine; class StSource; class StTarget; class StSource : public sc::simple_state<StSource, MyStateMachine> { public: typedef sc::custom_reaction<EvTest> reactions; sc::result react(const EvTest &event) { // How to pass event.getValue() to the target state ? transit<StTarget>(); } }; class StTarget : public sc::simple_state<StTarget, MyStateMachine> { public: StTarget(std::size_t val) : val(value) {} private: std::size_t value; }; Thanks, Christophe

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Help needed for boost polygon get trapezoid
by Lei Yin 15 Nov '16

15 Nov '16

Hello all, I recently moved to use boost.polygon for doing non-manhattan shape boolean operation, and I'm using get_trapezoids() function to convert output polygons to trapezoids. There're two problems I'm facing and couldn't overcome: 1. Somehow boost.polygon not always give me the largest polygon as possible. In the result, frequently I saw there are two trapezoids are neighboring each other, and they can be perfectly combined into one big trapezoid, but for some reason, boost.polygon give me separated two instead of one. 2. It maybe due to floating point snapping issue (I'm operating on integer base), for some special cases, I got very slim trapezoid like 1 db unit in width. Preferably, this trapezoid Any suggestion to solve above issues would be much appreciated! Thanks in advance. Lei

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How to get response of the questions I posted?
by Bruce 15 Nov '16

15 Nov '16

Hi, I am not familiar with emails list. First time use or I don't known where to post boost.log questions. I found I can't receive the response of my thread by email. I have to check the boost.user archive and I can't response in the archive list. I do subscribed to this list or I can't post. Anybody can help me? Many thanks.

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Questions about extending boost::log sink backend based on app_luncher example
by Bruce 15 Nov '16

15 Nov '16

Hi,I am extending the boost::log backend sink to show log record into GUI ListBox control, which is gui_logger. I modify based on the app_luncher example which extends backend sink of :basic_formatted_sink_backend. Below are the questions that I have for now: 1) when modifying the consume function, I don't know how to get the message body. void consume(logging::record_view const& rec, string_type const& command_line); I using TRACE of visualstudio 2015 to first log the message out into vs2015 console. But I don't know how the get the message from record_view? 2) When I TRACE(command_line.c_str()) of consume function, I logged every record out into vs2015 console. I need to set a filter to only output some of the log. How to set filters with gui_logger? I notice there is sink->set_filter function, but I don't know how to set in my situation.In my scenario, I setup a src::severity_channel_logger (db_logger) with keywords::channel = "dblog", which output to db.log file. I want to use gui_logger to show the latest 200 records on the ListBox. gui_logger should use the same filter with db_logger. gui_logger log the latest 200 records into gui ListBox. db_logger log all the records into text file. So I need to set the same filter with db_logger. 3) I read settings from the ini file for db_logger. I want also to read setting from ini file for gui_logger. How to do it?

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How to wrap boost::log class to user?
by Bruce 14 Nov '16

14 Nov '16

Hi, I am coding a project and I use boost::log. I need to supply the log function to user, but I don't want the user use boost::log directly. I want to wrap the boost::log into my class. But I still want to keep the << cascade feature. Basically, I need to implement a MyLogger class, which support: MyLogger(info) << bla bla bla; MyLogger(trace) << bla bla bla; and in the operator << function, I can use: BOOST_LOG_SEV macro. I don't know how to implement the operator << in MyLogger class. Can anybody helps me, Thanks.

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How to use boost::log to setup multiple logger?
by 刘宝良 14 Nov '16

14 Nov '16

Hi, I want to use boost::log to setup 3 logger for different purpose. Not one logger to have multiple output file. And I also want one logger to have one file output and a GUI output to be viewed by the end user. How to do it? -Bruce

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boost::filesystem::path::iterator and libstdc++ std::search
by Oleksandr Senkovych 11 Nov '16

11 Nov '16

Hi guys. Several days ago I've faced a strange issue with boost::filesystem::path::iterator - it segfaults when used in some STL algorithms. Here's a sample code that crashes: http://melpon.org/wandbox/permlink/58aIbfJWeGgMKMdF I looked at the issue a little bit and discovered that the reason for that is this part of iterator code: const path& dereference() const { return m_element; } So when using std::search libstdc++ has to convert binary predicate to unary for later use in std::find_if: __first1 = std::__find_if(__first1, __last1, __gnu_cxx::__ops::__iter_comp_iter(__predicate, __first2)); It does this by capturing dereferenced value of second iterator (__first2 in a piece of code above) but since iterator is passed by-value, this wrapper holds dangling reference to local member of iterator.m_element. Now according to C++ standard part 24.2.1 [iterator.requirements.general]: 10. Destruction of an iterator may invalidate pointers and references previously obtained from that iterator. So this looks like a violation of a standard by libstdc++ library. Unfortunately I couldn't get my account registered at https://gcc.gnu.org/bugzilla/ and was not able to file a bug, so can I ask you to help me with it?

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