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

[Polygon] using polygon for linesegment intersection
by gast128 26 Apr '11

26 Apr '11

Hello all, I was trying to use the Boost.Polygon library to test for line segment intersection. I define 2 polygons (lines) and use the Boolean operators of the polygon_set. However it gives an empty result: void TestBoostPolygonIntersectLineSegment() { using namespace boost::polygon::operators; typedef boost::polygon::polygon_data<int> Polygon; typedef boost::polygon::point_data<int> Point; typedef boost::polygon::polygon_set_data<int> PolygonSet; typedef std::vector<Polygon> PolygonVector; Point aPts1[] = { Point(0, 0), Point(10, 0) }; Point aPts2[] = { Point(5, 5), Point(5, -5) }; Polygon line1(aPts1, aPts1 + count_array(aPts1)); Polygon line2(aPts2, aPts2 + count_array(aPts2)); //both share point (5, 0) assert(boost::polygon::contains(line1, Point(5, 0))); assert(boost::polygon::contains(line2, Point(5, 0))); //eh..., expected it to be 1, but anyway assert(boost::polygon::size(line1) == 2); assert(boost::polygon::size(line2) == 2); PolygonSet ps1; PolygonSet ps2; ps1.insert(line1); ps2.insert(line2); PolygonSet ps3 = ps1 & ps2; //gives no result if (!ps3.empty()) //<--- { PolygonVector vec1; ps3.get(vec1); } } Also the documentation states that the size function gives the number of edges, but a line has only 1 edge: assert(boost::polygon::size(line1) == 2); //not 1?

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[MultiArray][Variant][Serialization]
by Johann Goetz 26 Apr '11

26 Apr '11

I am trying to serialize a multi_array object but keep the dimensions variable (I only want to support 1, 2 and 3 dimensions). So I attempted to create a Variant of the three multi_array's and the corresponding serialize methods as shown below, but I am getting a run-time error when for the 1-Dimensional case. Here is the minimal code example I came up with that shows the problem. I am using the boost SVN trunk as of this posting (April 26, 2011). Maybe I am implementing the load() method incorrectly for the multi_array. Should there be a special case for when Dim == 1? Running the program, I get the following error: > ./test test: /home/goetz/local/src/boost-trunk/boost/multi_array/multi_array_ref.hpp:487: boost::multi_array_ref<T, NumDims>& boost::multi_array_ref<T, NumDims>::operator=(const ConstMultiArray&) [with ConstMultiArray = boost::multi_array<float, 1ul>, T = float, long unsigned int NumDims = 1ul, boost::multi_array_ref<T, NumDims> = boost::multi_array_ref<float, 1ul>]: Assertion `std::equal(other.shape(),other.shape()+this->num_dimensions(), this->shape())' failed. Aborted (core dumped) /// Begin File: multiarray-variant-serialize.cpp /** * gcc compile command: * g++ multiarray-variant-serialize.cpp -otest -lboost_serialization * * to run: * ./test **/ #include <fstream> #include <string> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/array.hpp> #include <boost/serialization/variant.hpp> #include <boost/multi_array.hpp> typedef boost::variant< boost::multi_array<float,1>, boost::multi_array<float,2>, boost::multi_array<float,3> > multi_array_variant; namespace boost { namespace serialization { template<class Archive, typename T, size_t Dim> void save( Archive& ar, const boost::multi_array<T,Dim>& ma, const unsigned int version) { ar << boost::serialization::make_array(ma.shape(), Dim); ar << boost::serialization::make_array(ma.data(), ma.num_elements()); } template<class Archive, typename T, size_t Dim> void load( Archive& ar, boost::multi_array<T,Dim>& ma, const unsigned int version) { typedef typename boost::multi_array<T,Dim>::index index_t; boost::array<index_t,Dim> shape; ar >> boost::serialization::make_array(shape.data(), Dim); ma.resize(shape); ar >> boost::serialization::make_array(ma.data(), ma.num_elements()); } template<class Archive, typename T, size_t Dim> void serialize( Archive & ar, boost::multi_array<T,Dim>& ma, const unsigned int version) { split_free(ar, ma, version); } } /// namespace boost::serialization } /// namespace boost int main() { boost::multi_array<float,1> a1(boost::extents[5]); /// replacing the above line with either of the following two /// works as anticipated. Only the 1-Dimension breaks /// breaks at run-time. //boost::multi_array<float,2> a1(boost::extents[5][5]); //boost::multi_array<float,3> a1(boost::extents[5][5][5]); multi_array_variant a3 = a1; multi_array_variant a4; std::string filename = "archive.tmp"; { std::ofstream ofs(filename.c_str()); boost::archive::text_oarchive oa(ofs); oa << a3; } { std::ifstream ifs(filename.c_str()); boost::archive::text_iarchive ia(ifs); ia >> a4; } return 0; } /// EOF -- Johann T. Goetz

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[Review] Boost.Convert library is ongoing
by Edward Diener 26 Apr '11

26 Apr '11

Since there have been no reviews of this library yet, this is another reminder that formal review of the Boost.Convert library by Vladimir Batov is ongoing and ends on May 2. If you have felt that lexical_cast is not flexible enough for use, please take a look at this library and review it. *************** * Its Purpose * *************** The library builds on the past boost::lexical_cast experience, then takes those conversion-related ideas further to suit better today's applications and programing needs. It still offers simple, minimal interface, familiar conversion behavior and additionally provides: * throwing and non-throwing conversion-failure behavior; * support for the default/fallback value to be returned when conversion fails; * two types of the conversion-failure check - basic/simple and better/safe; * formatting support based on the standard std::streams and std::stream-based manipulators (like std::hex, std::scientific, etc.); * support for different locales; * support for boost::range-compliant char and wchar_t-based containers; * no DefaultConstructibility requirement for the Target/Destination type; * consistent framework to uniformly incorporate any type-to-type conversions, extensibility and additional room to grow. With its present support for string-to-type and type-to-string conversions it is an essential tool for applications making extensive use of configuration or MS-Windows-Registry-style files or having to process/prepare considerable amounts of data in, say, XML, etc. More so, it is easily extendable to accommodate, specialize and uniformly deploy new user-defined type-to-type conversions. ******************* * Where to get it * ******************* You can get the library, using Subversion, from https://svn.boost.org/svn/boost/sandbox/convert. The HTML documentation is part of the distribution and can be found at libs/convert/index.html in the distribution above. ******************** * Writing a review * ******************** The reviews and all comments should be submitted to the developers list, and the email should have "[convert] Review" at the beginning of the subject line to make sure it's not missed. Please explicitly state in your review whether the library should be accepted. The general review checklist: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Edward Diener, Review Manager

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boost.serializaion off by one error
by . lai 26 Apr '11

26 Apr '11

Hi all: Recently i come up with a problem in boost.serializaion when serializing primitives. with the following code, the output is: 1 0 input stream error But what i expect is: 1 input stream error test code: #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <sstream> #include <iostream> int main(int argc, char *argv[]) { std::stringstream stream; { boost::archive::text_oarchive oa(stream); int i = 1; oa << i; } try { boost::archive::text_iarchive ia(stream); int i = 0; ia >> i; std::cout << i << std::endl; i = 0; ia >> i; std::cout << i << std::endl; i = 0; ia >> i; std::cout << i << std::endl; }catch(boost::archive::archive_exception& ex){ std::cout << ex.what() << std::endl; } return 0; } the exception is threw in /usr/include/boost/archive/basic_text_iprimitive.hpp: basic_text_iprimitive:: template<class T> void load(T & t) { if(! is.fail()){ is >> t; //HERE SHOULD TEST IF READ IS SUCCUSSFULL return; } boost::serialization::throw_exception( archive_exception(archive_exception::input_stream_error) ); } In the function basic_text_iprimitive::load(T t), when T is a primitive, and is >> t fails, there is no exception threw, where there should. The same problem exsits in binary archive and text archive. Is it a bug or a feature? would it be fixed?

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Why can't I use boost graph write_graphviz with OutEdgeList=listS and VertexList=listS
by Allan Nielsen 25 Apr '11

25 Apr '11

Hi Why can't I compile the following simple app. If I changes listS to vecS every thing works just fine. (I'am using boost 1.46.1 and gcc 4.4.5) #include <iostream> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/graphviz.hpp> int main(int argc, const char *argv[]) { boost::adjacency_list< boost::listS, boost::listS, boost::bidirectionalS > g; boost::write_graphviz(std::cout, g); return 0; } Best regards Allan W. Nielsen

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[Date Time] time_duration Subsecond Truncation After Construction
by Hossein Haeri 24 Apr '11

24 Apr '11

Dear all, [GCC 4.5.1, MinGW32, WinXPSP3, Boost 1.46.0] I have a simple templatised class which stores references to the passed timestamps. I also have a helper function to ease some syntax awkwardness as follows: template<typename Timestamp> struct Container { Container(const Timestamp& t): t_(t) { cout << "In ctor, t = " << to_simple_string(t) << ", t_ = " << to_simple_string(t_) << endl; } template<typename T1, typename T2> void f(const T1&, const T2&) const { cout << "In f(), t_ = " << to_simple_string(t_); } const Timestamp& t_; }; template<typename Timestamp> Container<Timestamp> container(const Timestamp& t) {return Container<Timestamp>(t);} It happens that, in my release build, the subsecond resolution gets truncated once the passed time duration is stored in my Container. So, for the following code snippet for example container(milliseconds(400)).f(1.1, 2); I get the following nonsense output: In ctor, t = 00:00:00.400000, t_ = 00:00:00.400000 In f(), t_ = 00:00:00 Does anyone here know what's going on? TIA,--Hossein

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[filesystem] get relative path from recursive_directory_iterator
by Ivan Sorokin 24 Apr '11

24 Apr '11

Hello! I'm using boost::filesystem v3. Currently recursive_directory_iterator returns absolute path. So the program for (fs::recursive_directory_iterator it("/home/ivan"); it != fs::recursive_directory_iterator(); ++it) std::cout << *it << std::endl; may output /home/ivan/somedir/1.txt /home/ivan/somedir/2.txt But what I want is something like: ./somedir/1.txt ./somedir/2.txt I use function naive_uncomplete described in https://svn.boost.org/trac/boost/ticket/1976 fs::path base = "/home/ivan"; for (fs::recursive_directory_iterator it(base); it != fs::recursive_directory_iterator(); ++it) std::cout << naive_uncomplete(*it, base) << std::endl; Is there any plans to include this function is boost? Is there any possibility to get relative paths using only functions from boost?

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How to handle blank space in parsing??
by Ramon F Herrera 24 Apr '11

24 Apr '11

Hello all, Boost::regex has been a Godsent to me. Before it, I performed any parsing with Perl. Now I am becoming comfortable with the regex package. (a million thanks to the folks responsible for it, and for Boost in general, btw) My only problem is spaces. I design typical mini computer language syntaxes, for example: Table[1, 4] = Value AND Array[8, 4] My initial approach was to get rid of all spaces before parsing (I recall being taught ages ago that the FORTRAN compiler does just that). Such strategy works in some cases, but the above line would become: Table[1,4]=ValueANDArray[8,4] Which is obviously bad news. I solved this particular case with this syntax: Table[1, 4] = Value && Array[8, 4] My latest "language" looks like this and has the same problem described above: Table rows [1758, 1904, 2053, 2201, 2345, 2497] Table cols [372, 880, 1336, 1756, 2083, 2439] I guess I could insert a colon or something between the first two words, but I am sure there has to be a better way. TIA, -RFH

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[Test] muti-file-test modules and standalone library linking
by Jan Blunck 24 Apr '11

24 Apr '11

Is there a way to write a multi-file-test module in a way that allows me to link it to dynamic and/or a static library version? Currently the software is able to link against a static or a dynamic variant of the boost libraries. If I want to use the boost test framework there seems to be no way how I can build against both variant without changing defines. For the dynamic library variant I would need to define -DBOOST_TEST_ALTERNATIVE_INIT_API while for the static variant I need to use the traditional API. The problem is that the linker in the end decides what library it is linking against. Using the boost/test/included/* variant of the framework does not seem to be supported in a multi-file-test setup. Is there any way I can make this work? Thanks, Jan Jan Blunck Performance Architect RTS Realtime Systems Software GmbH, Rembrandtstrasse 13, D-60596 Frankfurt am Main T: +49.69.61009.0 / F: +49.69.61009.181 Sitz: Frankfurt am Main - HRB 84467 Amtsgericht Frankfurt am Main Geschäftsführer: Steffen Gemuenden, Mark van Vugt www.rtsgroup.net This email and any attachments are for the exclusive and confidential use of the intended recipient. If you are not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, please do not read, distribute or take action in reliance upon this message. If you have received this in error, please notify me immediately by return email and promptly delete this message and its attachments from your computer system.

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boost graph in_edges
by Peter Neher 23 Apr '11

23 Apr '11

hi, i'm using the boost graph library and i'm trying to find the incident edges of one vertex of the following graph: | typedef boost::adjacency_list< boost::vecS, // The container used for egdes boost::vecS, // The container used for vertices boost::bidirectionalS, // bidirectional edges Vertex, // The type that describes a Vertex. Edge // The type that describes an Edge > Graph;| if i try to find the incident edges now, the message "Interpolation failed" is printed. any suggestions? here the code to find the incident edges: |Graph::in_edge_iterator edgeIt, edgeEnd; tie(edgeIt, edgeEnd) = in_edges(vID, m_Graph);| thanks in advance, peter

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