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[Boost][BGL] Dynamic Property, dynamic_get_failure.
by Mathieu - 27 Apr '11

27 Apr '11

Hi, I'm trying to generate random graphs (with random edge weight) and write them to a dot file, but I get this exception in the write_graphviz_dp() function : "what(): dynamic property get cannot retrieve value for property: weight." The code looks like this : typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, property<edge_index_t, int>, property<edge_weight_t, int> > graph; boost::minstd_rand gen; graph g; boost::generate_random_graph(g, 10, 30, gen, false, false); boost::randomize_property<boost::edge_weight_t>(g, gen); dynamic_properties dp; dp.property("weight", get(edge_weight, g)); boost::write_graphviz_dp(std::cout, g, dp, std::string("weight")); (don't pay attention to the random generator it's just to keep it simple). I've been looking at the examples and at the doc and it doesn't seem to me that I'm doing something wrong... but apparently I am. Thanks in advance!.

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Re: [Boost-users] Boost versions and the Interprocess library
by David Ohlemacher 27 Apr '11

27 Apr '11

Ion: I think you are probably quite right...and I am just going to have to find another method. I guess I could always give a quick try, but testing would become an issue. How would I really know there are no broken edge cases... Nat: The CORBA implementation works this way. I submit an IDL file that defines my object model (OM) to a website. What I get back is a library (binary, no source) and a pile of additional source files. Together they implement my OM using CORBA. They have dependencies on Boost 1.31. When I link my application, I link in autogenerated COBRA libs, Boost 1.31 libs, and include in various places Boost header files. | I'm perplexed what "closed source" means in this context. Maybe it's | because I don't understand the CORBA environment. But if you have a | prebuilt CORBA executable using Boost version 1.31, I don't understand | how that would constrain in any way the version of Boost you yourself | choose? Thanks for the input, -d

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[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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[Review] Boost.Convert library, new subversion URL
by Edward Diener 23 Apr '11

23 Apr '11

This is a reminder that formal review of the Boost.Convert library by Vladimir Batov starts today, April 23, and is scheduled to last through May 2. *************** * 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 * ******************* Normally you can find Boost.Convert here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… However because the boostpro web site is having problems and will likely be down for the weekend, I have put the library into the Boost sandbox temporarily, since the Boost sandbox is up. So you can get the library, using Subversion, from https://svn.boost.org/svn/boost/sandbox/convert. This is exactly the same as the vault with the files unzipped. 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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How to prevent boost serialize from object tracking a pointer
by Frank 23 Apr '11

23 Apr '11

Hi all, I have a shared_ptr to an object that changes (the underlying object is non-const, that is, not the shared_ptr), and I'd like to serialize the object each time it changes (size of the archive is not an issue). The problem stems, I think, from object tracking: every time after the first serialization, boost detects that the pointer is the same, and does not write out the (full, updated) object. I've tried putting in BOOST_CLASS_TRACKING(T, boost::serialization::track_never) but it won't compile because there is a BOOST_STATIC_ASSERT in shared_ptr.hpp that prevents setting class T's tracking to track_never if it is then serialized via a shared_ptr, with the comment that "correct shared_ptr serialization depends upon object tracking being used." Am I missing something obvious here, or is another a way to accomplish this? Any help would be greatly appreciated... Thanks, Frank -- View this message in context: http://boost.2283326.n4.nabble.com/How-to-prevent-boost-serialize-from-obje… Sent from the Boost - Users mailing list archive at Nabble.com.

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[fusion] transform and transform_view
by Karsten Ahnert 23 Apr '11

23 Apr '11

Hi, I have a small functor: struct operation { template<class> struct result; template< class F > struct result<F(int)> { typedef long type; }; template< class F > struct result<F(float)> { typedef double type; }; template< class T > typename result< operation(T) >::type operator()( T t ) { typedef typename result< operation(T) >::type result_type; return result_type( t * T( 2 ) ); } }; and I wonder why a transform_view works as expected: typedef fusion::vector< int , float > vector_type; vector_type v( 1 , 3.4 ); fusion::transform_view< vector_type , operation > tv( v , operation() ); while result_of::transform does not: fusion::result_of::transform< vector_type , operation >::type tv2 = fusion::transform( v , operation() ); result in compile errors? Any hints?

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Boost versions and the Interprocess library
by David Ohlemacher 22 Apr '11

22 Apr '11

Hello all, I have a project that is stuck using an old closed src implementation of CORBA that depends on Boost 1.31. Upgrading to a newer version of Boost is not possible. I we have a new requirement that could be partially met using shared memory. Is it possible to use the Interprocess library (first available in Boost 1.35) in our project? I see it only requires the inclusion of a single hdr file, but of course that doesn't mean it would work in a 1.31 environment. Any thoughts would be greatly appreciated. The project is currently using WinXP using Visual Studio 2003. There are much delayed plans to port this to Linux. Thanks, -d -- David Ohlemacher Senior Software Engineer Scientific Solutions Inc. 99 Perimeter Rd Nashua New Hampshire 03063 603-880-3784 . o . . . o o o o

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[units] atan2 functionality with same dimension for y and x
by Ryan 22 Apr '11

22 Apr '11

I found that when I passed atan2 a quantity<si::length> value for both y and x the compiler gave me an error. Upon examination of the atan2 method in "boost/units/cmath.hpp" I found it expected both inputs to atan2 to be dimensionless. The method atan2 can be represented simplistically as atan(y / x). As long as both dimensions to y and x are the same the results is a dimensionless value of (y / x). So shouldn't the inputs to boost::units::atan2 accept any dimension of y and x as long as they are the same? Ryan

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[Review] Formal review of Boost.Convert library starts Saturday
by Edward Diener 21 Apr '11

21 Apr '11

This is a reminder that formal review of the Boost.Convert library by Vladimir Batov starts on Saturday, April 23, and is scheduled to last through May 2. *************** * Its Purpose * *************** From the introduction: Boost.Convert builds on the boost::lexical_cast experience and still offers a simple, minimal interface, familiar conversion behavior and more: * throwing and non-throwing behavior when conversion fails; * 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 string containers (std::string, std::wstring, char const*, wchar_t const*, char array[], etc.); * no DefaultConstructibility requirement for the Target/Destination type; * extendibility and additional room to grow. ******************* * Where to get it * ******************* You can find the Boost.Convert here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… 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_AUTO and boost::fusion
by Niitsuma Hirotaka 21 Apr '11

21 Apr '11

This cause err BOOST_AUTO(xx , boost::fusion::list<double,int,double>(1.12, 3 ,3.4) ); How to use BOOST_AUTO with boost::fusion ?

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[serialization] Best way to serialize to an old file version
by Richard Ulrich 21 Apr '11

21 Apr '11

What is the best way to write archives to an old version? Say I have version 23 of our product and want to write an archive that another user with version 22 can read. The serialization keeps track of the version on a class level. But in this use case I need to know the version of each class at a specific point in time. Sure, I could implement some global variable and completely work around the version system of boost serialization. But I hope there is a better, preferred way. Rgds Richard

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[Review] Type Traits Extension by Frederic Bron - Review summary and decision
by Joel Falcou 20 Apr '11

20 Apr '11

Hello all, Frederic Bron's type traits extension proposal review ended up last week. In so far, we received SEVEN reviews which are all voting YES for the inclusion of Type Traits extension in Boost. So the result is that the Type Traits Extension is ACCEPTED into Boost. Suggestions include: - some clean-up in the implementation like "Renam[ing] the detail classes inside the specific namespace without using number, i.e. with a clear meaning. The use of tag, tag 2 could be renamed check_pass, check_fail or something like that." - Sensibility on cv-ref qualifiers in traits call is important. This is being addressed by Frederic. - Frederic is OK to keep the detection of void as a valid return type by using some dont_check type as default. - small comprehensive example of some of the traits like a "maybe_print function, which prints a value if the appropriate operator<< ostream overload exists, else prints "<NOT PRINTABLE>". [...] a small example like this would show a practical use of the library, and how to make use of enable_if, or some other overload method." - The main recurring suggestions found was the choice of name for the operator traits with respect to the standard naming, naming in proto and other boost libraries. This topic is still hot and alive. An alternative to the naming scheme consensus was proposed in the form of alias of commonly used operator traits. This issue is I think beyond bikeshed-color argumentation and I think it is a good point if Frederic could step up and provide a definite and rationalized answer to this point. The current status is : * the namespace options is out casue the standard didnt choose this way; * Frederic and a few other seems to favor the proto naming scheme (more or less the negate issue and the pre/post operator) * the question of a common prefix is still open * the std:: like naming seems limited as not all operators are there. Thanks to all reviewers and people participating to the discussions. Thanks to Frederic for his work.

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boost::filesystem - replace_extension question
by Archie14 20 Apr '11

20 Apr '11

I am constructing full path out of directory (c:\temp), filename(test) and extension (txt). boost::filesystem::path mypath(dir); // mypath="c:\temp" mypath /= filename; // mypath="c:\temp\test" If I call mypath.replace_extension("txt") it will fail because there is no dot character yet. To proceed further I have to add "." using direct string manipulation, that kind of break the logic of using filesystem::path. Question: how to construct full path using directory, filename and extension strings using only filesystem::path methods?

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boost::filesystem::current_path().string()
by buster buster 20 Apr '11

20 Apr '11

(11:23:04 PM) epure_: hi (11:23:13 PM) epure_: i'm using "boost::filesystem::current_path().string()" from a dll (11:23:27 PM) epure_: windows 7, it prints the paths to the executable which uses the DLL (11:23:38 PM) epure_: window xp , it prints the path to my desktop (11:23:54 PM) epure_: how do I make it so that it behaves like windows 7 ? Thanks, epure

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[BGL] vis passed by value to depth_first_visit
by Shaun Jackman 20 Apr '11

20 Apr '11

Hi, I recently learned the hard way that the visitor parameter, vis, is passed by value to depth_first_visit, but passed by reference to detail::depth_first_visit_impl. I was writing a function that implemented depth_first_search, but starts each of the visits at vertices with indegree == 0. If my depth_first_search replacement calls boost::depth_first_visit, each call to depth_first_visit makes a copy of the output iterator, which doesn't work for an output iterator with any state (such as a pointer). Calling an internal boost function like detail::depth_first_visit_impl doesn't seem like a good plan. How should I solve this? My short-term work around is to use an output iterator that does not have any state, such as a back_inserter. Cheers, Shaun

2 3

error C2825: 'F': must be a class or namespace when followed by '::'
by simone pilozzi 20 Apr '11

20 Apr '11

Dear Users, I am using a pointer to a function member with the std::transform alorithm. The class is a QuantLib class called DayCounter and the method is called yearFraction and takes in two mandatory dates and two optionals to return the corresponding year fraction. *yearFraction ( QuantLib::Date t1,QuantLib::Date t2,QuantLib::Date t3 = Date(),QuantLib::Date t4=Date())* Now I tried to fill a vector called yearfracs in this way boost::shared_ptr<QuantLib::DayCounter> dc( new QuantLib::ActualActual); QuantLib::Date t = todaysDate() std::vector<QuantLib::Time> yearfracs; std::transform(subsample.begin(),subsample.end(), yearfracs.begin(),boost::bind(&QuantLib::ActualActual::yearFraction,&dc,t,_2)) subsample is the originary vector of dates. The compiler reported the following error error C2825: 'F': must be a class or namespace when followed by '::' What is the correct syntax for doing this? Thanks in advance Simone

3 5

A problem with using boost::regex
by Michael Lindner 20 Apr '11

20 Apr '11

I have been a boost users for years, but this is the first time I've come across a problem with using it. I'm posting this in the hopes that one of you will say "oh yeah you did 'X' wrong", because I have been beating my head against the wall with this for some time. Thanks for taking a look. -- Michael Lindner I have the following program: #include "boost/regex.hpp" #include <string> int main(int argc, char** argv) { std::string re("[123]abc"); boost::regex reg(re); return 0; } It compiles and runs just fine on my Mac and Linux machines. On Windows, however, it compiles fine, and runs fine compiled under the "Debug" configuration. When I change that to "Release" however, it crashes with the following stack trace: msvcr90.dll!7858cc9d() msvcr90.dll!7858ccb5() dme.exe!boost::re_detail::w32_ transform() + 0xd5 bytes C++ dme.exe!boost::re_detail::w32_regex_traits_implementation<char>::transform() + 0x21 bytes C++ dme.exe!boost::re_detail::find_sort_syntax<boost::re_detail::w32_regex_traits_implementation<char>,char>() + 0x64 bytes C++ dme.exe!boost::re_detail::w32_regex_traits_implementation<char>::w32_regex_traits_implementation<char>() + 0x399 bytes C++ dme.exe!boost::object_cache<unsigned int,boost::re_detail::w32_regex_traits_implementation<char> >::do_get() + 0x28f bytes C++ dme.exe!boost::object_cache<unsigned int,boost::re_detail::w32_regex_traits_implementation<char> >::get() + 0x69 bytes C++ dme.exe!boost::re_detail::create_w32_regex_traits<char>() + 0x1b bytes C++ dme.exe!boost::re_detail::regex_data<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >::regex_data<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >() + 0x5d bytes C++ dme.exe!boost::basic_regex<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >::do_assign() + 0x5f bytes C++ > dme.exe!boost::basic_regex<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >::assign(const char * p1=0x0012ff4c, const char * p2=0x0012ff54, unsigned int f=0) Line 380 C++ dme.exe!boost::basic_regex<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >::assign<std::char_traits<char>,std::allocator<char> >(const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & s="[123]abc", unsigned int f=0) Line 418 C++ dme.exe!boost::basic_regex<char,boost::regex_traits<char,boost::w32_regex_traits<char> > >::basic_regex<char,boost::regex_traits<char,boost::w32_regex_traits<char> > ><std::char_traits<char>,std::allocator<char> >(const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & p="[123]abc", unsigned int f=0) Line 393 C++ dme.exe!main(int argc=1, char * * argv=0x00345628) Line 9 C++ I am using boost 1.46.0 Microsoft Visual Studio 2008 Version 9.0.30729.1 SP Microsoft .NET Framework Version 3.5 SP1

3 5

Interval: checking for equality
by gast128 20 Apr '11

20 Apr '11

Hello all, I was (mis)using the interval library for time intervals. However the equality operator fails for a simple test: boost::numeric::interval<int> intv1(1, 3); boost::numeric::interval<int> intv2 = intv1; //throws bool b = (intv1 == intv2); probably i don't understand the whole idea about this interval arithmetic library then. Could somebody tell me what I do wrong?

1 0

[phoenix] v3 extension mechanism for template functions
by alfC 20 Apr '11

20 Apr '11

Hi, In Phoenix2 I used to have the following code to add expressions of type pow<N>(... expr...) which where useful for expressions involving Boost.Units. Is it possible to do something similar with Phoenix3. The usage if macros in the tutorial examples obscures how to add template parameters to the phoenix expression. In Phoenix2 it was straight forward, but I can figure out how to do this in Phoenix3. // phoenix2 code: #include <boost/units/pow.hpp> namespace boost{ namespace phoenix{ template<long N> struct pow_eval{ template <typename Env, typename Arg_> struct result{ typedef typename boost::units::power_typeof_helper<typename boost::mpl::at_c<typename Env::args_type, 0>::type, boost::units::static_rational<N> >::type type; }; template <typename RT, typename Env, typename Arg_> static RT eval(Env const& env, Arg_ const& arg_){ return boost::units::pow<N>(arg_.eval(env)); } }; template<long N, typename Arg_> actor<composite<pow_eval<N>, boost::fusion::vector<Arg_ > > > pow(actor<Arg_> const& arg_){ return compose<pow_eval<N> >(arg_); } }} use as pow<3>(arg1)(l)

2 4

Accumulators: what is the difference between features<> and stats<> ?
by Andrew A 20 Apr '11

20 Apr '11

Is there any difference for example, between accumulator_set< double, features< tag::mean > > acc; and accumulator_set< double, stats< tag::mean > > acc; features and stats seems to be synonyms?

2 1

can't take const ref to tribool's indeterminate
by Phil Nash 19 Apr '11

19 Apr '11

Hi all, The following does not compile (GCC 4.2): #include <boost/logic/tribool.hpp> template<typename T> void byRef( const T& v ) { } // ... byRef( boost::indeterminate ); I realise that indeterminate is actually a function. If I write my own, equivalent, function I can substitute it here and it compiles, however. I can't see what is stopping it from working in indeterminate's case - but I suspect it is to do with some of the operator overloading going on. I couldn't pin it down, though. I can take it by value, of course. What am I missing? Before you ask - yes this is boiled down code. In my real situation I have generic code that doesn't even know about tribool, so I can't special-case it. And I'd rather get to the bottom of why it doesn't work for me - even if the end result is "you can't do that". Thanks and regards, [)o IhIL..

2 2

To produce bjam, put Boost Version 1.46.1 in a deep folder (at least 4 levels I guess)
by JIA Pei 19 Apr '11

19 Apr '11

Hi, to whom it may concern: It looks like many Boost users are arguing that "bjam won't be successfully produced". By reading bootstrap.bat, around line 13, you may notice something like "../../../../******", Yes, that means, Boost root directory must be put at least 4 levels (directory depth). This seems to be a bug of current Boost 1.46.1 Rgds JIA -- Email: jp4work(a)gmail.com cell: +1 7783185816 Welcome to Vision Open http://www.visionopen.com

2 1

[network] Release 0.9.0
by Dean Michael Berris 19 Apr '11

19 Apr '11

Good day everyone, apologies for the cross-post. I just wanted to point everyone interested in the development of the cpp-netlib project to the 0.9.0 release announcement over at C++ Soup: http://cplusplus-soup.com/2011/04/18/cpp-netlib-0-9-0-released/ -- more information about what happened in the library between the beta and the official release can be found there. As earlier mentioned, this version is the pre-1.0 snapshot that is being officially submitted to the Boost C++ Library as Boost.Network. I would like to ask the review wizards to please accept this announcement as a request to put Boost.Network/cpp-netlib into the review queue pending a review manager. I would greatly appreciate volunteers who would like to be the review manager(s) for the Boost.Network review. Have a good one and I definitely hope this helps. Cheers from down under! -- Dean Michael Berris http://about.me/deanberris

1 0

[OT] Boost Users/Developers Down Under?
by Dean Michael Berris 19 Apr '11

19 Apr '11

Hey Everyone! Apologies for the cross post and off-topic, but I just moved to Sydney, Australia and I was wondering whether there are any Boost users/developers that are based here who'd like to get together for a geek out session somewhere in the city? I tried to look at the Boost Users Map (http://goo.gl/O1I15) and I only saw one other Boost user in the area -- maybe there are others lurking around who'd be interested in a meet-up here? :) Cheers from down under! :D -- Dean Michael Berris http://about.me/deanberris

1 0

Select outer face for "Chrobak-Payne Straight Line Drawing"
by jakob brandt 19 Apr '11

19 Apr '11

Hello, I'm a boost-newbie and don't know excactly where to post my question - not only because I have some trouble with my English… sorry for that. My Problem is: I have builded some graphs which always can be drawn with an outer face consisting of 3 certain vertices. Now I am trying to find out if it is possible to select the vertices for the outer face in the Chrobak-Payne Straight Line Drawing. Because if I dont, the drawing-algorithm finds other vertices to set the outer face. Could someone tell me if this was possible without a hugh affort and maybe help me with it? (My cpp-skills arent the best :( … to play things down) I would be very thankfull and happy for any advise or help. Best wishes Jakob

1 0

[system] Dynamic error message with context (like MySQL client API)
by Lian Cheng 19 Apr '11

19 Apr '11

Hi, everyone, I'm writing a MySQL client API wrapper with Boost.Asio and Boost.System. And I want to encapsulate all MySQL error codes with boost::system::error_code. But I found out that error messages corresponding to a specified error code value is designed to be unique within Boost.System, which retrieves the error message from the `message()' method of corresponding boost::system::error_category subclass. MySQL provides an API mysql_error, which accepts a connection handle and returns the error message of the last error on this connection. Also, the content of the error message is dynamic. So here is my question: is there any way to provide context related rather than static error messages with Boost.System? Any reply would be appreciated! Cheers Lian

1 0

Creating interprocess::shared_ptr across processes
by GxL 18 Apr '11

18 Apr '11

Hi all, I've been looking into the "boost::interprocess" library to use shared memory the resides in a non-paged physical memory facilitated by RTX (Real-time Windows extension). According to my understanding it's best to use "managed_external_buffer". I have managed to create the shared memory and create and share objects using raw pointers. I would however prefer using smart_ptr that is offered by the boost::interprocess. The problem I'm having is that I can create the shared pointer for any shared object in one process but when I want to create it's counter-part in the other process, it does not share the "share_count" with the original shared_ptr in the first process. For instance I tried to share a list of integers. So I used the interprocess::list as "named" object and once I crated it (following that "interprocess" documentation) I placed that pointer into a interprocess::shared ptr that I created using the helper function "make_managed_shared_ptr". Now in another process I am able to get hold of the raw pointer to that same list by looking up by the name but cant figure out (did lots of searches about this to no avail) how to instantiate an interprocess::shared_ptr such that it would get the same shared_count object. When I use the "make_managed_shared_ptr" and pass in the raw pointer to the shared object it will create one but with a new "shared_count" which is obviously bad. First I thought that the "make_managed_shared_ptr" is able to resolve and find the already existing "shared_count" and link to that but figured it wasn't the case. Then I thought maybe I need to instantiate the shared_ptr as a named object and then retrieve the same object in another process but can't see the "make_managed_shared_ptr" would support such concept. Then I thought maybe the pre-implemented interprocess shareable types (e.g. vector, list, etc.) derive from "enable_shared_from_this" so I could just call the shared_from_this on the retrieved raw pointer to retrieve the shared_ptr that will be guaranteed to share the "shared_count". None of the above yielded the desired results. I didn't find (by googling) anybody talking about the process of creating a shared_ptr (using the helper method of "make_managed_shared_ptr") across the process so I assume that probably is clear and is able to achieve the mentioned results and I must be missing something awfully obvious. Can somebody please advise on how to achieve this? I am loath to just jump and implement my version of "make_managed_shared_ptr" unless I really have to and I'm sure it's designed to work across the processes. Thanks a in advance for help and guidance. Kind regards gxl

2 2

Re: [Boost-users] [filesystem] std::bad_alloc during dll initialization when migrating to filesystem v3
by Richard Ulrich 18 Apr '11

18 Apr '11

I can not reproduce the behavior with a toy project containing 3 dlls that all use boost::filesystem. It might be some incompatibility with another library. But with filesystem v2 it works. So, what should I look for. I searched google extensively for std::bad_alloc during dll initialization, but found no solution so far. Rgds Richard > Date: Wed, 13 Apr 2011 16:51:41 +0200 > From: Richard Ulrich <richi(a)paraeasy.ch> > To: boost-users(a)lists.boost.org > Subject: [Boost-users] [filesystem] std::bad_alloc during dll > initialization when migrating to filesystem v3 > Message-ID: <1302706301.2665.13.camel@one> > Content-Type: text/plain; charset="us-ascii" > > Hi Guys, > > I'm currently migrating our system consisting of multiple dll's and and > executable to filesystem v3. > The first two dll's that use boost::filesystem load ok, but the third > fails with std::bad_alloc in the locale copy constructor called from > default_locale during the construction of dot_path. > > I don't know if it's relevant, but we usually work with char while > filesystem uses wchar_t for BOOST_WINDOWS_API > > Rgds > Richard

3 3

[Serialization] creating an archive fails under GCC-4.6.0
by doug livesey 18 Apr '11

18 Apr '11

Hi -- I have some code that runs when compiled with GCC-4.2 (on OSX Snow Leopard), but that throws the following error with my fresh compile of 4.6.0: run_features(2872) malloc: *** error for object 0x100502060: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug The line that creates this error is here, on line 24: https://gist.github.com/923262 (Apologies for any egregious code abuses in there, I'm just learning!) In the debugger, it lets me step from that line to the constructor of xml_oarchive (line 114 of xml_oarchive.hpp), and when I try to step any further, I get this: run_features(2885) malloc: *** error for object 0x100501b00: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug Program received signal SIGABRT, Aborted. 0x00007fff871a95d6 in __kill () Could anyone advise me on what I could do to fix this? I really want to be working with GCC 4.6.0 and the boost serialisation libraries. Incidentally, I reinstalled boost after I installed the latest GCC (with homebrew), and I'd set cc, gcc, and g++ symlinks to GCC-4.6.0 before I did that, so boost should be compiled with the latest. Thanks very much for any & all assistance. Doug.

3 3

Boost asio lib question: async_accept and EBADF
by olegb＠it-forces.com 18 Apr '11

18 Apr '11

Cheers, I have a question regarding handling error bad file descriptor in asio async_accept. Standard example doesn't expose whether it's fatal or not. If I understand correctly bad_descriptor error is not fatal here, like it would be for usual POSIX accept() call, and we should continue accepting new incoming calls, no? void handle_accept(tcp_connection::pointer new_connection, const boost::system::error_code& error) { if (!error) { new_connection->start(); start_accept(); } } e.g. if (!error) { new_connection->start(); start_accept(); } else if (error == bad_descriptor) { start_accept(); } -- King regards, Oleh

1 0

Pimpl framework comments/suggestions
by Clinton Mead 18 Apr '11

18 Apr '11

Hi All I've been experimenting with pimpl recently. What I've seen written about the pimpl idiom is that you have an interface class and an implementation class, and in the interface class you put some kind of pointer to the implementation. However, I thought, sometimes you might want that to be a shared pointer. Or an intrusive pointer. Or unique pointer. Or maybe sometimes you might decide not to use pimpl at all. I thought it was a bit silly that you had to make these decisions at the time you create the interface class. I thought it would be nice if you could write the interface independent of how it was going to be connected to the implementation, and then hook them together however you like. So this is what I've done. Basically I've broke things up into three separate parts: (1) Interface (2) Implementation (3) What joins them together (i've created unique_pimpl and shared_pimpl as examples) I've implemented a unique_ptr and shared_ptr pimpl implementations as examples. The idea is that you can basically do this: unique_pimpl<interface, impl>::create(...) or shared_pimpl<interface, impl>::create(...) make_your_own<interface, impl>::create(...) for any interface and implementation you choose. I've included all the code in a question at http://stackoverflow.com/questions/5666442 but it doesn't seem to be getting much attention there, so I thought I'd bring it up on this list. If something like this isn't in Boost, and people like it, with a bit of help I'd be happy to work on it to get it into Boost. Alternatively I'm happy for someone else to Boostify this. I've used a bit of c++0x in the code, gcc 4.4.5 will compile it though. However if I'm just (badly) reinventing the wheel, if someone could direct me to where this has already been done that would be good to. Thanks Clinton

2 5

filesystem v3, unicode and std::codecvt linker error
by archie14 18 Apr '11

18 Apr '11

I am porting the code from (boost44, msvc2008, Qt, unicode support) to (boost46, msvc2010, Qt, unicode support). I am getting following linker error: error LNK2001: unresolved external symbol "private: static class std::codecvt<unsigned short,char,int> const * & __cdecl boost::filesystem3::path::wchar_t_codecvt_facet(void)" (? wchar_t_codecvt_facet@path@filesystem3@boost@@CAAAPBV?$codecvt@GDH@std@@XZ) I found that std::codecvt defined in <xlocale>. May be the filesystem lib should be built in certain way to support widestrings? Any advise/help will be greatly appreciated.

1 1

[system] static linking + static member in y a dynamic design
by Amoriello Hutti 17 Apr '11

17 Apr '11

Hi everyone, I am facing a "design" issue while sharing error_codes across modules boundaries. Has I understand the design, error_categories like "generic_error_category" are static (maybe to provide unique way to represent error_category, avoiding error_category ID confilct, and allowing users to extend with there own categories). The question is : How can we share error_code across modules (A and B), when these modules are both statically linked with there own boost::system library (same version)? Under Windows operating system, both static version of boost::system library co-exist in the same process address space (that contains module A and module B), they do not share code or static data members. Comparison between error_code is made by looking error_value and error_category, but error_categroy doesn't has the same "static" address, causing comparison to fail, even when the semantic is respected (because of the co-existing static error_category with different address). sharing the boost::system has a unique shared library used by both module A and B could solve this issue, but this solution is not suitable for certain needs. Thanks for your help! -- Amoriello Hutti

1 0

[phoenix][accumulators] Is is possible to use phoenix v3 and accumulators in parallel?
by alfC 17 Apr '11

17 Apr '11

Hi, Last week I started a thread called "[Boost-users] [phoenix][spirit] Is is possible to use phoenix v3 and spirit in parallel? " . While that issue seems under control, now I found a compatibility problem between accumulators and phoenix 3. #include <boost/phoenix/phoenix.hpp> //#include <boost/spirit/home/ phoenix.hpp> #include<boost/accumulators/accumulators.hpp> #include<boost/accumulators/statistics/min.hpp> int main(){ return 0; } gives an error boost/accumulators/numeric/detail/function_n.hpp:83:1: error: ‘apply12’ in namespace ‘boost::mpl’ does not name a type I tried predefining certain macros but it didn't work: #define BOOST_SPIRIT_USE_PHOENIX_V3 #define BOOST_PROTO_MAX_ARITY 11 #define BOOST_PROTO_MAX_LOGICAL_ARITY 11 #define BOOST_MPL_LIMIT_METAFUNCTION_ARITY 12 Is there a workaround? Thank you, Alfredo

1 0

iterator_facade and distance()
by Andrej van der Zee 17 Apr '11

17 Apr '11

Hi, I am trying to implement an iterator using boost::iterator_facade. It works fine but it is very slow, I think because the distance() function takes lineair time as it is seems to be implemented in terms of increment(). I would like to implement the distance() function myself but I am not sure how. I tried to implement distance_to() like this: class const_data_stream_iterator : public boost::iterator_facade<const_data_stream_iterator, char const, boost::forward_traversal_tag> { public: typedef boost::iterator_facade<const_data_stream_iterator, char const, boost::forward_traversal_tag> facade_t; private: friend class boost::iterator_core_access; facade_t::difference_type difference_to(const_data_stream_iterator & to) const { ... } }; But this does not work. How can I do this? Thank you, Andrej

2 6

[BGL] Modifying graph in BFS
by Michal Sekletar 16 Apr '11

16 Apr '11

Hello everyove, I have a question about BGL. I want to traverse through graph using BFS and before actual algorithm I want to remove from graph structure (adjacency_list) some vertices and all edges connected to these vertices, so I wrote my own visitor class and implemented initliaze_vertex method to do check on every vertex (it's property) if it's satisfied then I iterate through all edges in graph and i store iterators to edges - edge must be connected to current vertex. Then I want to remove these edges and vertex itself. I store edge iterators for edges connected to vertex I want to remove, because I understand that calling remove_edge directly, while iterating through edges will lead to undefined behavior (if edges are stored in vector - removing invalidates iterators). My problem is that I can't compile source file, compiler is complaining about template instantiation(error message is very long and I don't understand what is cause of the problem) Any ideas, suggestions, code snippets, how to solve this issue would be much appreciated. Thank you Michal Sekletar

2 1

[phoenix][spirit] Is is possible to use phoenix v3 and spirit in parallel?
by alfC 16 Apr '11

16 Apr '11

Hi, I have a program that uses Phoenix and Spirit. Spirit uses indirectly Phoenix2. With some effort I modified the part that use Phoenix to phoenix3 but now when I want to put all together it complains. The obivous warnings are: usr/include/boost/phoenix/version.hpp:16:1: warning: "BOOST_PHOENIX_VERSION" redefined usr/include/boost/phoenix/core/limits.hpp:23:1: warning: "PHOENIX_LIMIT" redefined and the most serious is: usr/include/boost/phoenix/core/limits.hpp:112:5: error: #error "BOOST_PROTO_MAX_LOGICAL_ARITY < BOOST_PHOENIX_COMPOSITE_LIMIT" The question is how can I use Phoenix3 and Spirit in the same code (in parallel). thank you, Alfredo

3 4

[phoenix] function object that is also lazy
by alfC 16 Apr '11

16 Apr '11

Hi, Is this possible at all? struct A : boost::phoenix::function<A const&>{ double operator()(double const& d) const{return 5.;} } such that an object function it is not only a function but also a lazy function of itself? std::clog << a(4.) << std::endl; std::clog << a(arg1 + 1.)(4.) << std::endl; the code above doesn't work because A is not complete when the type function<A> is instatiated. However after some experimentation I got the following. The question is, does it really work in more exotic context? Is there a possible simplification? Am I reinventing the wheel? template<class Self> struct lazy{ boost::phoenix::function<Self const&> const* const lazy_; lazy(Self const& self) : lazy_(new boost::phoenix::function<Self const&>(self)){} template<class Arg> const boost::phoenix::actor<boost::proto::exprns_::basic_expr<boost::phoenix::detail::tag::function_eval, boost::proto::argsns_::list2<boost::proto::exprns_::basic_expr<boost::proto::tag::terminal, boost::proto::argsns_::term<Self>, 0l>, Arg >, 2l> > operator()(Arg const& arg) const{return (*lazy_)(arg);} ~lazy(){delete(lazy_);} }; struct A : lazy<A>{ using lazy<A>::operator(); A() : lazy<A>(*this){} A(A const& other) : lazy<A>(*this){} typedef double result_type; result_type operator()(double const& d) const{return d;} }; so, any function object B can be a lazy function of it self provided that we use the correct CRTP argument (lazy<B>) and manually add the code: using lazy<A>::operator(); B() : lazy<A>(*this){} B(A const& other) : lazy<A>(*this){} inside the class. This feature seems to make the usage of the function object b more flexible, since it can we used in many different contexts. For example, as integrate ( b, 1., 2.); or as integrate ( 2.*b(arg1 + 1.) , 1., 2.) Thanks, Alfredo

1 1

Byte stream with multiple internal buffers
by Andrej van der Zee 16 Apr '11

16 Apr '11

Hi, I am writing a network sniffer that receives a variable number of TCP packets with payload strings of variable length that i need to concatenate. Using std string concatination is too expensive because of extra copying and possible reallocation of the internal buffer when it runs out of capacity. Better would be a special byte stream that stores its data in multiple variable-length buffers with an interface that works as if the buffers are just one buffer, with operations similar to std string. I was wondering if boost provides a supporting library for this. Thanks, Andrej

2 2

[karma] auto_ + default floating point precisions
by Brian Budge 15 Apr '11

15 Apr '11

Hi all - I'm using boost karma to generically generate strings from many different types use auto_. I've noticed that if I specify some double precision numbers like 1.123456, I will only get "1.123" out as a string. While looking around the documentation, it seems that it is possible to specify the precision up to numeric_limits<real>::digits10 + 1. I couldn't find an example for how to do this with double_ let alone auto_. Can anyone point me in the right direction? Is there documentation that google couldn't find for me? Thanks, Brian

2 2

[thread] : pause/resume thread
by Kazz 15 Apr '11

15 Apr '11

Hi All, I have just started learning boost. I want my thread to support following functions Pause(); Resume(); Stop();. I have come up with following code, which ends up as dead lock. Can some one please guide me as how to achieve the desired functionality. Would really appreciate any help. Thanks. Kaz class qthread { public: boost::thread* mThread; boost::condition_variable mCond; boost::mutex mMutex; bool mExit; qthread(): mExit(false) { // create function pointer to local Execute function boost::function<void (qthread*)> fptr = &qthread::Execute; fptr(this); // pass on function pointer along with this reference to boost thread boost::thread th0( fptr, this); // assign temp thread to local variable mThread = &th0; } void Resume() { mMutex.unlock(); mCond.notify_all(); } void Stop() { mThread->interrupt(); mExit = true; Resume(); } void Pause() { // todo } virtual void Execute() { std::cout<<"Entering thread Execution"<<std::endl; boost::unique_lock<boost::mutex> lock(mMutex); mCond.notify_all(); mCond.wait(lock); //<< DEAD LOCK int i = 0; while ( !mExit ) { try { while ( 1 ) { std::cout<<"Executing thread, cycle i = "<<++i<<std::endl; boost::this_thread::interruption_point(); } } catch( boost::thread_interrupted&) { std::cout<<"thread_interrupt exception"<<std::endl; mCond.wait(lock); } } std::cout<<"Exiting thread"<<std::endl; } }; //-------------------------- int main() { qthread qt; ///<< DEAD LOCK boost::this_thread::sleep(boost::posix_time::seconds(3) ); qt.Resume(); boost::this_thread::sleep(boost::posix_time::seconds(3) ); qt.Stop(); }

3 5

All-pairs SP algorithms -> Determine the path
by GOO Creations 15 Apr '11

15 Apr '11

Hi again I've noticed that the all-pairs SP algorithms (eg: Johnson, Floyd-Marshall) only "return" a distance matrix that hold the shortest distances between any node n and n'. Is there a way to determine the actual path (eg: n2-n4-n5-n1-n0) between these nodes using the all-pairs algorithms? Chris

3 2

Longest path from u to v in a directed weighted graph
by Shaun Jackman 15 Apr '11

15 Apr '11

Hi, I would like to find the longest path from vertex u to vertex v through a directed graph with positive edge weights. I know that u and v are choke points in the graph, in that if you start from vertex u and start following random edges, you will end up at vertex v in pretty short order. Is dijkstra_shortest_paths the best function for this purpose? The vertices reachable from u without travelling through v form a small subgraph of the total graph. I want to avoid exploring beyond v, and I definitely don't need to know the distances to vertices beyond v. Cheers, Shaun

4 6

Floyd-Warshall Example
by GOO Creations 15 Apr '11

15 Apr '11

Hi all I'm trying to figure out how to use the Floyd-Warshall algorithm. It seems like there is no example (like with the other algorithms); can someone maybe point me to an example. I'm having problems with the parameters, especially with the DistanceMatrix. Thank you Chris

2 2

[boost::iostreams] Is it possible to take char_type other than char or wchar_t
by 甜瓜 15 Apr '11

15 Apr '11

Hi, all, I have a proposal to make boost::iostreams support char_type other than char or wchar_t. Since the library gives users the opportunity to define char_type in Device, it should be available to boost::iostreams::copy from any source to any sink with the *same* char_type. Eg, If both Devices have UserDefinedStructure as char_type, boost::iostreams::copy should copy UserDefinedStructure objects from source to sink and return the number of objects copied. Currently, it is forbidden by a mistake (or not?) in boost::iostreams::copy. That is "detail::basic_buffer<char_type>" only allocate the raw space without construct them by using UserDefinedStructure constructor. I really appreciate this library, so would boost::iostreams please to concider my proposal? Or there are other ways to achieve this? Thank you in advance. -- leishen

1 0

boost.parameter - best practices
by Christoph Heindl 15 Apr '11

15 Apr '11

Hi, I have a set of classes that offer named parameter enabled constructors through the use of argument packs. Currently I have one huge header container all the available arguments of all classes. // params.h namespace geo { namespace keywords { BOOST_PARAMETER_NAME(a) BOOST_PARAMETER_NAME(b) } } // thing.h namespace geo { class thing { public: template<class Opts> thing(const Opts &o) { _m_x = o[Keywords::_a | 10]; //etc.. } }; } // thing2.h namespace geo { class thing2 { public: template<class Opts> thing2(const Opts &o) { _m_x = o[Keywords::_b | 10]; //etc.. } }; } First question: I'd like to place the BOOST_PARAMETER_NAME keywords as close to its usage as possible. I.e. I'd like to place BOOST_PARAMETER_NAME(a) on top of thing.h. If I do so, I think that over time other classes will start to have their own BOOST_PARAMETER_NAME(a) constructs in their header files, which I think would lead to multiple defined symbols if two class headers are included in the same translation unit, correct? So, is their any way to declare a parameter inside a class, through a typedef or similar? Let me illustrate class x { public: typedef boost::parameter::keyword<...> a; template<class Opts> x(const Opts &o) { _m_x = o[a | 10]; } }; x my_x(x::a = 5); If that is not possible, is there any way to limit the template parameter Opts in the above example to set of possible parameters? Best regards, Christoph

2 2

[Preprocessor] MSVC, File Iteration, and FLAGS()
by Robert Rumpf 14 Apr '11

14 Apr '11

I’ve reduced my problem to the following code snippet which compiles fine on GCC, but which fails to compile on MSVC (versions 9 and 10). The error provided by MSVC is “fatal error C1012: unmatched parenthesis : missing ')'”. It seems to have to do with the BOOST_PP_ITERATION_FLAGS() directive. I’m using Boost 1.45.0. Any thoughts on workarounds or bug-fixes? Thanks, Rob Rumpf *#if* !BOOST_PP_IS_ITERATING *# ifndef* __FILE_HPP__ *# define* __FILE_HPP__ *# include* <boost/preprocessor/iteration/iterate.hpp> *# include* <boost/preprocessor/seq/size.hpp> *# include* <boost/preprocessor/arithmetic/dec.hpp> /// Set up the first (most outer) nested FOR loop. *# define* INDICES_1 (A)(B) /// Set up the second (middle) nested FOR loop. *# define* INDICES_2 (C)(D) /// Set up the third (inner) nested FOR loop (1 of 3). *# define* INDICES_3a (E)(F) /// Set up the third (inner) nested FOR loop (2 of 3). *# define* INDICES_3b (G)(H) /// Set up the third (inner) nested FOR loop (3 of 3). *# define* INDICES_3c (I)(J) // Set up the number of iterations (see the Boost.Preprocessor library). // Set up the filename to be called (which is this one, see the Boost.Preprocessor library). *# define* BOOST_PP_ITERATION_PARAMS_1 (3, (0, BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(INDICES_1)), "file.hpp")) // Iterate (see the Boost.Preprocessor library) on the first (most outer) nested FOR loop. *# include* BOOST_PP_ITERATE() *# endif* // __FILE_HPP__ // Choose the first iteration. *#elif* BOOST_PP_ITERATION_DEPTH() == 1 // Set up the number of iterations (see the Boost.Preprocessor library). // Set up the filename to be called (which is this one, see the Boost.Preprocessor library). *# define* BOOST_PP_ITERATION_PARAMS_2 (3, (0, BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(INDICES_2)), "file.hpp")) // Iterate (see the Boost.Preprocessor library) on the second (middle) nested FOR loop. *# include* BOOST_PP_ITERATE() // Choose the second iteration. *#elif* BOOST_PP_ITERATION_DEPTH() == 2 // Set up the number of iterations (see the Boost.Preprocessor library). // Set up the filename to be called (which is this one, see the Boost.Preprocessor library). *# define* BOOST_PP_ITERATION_PARAMS_3 (4, (0, BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(INDICES_3a)), "file.hpp", 0)) // Iterate (see the Boost.Preprocessor library) on the third (inner) nested FOR loop (1 of 3). *# include* BOOST_PP_ITERATE() // Set up the number of iterations (see the Boost.Preprocessor library). // Set up the filename to be called (which is this one, see the Boost.Preprocessor library). *# define* BOOST_PP_ITERATION_PARAMS_3 (4, (0, BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(INDICES_3b)), "file.hpp", 1)) // Iterate (see the Boost.Preprocessor library) on the third (inner) nested FOR loop (2 of 3). *# include* BOOST_PP_ITERATE() // Set up the number of iterations (see the Boost.Preprocessor library). // Set up the filename to be called (which is this one, see the Boost.Preprocessor library). *# define* BOOST_PP_ITERATION_PARAMS_3 (4, (0, BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(INDICES_3c)), "file.hpp", 2)) // Iterate (see the Boost.Preprocessor library) on the third (inner) nested FOR loop (3 of 3). *# include* BOOST_PP_ITERATE() // Look for the third nested loop, but index over INDICES_3a this time. *#elif* BOOST_PP_ITERATION_DEPTH() == 3 && BOOST_PP_ITERATION_FLAGS() == 0 // Look for the third nested loop, but index over INDICES_3b this time. *#elif* BOOST_PP_ITERATION_DEPTH() == 3 && BOOST_PP_ITERATION_FLAGS() == 1 // Look for the third nested loop, but index over INDICES_3c this time. *#elif* BOOST_PP_ITERATION_DEPTH() == 3 && BOOST_PP_ITERATION_FLAGS() == 2 *#endif* // BOOST_PP_IS_ITERATING

1 0

[boost::threads] -D_REENTRANT?
by Panagiotis Foteinos 14 Apr '11

14 Apr '11

Hello users. I am using boost::threads for an application that allocates space in heap with the new operator. Therefore, different threads allocate memory in parallel. Do I have to link my application to any other library apart from the libboost_thread to guarantee a thread safe memory allocation? I searched online, but I got more confused. Do I have to define the -D_REENTRANT or the -pthread symbol? Best Regards, Panagiotis Foteinos

3 3

Boost::bind member function and save to function pointer
by David McCallum 14 Apr '11

14 Apr '11

I'd like to implement an event-handling scheme that supports member functions. For example, I would have a class that accepts a function pointer, stores it, and calls that function when some event occurs. I'd like to be able to store a pointer to a member function with boost::bind(): void staticReceiver(std::string message) { cout << message << endl; }//staticReceiver void ChatClient::memberReceiver(std::string message) { cout << message << endl; }//testReceiver void ChatClient::testBind(void) { void (*funcPointer)(std::string message); boost::bind(&ChatClient::memberReceiver, this, _1)("Bind works"); funcPointer = staticReceiver; (*funcPointer) ("Function pointer works"); //##### THIS LINE WILL NOT COMPILE ##### funcPointer = boost::bind(&ChatClient::memberReceiver, this, _1); }//testBind However, I get the following compiler error: g++ -DHAVE_CONFIG_H -I. -I./libdasyne/lowlevel -I/opt/boost/include -D_REENTRANT -Wall -g -O2 -MT ChatClient.o -MD -MP -MF .deps/ChatClient.Tpo -c -o ChatClient.o `test -f 'examples/ChatClient.cpp' || echo './'`examples/ChatClient.cpp examples/ChatClient.cpp: In member function ‘void ChatClient::testBind()’: examples/ChatClient.cpp:56: error: cannot convert ‘boost::_bi::bind_t<void, boost::_mfi::mf1<void, ChatClient, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::_bi::list2<boost::_bi::value<ChatClient*>, boost::arg<1> > >’ to ‘void (*)(std::string)’ in assignment make: *** [ChatClient.o] Error 1 Can it be done? Thanks in advance.

5 5

[phoenix] v2 to v3 transition of extension mechanism
by alfC 14 Apr '11

14 Apr '11

Hi, I am updating some of my code to use Phoenix3 instead of Phoenix2. For example in Phoenix2 I used to have this extension to support 'cos(...)' expressions: namespace boost{ namespace phoenix{ struct cos_eval{ template<class Env, typename Arg_> struct result{typedef double type;}; template<class RT, typename Env, typename Arg_> static RT eval(Env const& env, Arg_ const& arg_){ return cos(arg_.eval(env)); } }; template<typename Arg_> void cos(Arg_ const& arg_){ return compose<cos_eval>(arg_); } }} In Phoenix3, if I followed things correctly (from here https://svn.boost.org/svn/boost/sandbox/SOC/2010/phoenix3/libs/phoenix/doc/…) the new framework ask for the following, which doesn't work. The error (see at end) is difficult to decipher. What am I missing to implement this simple expression extension? -- Thanks. #include<boost/phoenix/phoenix.hpp> //v3 BOOST_PHOENIX_DEFINE_EXPRESSION( (boost)(phoenix)(cos_) , (meta_grammar) // Arg ) namespace boost { namespace phoenix { struct cos_eval{ typedef double result_type; template <typename Context, typename Arg> result_type operator()(Context const& ctx, Arg const& arg) const{ return std::cos(eval(arg, ctx)); } }; template <typename Dummy> struct default_actions::when<rule::cos_, Dummy> : call<cos_eval, Dummy> {}; template <typename Arg> typename expression::cos_<Arg>::type const cos_(Arg const& arg){ return expression::cos_<Arg>::make(arg); } }} usr/include/boost/proto/matches.hpp:846:13: error: no type named ‘proto_tag’ in ‘const struct boost::phoenix::vector2<boost::phoenix::vector2<const boost::phoenix::actor<boost::proto::exprns_::basic_expr<boost::phoenix::tag::cos_, boost::proto::argsns_::list1<boost::phoenix::actor<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<boost::phoenix::argument<1> >, 0l> > >, 1l> >*, double&>&, const boost::phoenix::default_actions&>’ compilation terminated due to -Wfatal-errors.

3 7

[phoenix] Basic recursive function.
by Robert Jones 14 Apr '11

14 Apr '11

I'm a newbie to Phoenix, just exploring, but I guess my intent in this code is obvious. Can anyone tell me what I'm doing wrong? Thx - Rob. #include <iostream> #include <boost/spirit/include/phoenix_core.hpp> #include <boost/spirit/home/phoenix/operator.hpp> #include <boost/spirit/home/phoenix/statement.hpp> #include <boost/function.hpp> using namespace boost::phoenix; using namespace boost::phoenix::arg_names; using namespace std; int main() { boost::function<unsigned( unsigned )> factorial; factorial = if_else( _1 == 0, 1, _1 * factorial( _1 - 1 ) ); cout << factorial( 3 ) << endl; return 0; }

3 4

run time error for min_max_paths.cpp of Graph Library 1.46.1 on Fedora 12
by albert kao 14 Apr '11

14 Apr '11

I compiled the min_max_paths.cpp in the example directory of BGL 1.46.1 on Fedora 12. $ g++ -I ~/boost_1_46_1 min_max_paths.cpp -o min_max_paths \ -L ~/boost_1_46_1_build/boost/bin.v2/libs/graph/build/gcc-4.4.4/release/link-static/threading-multi/ -lboost_graph Please help to solve the following run time error. $ min_max_paths terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::negative_edge> >' what(): The graph may not contain an edge with negative weight. Aborted (core dumped) My configuration is as follows: $ uname -a Linux triplecore 2.6.31.5-127.fc12.i686 #1 SMP Sat Nov 7 21:41:45 EST 2009 i686 athlon i386 GNU/Linux $ g++ -v Using built-in specs. Target: i686-redhat-linux Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla--enable-bootstrap --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre --enable-libgcj-multifile --enable-java-maintainer-mode --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib --with-ppl --with-cloog --with-tune=generic --with-arch=i686 --build=i686-redhat-linux Thread model: posix gcc version 4.4.4 20100630 (Red Hat 4.4.4-10) (GCC)

2 1

[format] Reuse of the format object
by Maxime van Noppen 14 Apr '11

14 Apr '11

Hi, I've got a question about the reuse of the boost::format object. Given this minimal testcase: ----------------------------------------------------------- #include <iostream> #include <boost/format.hpp> int main() { boost::format fmt("%|=12| %|=12| %|=12|\n"); // 1 std::cout << boost::str(fmt % "a" % "b" % "c") << boost::str(fmt % 1 % 2 % 3); // 2 std::cout << fmt % "a" % "b" % "c" << fmt % 1 % 2 % 3; } ----------------------------------------------------------- Why is 1 working while 2 produces the runtime exception: > terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::io::too_many_args> >' > what(): boost::too_many_args: format-string referred to less arguments than were passed ? I didn't find an explanation about this in the doc & the example about the reuse of format objects here: http://www.boost.org/doc/libs/1_46_1/libs/format/example/sample_advanced.cpp Using boost 1.46.0 and g++ 4.5.2. Thanks, -- Maxime

3 5

Re: [Boost-users] Boost::bind member function and save to function pointer
by justin allen 14 Apr '11

14 Apr '11

you probably really do want to look into an event system that will prescribe a bit of pre-built organization but if you just want to store the bind for later boost function will do it. http://www.boost.org/doc/libs/1_46_1/doc/html/function.html #include <boost/bind.hpp> #include <boost/function.hpp> #include <iostream> boost::function<void (std::string)> func; class Object { void runner(std::string message) { std::cout << message << std::endl; } public: void assign() { func = boost::bind(&Object::runner, this, _1); } }; int main(int argc, char **argv) { Object obj; obj.assign(); func("my message"); return 0; }

1 0

[filesystem] std::bad_alloc during dll initialization when migrating to filesystem v3
by Richard Ulrich 13 Apr '11

13 Apr '11

Hi Guys, I'm currently migrating our system consisting of multiple dll's and and executable to filesystem v3. The first two dll's that use boost::filesystem load ok, but the third fails with std::bad_alloc in the locale copy constructor called from default_locale during the construction of dot_path. I don't know if it's relevant, but we usually work with char while filesystem uses wchar_t for BOOST_WINDOWS_API Rgds Richard

1 0

Intrusive
by asif saeed 13 Apr '11

13 Apr '11

Hi, I frequently come across the term "intrusive" in boost users mailing list. What does it mean? Would any of you please provide a reference such as an online reference/link, etc? TIA, Asif

3 2

Writing large binary files with boost gzip
by Anders Knudby 13 Apr '11

13 Apr '11

Hello all, please help! I'm truly banging my head against the wall here. I am trying to write a function that will allow me to write gzipped binary files (~50 MB) and read them again. I have data in memory. Here's my code for writing: namespace io = boost::iostreams; filename = "c:/test.bin.gz"; //My output file int size = 5000000; //Data size in bytes, ~5 MB //Create filtering_ostream io::filtering_ostream out; //Creates a filtering_ostream called out out.push(io::gzip_compressor()); //Assigns the gzip_compressor to out out.push(io::file_sink(filename)); //Assigns a file sink to out char* memblock = new char [size]; //This is my data. In reality memblock will have been created earlier and filled with real data out.write(memblock, size); //Do the writing delete[] memblock; //Clean up As written above the resulting file, c:/test.bin.gz, is corrupt. If I try to decompress it, either with gzip or winrar, I get an error message. However, if I instead set size = 4000000 (~4 MB) (slightly smaller), the resulting file works just fine. My problem therefore is that my actual size is 50 MB... Please help! Anders (not a real programmer)

4 6

[Floating Point Utilities] where is the "nonfinite_num_facets.hpp"
by François Mauger 13 Apr '11

13 Apr '11

Hi As far as I understood, the Floating Point Utilities vault contribution by Johan R°ade has been integrated in the Boost official release. I've been using the "nonfinite_num_facets.hpp" header file for a few years within old Boost versions, directly extracted from the vault ZIP file released by Johan. Now, I can use the "fpclassify.hpp" file directly from the "boost/spirit/home/support/detail/math/" directory. Unfortunately I cannot find the "nonfinite_num_facets.hpp" file. Where can I find the "nonfinite_num_put/get" template class in say Boost 1.44 ? Maybe it has not been renamed in some other file or even not accepted at all... It is very useful for making my text and xml archives protable with NaNs and infinity support. Thanks for any hint or help. frc -- François Mauger Groupe "Interactions Fondamentales et Nature du Neutrino" NEMO-3/SuperNEMO Collaboration LPC Caen-CNRS/IN2P3-UCBN-ENSICAEN Département de Physique -- Université de Caen Basse-Normandie Adresse/address: Laboratoire de Physique Corpusculaire de Caen (UMR 6534) ENSICAEN 6, Boulevard du Marechal Juin 14050 CAEN Cedex FRANCE Courriel/e-mail: mauger(a)lpccaen.in2p3.fr Tél./phone: 02 31 45 25 12 / (+33) 2 31 45 25 12 Fax: 02 31 45 25 49 / (+33) 2 31 45 25 49

2 8

[Boost Serialization] Cannot handle UTF-8 BOM bytes in XML file
by Tijmen van Voorthuijsen 13 Apr '11

13 Apr '11

Hi, I am using boost::archive::xml_woarchive to create XML files under Windows, Visual Studio 2008, and in wide character mode. The boost::archive::xml_woarchive does not write the UTF-8 three BOM bytes to the file and from http://en.wikipedia.org/wiki/Byte_order_mark I understand that this is all right since it is optional and even not recommended. Problems start when I want to edit the file in for example XML Notepad which adds the three BOM bytes when saving. Under Windows this seems normal behavior. Then parsing the XML file throws an exception through the boost::archive::xml_wiarchive. My question/recommendation: - Why can't the boost::archive::xml_serialization library not cope with the UTF-8 BOM bytes? - I would recommend that the library can handle XML UTF-8 files, with and without the three BOM bytes. Both are in fact valid UTF-8 XML files. I now check for the BOM bytes myself before I parse the ifstream in boost::xml_serialization and that works fine. Many thanks for your answer. Tijmen van Voorthuijsen

2 1

Re: [Boost-users] Cycle detection in a directed graph with adjacency_matrix
by Jeremiah Willcock 13 Apr '11

13 Apr '11

On Tue, 12 Apr 2011, albert kao wrote: > After adding "boost::" before "graph_traits", the compile errors are: > adjacency_matrix_is_cyclic.cpp:9: error: expected class-name before ‘{’ token > adjacency_matrix_is_cyclic.cpp: In function ‘bool has_cycle(const Graph&)’: > adjacency_matrix_is_cyclic.cpp:26: error: ‘generic_dfs_v1’ was not declared in this scope > > adjacency_matrix_is_cyclic.cpp: > #include <iostream> > #include <boost/graph/graph_utility.hpp> > #include <boost/graph/adjacency_matrix.hpp> > > typedef boost::adjacency_matrix<boost::directedS> Graph; > typedef boost::graph_traits<Graph>::edge_descriptor edge_t; > > struct cycle_detector : public dfs_visitor_default > { > cycle_detector(bool & cycle): has_cycle(cycle) > { > } > void > back_edge(edge_t, const Graph &) > { > has_cycle = true; > } > bool & has_cycle; > }; > > bool > has_cycle(const Graph & g) > { > bool has_cycle = false; > cycle_detector vis(has_cycle); > generic_dfs_v1(g, vis); > return has_cycle; > } > > enum { A, B, C, D, E, F, N }; > const char* name = "ABCDEF"; > > int main(int argc, char *argv[]) > { > Graph g(N); > add_edge(B, C, g); > add_edge(B, F, g); > add_edge(C, A, g); > add_edge(C, C, g); > add_edge(D, E, g); > add_edge(E, D, g); > add_edge(F, A, g); > > std::cout << "vertex set: "; > boost::print_vertices(g, name); > std::cout << std::endl; > > std::cout << "edge set: "; > boost::print_edges(g, name); > std::cout << std::endl; > > std::cout << "out-edges: " << std::endl; > boost::print_graph(g, name); > std::cout << std::endl; > > std::cout << "has_cycle(g) " << has_cycle(g) << std::endl; > > return 0; > } You also need boost:: before dfs_visitor_default. You should also use boost::depth_first_search instead of generic_dfs_v1 (which is internal). -- Jeremiah Willcock

2 2

Cycle detection in a directed graph with adjacency_matrix
by albert kao 13 Apr '11

13 Apr '11

Is it possible to detect any cycle in a directed graph with the adjacency_matrix of the Boost Graph Library? My test program has this compile errors: adjacency_matrix_is_cyclic.cpp:6: error: expected initializer before ‘<’ token adjacency_matrix_is_cyclic.cpp:9: error: expected class-name before ‘{’ token adjacency_matrix_is_cyclic.cpp:14: error: ‘edge_t’ has not been declared adjacency_matrix_is_cyclic.cpp: In function ‘bool has_cycle(const Graph&)’: adjacency_matrix_is_cyclic.cpp:26: error: ‘generic_dfs_v1’ was not declared in this scope $ cat adjacency_matrix_is_cyclic.cpp #include <iostream> #include <boost/graph/graph_utility.hpp> #include <boost/graph/adjacency_matrix.hpp> typedef boost::adjacency_matrix<boost::directedS> Graph; typedef graph_traits<Graph>::edge_descriptor edge_t; struct cycle_detector : public dfs_visitor_default { cycle_detector(bool & cycle): has_cycle(cycle) { } void back_edge(edge_t, const Graph &) { has_cycle = true; } bool & has_cycle; }; bool has_cycle(const Graph & g) { bool has_cycle = false; cycle_detector vis(has_cycle); generic_dfs_v1(g, vis); return has_cycle; } enum { A, B, C, D, E, F, N }; const char* name = "ABCDEF"; int main(int argc, char *argv[]) { Graph g(N); add_edge(B, C, g); add_edge(B, F, g); add_edge(C, A, g); add_edge(C, C, g); add_edge(D, E, g); add_edge(E, D, g); add_edge(F, A, g); std::cout << "vertex set: "; boost::print_vertices(g, name); std::cout << std::endl; std::cout << "edge set: "; boost::print_edges(g, name); std::cout << std::endl; std::cout << "out-edges: " << std::endl; boost::print_graph(g, name); std::cout << std::endl; std::cout << "has_cycle(g) " << has_cycle(g) << std::endl; return 0; }

2 1

[Fusion] Adapting read-only fields of ADTs
by Sebastian Redl 12 Apr '11

12 Apr '11

Hi, How would I use BOOST_FUSION_ADAPT_ADT to turn an ADT that doesn't expose setters into a read-only sequence? In other words, what do I pass as set_exprN if there is no valid set expression? Sebastian

4 4

a quick question regarding boost::bind, with a test case
by Littlefield, Tyler 12 Apr '11

12 Apr '11

Hello all: I have a quick question regarding boost::bind, as the subject line says. This isn't a very viable example, but it works well enough to show what I want. I have a callback I am using boost::bind to bind to, and I am passing a function object in as shown by the following code: #include <cstdio> #include <boost/bind.hpp> #include <boost/function.hpp> class Math { public: void Add(int a, int b, int c, boost::function<void (int)> printer); { printer(a+b+c); } }; void Printer(int p) { printf("%d\n", p); }How might I make this work? I am not sure how I can pass that as the fourth argument so that the function can be called like (1,2,3) etc. Also, in the actual problem I moved the function object to the first argument, (which just ment changing the prototype and actual function), but I still got errors. -- Thanks, Ty

3 5

[function] How to get boost::function parameters, return type.
by Mostafa 12 Apr '11

12 Apr '11

Hi, Is it possible to decompose boost::function into it's "constituent" parameters and return type, a la Boost.FunctionTypes? Thanks, Mostafa

3 4

[boost-user][asio] is packet analysis feasible, and if so how to proceed (references for learning about it needed)
by Ted Byers 12 Apr '11

12 Apr '11

I am investigating the possibility of developing something like a web-shield using boost::asio. What I mean is this. One vulnerability for ecommerce sites is that a session may be hijacked once a user has been validated. Someone intent on fraud may then use that session for a variety of different kinds of fraud. I expect that the lowest level IP address has to be the actual machine making each request (otherwise the attacker would not be able to get the responses to requests he's made), and that one of the things a fraudster may be doing is falsifying the IP addresses in HTTP headers. I also expect some may be using proxy servers to hide their real identity or location. The first thing I need to learn about is whether there are classes or structs defined within asio that facilitate getting packets in a form that would support the sort of packet analysis that may be useful. I would suppose I would need to make a set of classes that collects HTTP headers, to ease examining them particularly for IP data. Ideally, I'd like to be able to examine each major OSI layer (in part, just to learn how they work in real life). And I' like to try to examine the route by which a given HTTP request as arrived at the server that is to handle it, if that is at all possible. And, I'd like to investigate what sorts of patterns ought to be considered with a view toward detecting any form of misbehaviour a fraudster may resort to. If any of this proves feasible, I'd like to create an intelligent 'shield' based on asio that receives incoming http traffic, examines it for misconduct, and if no such behaviour is found just forward the request on to the real server, and if there is evidence of misbehaviour, redirect the user to either static advertizing pages or whatever challenge-response system a merchant may want to try to use in order to reduce his vulnerability to online fraud. I have yet to see any ecommerce software that tries to protect both consumers and merchants from online fraud in this manner, and have spent much of my time writing code that tries to detect fraud, among other problems, after the fact. But it is such a costly process for some merchants, I would like to become more pro-active, to try to prevent it. Alas, although I have written plenty of quantitative code, I have no experience with network programming in C++, so I don't really know what is feasible (but being an R&D kind of guy, I have no qualms about trying to learn stuff that is new to me ;-) Any insights into what is available and what is possible (with URLs to useful resources) would be greatly appreciated. Thanks Ted

1 0

[Boost.MPI] Scattering/Sending a complicated object
by Ryan Lewis 12 Apr '11

12 Apr '11

I have an object which has as a private type a boost::unordered_map<Object,Struct>, and an iterator, which iterates over the map elements. For a given <Object, Struct> map element, the value Struct has a member variable, which is an integer storing a value between 0,...,#NUM_PROCESSORS-1. I'd like to 'scatter' the object by creating new instances of this object on all the threads, where a given <key,value> pair is on processor i, if value has this integer set to be value i. I suppose I could perform a large number of Sends and Receives, i.e. iterate over the complex, and then send a <key,value> pair to the correct worker node every time I find it, but, this seems bad communication wise? Would there be a way to somehow buffer the sends happen at once? Or is there possibly an even better way of doing this? -rhl

1 0

[Serialization] How to serialize a derived type but deserialize it as a base type pointer?
by Jerry 12 Apr '11

12 Apr '11

I know that we can serialize/deserialize a derived type through a base type pointer (using register_type()). But I cannot serialize a derived type and deserialize it through a base type pointer. It seems to me the data type in serialization and deserialization should be extactly the same one. What I want is, Base{...}; Derived : Base{...}; Derived d; boost::archive::binary_oarchive oa(...); oa << d; // serialize a derived object Base *b; boost::archive::binary_iarchive ia(...); ia.register_type(); ia >> b // Deseiralize to a base type pointer I have tried this but it does not work. Is there any way to make this work? Many thanks!!! -- View this message in context: http://boost.2283326.n4.nabble.com/Serialization-How-to-serialize-a-derived… Sent from the Boost - Users mailing list archive at Nabble.com.

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Boost Install fails?
by Dreamcat4 12 Apr '11

12 Apr '11

Hello, I am completely new to Boost framework. However like many others I am finding the initial stage(s) - namely that what is happening during the install seems particularly complicated. I guess most people here have been able to get going with Boost by glazing over the install and "it just works". Other people can run into a myriad of issues. So I guess my problem sits somewhere in-between those two extremes. One thing I cannot vouch for is not knowning (or wanting to know!) what boost is doing, and not seeing anywhere some firm list of requirements (eg system paths for libraries, etc) - I cannot be sure that my system has some misconfiguration somewhere that (is probably) causing this issue. However what is clear to me is that many other people can install boost on *their* systems with no apparent issue. So... whats the problem? In a nutshell, boost will only compile if i am UID=0 (root user / sudo superuser). As a normal, regular user boost install fails with the following error(s): janitors-Mac-mini:boost_1_46_1 id$ ./bootstrap.sh --show-libraries -n Building Boost.Jam with toolset darwin... Failed to build Boost.Jam Consult 'bootstrap.log' for more details bootstrap.log: https://gist.github.com/915620 It doesnt seem to matter the exact version of boost, or even the "CMake" version of boost. They all behave the same way. Whats unfortunate for me especially is that after successfully compiling jam (as root), and chown'ing down all the created files in the boost directory. The same error still seems to occur afterward. For example to compile such selected library. Has anyone seen anything like this? What could be the possible issue here? Is it really normal to compile everything as root?!!? Operating system - Mac OS-X Snow Leopard. Thanks in advance. dreamcat4 dreamcat4(a)gmail.com

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[optional] Comparing boost::optional<T> to NULL yield inconsistent results
by Martin B. 12 Apr '11

12 Apr '11

Hi. I have the following problem: One of our devs used (my_opt != NULL) to check an boost::optional for emptiness. This lead me to write the following test case: ... using namespace std; boost::optional<int> num_opt; boost::optional< std::string > obj_opt; if(obj_opt) { cout << "(3) Object: " << *obj_opt << endl; } // Compiles and does what the user intended - // BUT is this what the boost optional interface intends?? - // namely checking the optional for empty: if(obj_opt != NULL) { cout << "(4) Object: " << *obj_opt << endl; } if(num_opt) { cout << "(1) Integer: " << *num_opt << endl; } // Compiles and crashes, because the user actually // should have written if(num_opt) but, being used to pointers, // wrote the below, which compiles fine, but does not check for empty // but for equality with zero: if(num_opt != NULL) { cout << "(2) Integer: " << *num_opt << endl; } ... I find the behaviour of boost::optional<int> vs. opt<ClassType> highly un-intuitive. Wouldn't it be better if comparing an boost::optional always required to "dereference" it? I checked the headers (Boost 1.44) and sadly there doen't seem to be a preprocessor switch to disable the implicit comparison operators ... I would appreciate if other users could comment on my observations. Thanks! cheers, Martin

1 0

[PBGL] add_edge return type
by Cosimo Calabrese 12 Apr '11

12 Apr '11

Hi to all, I'm trying to use the PBGL lib on VS2010, WinXP, with OpenMPI support; I've compiled without any problem the "dijkstra_shortest_paths.cpp" that I've found in \boost\libs\graph_parallel\example. So I've tried to add a new edge to the graph, and to assign a property value to it. The "classical" mode that I always have used in sequential BGL is: boost::graph_traits<Graph>::edge_descriptor ed; bool inserted; boost::tie( ed, inserted ) = boost::add_edge( boost::vertex( 0, g ), boost::vertex( 0, g ), g ); But the compiler scream... it seems that I can't initialize a tie object in that manner (I've reported the compiler log below). Instead if I first add an edge (with no assignment to tie object), and retrive it with boost::edge function, all works: boost::property_map<Graph, boost::edge_weight_t>::type weightMap = boost::get( boost::edge_weight, g ); boost::graph_traits<Graph>::edge_descriptor ed; bool exists; boost::add_edge( boost::vertex( 0, g ), boost::vertex( 0, g ), g ); boost::tie( ed, exists ) = boost::edge( boost::vertex( 0, g ), boost::vertex( 0, g ), g ); weightMap[ ed ] = 10; What's wrong? Thanks, Cosimo Calabrese. 1>src\main.cpp(75): error C2679: '=' binario: non è stato trovato alcun operatore che accetti un operando destro di tipo 'boost::adjacency_list<OutEdgeListS,VertexListS,DirectedS,VertexProperty,EdgeProperty>::lazy_add_edge'. È anche possibile che non vi siano conversioni accettabili. 1> with 1> [ 1> OutEdgeListS=boost::vecS, 1> VertexListS=boost::distributedS<boost::graph::distributed::mpi_process_group,boost::vecS>, 1> DirectedS=boost::undirectedS, 1> VertexProperty=vertex_prop, 1> EdgeProperty=boost::property<boost::edge_weight_t,float> 1> ] 1> D:\dev\lib\boost\boost/tuple/detail/tuple_basic.hpp(588): potrebbe essere 'boost::tuples::tuple<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9> &boost::tuples::tuple<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9>::operator =(const boost::tuples::tuple<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9> &)' 1> with 1> [ 1> T0=boost::detail::parallel::edge_descriptor<boost::detail::edge_desc_impl<boost::directed_tag,unsigned int>> &, 1> T1=bool &, 1> T2=boost::tuples::detail::tie_traits<void>::type, 1> T3=boost::tuples::detail::tie_traits<void>::type, 1> T4=boost::tuples::detail::tie_traits<void>::type, 1> T5=boost::tuples::detail::tie_traits<void>::type, 1> T6=boost::tuples::detail::tie_traits<void>::type, 1> T7=boost::tuples::detail::tie_traits<void>::type, 1> T8=boost::tuples::detail::tie_traits<void>::type, 1> T9=boost::tuples::detail::tie_traits<void>::type 1> ] 1> durante la ricerca di corrispondenza con l'elenco di argomenti '(boost::tuples::tuple<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9>, boost::adjacency_list<OutEdgeListS,VertexListS,DirectedS,VertexProperty,EdgeProperty>::lazy_add_edge)' 1> with 1> [ 1> T0=boost::detail::parallel::edge_descriptor<boost::detail::edge_desc_impl<boost::directed_tag,unsigned int>> &, 1> T1=bool &, 1> T2=boost::tuples::detail::tie_traits<void>::type, 1> T3=boost::tuples::detail::tie_traits<void>::type, 1> T4=boost::tuples::detail::tie_traits<void>::type, 1> T5=boost::tuples::detail::tie_traits<void>::type, 1> T6=boost::tuples::detail::tie_traits<void>::type, 1> T7=boost::tuples::detail::tie_traits<void>::type, 1> T8=boost::tuples::detail::tie_traits<void>::type, 1> T9=boost::tuples::detail::tie_traits<void>::type 1> ] 1> and 1> [ 1> OutEdgeListS=boost::vecS, 1> VertexListS=boost::distributedS<boost::graph::distributed::mpi_process_group,boost::vecS>, 1> DirectedS=boost::undirectedS, 1> VertexProperty=vertex_prop, 1> EdgeProperty=boost::property<boost::edge_weight_t,float> 1> ]

1 0

How to skip a sub-directory with filesystem3::recursive_directory_iterator in case of exception?
by Tan, Tom (Shanghai) 12 Apr '11

12 Apr '11

> >Again, I tried something like below. >for (recursive_directory_iterator itr(root, ec), itr_end; itr!=itr_end; >) >{ > ... ; > itr.increment(ec); > if(ec) itr.pop(); >} > This time itr.pop() assertion fails because "pop() on >recursive_directory_iterator with level < 1" > >Anybody got some advice? Thanks. For others facing the same problem, I've reported it as a bug and created Ticket #5403(https://svn.boost.org/trac/boost/ticket/5403). A fix was also attached

1 0

[serialization] enable_if managed serialize function
by Noah Roberts 11 Apr '11

11 Apr '11

I want to do something like so: template < typename Archive, typename T > typename boost::enable_if<some_meta_check<T>>::type serialize(Archive & ar, T & rec, unsigned int const) { ar & boost::serialization::base_object<T::type>(rec); } Unfortunately I run into trouble with ambiguous function call referring to a different <Archive,T> version of serialize declared in the serialization library. Does anyone know of a workaround for this?

1 0

[optional] Could (& should) optional be more space efficient?
by David Blaikie 11 Apr '11

11 Apr '11

>From my initial look through boost::optional's implementation, it seems as though it's doing nothing to optimize its space usage in some trivial cases. The first one I was surprised by was optional<T&> - still uses sizeof(struct { T& t; }) + sizeof(bool) space, rather than simply using a pointer to represent both the reference and the unspecified state (using null, since a reference doesn't use that state). Is there a reason for this (perhaps I'm missing something & a reference is smaller than a pointer in certain implementations). Similarly - would it be worth considering optimizing optional<bool> (though, as per the documentation, this is perhaps a little "tricky" at best, owing to the implicit bool of optional itself) to use one byte instead of two? [long term - I'm wondering if a generic "efficient optionality" could be implemented by arbitrary types - privately exposing an extra unused state from their representation for use by optional only. Then, potentially, making versions of (boost/std)::shared_ptr/unique_ptr that would be never-null (only constructible via make_shared like machinery) & optional<shared_non_null_ptr<T>> would then be an explicit representation of the optional situation, but without any overhead - shared_non_null_ptr<T> would simply expose its null state only to optional<shared_non_null_ptr<T>>]

2 1

Seeking to particular array element while deserializing
by rajiv82 11 Apr '11

11 Apr '11

I have a structure like: struct Header { vector foo; vector bar; }; I have created an array of above structure: Header *ptr = new Header[1000]; Now doing serialization/deserialization works fine with binary_oarchive. But, in some situation, I want to just deserialize particular element of array(say element at index 80). Is it possible using binary archive ? I have a work around of writing each element one by one & while de-serialization, ignore irrelevant data(in our case index 0-79) & then use proper data. But it is not optimum solution. I even tried xml archive with name as index & value as binary object by using make_binary_object. Doing something like: for(int i = 0 ; i<1000; i++) { stringstream ss ; ss << i; ar << make_nvp(ss.str().c_str(), make_binary_object(&ptr[i], 1)) ; } And deserializing 80th index object like: ar >> make_nvp("80", make_binary_object(&ptr[80], 1)) ; Program compiles fine, but result is inconsistent. Please suggest is there any better way to read(deserialize) just one element of an array. -- View this message in context: http://boost.2283326.n4.nabble.com/Seeking-to-particular-array-element-whil… Sent from the Boost - Users mailing list archive at Nabble.com.

1 0

Monitoring thread liveness using multiple threads with a single asio io_service
by Krajnak, Mike (GE Healthcare) 11 Apr '11

11 Apr '11

We have a server implemented with boost::asio that uses a vector of threads with a single io_service as in the asio http server 3 sample program. We want to check on the liveness of threads by having each thread periodically call back to a thread manager so that we can confirm it is still running. To do that we have an inner loop that uses run_one() so we can call our heartbeat function after each action is completed (pseudo code): do { num_ops = io_svc.run_one(ec) heartbeat_to_thread_manager(); } while (num_ops > 0); However, asio makes no garantees on how work is dispatched to threads. In our testing work seems to go prefentially to one thread for several iterations before going to another thread with no pattern that we can find. Is there some way we can change this solution so that we can be reasonably sure each thread will be called at least once in a some period of time or some other mechanism for monitoring thread liveness? Thanks, Mike

1 0

Re: [Boost-users] Compiling Boost with 4 byte packing...
by Brian Nantz 11 Apr '11

11 Apr '11

I finally got boost to build with visual studio 2008 and 4-byte packing. Here is what I had to do: 1. Edit the tools\build\v2\user-config.jam and add: using msvc : vc9 : "D:/Program Files/Microsoft Visual Studio 9.0/VC/bin/cl.exe" : <compileflags>-DBOOST_HAS_ABI_HEADERS <compileflags>-DBOOST_PROTO_MAX_ARITY=10 <compileflags>-DBOOST_MPL_CFG_NO_PREPROCESSED_HEADERS <compileflags>-DBOOST_MPL_LIMIT_METAFUNCTION_ARITY=10 <compileflags>-DWIN32 <compileflags>-D_DEBUG <compileflags>-D_LIB <compileflags>-D_WIN32_WINNT=0x0501 <compileflags>-D_UNICODE <compileflags>-DUNICODE <compileflags>-DBOOST_ASIO_ENABLE_BUFFER_DEBUGGING <compileflags>-Gm <compileflags>-EHsc <compileflags>-RTC1 <compileflags>-MTd <compileflags>-Zp4 <compileflags>-W4 <compileflags>-c <compileflags>-ZI <compileflags>-TP <linkflags>/MACHINE:X86 ; 2. On the bjam command line use the options: --toolset=msvc-9.0 cxxflags=-Zp4 3. Edit boost/config/user.hpp: // BOOST_ABI_PREFIX: A prefix header to include in place of whatever // boost.config would normally select, any replacement should set up // struct packing and alignment options as required. #define BOOST_ABI_PREFIX <boost/config/abi/saplib_prefix.hpp> // BOOST_ABI_SUFFIX: A suffix header to include in place of whatever // boost.config would normally select, any replacement should undo // the effects of the prefix header. #define BOOST_ABI_SUFFIX <boost/config/abi/saplib_suffix.hpp> The prefix header just contains #pragma pack(push,4) and the suffix just has #pragma pack(pop) 4. For some reason ASIO does not use the boost ABI header prefix and suffix. It has its own. Edit boost/asio/detail/push_options.hpp to use #pragma pack(push,4). The boost build now completes cleanly (with no errors or warnings) on boost 1.43. There seems to be some room for simplification or improvement here?

1 0

[boost-users][parameter] ArgumentPack Documentation Best Practices
by Christoph Heindl 11 Apr '11

11 Apr '11

Hi, I wonder if anyone could share his best practices as far as documenting Boost.Parameter enabled constructors is concerned. I'm currently doing something along the lines of /** Construct from named parameters and use defaults where parameters are empty * * * \tparam Opts ArgumentPack of options. The following options are supported * - \a min_group_size minimum number of supporting correspondences to form a group. * - \a ntrials number of times to form basis from two randomly selected correspondences. * - \a bin_size_pos quantization size for transformed point coordinates. * - \a bin_size_orientation quantization in radians for surface orientation angles. * */ template<class Opts> group_geo_hash(const Opts &opts) { this->init( opts[Keywords::_min_group_size | 10], opts[Keywords::_bin_size_pos | LibFundament::rasFloat(10)], opts[Keywords::_orientation_rad | LibFundament::rasFloat(0.2)], opts[Keywords::_ntrials | 0]); } } which is sub-optimal, because default values for options and option types are missing. Doxygen can deduce types for regular parameters as well as default values. Ideally this should work for boost.parameters as well :) Even better, Doxygen could warn about undocumented parameters. Any thoughts? Best regards, Christoph

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Re: [Boost-users] [Boost.Thread] Multithreaded Multithreaded Server (Ian Mallett)
by Marat Abrarov 11 Apr '11

11 Apr '11

> Hi, > > Fairly new to Boost. Bear with me. > > I'm trying to write a multithreaded multithreaded server (two multithreaded > operations): ideally, there should be a single process, containing at least two threads. The first > thread handles various tasks (and can start other threads to help it as well). The other thread waits > for incoming connections, and adds a new thread for each one: http://sourceforge.net/projects/asio-samples/ Look at projects "echo_server" and "qt_echo_server". They use 2 thread pools among main (GUI) thread. One thread pool (size is 1-2 threads) executes session management loop: acceptance (with limited number of active sessions), start of accepted session, end of all sessions. Second thread pool (by default is CPU number bounded) executes sessions' loops: start of asynchronous read, start of asynchronous write, IO operation completion handling. Regards, Marat Abrarov.

1 0

Re: [Boost-users] [MSM] problem compiling a functor-guard using a flaginside.
by Christophe Henry 11 Apr '11

11 Apr '11

>while developing I want to use functors for a guard. The state machine compiles well until I added a >function call to the FSM which has a template parameter. Then I always got the following error message >while compiling it with gcc 4.4.1. >SubtractionControllerNew.cpp: In member function ‘bool<unnamed>::player_::isCDLoaded::operator()(const EVT&, FSM&, SourceState&, TargetState&)’: >SubtractionControllerNew.cpp:175: error: expected primary-expression before ‘>’ token >SubtractionControllerNew.cpp:175: error: expected primary-expression before ‘)’ token >Does anybody know why this happens and how to circumvent it? I admit C++ is sometimes full of hard-to-get rules :( Try adding a template keyword: struct isCDLoaded { template <class EVT,class FSM,class SourceState,class TargetState> bool operator()(EVT const& ,FSM& fsm,SourceState& ,TargetState& ) { //return fsm.is_contained(); // this works well return fsm.template is_flag_active<CDLoaded>(); // Line 175 } }; HTH, Christophe

2 1

[Fusion] Output of adapted ADT
by Tore Halvorsen 11 Apr '11

11 Apr '11

Hi, I'm trying to output a string from an adapted class, but I'm getting 1>main.cpp(33): error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'boost::fusion::extension::adt_attribute_proxy<foo,0,false>' (or there is no acceptable conversion) for the following code (boost 1_46_1, msvc2010) Is there a header I'm missing? Very similar code works for BOOST_FUSION_DEFINE_STRUCT - and using ints or doubles also work... #include <iostream> #include <string> #include <ostream> #include <boost/fusion/include/adapted.hpp> #include <boost/fusion/sequence.hpp> class foo { public: foo(std::string const& str) : s(str) { } std::string const& get_s() const { return s; } void set_s(std::string const& str) { s = str; } private: std::string s; }; BOOST_FUSION_ADAPT_ADT( foo, (std::string const&, std::string const&, obj.get_s(), obj.set_s(val)) ); int main(int argc, char* argv[]) { foo f("foo"); std::cout << boost::fusion::front(f) << std::endl; return EXIT_SUCCESS; } -- Eld på åren og sol på eng gjer mannen fegen og fjåg. [Jøtul] <demo> 2011 Tore Halvorsen || +052 0553034554

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[Boost.Thread] Multithreaded Multithreaded Server
by Ian Mallett 10 Apr '11

10 Apr '11

Hi, Fairly new to Boost. Bear with me. I'm trying to write a multithreaded multithreaded server (two multithreaded operations): ideally, there should be a single process, containing at least two threads. The first thread handles various tasks (and can start other threads to help it as well). The other thread waits for incoming connections, and adds a new thread for each one: Server process: -Thread 1 (Handle background server operations, etc.) -helper thread 1 -helper thread 2 ... -helper thread *n* -Thread 2 (Listen for incoming connections. When found, make a new connection thread to handle it) -connection thread 1 -connection thread 2 ... -connection thread *n* I began by making heavy use of the example here<http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/example/echo/async…>. Please see my attached files for my implementation. The classes "mMindThreadServerListener" and "mMindServerHandlerClient" correspond to "server" and "session", respectively. "mMindServer" is the highest level (server process). In it, there's a thread group that contains "Thread 1" ("_thread_connection_pruner", which kills unused connections, and represents a background server operation) and "Thread 2" ("_thread_listener", which listens for incoming connections). Thread 2's need to make other threads seems to be handled by boost::asio::io_service. Unfortunately, when a connection is found, Thread 1 stops. I can only attribute this to a lock boost::asio::io_service puts, although I have no idea. Can someone explain what's going on, and possibly a better way to do this? Thanks, Ian

2 2

BOOST and Android
by Claude 10 Apr '11

10 Apr '11

Hi! It is possible compile/use BOOST with Android (3.0?) NDK? -- View this message in context: http://boost.2283326.n4.nabble.com/BOOST-and-Android-tp3439871p3439871.html Sent from the Boost - Users mailing list archive at Nabble.com.

2 1

Re: [Boost-users] [MSM] Use events twice
by Christophe Henry 10 Apr '11

10 Apr '11

> I'm using MSM to implement a client for a simple network application. Basically, the server sends messages and the client changes state and responds to them as appropriate. > > One of these messages is THROW. THROW gets two arguments: an identifier (0-3) and a value. My client is supposed to sum up the values for consecutive THROW events with the same identifier, and on a change of identifier, store the sum somewhere and start over for the new identifier. > > So I have three states (id0, id1, id2 - there's some special handling, which is why they're separate states) and an event Throw(id, value). The transitions for idN are: > Throw(my id, value) -> no switch, state.sum += value > Throw(other id, value) -> switch to state of other id, reprocess event, storing the sum is handled by the exit action > > In other words, I want the next state to immediately handle the event as well, because there's a value there I need to store. The question is, how do I do this? > > Here's a sequence of events and actions that could occur: > E1: [init] Throw(0, 4) -> [id0: ?] > Entry [id0: ?] -> [id0: 0] > [id0: 0] reprocess E1 -> [id0: 4] > E2: [id0: 4] Throw(0, 8) -> [id0: 12] > E3: [id0: 12] Throw(1, 7) -> [id1: ?] > Exit [id0: 12] -> save 12 > Entry [id1: ?] -> [id1: 0] > [id1: 0] reprocess E3 -> [id1: 7] Hi Sebastian, Let's see if I get it. Reprocessing is not going to be the problem, I suppose. An action reprocessing an event untouched would be: struct reprocess { template <class Fsm,class Evt,class SourceState,class TargetState> void operator()(Evt const& evt,Fsm& fsm,SourceState& ,TargetState& ) { fsm.process_event(evt); } }; MSM has a message queue by default so you have no risk of deadlocking yourself. Actually you might not even need to reprocess if you use internal actions and transition conflicts, so I suggest a different version. For every Throw event, sou create a conflict between a state internal transition (not necessary but more elegant and with more reuse, see below) and an external one, leading to another state if the id contained in Throw is not the one from the current state. If it is the one from the current state, we add the value from the event. I also added an Init state to make it simpler. Now, all I need to do is make the states template classes and write just one. I attach an example. Please tell me if that's what you're looking for. Christophe

2 1

any_range vs. “canonical form” - what is the latter?
by John Funnell 10 Apr '11

10 Apr '11

Boost's any_range documentation says the following: "Despite the underlying any_iterator being the fastest available implementation, the performance overhead of any_range is still appreciable due to the cost of virtual function calls required to implement increment, decrement, advance, equal etc. Frequently a better design choice is to convert to a canonical form." What does the author mean by a "canonical form"? Can someone give an example? Many thanks [question originally asked at http://stackoverflow.com/questions/5601303]

4 5

boost::mpl::plus changes type
by Peter Foelsche 10 Apr '11

10 Apr '11

It is a major annoyance that these arrithmetic operations return a different type than the input! I mean I input boost::mpl::long_ and I get a boost::mpl::integral_c Peter

3 5

boost::mpl::abs missing
by Peter Foelsche 10 Apr '11

10 Apr '11

There is no boost::mpl::abs Peter

4 4

[network] cpp-netlib v0.9-beta out now!
by Dean Michael Berris 09 Apr '11

09 Apr '11

Hi Everyone, Apologies for the cross-post, but I just want to announce that after a couple months delay because of some outstanding bugs and TODO items that needed to get dealt with, I am now ready to package a 0.9 release and with that in mind I've just uploaded the 0.9-beta release of cpp-netlib. When the beta period (1 week) is over and all outstanding bugs are addressed, the 0.9 release will be the basis for submission for review to the Boost C++ Library. You can get the beta from: https://github.com/cpp-netlib/cpp-netlib/downloads What's New in 0.9 (taken from the documentation): - IMPORTANT BREAKING CHANGE: By default all compile-time heavy parser implementations are now compiled to external static libraries. In order to use cpp-netlib in header-only mode, users must define the preprocessor macro BOOST_NETWORK_NO_LIB before including any cpp-netlib header. This breaks code that relied on the version 0.8.x line where the library is strictly header-only. - More consistent message API for client and server messages (request and response objects). - Refactoring of internal implementations to allow better separation of concerns and more manageable coding/documentation. - Client and Server constructors that support Boost.Parameter named parameters. - Client and Server cosntructors now take in an optional reference to a Boost.Asio io_service to use internally. - Documentation updates to reflect new APIs. This Beta has been tested mainly on Linux (GCC 4.4, 4.5) and Mac OS X (10.6.7, Xcode 3.2.x w/ GCC 4.2.1) builds against Boost trunk and Boost 1.45. Note that cpp-netlib does NOT work with Boost 1.46.1 because of some breaking changes in the Boost.Spirit customization points have caused cpp-netlib to cease to play well with it. That said, the issues have been addressed in Boost trunk and should be fixed in Boost.147. Thanks to everyone who contributed to making this Beta possible, namely Emre Turkay, Oleg Malashenko, and other users that filed issues on the Github issue tracker. Have a good day everyone and I do look forward to feedback! -- Dean Michael Berris http://about.me/deanberris

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[Interprocess] shared_ptr in a non-throwing mode
by Pietro Versari 09 Apr '11

09 Apr '11

Hi Ion (and everyone else), I'm a newbye and I have only one simple question: how can I construct a shared_ptr in a non-throwing mode? This example throw if there is enough space for MyType but isn't enough for my_shared_ptr: typedef managed_shared_ptr<MyType,managed_shared_memory>::type my_shared_ptr; my_shared_ptr sh_ptr = make_managed_shared_ptr( segment.construct<MyType>("object to share", std::nothrow)(), segment); Thanks, Pietro Versari

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enable_if and multiple partial specializations
by Gennadiy Rozental 09 Apr '11

09 Apr '11

Hi, It's late and I might be missing something, but I can't figure out how can I use enable_if to disambiguate 2 partial specializations where one is subcase of another one: #include <boost/utility/enable_if.hpp> #include <boost/type_traits/is_enum.hpp> #include <boost/type_traits/is_scalar.hpp> #include <iostream> template<typename T, typename Enabler=void> struct M { static void foo() { std::cout << "generic" << std::endl; } }; template<typename T> struct M<T, typename boost::enable_if<boost::is_scalar<T> >::type> { static void foo() { std::cout << "scalar" << std::endl; } }; template<typename T> struct M<T,typename boost::enable_if<boost::is_enum<T> >::type> { static void foo() { std::cout << "enum" << std::endl; } }; struct S {}; enum FOO { FOO1, FOO2 }; int main() { M<S>::foo(); M<int>::foo(); M<FOO>::foo(); } --------------- M<FOO>::foo() fails to compile due to ambiguity. Any pointers? Or How to get what I want? Gennadiy

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[multi_array] Is there interest for an [index_list] library?
by Pierre-Andre Noel 08 Apr '11

08 Apr '11

Dear all, I would like to gauge the interest of the community in a library that can serve 1) as a complement to Boost.MultiArray and 2) as an alternative to Boost.MultiArray. For the first type of use, an example of the candidate library's capabilities is that it makes available a special iterator "it" that allows to browse all the elements of a MultiArray "m". This special iterator has an it.indices() members that returns a "list" Collection of indices (i.e. an IndexList) such that "m(list)" and "*it" are the same elements. This can be useful for functions whose effect on an element of "m" depends on where this element is situated in "m". The second way to use the candidate library is as an alternative to Boost.MultiArray of dynamically chosen (execution time) dimensionality. Moreover, the elements do not necessarily need to be arranged in a multi-dimensional "box", as is the case in a MultiArray. For example, a "simplex" organization of the elements is already implemented. If you are interested to know more, I strongly suggest you to take a look at the example file in sandbox/index_list/libs/index_list/examples.cpp . The library itself is in sandbox/index_list/boost and a readme file (with some details concerning concepts and "priorities") is in sandbox/index_list/libs/README . An automatically generated (Doxygen) documentation is located in sandbox/index_list/libs/index_list/doc/index.html . Sadly, there is no "real" documentation for now. Many thanks for your time. Sincerely, Pierre-André Noël

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[BGL] Accelerating property value-retrieval
by Cedric Laczny 08 Apr '11

08 Apr '11

Hi, I would like to know if there is a way to accelerate the retrieval of properties of an edge or a vertex? Actually, I define a new vertex-property (vertex_properties) and this again uses a "struct VertexProperties { ... }" to specify the details of the properties. However, when I want to get the properties of say vertex v, I need to first get the properties-map from the graph and then get the property for v. This obviously suffers from the lookup in the property_map and I would like to know if there is a way to accelerate this? In particular, when using vecS as the vertex_container because the vertices could generally be used as indices... I would find this very convenient, especially in combination with filtered_graph when filtering only on vertices that have certain properties (e.g. a category) and one only wants to see those that have a specific character (e.g. color). Best, Cedric

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