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

Re: [Boost-users] Boost::bind member function and save to function pointer
by justin allen 14 Apr '11

14 Apr '11

you probably really do want to look into an event system that will prescribe a bit of pre-built organization but if you just want to store the bind for later boost function will do it. http://www.boost.org/doc/libs/1_46_1/doc/html/function.html #include <boost/bind.hpp> #include <boost/function.hpp> #include <iostream> boost::function<void (std::string)> func; class Object { void runner(std::string message) { std::cout << message << std::endl; } public: void assign() { func = boost::bind(&Object::runner, this, _1); } }; int main(int argc, char **argv) { Object obj; obj.assign(); func("my message"); return 0; }

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[filesystem] std::bad_alloc during dll initialization when migrating to filesystem v3
by Richard Ulrich 13 Apr '11

13 Apr '11

Hi Guys, I'm currently migrating our system consisting of multiple dll's and and executable to filesystem v3. The first two dll's that use boost::filesystem load ok, but the third fails with std::bad_alloc in the locale copy constructor called from default_locale during the construction of dot_path. I don't know if it's relevant, but we usually work with char while filesystem uses wchar_t for BOOST_WINDOWS_API Rgds Richard

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Intrusive
by asif saeed 13 Apr '11

13 Apr '11

Hi, I frequently come across the term "intrusive" in boost users mailing list. What does it mean? Would any of you please provide a reference such as an online reference/link, etc? TIA, Asif

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Writing large binary files with boost gzip
by Anders Knudby 13 Apr '11

13 Apr '11

Hello all, please help! I'm truly banging my head against the wall here. I am trying to write a function that will allow me to write gzipped binary files (~50 MB) and read them again. I have data in memory. Here's my code for writing: namespace io = boost::iostreams; filename = "c:/test.bin.gz"; //My output file int size = 5000000; //Data size in bytes, ~5 MB //Create filtering_ostream io::filtering_ostream out; //Creates a filtering_ostream called out out.push(io::gzip_compressor()); //Assigns the gzip_compressor to out out.push(io::file_sink(filename)); //Assigns a file sink to out char* memblock = new char [size]; //This is my data. In reality memblock will have been created earlier and filled with real data out.write(memblock, size); //Do the writing delete[] memblock; //Clean up As written above the resulting file, c:/test.bin.gz, is corrupt. If I try to decompress it, either with gzip or winrar, I get an error message. However, if I instead set size = 4000000 (~4 MB) (slightly smaller), the resulting file works just fine. My problem therefore is that my actual size is 50 MB... Please help! Anders (not a real programmer)

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[Floating Point Utilities] where is the "nonfinite_num_facets.hpp"
by François Mauger 13 Apr '11

13 Apr '11

Hi As far as I understood, the Floating Point Utilities vault contribution by Johan R°ade has been integrated in the Boost official release. I've been using the "nonfinite_num_facets.hpp" header file for a few years within old Boost versions, directly extracted from the vault ZIP file released by Johan. Now, I can use the "fpclassify.hpp" file directly from the "boost/spirit/home/support/detail/math/" directory. Unfortunately I cannot find the "nonfinite_num_facets.hpp" file. Where can I find the "nonfinite_num_put/get" template class in say Boost 1.44 ? Maybe it has not been renamed in some other file or even not accepted at all... It is very useful for making my text and xml archives protable with NaNs and infinity support. Thanks for any hint or help. frc -- François Mauger Groupe "Interactions Fondamentales et Nature du Neutrino" NEMO-3/SuperNEMO Collaboration LPC Caen-CNRS/IN2P3-UCBN-ENSICAEN Département de Physique -- Université de Caen Basse-Normandie Adresse/address: Laboratoire de Physique Corpusculaire de Caen (UMR 6534) ENSICAEN 6, Boulevard du Marechal Juin 14050 CAEN Cedex FRANCE Courriel/e-mail: mauger(a)lpccaen.in2p3.fr Tél./phone: 02 31 45 25 12 / (+33) 2 31 45 25 12 Fax: 02 31 45 25 49 / (+33) 2 31 45 25 49

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[Boost Serialization] Cannot handle UTF-8 BOM bytes in XML file
by Tijmen van Voorthuijsen 13 Apr '11

13 Apr '11

Hi, I am using boost::archive::xml_woarchive to create XML files under Windows, Visual Studio 2008, and in wide character mode. The boost::archive::xml_woarchive does not write the UTF-8 three BOM bytes to the file and from http://en.wikipedia.org/wiki/Byte_order_mark I understand that this is all right since it is optional and even not recommended. Problems start when I want to edit the file in for example XML Notepad which adds the three BOM bytes when saving. Under Windows this seems normal behavior. Then parsing the XML file throws an exception through the boost::archive::xml_wiarchive. My question/recommendation: - Why can't the boost::archive::xml_serialization library not cope with the UTF-8 BOM bytes? - I would recommend that the library can handle XML UTF-8 files, with and without the three BOM bytes. Both are in fact valid UTF-8 XML files. I now check for the BOM bytes myself before I parse the ifstream in boost::xml_serialization and that works fine. Many thanks for your answer. Tijmen van Voorthuijsen

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Re: [Boost-users] Cycle detection in a directed graph with adjacency_matrix
by Jeremiah Willcock 13 Apr '11

13 Apr '11

On Tue, 12 Apr 2011, albert kao wrote: > After adding "boost::" before "graph_traits", the compile errors are: > adjacency_matrix_is_cyclic.cpp:9: error: expected class-name before ‘{’ token > adjacency_matrix_is_cyclic.cpp: In function ‘bool has_cycle(const Graph&)’: > adjacency_matrix_is_cyclic.cpp:26: error: ‘generic_dfs_v1’ was not declared in this scope > > adjacency_matrix_is_cyclic.cpp: > #include <iostream> > #include <boost/graph/graph_utility.hpp> > #include <boost/graph/adjacency_matrix.hpp> > > typedef boost::adjacency_matrix<boost::directedS> Graph; > typedef boost::graph_traits<Graph>::edge_descriptor edge_t; > > struct cycle_detector : public dfs_visitor_default > { > cycle_detector(bool & cycle): has_cycle(cycle) > { > } > void > back_edge(edge_t, const Graph &) > { > has_cycle = true; > } > bool & has_cycle; > }; > > bool > has_cycle(const Graph & g) > { > bool has_cycle = false; > cycle_detector vis(has_cycle); > generic_dfs_v1(g, vis); > return has_cycle; > } > > enum { A, B, C, D, E, F, N }; > const char* name = "ABCDEF"; > > int main(int argc, char *argv[]) > { > Graph g(N); > add_edge(B, C, g); > add_edge(B, F, g); > add_edge(C, A, g); > add_edge(C, C, g); > add_edge(D, E, g); > add_edge(E, D, g); > add_edge(F, A, g); > > std::cout << "vertex set: "; > boost::print_vertices(g, name); > std::cout << std::endl; > > std::cout << "edge set: "; > boost::print_edges(g, name); > std::cout << std::endl; > > std::cout << "out-edges: " << std::endl; > boost::print_graph(g, name); > std::cout << std::endl; > > std::cout << "has_cycle(g) " << has_cycle(g) << std::endl; > > return 0; > } You also need boost:: before dfs_visitor_default. You should also use boost::depth_first_search instead of generic_dfs_v1 (which is internal). -- Jeremiah Willcock

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Cycle detection in a directed graph with adjacency_matrix
by albert kao 13 Apr '11

13 Apr '11

Is it possible to detect any cycle in a directed graph with the adjacency_matrix of the Boost Graph Library? My test program has this compile errors: adjacency_matrix_is_cyclic.cpp:6: error: expected initializer before ‘<’ token adjacency_matrix_is_cyclic.cpp:9: error: expected class-name before ‘{’ token adjacency_matrix_is_cyclic.cpp:14: error: ‘edge_t’ has not been declared adjacency_matrix_is_cyclic.cpp: In function ‘bool has_cycle(const Graph&)’: adjacency_matrix_is_cyclic.cpp:26: error: ‘generic_dfs_v1’ was not declared in this scope $ cat adjacency_matrix_is_cyclic.cpp #include <iostream> #include <boost/graph/graph_utility.hpp> #include <boost/graph/adjacency_matrix.hpp> typedef boost::adjacency_matrix<boost::directedS> Graph; typedef graph_traits<Graph>::edge_descriptor edge_t; struct cycle_detector : public dfs_visitor_default { cycle_detector(bool & cycle): has_cycle(cycle) { } void back_edge(edge_t, const Graph &) { has_cycle = true; } bool & has_cycle; }; bool has_cycle(const Graph & g) { bool has_cycle = false; cycle_detector vis(has_cycle); generic_dfs_v1(g, vis); return has_cycle; } enum { A, B, C, D, E, F, N }; const char* name = "ABCDEF"; int main(int argc, char *argv[]) { Graph g(N); add_edge(B, C, g); add_edge(B, F, g); add_edge(C, A, g); add_edge(C, C, g); add_edge(D, E, g); add_edge(E, D, g); add_edge(F, A, g); std::cout << "vertex set: "; boost::print_vertices(g, name); std::cout << std::endl; std::cout << "edge set: "; boost::print_edges(g, name); std::cout << std::endl; std::cout << "out-edges: " << std::endl; boost::print_graph(g, name); std::cout << std::endl; std::cout << "has_cycle(g) " << has_cycle(g) << std::endl; return 0; }

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[Fusion] Adapting read-only fields of ADTs
by Sebastian Redl 12 Apr '11

12 Apr '11

Hi, How would I use BOOST_FUSION_ADAPT_ADT to turn an ADT that doesn't expose setters into a read-only sequence? In other words, what do I pass as set_exprN if there is no valid set expression? Sebastian

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a quick question regarding boost::bind, with a test case
by Littlefield, Tyler 12 Apr '11

12 Apr '11

Hello all: I have a quick question regarding boost::bind, as the subject line says. This isn't a very viable example, but it works well enough to show what I want. I have a callback I am using boost::bind to bind to, and I am passing a function object in as shown by the following code: #include <cstdio> #include <boost/bind.hpp> #include <boost/function.hpp> class Math { public: void Add(int a, int b, int c, boost::function<void (int)> printer); { printer(a+b+c); } }; void Printer(int p) { printf("%d\n", p); }How might I make this work? I am not sure how I can pass that as the fourth argument so that the function can be called like (1,2,3) etc. Also, in the actual problem I moved the function object to the first argument, (which just ment changing the prototype and actual function), but I still got errors. -- Thanks, Ty

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