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[proto] vec3 sample error
by Kamil Zubair 02 Nov '10

02 Nov '10

I found a strange error when I try the vec3 sample from proto, my code is like this: struct Vec3SubscriptCtx : proto::callable_context< Vec3SubscriptCtx const > { typedef int result_type; Vec3SubscriptCtx(int i) : i_(i) {} // Index array terminals with our subscript. Everything // else will be handled by the default evaluation context. int operator ()(proto::tag::terminal, int const (&arr)[3]) const { return arr[this->i_]; } int i_; }; struct Vec3 : proto::extends<proto::terminal<int[3]>::type, Vec3> { explicit Vec3(int i=0, int j=0, int k=0) { (*this)[0] = i; (*this)[1] = j; (*this)[2] = k; } int &operator [](int i) { return proto::value(*this)[i]; } int const &operator [](int i) const { return proto::value(*this)[i]; } // Here we define a operator = for Vec3 terminals that // takes a Vec3 expression. template< typename Expr > Vec3 &operator =(Expr const & expr) { typedef Vec3SubscriptCtx const CVec3SubscriptCtx; (*this)[0] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(0)); (*this)[1] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(1)); (*this)[2] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(2)); return *this; } template< typename Expr > Vec3 (Expr const & expr) { typedef Vec3SubscriptCtx const CVec3SubscriptCtx; (*this)[0] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(0)); (*this)[1] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(1)); (*this)[2] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(2)); } void print() const { std::cout << '{' << (*this)[0] << ", " << (*this)[1] << ", " << (*this)[2] << '}' << std::endl; } }; int main(int argc, const char* argv[]) { Vec3 a(1, 2, 3); Vec3 b(3, 2, 1); Vec3 c; c = b; c.print(); return 0; } I expected that when c is printed it will display 3, 2, 1 ( the value of b ) but instead it print 0,0,0 like b is never assigned to c. I try this using vs 2010 with boost 1.44 in windows 7 64.

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[serialization] Class version in binary archive
by Guy Prémont 02 Nov '10

02 Nov '10

Hi all, I have a whole hierarchy of classes that is serialized without problem using XML archive. When I wanted to use binary archive (that should be faster and smaller), i met an little problem. A bit of history, to make it easier to spot related changes in class versions, we decided not to go with serial class version numbers (1, 2, 3...) but with meaningful version numbers: internal branch number + date. We end up with class versions like 420100714 or 520101102. In XML or text, no problem at all. In binary, it took me a while to find out that class version numbers are serialized as unsigned char! However, the documentation here <http://www.boost.org/doc/libs/1_44_0/libs/serialization/doc/archive_referen ce.html> says unsigned int. It is a bit surprising, since the type passed to the serialization method is int. I understand that I need to create my own binary archive to implement save_override and load_override for version_type. However, doing the override means that i am preventing the use of standard boost binary archive. Is that a known bug, or is it even considered a bug? Thanks -- Guy Prémont, D.Sc. Architecte logiciel senior / Senior software architect CM Labs Simulations Inc. <blocked::http://www.cm-labs.com/> http://www.cm-labs.com/ Tel. 514-287-1166 ext. 237

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Re: [Boost-users] [1.44 MSM meta state machine] accessing objects fromactions
by Christophe Henry 02 Nov '10

02 Nov '10

> Currently my queue object is a member of the state machine itself, so I > can write > > struct Send_ : public msm::front::state_machine_def<Send_> > { > string m_next_line_to_send; > socket m_socket; > string get_next_send_line(); > }; > > and in my a_send action > void operator()(Event &const &evt, Fsm &fsm, S&, T&) > { > fsm.m_next_line_to_send=fsm.get_next_send_line(); > fsm.m_socket.async_write(fsm.m_next_line_to_send); > } > > This works well as long as I am not using sub-statemachines. > > Here is my problem: > I would like to use a substate machine for the actual sending. The main > state machine has the states Disconnected, Working, Error, Shutdown. The > Working state should actually be a substate machine. > > The problem is, when a_send gets called by the substate machine Working, > the fsm object is of type Working. Correct. There is no "fsm call stack" yet. This gets complicated if you have a submachine of a submachine of ... For the moment I don't have this. > How can I access the member variables of the parent of a substate > machine? Or is there a better way of accessing the objects the state > machine should work with from actions? For the moment, all we can do is adding a pointer to the main fsm's data in the submachine. It is less elegant with the 1.44 than the coming 1.45: With 1.44 (for example inside the on_entry method of Send_): Send_::Working& w = fsm.get_state<Send_::Working&>(); w.data = &fsm.data; // w.data is a pointer True, this is not really nice. With the upcoming 1.45 (or trunk for the moment), you could use the new constructors: Send myfsm (msm::back::states_ << Working(data) ); //data being externally defined and Working_ having a corresponding constructor But this won't work for your case where data is contained in Send_ (and therefore does not exist at the time of construct). You can however reuse the same syntax with the new set_states method: Replace the version with get_state by: fsm.set_states(msm::back::states_ << Working(fsm.data)); //data being defined in Send_ and Working_ having a corresponding constructor. The whole explanation is there (http://svn.boost.org/svn/boost/trunk/libs/msm/doc/HTML/ch03s05.html#backend…) > The tutorial explains state machines very nicely with the example of a > CD player. But all the actions are empty and nowhere is explained, how > you would actually access a CD player member variable or other such > object so that you could actually manipulate the player to do something. Seems that I need to improve my doc here. It's too late for the 1.45 but I'll do it for the 1.46. I agree that this is still not perfect and it's on my list but the list is still pretty long so I hope this solution will be ok for the time being. Regards, Christophe

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iostreams zip header
by Kraus Philipp 02 Nov '10

02 Nov '10

Hi, I'm using the gzip and bzip2 compression for compress data. That works fine, but can I remove the zip header in the output stream? The compressor is pushed into a filtering_streambuf and output stream, but I don't need the the zip header (only the compressed data). Is there any method to remove the zip header or should I write my own code at the gzip / bzip2 specifiation? Thanks Phil

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[Review][Ratio] Boost.Ratio has been ACCEPTED
by Anthony Williams 02 Nov '10

02 Nov '10

The following message is a courtesy copy of an article that has been posted to gmane.comp.lib.boost.devel as well. Hi, I am pleased to announce that Boost.Ratio has been ACCEPTED into Boost. There were not as many reviews for Boost.Ratio as for some libraries, but they were overwhelmingly positive. Boost.Ratio is an important building block for other upcoming submissions, and provides an implementation of the C++0x rational arithmetic facilities. A few changes were requested by the reviewers, which I will list below. I know that Vicente has already started working on some of these. These changes should be addressed before the library appears in a Boost release. * Some of the macros had names with RATIO_RATIO in. These should be changed to just RATIO * The ratio_add, ratio_sub, ratio_multiply and ratio_divide templates should derive from the resulting ratio type as well as providing the nested ::type member, in order to closely emulate the template alias facility from C++0x * The typos in the documentation should be fixed, and the documentation reviewed for correctness and clarity (though several of the reviewers made positive comments on the quality of the documentation). * The library needs more tests under the Boost Software License. * All references to names from the boost namespace should be qualified with boost:: to avoid potential name clashes and ambiguity with names from the global namespace. * Sections commented out with #if 0 should be removed * The extensions beyond the facilities required by the C++0x draft should be able to be enabled or disabled through use of a configuration macro. * References to the tests, examples and documentation from within the code should be checked for correctness. I would like to thank Vicente for submitting the library and those that took the time to write a review. Anthony -- Author of C++ Concurrency in Action http://www.stdthread.co.uk/book/ just::thread C++0x thread library http://www.stdthread.co.uk Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk 15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK. Company No. 5478976

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how to build non-boost asio without boost
by Jeff Graham 02 Nov '10

02 Nov '10

Everyone, I need a header-only version of ASIO for a stripped-down embedded system. I downloaded the latest and greatest asio version 1.4.5 from Chris Kohlkoff's think-asyn.com website. This version is supposedly the "boost-free" version. But I cannot get it to configure without boost. The web page certainly suggests "building" asio boost-free is possible. The release notes do not indicate otherwise. OTOH, the documentation only mentions configuring WITH boost. And, as mentioned in other discussions, the headers are full of #includes for boost files. I tried several obvious variations for configure that all fail, insisting on using boost (which does not exist on my system): ./configure -without-boost ./configure -without-boost ./configure -with-boost=no ./configure -with-boost= Could some kind soul please explain what I am doing wrong? I don't have bcp, but if I did, would that work? Thanks

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Removing edges using remove_edge in adjacency list
by giridhar 02 Nov '10

02 Nov '10

Hello All, I am completely new to using BGL and STL. I know the concept of STL but had never used it before. I have to implement an algorithm for my thesis and I am trying to use BGL for that. I have made use of Dijkstra's algorithm that is inbuilt in BGL. Below is the code, which is similar to that in the reference manual with few changes. #include <iostream> #include <boost/config.hpp> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/dijkstra_shortest_paths.hpp> using namespace std; using namespace boost; /*struct flow_t { typedef edge_property_tag kind; }; struct capacity_t { typedef edge_property_tag kind; }; namespace boost { enum edge_flow_t { edge_flow}; enum edge_capacity_t {edge_capacity}; BOOST_INSTALL_PROPERTY(edge,capacity); } */ int main() { typedef property<vertex_distance_t,int, property <vertex_name_t,std::string> > VertexProperty; // typedef property<flow_t,capacity_t, int> Cap; typedef property<edge_weight_t,int> EdgeProperty; typedef adjacency_list < listS, vecS, directedS, VertexProperty, EdgeProperty > graph_t; typedef graph_traits < graph_t >::vertex_descriptor vertex_descriptor; // typedef graph_traits < graph_t >::edge_descriptor edge_descriptor; typedef std::pair<int, int> Edge; const int num_nodes = 5; enum nodes { A, B, C, D, E }; char name[] = "ABCDE"; Edge edge_array[] = { Edge(A, B), Edge(A, C), Edge(B, E), Edge(C, B), Edge(C, D), Edge(D, E) // , Edge(D, E), Edge(E, A), Edge(E, B) }; int weights[] = { 4, 1, 3, 2, 2, 3}; int num_arcs = sizeof(edge_array) / sizeof(Edge); graph_t g( edge_array, edge_array+num_arcs, weights, num_nodes); std::vector<vertex_descriptor> p(num_vertices(g)); std::vector<int> d(num_vertices(g)); vertex_descriptor s= vertex(A,g); dijkstra_shortest_paths(g,s,predecessor_map(&p[0]).distance_map(&d[0])); // std::cout<<"timepass"<<s<<std::endl; std::cout<<"Distaces and Parents"<<std::endl; graph_traits<graph_t>::vertex_iterator vi,vend; for(tie(vi,vend)=vertices(g);vi!=vend;++vi) { std::cout<<"distance("<<name[*vi]<<")= "<<d[*vi]<<","; std::cout<<"parent("<<name[*vi]<<")= "<<name[p[*vi]]<<std::endl; } std::cout<<std::endl; graph_traits<graph_t>::vertex_iterator i,iend; // std::cout<<"testing iterators "<<i<<","<<iend<<std::cout; for(tie(i,iend)=vertices(g);i!=iend;++i) { if(s==*i) continue; else remove_edge(name[*i],name[p[*i]],g); } cout<<"After removal of working path"<<std::endl; vertex_descriptor s1= vertex(A,g); std::vector<vertex_descriptor> p1(num_vertices(g)); std::vector<int> d1(num_vertices(g)); dijkstra_shortest_paths(g,s1,predecessor_map(&p1[0]).distance_map(&d1[0])); std::cout<<"Distaces and Parents"<<std::endl; graph_traits<graph_t>::vertex_iterator i1,end1; for(tie(i1,end1)=vertices(g);i1!=end1;++i1) { std::cout<<"distance("<<name[*i1]<<")= "<<d1[*i1]<<","; std::cout<<"parent("<<name[*i1]<<")= "<<name[p1[*i1]]<<std::endl; } std::cout<<std::endl; } Now I want to remove the edges that has been found by Dijkstra's algorithm or alter the weights of those edges found by dijkstra's to some high value. This is mainly to find different route to target. I know I am doing something wrong with iterator's. But I am not able to figure it out due to lack of knowledge in STL. I tried to find it online, but could not find satisfactory explanation. If someone could give some explanation, it would be really helpful for me. Please help. -- Regards, Giridhar

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boost::pool segfault
by Robert Dean 02 Nov '10

02 Nov '10

Hello, I attempted to use the boost::pool STL allocators for a work project which uses millions of objects as part of a memory resident data store. Unfortunately, this caused the program to always segfault with a std::bad_alloc error during initialization. Looking into the problem, it seems to be due to the "next_size <<= 1;" line found in malloc_need_resize and ordered_malloc_need_resize methods. Near as I can tell, every-time boost::pool allocates a new storage chunk it doubles the size request for the next allocation. For an application which uses gigabytes of storage, this means the memory pool requests more memory than the application uses without the pool, as well as sizes larger than the kernel can supply. Is there any way to control this behavior? Or do I have to write my own memory pool? Thanks you, Bob

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Is it possible to use boost:serialization with Managed c++?
by سیّد امین میرزایی 02 Nov '10

02 Nov '10

We have a native c++ class that is serialized perfectly using * boost::serialization*. Now we want to change some of its member fields to *property*, so we could use them in *PropertyGrids*. When we changed the class definiction to *ref class X*, we got a huge number of these compilation errors: #1: error C2893: Failed to specialize function template 'boost::archive::text_oarchive &boost::archive::detail::interface_oarchive<Archive>::operator <<(T &)' d:\someAddress\someFile.cpp 58 #2: error C2784: 'std::basic_ostream<_Elem,_Traits> &std::operator <<(std::basic_ostream<_Elem,_Traits> &,const std::_Smanip<_Arg> &)' : could not deduce template argument for 'std::basic_ostream<_Elem,_Traits> &' from 'boost::archive::text_oarchive' d:\someAddress\someFile.cpp 58 We have a lot of tiny classes here, so it would be a pain to write a wrapper for each of them! Here is the sample class we used: ref class gps_position2 { public: template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & seconds; } public: gps_position(){}; gps_position(float s) { this->seconds = s; } property float seconds; }; And here is the main test code: int main() { std::ofstream ofs("out.txt"); gps_position2 g(24.567f); // save data to archive { boost::archive::text_oarchive oa(ofs); // write class instance to archive oa << g; } // ................ return 0; } Is it even possible to use *boost::serialization* with managed classes? p.s. If we change the class usage code to this: ... gps_position2^ g = gcnew gps_position2(24.567f); ... then we get only 1 error: error C2027: use of undefined type 'boost::STATIC_ASSERTION_FAILURE<x>' D:\path\to\Boost\boostw\boost\archive\detail\check.hpp 60

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[lexical_cast] fails to convert between basic_strings with different traits
by Paul Graphov 01 Nov '10

01 Nov '10

Hello Boost Users, boost::lexical_cast fails to compile when both Target and Source template parameters are std::basic_string instantiations with different traits because deduce_char_traits class template has two suitable instantiations which are ambiguous. This is example where I use custom basic_string that is case insensitive: http://pastebin.com/jGF0yN2m Thanks.

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