May 2011 - Boost-users - lists.preview.boost.org

[BGL] Subgraphs: Name-to-Index Property Map.
by Cedric Ginestet 25 May '11

25 May '11

Dear BGL users, I am trying to produce a simple routine to extract the subgraph of a graph, by using the vertex names of the subgraphs. That is, for two graphs G and H, I want to define the following operator: G -= H; Here, the resulting subgraph of G should have all the vertices that H doesn't have. During this process, the incident edges of the removed vertices are also removed. I have checked the subgraph class in BGL, but this refers to a substantially different concept. I have tried the following code, which works, but is extremely slow for the type of application that I had in mind: ////////////////////////////////////////////////// class Graph { public: typedef adjacency_list<vecS, vecS, undirectedS, property<vertex_name_t,int> > UndirectedGraph; Graph(); ~Graph(); int Nv(); // Return number of vertices Rcpp::IntegerVector V(); // Return vector of NAMES of vertices as integers. Graph& operator-= (Graph& H); private: UndirectedGraph G; }; ///////////////////////////////////////////////////////////////////////// // Overloaded Operators. Graph& Graph::operator-= (Graph& H){ typedef graph_traits<UndirectedGraph>::vertex_descriptor Vdescriptor; typedef property_map<UndirectedGraph,vertex_name_t>::type VertexNameMap; typedef iterator_property_map <int*, identity_property_map> name_to_vertex_map; Rcpp::IntegerVector vec = H.V(); VertexNameMap NameIndex; for(ivIter t=vec.begin(); t!=vec.end(); ++t){ // Create/Update Iterator map (LValuePropertyMap). int x[this->Nv()]; NameIndex = get(vertex_name,G); for(int i=0; i < this->Nv(); ++i) x[NameIndex[i]]=i; name_to_vertex_map NVmap(x); // Remove vertex from name of *t in H. Vdescriptor u=NVmap[*t]; clear_vertex(u,G); remove_vertex(u,G); }//t return *this; }//-= ////////////////////////////////////////////////// The problem seems to be that I re-create an iterator map (from vertex NAMES to vertex INDICES) every time I remove a single vertex. This seems counter-efficient. I would need to be able to create a reference to a similar map that is automatically updated every time I remove a vertex. However, since vertices in BGL are indexed from 0 to Nv-1, I don't see a way to produce a LValuePropertyMap from vertex's names to vertex's indices. Any help/opinion would be greatly appreciated, -- Cedric Ginestet Centre for Neuroimaging Sciences (L3.04) NIHR Biomedical Research Centre Department of Neuroimaging Institute of Psychiatry, Box P089 King's College London De Crespigny Park London SE5 8AF

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iostreams stream file error
by Kraus Philipp 25 May '11

25 May '11

Hello, I use this code excerpt for copy file content: bio::stream< bio::basic_file_source<char> > l_file(p_str1); if (!l_file.is_open()) throw exception::runtime(_("file can not be opened")); std::copy( std::istream_iterator<char>(l_file), std::istream_iterator<char>(), std::ostreambuf_iterator<char>(&l_deflate) ); (*) l_file.close(); p_str1 is the filename and bio ist shorten for boost::iostreams, l_deflate is a bio::filtering_streambuf< bio::output > with a bzip2 compressor. I can set anything else to p_str1 (some not existing filesnames) and the code runs not into the if construction, the std::copy seems to copy any data, but which if there is no file under the stream !? The l_deflate is define with: bio::counter l_counter; bio::basic_null_sink<char> l_null; bio::filtering_streambuf< bio::output > l_deflate; l_deflate.push( bio::bzip2_compressor( m_bzip2param ) ); break; l_deflate.push( boost::ref(l_counter) ); l_deflate.push( l_null ); I would count the compressed bytes of a file (without writing the file), but I need to copy the filecontent without closing after copying, so I can't use boost::iostream::copy (it closes the streams after copy). On the (*) can be some other std::copy with other files Can anyone help me please to create a correct code ? Thanks a lot Phil

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linking boost libraries to custom c and c++ runtime on windows
by Adrian Gierakowski 25 May '11

25 May '11

Hello, Is it possible to tell bjam (on windows) to compile boost libraries and link them to custom c\c++ runtime libraries instead of the ones provided bt Microsoft? Thanks! -- Adrian Gierakowski

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[Lambda] Handling Bind/Lambda name clashes.
by Robert Jones 25 May '11

25 May '11

Im compiling in an environment which #includes <boost::bind.hpp>, so I can't get away from it! I'd like to use Boost.Lambda sometimes, but run into namespace clashes. This code snippet works... #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <boost/range.hpp> #include <vector> #include <numeric> // and also this... #include <boost/bind.hpp> struct X { int f( ) const { return 1; } }; int sum( int a, int b ) { return a + b; } int main( ) { boost::lambda::placeholder1_type x; boost::lambda::placeholder2_type y; std::vector<X> v; std::accumulate( boost::begin( v ), boost::end( v ), 0, bind( sum, x, bind( &X::f, y ) ) ); } but as soon as I extract the innermost bind into a Boost.Function, I seem to need to fully qualify all the binds, ie int main( ) { boost::lambda::placeholder1_type x; boost::lambda::placeholder2_type y; std::vector<X> v; boost::function<int(int, int)> my_sum = bind( sum, x, y ); std::accumulate( boost::begin( v ), boost::end( v ), 0, boost::lambda::bind( my_sum, x, bind( &X::f, y ) ) ); } Is there any easy way around this? It would be nice to able to name my inner binds in a meaningful way, but all the explicit qualification gets a bit cumbersome! Thx - Rob.

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Re: [Boost-users] [boost][msm] std::vector<MyStateMachine> generate stack overflow
by Christophe Henry 25 May '11

25 May '11

>It's not the vector, it's the copy constructor. You can see the same problem with : > > > RealStateMachine sma; > RealStateMachine smb( sma ); > >At the moment I'm not sure exactly what makes it a recursive call. Was the generated state machine not thought to be copied, or did I made a mistake? Yes, a state machine can be copied and no you didn't make any mistake. I think it's a compiler bug because: - it works fine with g++ 4.5 - the debugger doesn't even make it to the copy-constructor. I remember I had in the past problems when inheriting from a state machine with VC. The only solutions I see is to use a typedef instead or using aggregation instead of inheritance. This works: typedef boost::msm::back::state_machine< StateMachine > RealStateMachine; Unfortunately, I cannot help on this. Maybe Stephan is aware of this problem? Christophe

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how are the iterative/looping mechanism implemented in boost preprocessor?
by R A 25 May '11

25 May '11

at first i thought that the boost library came with it's own implementation of a c preprocessor, as i thought that was the only way it could be doing all that iteration (multiple "patterned" declarations, etc, etc) and the c standard hasn't introduced a notion of counters... i've considered concatenation, but that incurs a "final" string to be compared which cannot be generated automatically a priori (correct me if i'm mistaken). but when i looked at boost thoroughly, it seems to be doing everything in standard. so can anybody tell me how that is done? a sort of pseudo-code for doing this will be very helpful: #define MULTIPLE_ENUMS(my_enum, n) /* ^ will declare n enumerations using prefix "my_enum" and having concatenated 0 to n each. optional: having ALL the minimum value of each enum be 0 (easy) and maximum values for each multiplied by a magnitude of 2 starting from an initial value (which then becomes): #define MULTIPLE_ENUMS(my_enum, init, 5) */ i know this may sound trivial and totally beginner-like, but can anyone explain it to me, as i don't have the whole day just trying to decipher everything out.

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Test Reports for older Releases
by spam-receiver＠web.de 24 May '11

24 May '11

Hello! Where can I find the test results for older releases on the Boost homepage? I can only find the results for the current release under: http://www.boost.org/development/tests/release/developer/summary.html Thanks in advance, Thomas

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regular expression too complex
by Kraus Philipp 24 May '11

24 May '11

Hello, I'm generating a complex regular expression for removing word of textes, but now I get this exception: terminate called after throwing an instance of 'boost ::exception_detail ::clone_impl <boost::exception_detail::error_info_injector<std::runtime_error> >' what(): The complexity of matching the regular expression exceeded predefined bounds. Try refactoring the regular expression to make each choice made by the state machine unambiguous. This exception is thrown to prevent "eternal" matches that take an indefinite period time to locate. Is there a solution to create any removing operation? I have got a vector with strings and I must remove each element on the texts, so I create a regular expression with "or" and case-insensitive search ans use regex_replace to remove the words Thanks Phil

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Help needed with Boost header only libraries
by vikash sharma 24 May '11

24 May '11

Hi, Could anyone please help me out. I need boost header only libraries for boost shared pointer and boost foreach. But i am not able to find the header libraries available for download any where on the boost website. I remember seeing the header only libraries some time back. But right now dont see the header only libraries for any of the boost versions released till date. Regards, Vikash

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simple thread program hardtocompile/link with 1.46.1
by Eric Lin 24 May '11

24 May '11

Dear boost program(for c++,(or g++)): after I download 1.46.1 and try to baseon it to compile a simple program from book C++cookbook, at page 447, 12.1 Creating a Thread ---------- // example 12-1. Creating a thread #include <iostream> #include <boost/thread/thread.hpp> #include <boost/thread/xtime.hpp> struct MyThreadFunc { void operator()() { // Do something long-running... } } threadFun; int main() { boost::thread myThread(threadFun); // Create a thread that starts // running threadFun boost::thread::yield(); // give up the main thread's timeslice // so the child thread can get some work // done. // Go do some other work... myThread.join(); // The current (i.e., main) thread will wait // for myThread to finish before it returns } ----------------------------------------------------------- eric@eric-laptop:~/cppcookbook$ ls example12-1.cpp eric@eric-laptop:~/cppcookbook$ g++ -I/home/eric/boost1/boost_1_46_1/ example12-1.cpp -lboost_thread-mt /usr/bin/ld: cannot find -lboost_thread-mt collect2: ld returned 1 exit status eric@eric-laptop:~/cppcookbook$ g++ -I/home/eric/boost1/boost_1_46_1/ example12-1.cpp -lboost /usr/bin/ld: cannot find -lboost collect2: ld returned 1 exit status eric@eric-laptop:~/cppcookbook$ cd ../boost1/boost_1_46_1/ eric@eric-laptop:~/boost1/boost_1_46_1$ -------------------------- I am in Ubuntu linux 10.04, g++ 4.4.3 looking to see any suggestion and thanks a lot in advance, Eric Lin, Us citizen, in Los Angeles I am glad to meet anyone in Los Angeles on computer science meeting

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