May 2012 - Boost-users - lists.preview.boost.org

[Sandbox - endian] Why is endian still in sandbox?
by Nathaniel J Fries 07 Oct '12

07 Oct '12

A fairly novel (at least when put up against more intricate labours like asio, filesystem, and their like) project which appears to be finished and would be a very useful companion to existing libraries sits in the sandbox. Is there a reason for this?

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[BGL] vecS for vertex container and vertex index adjustments
by Sergey Mitsyn 03 Oct '12

03 Oct '12

Hi all, I know that while using vecS for vertices one has no vertex iterator stability upon removing vertices. But I have a question if there exists something like vertex _index_ stability. The documentation says that indices for vertices are automatically adjusted so that they are still in contiguous range, but it is not specified how it is done. Is it okay to assume that if a vertex with an index I is removed, then vertices with indices < I have their indices unchanged, while vertices with indices > I have their indices decreased by one? The actual problem is removing all vertices meeting some condition. Is the following code ok? // traverse all vertices and remove those for which predicate // condition_to_remove_vertex returns true. // graph is adjacency_list<.., vecS, ...> vertex_iterator vi = vertices(graph).first, vi_end = vertices(graph).second; while (vi != vi_end) { if (condition_to_remove_vertex(vi, graph)) { vertices_size_type end_index = vertex_index[*vi_end] , vi_index = vertex_index[*vi]; remove_vertex_f(*vi, graph); // vi and vi_end are invalid --end_index; vi = vertices(graph).first + vi_index; vi_end = vertices(graph).first + end_index; // now vi and vi_end are valid again } else ++vi; } This way seems to be more effective than to start iteration again every time a vertex is removed. ------------ Sergey Mitsyn.

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[Range] insert algorithm fails if target is a map
by Robert Jones 11 Sep '12

11 Sep '12

The title says it all really. The failure occurs because the insert algorithm expects the container to provide a 3-arg insert of the form container.insert( position, begin, end ); whereas map's, multimap's and set's insert method only takes two arguments... map.insert( begin, end ); Is this limitation by design? It would be easy to provide specialisations for maps, mmaps and sets, but that would not be a completely general solution. - Rob.

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filesystem directory_iterator run-time error during construction after upgrading to OSX Lion
by Martin Searancke 04 Sep '12

04 Sep '12

I have just upgraded my Mac to Lion and code that worked fine under snow leopard is giving me a run-time exception when constructing a directory_iterator. The error I am getting is "malloc: pointer being freed was not allocated" The line in question that raises this error is: for ( directory_iterator itr( my_path ); itr != end_itr; ++itr ) taken directly from the example and working fine under windows. This is version 1.49 installed with MacPorts. Is this a known problem? I found some vague references to a similar problem in an earlier version of boost but no solution. I have confirmed that I only have 1 copy of the headers and libs on the system and in the correct path. The date stamp on the files matches the last time I did a macports update so this should be the matching library for the header. Please note that I am a real novice to Mac development and have only just started porting code from windows for less than a month. Thanks in advance, Martin

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[Graph] compilation error under Windows but not under Linux
by Gaël de Chalendar 29 Aug '12

29 Aug '12

Hello, I have a compilation error under Windows (Visual C++ 2008) with a code that works well under Linux (gcc 4.6.1 and before). The compilation error is: =========== /FsaAccess16.tcc(833) : error C2784: 'std::pair<graph_traits<G>::in_edge_iterator,graph_traits<G>::in_edge_iterator> boost::in_edges(graph_traits<G>::vertex_descriptor,const boost::subgraph<Graph> &)'ÿ: impossible de d‚duire l'argument modŠle pour 'const boost::subgraph<Graph> &' … partir de 'FrCeaLic2m::Common::FsaAccess::selected_graph_types16::spareGraphType' C:\PROGRA~1\boost\BOOST_~1\boost/graph/subgraph.hpp(432)ÿ: voir la d‚claration de 'boost::in_edges' Z: \Projets\MoteurMultimedia\mm_common\src\common/FsaAccess/FsaAccess16.tcc(778)ÿ: lors de la compilation de la fonction membre '<Inconnu>' de la classe <Inconnu> z: \projets\moteurmultimedia\mm_common\src\common\fsaaccess\FsaAccessReader16.h(118)ÿ: voir la r‚f‚rence … l'instanciation de la classe modŠle 'FrCeaLic2m::Common::FsaAccess::FsaAccess16<graphType>' en cours de compilation with [ graphType=FrCeaLic2m::Common::FsaAccess::selected_graph_types16::spareGraphType ] z: \projets\moteurmultimedia\mm_common\src\common\fsaaccess\FsaAccessSpare16.h(35)ÿ: voir la r‚f‚rence … l'instanciation de la classe modŠle 'FrCeaLic2m::Common::FsaAccess::FsaAccessReader16<graphType>' en cours de compilation with [ graphType=FrCeaLic2m::Common::FsaAccess::selected_graph_types16::spareGraphType ] =========== The line that does not compile is boost::tie(iei,ie_end) = boost::in_edges(commonTarget,m_graph); The function being compiled is declared like that: template <typename graphType > std::pair< const typename boost::graph_traits<graphType>::vertex_descriptor, bool > FsaAccess16<graphType>::findEquivalentInRegister( dicoVertexType tempState ){ ... And here graphType, the type of m_graph is spareGraphType defined by: struct selected_graph_types16 { ... typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, dicoVertexCountProperty> spareGraphType; ... This is a cmake based project that I compile using qtcreator. I'm a Linux developer and I'm a little bit lost with VC outputs and tools under Windows... Regards, Gaêl -- Gael de Chalendar CEA LIST Centre de Fontenay-aux-Roses Laboratoire Vision et Ingénierie des Contenus (Vision and Content Engineering Laboratory) Bat. 38-2 ; 18, rue du Panorama ; BP 6 92265 Fontenay aux Roses Cedex ; France Tél.:01.46.54.80.18 ; Fax.:01.46.54.75.80 Email : Gael.D.O.T.de-Chalendar.A(a)T.cea.D.O.T.fr

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Re: [Boost-users] asio HTTP Server 3 example memory leak
by admin＠thefireflyproject.us 25 Aug '12

25 Aug '12

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[iostreams] Possible bug in gzip_decompressor?
by Gavin Band 18 Jun '12

18 Jun '12

Dear list, I have been using boost.iostreams to read gzipped files for some time, but recently have run into some problems with files that are compressed using tools other than gzip (namely bgzip from http://samtools.svn.sourceforge.net/viewvc/samtools/trunk/samtools/) Here is the file: $ hexdump -C ../hello.txt.bgz 00000000 1f 8b 08 04 00 00 00 00 00 ff 06 00 42 43 02 00 |............BC..| 00000010 35 00 f3 48 cd c9 c9 d7 51 28 c9 c8 2c 56 00 a2 |5..H....Q(..,V..| 00000020 44 85 92 d4 e2 12 85 b4 cc 9c 54 3d 2e 00 86 1e |D.........T=....| 00000030 ef a4 1c 00 00 00 1f 8b 08 04 00 00 00 00 00 ff |................| 00000040 06 00 42 43 02 00 1b 00 03 00 00 00 00 00 00 00 |..BC............| 00000050 00 00 |..| 00000052 I think this is valid gzip format (based on reading http://www.gzip.org/zlib/rfc-gzip.html) It differs from what you get by compressing the file using the gzip program in two respects: 1. it uses the 'extra' flag (FLG.EXTRA) to add extra data to each block header, and 2. it has two blocks, the second of which is empty. My file reading code is as follows: /* test.cpp */ #include <iostream> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/gzip.hpp> #include <boost/iostreams/copy.hpp> #include <boost/iostreams/device/file.hpp> int main( int, char** ) { boost::iostreams::filtering_istream stream ; stream.push( boost::iostreams::gzip_decompressor() ) ; boost::iostreams::file_source file( argv[1] ) ; stream.push( file ) ; boost::iostreams::copy( stream, std::cout ) ; } I am using boost 1.48.0 on Ubuntu linux. The compilation is $ g++ -o test -g test.cpp -L /home/gav/Projects/Software/usr/lib -lboost_iostreams-gcc46-mt-1_48 -I /home/gav/Projects/Software/boost_1_48_0 Using gunzip on the above file works fine: $ gunzip -c ../hello.txt.bgz Hello, this is a test file. Using the test program does not: $ ./test ../hello.txt.bgz terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::iostreams::gzip_error> >' what(): gzip error I was able to fix this problem with two code changes in the boost.iostreams implementation, as follows. *Change #1*: at libs/iostreams/src/gzip.cpp:65: change "state_ = s_extra;" to "state_ = s_xlen;" Rationale: without this change, it looks like state s_xlen is never entered so the length of the extra data is not parsed. *Update:* I notice this change was already raised in ticket #5908, and has already been fixed in trunk. * * *Change #2*: at libs/iostreams/src/zlib.cpp:153: change "crc_imp_ = 0;" to "crc_ = crc_imp_ = 0;" Rationale: without this change, an empty block of data does not re-initialise the member variable crc_ of zlib_base. This causes an exception on line 447 of boost/iostreams/filter/gzip.hpp. I confirmed this behaviour a second way, by concatenating two files compressed using gzip, the first nonempty and the second empty. This creates a file which looks like this: $ hexdump -C hello2.txt.gz 00000000 1f 8b 08 00 0d ea b4 4f 00 03 cb 48 cd c9 c9 57 |.......O...H...W| 00000010 28 c9 48 2d 4a e5 02 00 8e 45 d1 59 0c 00 00 00 |(.H-J....E.Y....| 00000020 1f 8b 08 00 18 ea b4 4f 00 03 03 00 00 00 00 00 |.......O........| 00000030 00 00 00 00 |....| 00000034 This file again decompresses with gunzip but not with the program above. Change #2 above fixes this. Could someone take a look at this and let me know if this change is really appropriate? (Or perhaps I'm doing something wrong.) I can create a bug report if desired. Many thanks, Gavin Band.

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[vector, PropertyGraph] Problem declaring a class member of the "vector<int>" type
by Alex Sadovsky 13 Jun '12

13 Jun '12

Hello everyone, > >I am trying to declare, in a header file, a class that has a member of type "vector<double>" (the code is included below). The compiler complains that I haven't included the appropriate namespace (the error message reads, "ISO C++ forbids declaration of ‘vector’ with no type"), and I understand that it is looking for this: > >using namespace boost::numeric::ublas; > >However, I tried putting it in the header file in various places (haven't programmed in C++ in 10 years and couldn't find any online documentation to clarify this specific situation), and still no luck. I am definitely doing something wrong, but cannot reason out the error, as it probably has to do with the specific syntax conventions. Any help is appreciated! > >Thanks, >-Al > >P.S. Code in header file: > >////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// >// File "airspace-graph-rectilinear-edges.h" >typedef char* string; >const int PHYSICAL_SPACE_DIMENSION = 2; >// Information needed about a waypoint used in an airspace: name and physical position >class WaypointConcept{ > private: > using namespace boost::numeric::ublas; > string waypoint_name; > vector<double> waypoint_position_xyh(PHYSICAL_SPACE_DIMENSION); > public: > string GetWaypointName(); > vector<double> GetWaypointPosition(); >} > >class AirspaceGraphConcept PropertyGraphConcept<class Graph, class WaypointConcept, class vertex_index_t>; >typedef Vertex* GraphPathType; >typedef string FlightIDType; >typedef boost::unordered_map<std::FlightIDType, GraphPathType> FlightIDToPathAssignmentType; >////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// > >Code in the .cpp file (which includes the above header file) I am trying to compile: >////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// >#include <boost/lambda/lambda.hpp> >#include <iostream> >#include <iterator> >#include <algorithm> >#include <boost/numeric/ublas/io.hpp> >#include <boost/numeric/ublas/vector.hpp> >#include "airspace-graph-rectilinear-edges.h" > >int main() >{ > using namespace boost::numeric::ublas; > > vector<double> v(3); > for (unsigned i = 0; i < v.size(); ++ i) > v (i) = 2.01*double(i); > > std::cout << v << std::endl; >} >////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// > > > > > > > > > > > > > > > >

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[property_tree] number of sections in an inifile
by Sean Farrow 13 Jun '12

13 Jun '12

Hi: If I have defined: boost::property_tree::ptree IniTree; What is the correct way to determine how many sections there are in an ini file. Should I use count, max_size, m_children or size? Any help appreciated. Cheers Sean.

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accumulator operations
by Olaf Peter 04 Jun '12

04 Jun '12

Hi, I like to collects some stats. There are several data slices where I can partially/separated collect them (each of them). Finaly I like to combine these stats to a single one to get summarized informations. How to? May this work: accumulator_set<..> acc1; accumulator_set<..> acc2; ... accumulator_set<..> acc_all; ... acc1(42); ... acc_all += acc1; ... acc_all += acc2; Because did not found informations about. The same problem woulde be probably for a threaded implementation too. Thanks, Olaf

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