September 2011 - Boost-users

[Context] Context library status?
by Nat Linden 14 Sep '11

14 Sep '11

http://lists.boost.org/boost-announce/2011/05/0310.php I'd like to ask Oliver about the current status of the Context library. I just spent a couple of weeks grappling with a mystery bug that was ultimately due to exceeding the stack size we'd allocated for a Boost.Coroutine. It made me think of the Boost.Context promise that each stack is protected by a read-only guard page, so that stack overflow is immediately and unambiguously caught. Once the Boost.Context API has stabilized, it would probably be worth it for me to replace the present Boost.Coroutine underpinnings with Boost.Context. I do realize that Oliver (and probably others) have Context-based high-level libraries in the pipeline, but at least for us, for now, Coroutine+Context would provide an immediate benefit.

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boost::xpressive : Get thousand separator as double
by Jens Saathoff 14 Sep '11

14 Sep '11

Hi! I'm playing a bit with boost::xpressive and have no clue how to get a 100,000 (comma as separator) to a double as 1000000.00 or 250,000.10 as a double 250000.10 or 12,00 as double 12.00 or 1,200,500.00 as double 1200500.00. I'm working with xpressive since a day. What's the regex for that? And how can i use it in xpressive-grammar as a nested regex? Example subject: "I payed 100,200.50 Dollar" Example Regex on subject: 'I payed' >> (s1=getdoubleregex) >> ' Dollar' Is it possible to do it like that? Set return-value/type in a regex? Thank you very much!

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begin (cout) or boost::copy to cout
by Krzysztof Żelechowski 13 Sep '11

13 Sep '11

== The Problem == Boost.Range defines boost:: begin to give you the iterator to every possible container — except ostream. == Solution 1 == === Implementation === I have the following function for you to add to Boost.Range: template < class P_I, class P_C, class P_T > std:: ostream_iterator < typename boost:: iterator_value < P_I >:: type, P_C, P_T > begin (std:: basic_ostream < P_C, P_T > &p_s, P_I const &, P_C const p_p [] = NULL) { return std:: ostream_iterator < typename boost:: iterator_value < P_I >:: type, P_C, P_T > (p_s, p_p); } === Application === to be used in the following way: void foo (std:: vector < int > const &v) { boost:: copy (v, boost:: begin (std:: cout, boost:: begin (v), " "); } This function eliminats the need of passing explicit template parameters to std:: ostream_iterator, which makes the code fragile and hard to read. == Solution 2 == === Motivation === Since an output stream iterator is not useful except for copying to an output stream, a further simplification is also possible: === Implementation === template < class P_R, class P_C, class P_T > std:: basic_ostream < P_C, P_T > &copy (P_R const &p_r, std:: basic_ostream < P_C, P_T > &p_s, P_C const p_p [] = NULL) { copy (p_r, std:: ostream_iterator < typename boost:: range_value < P_R >:: type, P_C, P_T > (p_s, p_p)); return p_s; } === Application === and it enables the following invocation: void foo (std:: vector < int > const &v) { boost:: copy (v, std:: cout, " "); } Please consider. Chris

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"weak" binding to member?
by John M. Dlugosz 13 Sep '11

13 Sep '11

I know that 'bind' (now in std::tr1) will bind pointers to member functions to smart pointers. But is there a simple way to bind to a "weak" pointer, such that the attempted call will realize the smart pointer and if successful perform the call, or if unsuccessful just not call anything without complaint? (In this case, it appears that the return is void) —John

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[Boost.Polygon] support for polygons with holes
by Björn Piltz 13 Sep '11

13 Sep '11

I'm playing around with Boost.Polygon and I'm wondering what functionality is supported for the polygon_with_holes concept. Specifically the boolean operators. For example, can I create a polygon_set with polygon_with_holes. I would like to punch a hole in a polygon and get a polygon with a hole as supposed to a key holed contour. Similarily, when combining the following rectangles: p += rectangle_data<int>(0, 0, 100, 10); p += rectangle_data<int>(90, 0, 100, 100); p += rectangle_data<int>(0, 90, 100, 100); p += rectangle_data<int>(0, 0, 10, 100); I would like to end up with +-----+ | | | +-+ | | | | | | +-+ | | | +-----+ as opposed to +-----+ | | | +-+ | | | | | | +-+ | | | | +---+-+

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[type_traits][function_traits] generic way of obtaining argument of *both* a function and function object
by alfC 13 Sep '11

13 Sep '11

Hi, Is there a uniform way to obtain the argument type of function object and of a function at the same time. For example: double fun(int a){ return ... ;} struct A{ double operator()(int a){ return ...;} typedef int argument_type; // or something like this (if needed) }; template<class F> print_argument_type(F f){ std::cout << typeid( argument_of<F>::type // or something like this ?? ).name() << std::endl; } A a; print_argument(fun); //should print "int" print_argument(a); //should print "int" Of course I am asking for something that at least works on objects in which operator() is not overloaded. For functions we have function_traits< ... >::arg1_type (and other MPL variants) but I can not find a generic solution that also works for objects. In other words I need something like boost/std::result_of but for the argument type; if this is not possible in general because of language limitations (e.g. because operator() can be overloaded) I am willing to accept any convention from out there that works both for functions and funciton objects. Just wanted to know what boost can say about this problem. Maybe something that looks into the arguments of the member-function A::operator() via type_traits in case A is a class? Thanks, Alfredo

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Boost MSM - Ways to send info out from state machine to outside world
by gauravk 13 Sep '11

13 Sep '11

Hi, I wanted to know what are different ways to send info from state machine to outside world. I am planning to use MSM in my project to represent connection between local computer and remote computer. This connection will be used as a channel to send data over to remote device. There can be >1 channels existing between local computer and the remote device. There will be a controller sitting at local computer monitoring all these channels. The data will be sent over connection that is idle/free at that point of time. Whenever the connection, i.e. FSM, is done sending the data, it will let the controller (which resides outside of the FSM) know that it is done sending the data and the controller will then send next lot of data over that connection. There can be 2 ways of achieving this: 1. Controller polling all the connections and knowing what "state" the FSM is in.(In this case, the outer world will need to know the current state of the state machine) 2. The FSM will proactively let the controller know that it is done with sending data. (In this case the FSM will have to send data to outside world). I would like to know about ways to implement both the cases (i.e knowing status/current state of the FSM and sending info from FSM). I would also like to know what are different ways to interact with (both to and from) FSM in general, apart from sending events. Thanks! -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-MSM-Ways-to-send-info-out-from-sta… Sent from the Boost - Users mailing list archive at Nabble.com.

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array alignment in ublas matrices
by petros 13 Sep '11

13 Sep '11

Hi, I am using the ublas matrices with mkl. The documentation of mkl suggests/requires that allocated arrays are aligned on 16 byte boundaries. The matrix structures within ublas delegate the memory management in the std allocator which at the very end reduces to new. I know that one way to address this is write my own allocator for the unbounded_array that lies on the basis of the storage structures. However, this is an error-prone job and it is suggested that this is avoided. Any other solutions? – hopefully more straightforward ? Thank you in advance for your help, Petros ps: using visual studio 2010 on winn7/visa 64 bit and mkl 10.3.

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[serialization] yaml archive compilation
by alfC 12 Sep '11

12 Sep '11

Hi, did any body succeed in compiling the YAML component of Boost.Serialization located in https://github.com/boost-vault/serialization ? I really don't understand what should I do with the yaml_oarchive.cpp yaml_iarchive.cpp, etc, contained in the src directory. The source don't have makefiles, should I put those in the boost source tree? Thanks, Alfredo

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LINK Error while building PBGL example breadth_first_search.cpp
by 余韬 12 Sep '11

12 Sep '11

Hi, I am trying to learn PBGL. I am using VS2008 on Win 7. I had built and installed open mpi 1.4.3, HPC Pack 2008 SDK, and Boost library 1.46.1 with "bjam --with-mpi --with-graph_parallel". I had set include and library directory for the above 3 libraries in VS2008. The additional dependency set for the project is "libboost_*mpi*-vc90-mt-gd.lib libboost_*serialization*-vc90-mt-gd.lib libboost_wserialization-vc90-mt-gd.lib libboost_graph-vc90-mt-gd.lib libboost_*graph_parallel*-vc90-mt-gd.lib libboost_system-vc90-mt-gd.lib libmpi_cxxd.lib libmpid.lib libopen-pald.lib libopen-rted.lib msmpi.lib" Here are the major references I had referred which helped to reduce errors significantly: http://terboven.wordpress.com/2008/09/09/building-and-using-boostmpi-on-win… http://lists.boost.org/boost-users/2009/11/54042.php However, while compiling D:\Development\boost_1_46_1\libs\graph_parallel\example\breadth_first_search.cpp on my machine, I still got the following 4 link errors: Error 4 error LNK2019: unresolved external symbol "*private: struct ompi_datatype_t * __thiscall boost::mpi::detail::mpi_datatype_map::get(class type_info const *)*" breadth_first_search.obj Error 3 error LNK2019: unresolved external symbol "*private: void __thiscall boost::mpi::detail::mpi_datatype_map::set(class type_info const *,struct ompi_datatype_t *)*" breadth_first_search.obj Error 2 error LNK2019: unresolved external symbol "*public: __thiscall boost::mpi::communicator::operator struct ompi_communicator_t *(void)const*" breadth_first_search.obj Error 1 error LNK2019: unresolved external symbol "void __cdecl boost::detail::bfs_helper<class boost::adjacency_list<struct boost::vecS,struct boost::distributedS<class boost::graph::distributed::mpi_process_group,struct boost::vecS,struct boost::defaultS>......" breadth_first_search.obj Am I missing something here? Thanks, Tao Yu http://about.me/Tao_Yu

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