October 2010 - Boost-users - lists.preview.boost.org

Function pointer to in/out_degree in BGL
by langermatze 27 Oct '10

27 Oct '10

Hi, I have a question regarding the boost graph library. I'd like to write a set of depth first search visitors to determine the maximum in/out-degree of a graph. The code should look pretty similar for both cases except for the function call to get the property of the visited node. boost:in_degree(node_id, graph) vs. boost:out_degree(vertexId, graph) At first glance the function signature pretty much the same, maybe: template<class Graph> graph_traits<Graph>::degree_size_type function(graph_traits<Graph>::vertex_descriptor u, const Graph &g) When looking at the BGL headers however, things seem to be a bit more complex, though. I tried to implement a generic dfs_visitor taking a general function pointer to get the in/out degree property of the visited node but I couldn't work out the type of the function pointer to be passed. All my attemtps failed badly. Hopefully, there is anybody on this list who has a better understanding of this business and could provide some help. Any hints/comments are appreciated! Thank you so much, Matthias -- View this message in context: http://boost.2283326.n4.nabble.com/Function-pointer-to-in-out-degree-in-BGL… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost::thread within a dll
by Matheus Araújo Aguiar 27 Oct '10

27 Oct '10

Hello list, I'm facing some problems with a dll that uses boost::thread, boost::mutex and boost::condition_variable. Currently i am clueless about what is causing the problem and wanted to know if it is ok to use boost::thread and the others aforementioned within a dll. Basically, in a singleton in the dll, some threads are created and consume tasks (wrapped with boost::bind) from a queue, using boost::mutex to avoid concurrency problems and boost::condition_variable to sleep and wake, depending on emptiness of the task queue. Sorry for the brief and rapid description of my problem. Could anyone point to me if using these might cause problems with dlls? Thank you all, -- Matheus Araújo Aguiar Computer Scientist matheus.pit(a)gmail.com

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Boost XML compile problem XML_SAVE_FORMAT
by Kraus Philipp 27 Oct '10

27 Oct '10

Hello, I would like to use the Boost XML structure. Is the package within the SVN compatible under OSX, Linux and MS Windows? I'm using it at the moment under OSX, but I must use the code later under Linux and Windows. Under OSX I use the libxml2 Library, but in the boost/xml/dom/io.hpp I get an compile error on line 36 "xmlSaveCtxt *ctx = xmlSaveToIO (detail::stream_write_callback, detail::stream_close_callback, sb, enc, XML_SAVE_FORMAT);" the XML_SAVE_FORMAT isn't defined (message: not declared in this scope). My problem is at this time, that I must parse XML data of a stream objekt on-fly and extract some nodes (and this with a cross-plattform library). Is this the correct way to do the parsing with Boost XML? Thanks Phil

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[geometry][ggl] boost array adapted mechanism
by alfC 27 Oct '10

27 Oct '10

The documentation of GGL (Generic Geometry Library) is still scattered and hard to follow. As usual the first test I do on a library is to see how well it can be adapted to existing code. GGL seems to be able to adapt c_arrays and tuples as nD points. I was wondering if boost::array and fusion::vector can be adapted as well. The manual says it is but the header file boost/geometry/geometries/adapted/boost_array_as_ring.hpp doesn't seem to have that purpose. In the following example, p4 doesn't work as a point #include<boost/geometry/geometry.hpp> #include<boost/geometry/geometries/cartesian3d.hpp> #include<boost/geometry/geometries/adapted/boost_array_as_ring.hpp> #include <boost/geometry/geometries/adapted/c_array_cartesian.hpp> #include <boost/geometry/geometries/adapted/tuple_cartesian.hpp> #include<iostream> int main(){ using namespace boost::geometry; point<double, 3, cs::cartesian> p1(1,2,3); double p2[3] = {4,5,6}; boost::tuple<double, double, double> p3(7,8,9); boost::array<double, 3> p4={{10,11,12}}; std::clog << distance(p1,p2) << std::endl; std::clog << distance(p2,p3) << std::endl; std::clog << distance(p3,p4) << std::endl; return 0; } In other words, why there is not boost/geometry/geometries/adapted/boost_array_cartesian.hpp ? And it indeed this adaptation of boost::array is not included in the library, what steps should I follow to make a boost::array adapted to GGL? Thank you, Alfredo

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[boostbook+quickbook] : A way to write latex math
by Bo Jensen 27 Oct '10

27 Oct '10

This is just some info, that might interest others : I just recently discovered : http://www.mathjax.org which is quite nice for writing math equations. I use quickbook for my documentation. Fortunately it is very easy to incorporate MathJax into quickbook, so you can write : ''' <my-latex-math>some formula in latex</my-latex-math> ''' I just added the following to the stylesheet : <xsl:template name="system.head.content"> <script type="text/javascript" src="somepath/MathJax/MathJax.js"></script> </xsl:template> <xsl:template match="my-latex-math"> <xsl:value-of select="."/> </xsl:template> I should say I am a totally newbie to xsl stylesheets, so I might be doing something bad, never the less it works fine :-)

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[math] round to fraction
by gast128 27 Oct '10

27 Oct '10

Hello all, I couldn't find a functionality like 'round to fraction', which would try round a floating point value to its nearby fraction portion: round2fraction(1.4, 0.5); -> 1.5 round2fraction(1.8, 0.5); -> 2.0 round2fraction(1.0, 0.5); -> 1.0 round2fraction(1.25, 0.5); -> 1.5 round2fraction(-1.6, 0.5); -> -1.5 We have here a private implementation, but this is probably not as optimised as those numerical guru's can come up with. Is this a good suggestion to add to Boost.Math or overkill?

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boost with Visual Studio 2005 (VC8) and 2010 (VC10)
by andrew.marlow＠uk.bnpparibas.com 27 Oct '10

27 Oct '10

I am using boost 1.42 and am considering moving to 1.44.0. I see from the release notes that 1.44.0 has improved support for VC10 especially with the TR1 parts. That's good because I would also like to move to VC10, I am currently on VC8 (i.e. 2005). Please don't laugh. The move to boost 1.44.0, if it happens, will most likely happen before the move to VC10. So does boost 1.44.0 work with VC8? It is not in the supported compilers list. Regards, Andrew Marlow ___________________________________________________________ This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and delete this e-mail. Any unauthorised copying, disclosure or distribution of the material in this e-mail is prohibited. Please refer to http://www.bnpparibas.co.uk/en/information/legal_information.asp?Code=ECAS-… for additional disclosures.

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getting started tutorial: link your program to a boost library
by Oliver Adams 27 Oct '10

27 Oct '10

Hi, I've just installed boost and have been going through the getting started guide (for unix variants). I am having problems with the section that discusses how to link your program to a boost library, using boost.regex as an example. $ c++ -I path/to/boost_1_44_0 example.cpp -o example \ ~/boost/stage/lib/libboost_regex-gcc34-mt-d-1_36.a That file does not exist. In fact there is no boost directory in my home directory. I'm not sure if running ./bjam install worked. It did build for a while, but the last few lines of output were: ...failed updating 60 targets... ...skipped 12 targets... ...updated 8866 targets... there seem to be a bunch of object files in /usr/local/boost_1_44_0/bin.v2/libs/regex/build/gcc-4.4.5/release/threading-multi unfortunately, when I try and use those files I end up getting: collect2: ld returned 1 exit status Any help's appreciated, Oliver

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[variant] assignment with possible casting
by Brian Budge 26 Oct '10

26 Oct '10

Hi all - I have a struct which holds parameter name/value pairs. The incoming data is not always exactly the same, as it's read from different sources, so sometimes I might have a parameter named "scale" which is a uint8_t, and other times "scale" is a uint32_t or int32_t. When I try to get() the data, I grab it as uint32_t, but it may be stored in the variant as an int32_t. We're using get<uint32_t> in that case, and this fails if the variant holds int32_t. On the other hand, since the variant can contain vector and matrix values, we can't simply use operator = for automatic casting (compile time errors). We don't expect to do any non-trivial casts (i.e. matrix to float or vice-versa). Are there any helper visitors or anything in the boost::variant library to assist with this, or do we need to write our own visitor? Code below. Thanks, Brian struct ParameterDesc { typedef boost::variant<bool, int32_t, uint32_t, float, Vec2f, Vec3f, Vec4f, Mat2f, Mat3f, Mat4f, std::string> ParamValue; typedef google::dense_hash_map<std::string, ParamValue> ParamMap; typedef ParamMap::iterator ParamMapIter; typedef ParamMap::const_iterator ParamMapCIter; std::string type; std::string name; ParamMap params; template <typename T> bool get(const std::string &name, T &val, const T &defaultValue) const { ParamMapCIter p_it; if( (p_it = params.find(name)) == params.end() ) { val = defaultValue; return false; } val = boost::get<T>(p_it->second); return true; } template <typename T> void get(const std::string &name, T &val) const { ParamMapCIter p_it; if( (p_it = params.find(name)) == params.end() ) { throw ParamException("couldn't find parameter with field name: " + name); } val = boost::get<T>(p_it->second); } ParameterDesc() { params.set_empty_key("__EMPTY__"); } };

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[asio] Error running as Windows service; runs fine from console
by Evan Burkitt 26 Oct '10

26 Oct '10

I have a Windows application that uses ASIO to implement a server that listens on a TCP port. When I run it from the console it starts and operates without error. When I start the same application as a Windows service (it's written to be run either way) my call to boost::asio::ip::tcp::acceptor::async_accept() immediately calls the passed accept handler to report error 995: "The I/O operation has been aborted because of either a thread exit or an application request". This occurs even when I run the service under the same account as the logged-in user. I know I'm a bit sketchy with the details of my implementation, but I think this is at least as likely to be some Windows weirdness as an ASIO problem per se. I'm hoping someone else has encountered and fixed this problem before. Thanks. -evan

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