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accessing last element in boost multi-index
by Mahmood Naderan 19 Mar '13

19 Mar '13

Hi Using boost::multiindex, I am looking for a method to retrieve the the last element. Something like rbegin(). As I looked in to the manual page, http://www.boost.org/doc/libs/1_53_0/libs/multi_index/doc/tutorial/basics.h…, I could not find such function. Problem with end() is that it points to the last_element+1 which is null. Regards, Mahmood

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[graph] problem with weight_map ? (brandes_betweenness_centrality)
by The Maschine 19 Mar '13

19 Mar '13

Hi all, I think I've got a problem with the way I use the weight property map in my betweenness_centrality (and maybe other locations too). I've got a graph like that: typedef boost::property<boost::edge_weight_t, double> EdgeWeightProperty; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, VertexProperties, EdgeWeightProperty> unGraph; And I add edges with weights like that (simplified): EdgeWeightProperty weight = getWeight(a, b); // 0f ... 2.0f std::pair<unGraph::edge_descriptor, bool> e = boost::add_edge(a, b, weight, m_ugraph); Than I try to do the brandes_centrality_betweenness: std::vector< double > v_centrality_vec(boost::num_vertices(m_ugraph), 0.0); boost::brandes_betweenness_centrality(m_ugraph , boost::centrality_map(boost::make_iterator_property_map(v_centrality_vec.begin(),boost::get(boost::vertex_index, m_ugraph),double())).vertex_index_map(get(boost::vertex_index, m_ugraph)).weight_map(get(boost::edge_weight, m_ugraph)) ); But I get crazy results... 1) I have checked by hand that my "getWeight" (my weights) are OK. 2) I have set _ALL_ weights to 1.0 (almost as if brandes was using BFS internally), Again I get the _SAME_ crazy results! So there is something wrong with the way Im using the weight_map. What am I missing?? Best, Tasos

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[regex] using partial_match?
by Armel Asselin 19 Mar '13

19 Mar '13

[boost 1.53.0] Hello, I'd like to find in a stream of text either "abcd" or "ab". The text is not bounded in size, so I think I should use partial_match. However I present it the following text: "hello abc<cut_here>d, how are you?" it reports to find "ab" and does not wait for the second block to be appended. #include "boost/regex.hpp" int main(int argc, char* argv[]) { boost::regex re ("abcd|ab"); std::string str ("hello abc"); boost::match_results<std::string::const_iterator> results; bool found = boost::regex_search (str.cbegin(), str.cend(), results, re, boost::regex_constants::match_partial); if (!found || results[0].matched) printf("problem...\n"); return 0; } Am I doing something wrong? I see in the specification that "Specifies that if no match can be found, then ....", isn't this specification flowed? should not it be "if the regular expression engine needs to check past the end of the block of text, and the start matches partially, ...." ? I hope I am wrong and there are good flags to pass.... Regards Armel

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[range] contiguous iterators
by Stefan Strasser 19 Mar '13

19 Mar '13

Hi everyone, is there any way to generically determine at compiletime whether an iterator or a boost range refers to contiguous memory? i.e. &*(it+1) == (&*it)+1 some type trait like is_contiguous<T *>::value == true is_contiguous<vector<T>::iterator>::value == true is_contiguous<std::list<T>::iterator>::value == false ?

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Android: segfault while writing to archive during Serialization
by wespaugh 18 Mar '13

18 Mar '13

Greetings! New to discussion, apologies in advance for any inadvertent misuse of terminology / standards. (also, I tried e-mailing this post directly last night, but it doesn't appear to have shown up, yet. double-apologies if double-post). I'm trying to port my project, which involves some serialization code, to Android. I followed instructions to build boost 1.49 found here: https://github.com/MysticTreeGames/Boost-for-Android and can successfully compile my application using crystax NDK r7 (gcc 4.5.3) , and link it to the Serialization library. Unfortunately! When my application calls the serialization code to send my object to the archive, it crashes. I've reduced my actual code to try and isolate the crash in a way I can post here. std::ofstream outStream(MAP_SAVE_FILE, std::ios_base::binary); boost::archive::text_oarchive outputArchive(outStream, 1); Classroom *c = new Classroom(); CCLog("Outputting archive"); // outputArchive << mapInstance; outputArchive << c; The crash occurs at outputArchive << c; "Fatal signal 11 (SIGEGV) at 0xdeadbaad (code=1), thread 1870 (Thread-97)" which is a segfault, in Androidvania. Ideally I want to be outputting that mapInstance variable that's commented out to archive, but for sanity's sake I made a silly little Classroom class, which I'll include for sanity's sake: class Classroom { friend class boost::serialization::access; template <class Archive> void serialize( Archive &ar, const unsigned int version ) { ar & studentCount; } int studentCount; public: Classroom() { studentCount = 1; } ~Classroom(){} }; I've run across several red flags about wchar support in Android or on gcc versions, so I'm inclined to think that's related. Then again, it appears as though my boost configuration files were aware of the compiler version when it built (that Mystic Tree link at the top really does seem to be on top of things, if anyone's interested), which is how the program was able to compile and run, at all. I'm almost 100% certain this is related to the Android NDK, either the gcc version or the gnu-stl, because I can compile and run this code on Windows through Visual studio with no problem, but it crashes on Android. I've made sure that my app has write permissions to the internal storage being used. I can even write out text files using basic std::ostreams without a crash. I am not at all familiar with dealing with these sorts of compiler- or platform-specific issues; I have a bachelor's in SE which taught me design patterns, architecture, and project management, but nothing like this. I'd greatly appreciate some direction in learning how to work through these kinds of problems, (although I'd even more greatly appreciate an actual solution to the problem I'm seeing). Thanks in advance for any assistance. -- View this message in context: http://boost.2283326.n4.nabble.com/Android-segfault-while-writing-to-archiv… Sent from the Boost - Users mailing list archive at Nabble.com.

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boost serialization of std::pair
by Andrew Smith 18 Mar '13

18 Mar '13

Hi, Is there any way of customizing the element names given to serialization of std::pair via xml_oarchive. Im think of something like the|||BOOST_SERIALIZATION_NVP mechanism. In particular Im looking to serialize std::map with custom elemnet names to replace '<first>' and '<second>' Thanks Andy |

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Trying to cross compile Boost.Python using mingw
by Leonardo Sá 18 Mar '13

18 Mar '13

Hello all, I'm trying to cross compile boost python under linux to windows using the mingw32 compiler. Static linking works great, but when trying to make a dll, I get the following errors: gcc.link.dll bin.v2/libs/python/build/gcc-mingw-mingw32/release/target-os-windows/threadapi-win32/threading-multi/libboost_python-mt.dll.a /usr/bin/i686-w64-mingw32-ld: cannot find -lutil /usr/bin/i686-w64-mingw32-ld: cannot find -lpthread /usr/bin/i686-w64-mingw32-ld: cannot find -ldl collect2: ld returned 1 exit status My compile line is: b2 --with-system --with-date_time --with-python --with-filesystem --with-program_options -j 4 toolset=gcc-mingw32 target-os=windows threadapi=win32 variant=release --layout=tagged -sNO_BZIP2=1 -sNO_ZLIB=1 link=shared All the other libraries (system, date_time, program_options) generate dlls sucessfully. Any help is appreciated. Thanks!

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linker error when using from_simple_string()
by Phil Huffman 18 Mar '13

18 Mar '13

Hello, This line of code: date birthday(from_simple_string(s)); causes this error: Undefined symbols for architecture x86_64: "boost::gregorian::greg_month::get_month_map_ptr()", referenced from: unsigned short boost::date_time::month_str_to_ushort<boost::gregorian::greg_month>(std::string const&) in boost2-aLwtLt.o ld: symbol(s) not found for architecture x86_64 Any help will be appreciated. Thanks. Regards, Phil

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how to reuse a thread
by Victor Yankee 17 Mar '13

17 Mar '13

Hello, I would like to create a boost thread that can be reused to run a variety of functions each with different number of args of different types. I am using C++11 gnu compiler and so maybe a solution using variadics might work? I posted to here: http://stackoverflow.com/questions/15237426/can-a-thread-be-reused-to-run-v… But I am not understanding how. Thank you

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[boost] [arm] Building for ARM
by Michael Powell 17 Mar '13

17 Mar '13

Hello, I wonder, has anyone built Boost for ARM? Specifically, we've got an ARM5 for which I want to use Boost for many of those features, a key one is Spirit2 for at least one domain-specific-language (DSL) exposure, possibly two or three. That I can say, we're working with Mentor Graphics, Code Sourcery Code Bench for ARM for the moment. I think they've got current GCC language support through 4.7.2 if it matters. My only questions are, how feasible a cross compile is Boost? Does the inclusion and linkage go about as smoothly as for any other ARM-destined output? Thanks much in advance. Regards, Michael Powell

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