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[Spirit/qi] parsing order, exact matches
by beet 02 Oct '13

02 Oct '13

Dear Boost-User list, I have modified the calc6-example from the Spirit docs, so that it uses double variables rather than integers. I have then added a number of mathematical functions. The rule for the unary functions (reduced to just sin and sinh here for readability) is: unary_function_rule_ = (string_("sin") > '(' > expression_rule_ > ')') | (string_("sinh") > '(' > expression_rule_ > ')') ; I would have expected the "sin" part of the rule to trigger only when there is a "sin" string, which is immediately followed by a '('. This works o.k. when the function in question really contains a sin(). However, when I pass a "sinh()", I get an error message that it failed parsing a "h(", so the "sin" part of the message has triggered. Changing the order of sinh and sin in the rule cures the problem. Still I would like to understand how I can make the sin-part of the rule only trigger for expressions like "sin(3.14)", but not for e.g. "sinh(2)". Thanks and best regards, Beet

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[Geometry] Triangulation?
by David Hynd 02 Oct '13

02 Oct '13

Hi, I want to use the boolean/CSG operations of the Geometry library of Boost, but I need the resultant polygons to be triangles (it's 3D data, by the way). Is there a way to achieve this with Boost? Or if not, what recommendations would you have for me? This is my first ever mailing list post, so forgive me if I didn't get it right :) Thanks, David

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[Iostreams] Zlib compression sometimes creates corrupt data on OSX
by Michael Jung 02 Oct '13

02 Oct '13

Hello, I’m having the following problem with my program: If I save data on OSX using a boost::iostreams::filtering_ostream with a boost::iostreams::zlib_compressor() the resulting file is sometimes corrupted. The following example code reproduces the problem: #include <fstream> #include <iostream> #include <vector> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/zlib.hpp> int main(int argc, char** argv) { if (argc != 2) return 1; std::ifstream file(argv[1]); if (file) { file.seekg(0, std::ios::end); std::streampos length = file.tellg(); file.seekg(0, std::ios::beg); std::vector<char> buffer1(length); std::vector<char> buffer2(length); file.read(&buffer1[0], length); { std::ofstream ofs("test.dat", std::ios_base::binary); boost::iostreams::filtering_ostream fos; fos.push(boost::iostreams::zlib_compressor()); fos.push(ofs); fos.write(&buffer1[0], length); } { std::ifstream ifs("test.dat", std::ios_base::binary); boost::iostreams::filtering_istream fis; fis.push(boost::iostreams::zlib_decompressor()); fis.push(ifs); fis.read(&buffer2[0], length); } std::cout << (buffer1 == buffer2 ? "equal" : "not equal") << std::endl; } } This piece of code reads a file that is specified as command line argument, compresses and saves it to “test.dat”, reloads and decompresses it and then compares the result with the content of the original file. Using it with two files linked below leads to the following output: $ ./bugtest example1_working.txt equal $ ./bugtest example1_not_working.txt not equal i.e. in the second case the compression creates corrupt data. I verified that the problem is in the compression part by trying to decompress test.dat on Linux using zlib-flate which gives an error (incorrect data check). If I compress the file manually on Linux using zlib-flate and decompress it on OSX with code similar to the above, the input file is reproduced correctly. The two files used above are save files of my software. You can download them from: http://neptun.iup.uni-heidelberg.de/files/example1_working.txt http://neptun.iup.uni-heidelberg.de/files/example1_not_working.txt Another pair of files with the problem is: http://neptun.iup.uni-heidelberg.de/files/example2_working.txt http://neptun.iup.uni-heidelberg.de/files/example2_not_working.txt I haven’t been able to find out what is special about the ones causing the problem, so I just put them up as they are. The files are quite similar, but show a few differences on every (or almost every?) line. If needed, I can create other pairs of files showing the same problem. I compiled the above code in the following way: c++ -stdlib=libc++ -std=c++11 test.cpp -I /Users/michael/projects/boost-svn-build/include/ -c c++ -stdlib=libc++ -std=c++11 -o test test.o /Users/michael/projects/boost-svn-build/lib/libboost_iostreams.a -lz The boost libraries were built from svn as follows: ./bootstrap.sh --prefix=../boost-svn-build --with-libraries=iostreams --with-toolset=clang ./b2 -j6 link=static toolset=clang cxxflags="-std=c++11 -stdlib=libc++" linkflags="-stdlib=libc++" install Clang version is: “Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)” I am running OS X 10.8.2. The same files are compressed correctly with the above code on Linux, compiled with GCC 4.6.3. I think this problem might be a bug in boost or maybe also in the llvm libraries (c.f. https://svn.boost.org/trac/boost/ticket/8150 , which looks like a similar problem). Compiling boost with zlib 1.2.8 instead of using zlib 1.2.5, which is shipped with OSX, leads to the same problem. Both Boost 1.54.0 and the svn version are affected. Should I create a ticket for this on the bug tracker? Or is this just me using the library incorrectly?? Best regards, Michael -- Michael Jung michaeljung(a)mailhaven.com

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virtual memory exhausted: cannot allocate memory
by rahul baruah 02 Oct '13

02 Oct '13

Has anyone found solution to the problem. When i include many statemachine, i get this error while compile. Urgently need help Regards Rahul

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Boost.Coroutine + objects
by Van Pers 02 Oct '13

02 Oct '13

Hello guys, I am using Boost Coroutines but I would like to use them in a Objected-Oriented way. So, I tried to rewrite parallel.cpp (boost/libs/coroutine/example) using the example functions like class methods, but it did not work. This is my code, anybody can help me? My code: typedef boost::coroutines::coroutine< void() > coroutine_t; class Abc{ public: void first( coroutine_t::caller_type & self) { std::cout << "started first! "; for ( int i = 0; i < 10; ++i) { self(); std::cout << "a" << i; } } void second( coroutine_t::caller_type & self) { std::cout << "started second! "; for ( int i = 0; i < 10; ++i) { self(); std::cout << "b" << i; } } void third(){ coroutine_t c1( boost::bind( first, _1) ); coroutine_t c2( boost::bind( second, _1) ); while ( c1 && c2) { c1(); std::cout << " "; c2(); std::cout << " "; } } }; int main( int argc, char * argv[]) { Abc* myabc = new Abc(); myabc->third(); std::cout << "\nDone" << std::endl; return EXIT_SUCCESS; } Thank you, Van

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returning range adaptor generator
by Nick Stokes 02 Oct '13

02 Oct '13

What should be the return type for a function that returns an adapted range? E.g. template<class Range> xxx getIndirected( const Range& r ) { return r | boost::adaptors::indirected; } The use case being, providing a API with these little useful helpers without forcing the user to know about Boost.Range at all. Like so: #include <myapi.hpp> #include <boost/foreach.hpp> LegacyPointerContainers f; // contains Foo pointers BOOST_FOREACH( Foo& f, TraverseFoo( f ) ) { } /// where in myapi.hpp xxx TraverseFoo( LegacyPointerContainers& f ) { return getIndirected( makeRange(f) ) ; } PS: This is all C++03. No autos. Thanks Nick

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BGL: write_graphviz_dp taking in count values of dynamic_properties
by Pablo Madoery 30 Sep '13

30 Sep '13

Hi, I have the following code that print a graph taking in count values of dynamic_properties: #include<iostream> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/graphviz.hpp> using namespace std; using namespace boost; struct VertexInfo { int id; }; struct EdgeInfo { double weight; bool enable; }; typedef adjacency_list<listS, vecS, bidirectionalS, VertexInfo, EdgeInfo> Graph; int main() { //////////////////////////////////////////////////////////////////////////////////////////// Graph graph; Graph::vertex_descriptor a = add_vertex(graph); Graph::vertex_descriptor b = add_vertex(graph); Graph::vertex_descriptor c = add_vertex(graph); Graph::vertex_descriptor d = add_vertex(graph); Graph::edge_descriptor e1 = (add_edge(a, b, graph)).first; Graph::edge_descriptor e2 = (add_edge(a, b, graph)).first; Graph::edge_descriptor e3 = (add_edge(b, c, graph)).first; Graph::edge_descriptor e4 = (add_edge(c, a, graph)).first; Graph::edge_descriptor e5 = (add_edge(c, a, graph)).first; Graph::edge_descriptor e6 = (add_edge(c, d, graph)).first; graph[e1].weight = 5; graph[e2].weight = 10; graph[e3].weight = 6; graph[e4].weight = 14; graph[e5].weight = 2; graph[e6].weight = 3; graph[e1].enable = true; graph[e2].enable = false; graph[e3].enable = true; graph[e4].enable = false; graph[e5].enable = true; graph[e6].enable = false; ofstream ofs("graph.dot"); dynamic_properties dp; dp.property("node_id", get(vertex_index, graph)); dp.property("label", get(&EdgeInfo::weight, graph)); dp.property("taillabel", get(&EdgeInfo::enable, graph)); write_graphviz_dp(ofs, graph, dp); cout << "fin" << endl; return 0; } /////////////////////////////////////////////////////////////////////////////////// there is a property called "enable" in the edges that I print in the tails of the arrows. But what i really want is that when enable = false the style of the arrow be different ("invis" for example). How can i do that? Thanks!

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Tree traversal in boost spirit
by Olivier Austina 30 Sep '13

30 Sep '13

Hi, I would like to traverse a parsed tree. The parsing is fine. I am using this tutorial : http://en.highscore.de/cpp/boost/parser.html This is the instruction used for parsing : boost::spirit::parse_info<> pi = boost::spirit::parse(data.c_str(), g, boost::spirit::space_p); I would like to traverse the parsed tree like classical tree (Pre-order, In-order, Post-order) to have data in a given order. Any suggestion will be appreciated. Thank you. Regards Olivier

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[Graph] Stable topological_sort? And topological_sort woes in general.
by Dominique Devienne 30 Sep '13

30 Sep '13

I'm sorting a set of SQL tables with foreign-key constraints. I'm currently using BGL's topological_sort for that, but struggled quite a bit because: * I didn't manage to adapt my own data-structure, so ended-up sorting indices to an array of my entries, and generated the edges as indice pairs on in this array (like the doc example). * Discovered via unit testing topological_sort didn't like vertices with no associated edges (a "free standing" table, with no relationships), so I'm "manually" removing those. * Discovered via unit testing topological_sort didn't like "duplicate" edges (a table with several columns referencing the same parent table), so I'm also manually removing those too. I confess to not trying to fully understand the BGL, nor to have read the book. Given what I was trying to do, as outlined above, was using topological_sort really the best tool for the job? What are the alternatives, if any? For my own education, why "singleton" vertices and duplicate edges make topological_sort break? But what brings me here today is to ask about a "stable" topo-sort. When I have several vertices which are all "unrelated" and thus sort at the same "level", topological_sort does not preserve the relative order of those "sibling" vertices, and I'd like something fully deterministic that I can count on. What are my options? Does BGL provide something like this? As a concrete example, given tables A, B, C, with A depending on both B, C, topological_sort gives me the C, B, A order (or adding the "levels" (C, B), A), while I'd like B, C, A, i.e. preserving the relative order of B, C. Thanks for any insight. --DD PS: What about getting a topo-sort, but which also gives you the "levels", so that you can schedule those independent tasks (on each level) in parallel for example? Does BGL provide something like this? I've done it in the past with the help of the Sedgewick book, but I see a single topo-sort in BGL.

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[Serialization] How do I make boost::serialization work with std::shared_ptr?
by Arman Schwarz 30 Sep '13

30 Sep '13

Hi everyone, this is my first post so I apologies if I got some of the housekeeping wrong. I did my best. I also realise that this is likely to be a common question but all the responses I could find on Stackoverflow (among others) were related to older implementations of boost. My understanding is that Boost 1.54 is supposed to support `std::shared_ptr`. To illustrate the issue I am having, suppose we want to serialize a class containing a vector of shared pointers, along with a static `load` function that will build the class from a file and a `save` function that will store the instance to a file, and suppose that we can't just use the `serialize` member function for whatever reason (this particular example doesn't really illustrate such a case but in my code I can't use the `serialize` member function so this example doesn't use it either): #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/serialization/vector.hpp> #include <boost/serialization/shared_ptr.hpp> #include <fstream> #include <memory> #include <vector> class A { public: std::vector<std::shared_ptr<int>> v; void A::Save(char * const filename); static A * const Load(char * const filename); ////////////////////////////////// // Boost Serialization: // private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int file_version) {} }; // save the world to a file: void A::Save(char * const filename) { // create and open a character archive for output std::ofstream ofs(filename); // save data to archive { boost::archive::text_oarchive oa(ofs); // write the pointer to file oa << this; } } // load world from file A * const A::Load(char * const filename) { A * a; // create and open an archive for input std::ifstream ifs(filename); boost::archive::text_iarchive ia(ifs); // read class pointer from archive ia >> a; return a; } namespace boost { namespace serialization { template<class Archive> inline void save_construct_data( Archive & ar, A const * t, unsigned const int file_version ) { ar << t->v; } template<class Archive> inline void load_construct_data( Archive & ar, A * t, const unsigned int file_version ) { ar >> t->v; } } } int main() { } Why doesn't this code compile? What am I doing wrong here? The error message states that 'serialize' is not a member of 'shared_ptr'. Why am I am getting this message?

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