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

Boost Graph Library: edge retrieval using edge descriptor between square brackets fails
by Nicholas Mario Wardhana 12 Jan '11

12 Jan '11

Hi all, I am wrapping the Boost Graph Library with a thin class, and I am having a problem in retrieving the edge. I use a mechanism similar to the one in here: http://stackoverflow.com/questions/3100146/adding-custom-vertices-to-a-boos… For testing, I add two vertices (suppose pNode1 and pNode2) successfully, and they can be retrieved as well by passing in their vertex descriptors. However, this is not the case for the edges: when I add an edge from pNode1 to pNode2, the edge is correctly stored as the out_edge of pNode1, but when I retrieve the edge using its edge descriptor, which is the (valid) return value of the add_edge() function, the pointer value is NULL. Also, when I debug the code, I find that inside the graph, there are two variables m_edges and m_vertices. The m_vertices correctly contains two vertex descriptors, but the m_edges is empty. So, do I make a mistake here? I have been looking for some information in Boost's archive and other sources (StackOverflow, ...), but so far haven't found anything helpful. I include a snippet at the end of this e-mail. I am using Visual Studio 2008 SP1 on Windows Vista SP2, and Boost 1.44.0 (haven't upgraded yet to 1.45, but the latter doesn't seem to address this issue). Thank you! Best regards, Nicholas Mario Wardhana //--------------------------- snippet ----------------------------- template <class NodeData, class EdgeData> class BoostGraphWrapper : public Graph<NodeData, EdgeData> { typedef boost::adjacency_list<boost::listS, boost::listS, boost::directedS, Node<NodeData>*, Edge<NodeData, EdgeData>*, boost::listS> BoostGraph; typedef typename boost::graph_traits<BoostGraph>::vertex_descriptor BoostVertexDescriptor; typedef typename boost::graph_traits<BoostGraph>::edge_descriptor BoostEdgeDescriptor; //... public: void AddNode(Node<NodeData>* pNode); Edge<NodeData, EdgeData>* AddEdge(Node<NodeData>* pNode1, Node<NodeData>* pNode2); //... private: BoostGraph m_graph; //... }; template <class NodeData, class EdgeData> void BoostGraphWrapper<NodeData, EdgeData>::AddNode(Node<NodeData>* pNode) { Graph<NodeData, EdgeData>::AddNode(pNode); // 1. Get the descriptor BoostVertexDescriptor vertexDescriptor = boost::add_vertex(m_graph); // 2. Fill with the node m_graph[vertexDescriptor] = pNode; // ... } template <class NodeData, class EdgeData> Edge<NodeData, EdgeData>* BoostGraphWrapper<NodeData, EdgeData>::AddEdge( Node<NodeData>* pNode1, Node<NodeData>* pNode2 ) { Graph<NodeData, EdgeData>::AddEdge(pNode1, pNode2); // 1. Get vertex descriptors of the nodes BoostVertexDescriptor vertexDescriptor1 = GetBoostVertexDescriptor(pNode1); BoostVertexDescriptor vertexDescriptor2 = GetBoostVertexDescriptor(pNode2); Node<NodeData>* tempNode = m_graph[vertexDescriptor1]; Node<NodeData>* tempNode2 = m_graph[vertexDescriptor2]; // 2. Add an empty edge BoostEdgeDescriptor edgeDescriptor; bool inGraph = false; boost::tie(edgeDescriptor,inGraph) = boost::add_edge(vertexDescriptor1, vertexDescriptor2, m_graph); if(!inGraph) { return NULL; } assert(BoostEdgeSize() == 1); // successful // 3. Fill the edge with the vertices Edge<NodeData, EdgeData>* temp = m_graph[edgeDescriptor]; assert(NULL != temp); // fails here //.... return pEdge; } void SomeFunction() { BoostGraphWrapper<int, int> graphWrapper; Node<int>* pNode1 = new Node<int>(); Node<int>* pNode2 = new Node<int>(); Edge<int, int>* pEdge; graphWrapper.AddNode(pNode1); graphWrapper.AddNode(pNode2); pEdge = graphWrapper.AddEdge(pNode2, pNode1); // fails here }

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[proto] learning proto slowly, a small (math)complex library
by alfC 12 Jan '11

12 Jan '11

Hi, I find proto pretty intriguing and I can see the power in it but I am still not able to create a context in which it can help in my design. I also find the Boost.Proto examples very confusing and not usually in the context I always imagine to use the library. There are several concepts that I don't yet fully understand like "context" and "grammars". Also besides the power I see in the library sometimes the resulting syntax in the examples is pretty disappointing, with all those "eval" functions. In general I can't see whether this is a result of limitations of the library or a tool to make the examples more pedagogical. If someone is kind enough to follow me and help me during this discovery of the library along these posts I will continue. The idea of this post is try to bring a simple example of boost at a context that I am able to understand. In order to be useful for many other people I will try to bring proto to a purely mathematical level. Suppose I want to build a new (kind of mathematical) library. Typically I would start defining a lots of arithmetical objects and members and friends operators, all of them eager (member)functions, lots of operators (many bugs also), also use boost.operators (to make less bugs) and then realise that the library has not any real deep mathematical structure on it, not to the compile-time/programmer level. Yes, the program will be able to do a lot of mathematics at runtime via numerical representations but there will be no insight from the point of view of the program code or the "type system". Let's start by an example, I define a complex type, after a lot of work I would have made the equivalent of std::complex<T>. Then the program replaces T by double and the program can (at runtime) do some "math". The problem is that I as a programmer can not do any math with that type. Let me give a concrete example, the complex_unit_circle is a set of complex numbers with modulus =1. One is tempted to implement complex_unit_circle in terms of the "complex type" or some parameterisation (angle). >From a mathematical point of view the complex z is a complex number of course, and z/|z| (z/abs(z)) is not only also a complex number but also potentially a complex_unit_circle element with very spefic properties. For example the product of two elements of the unit circle can be interpreted as a unit circle element again. The only way to express this potentiality at compile time is by expression templates, i.e. in its most glorious state by Boost.Proto. z/abs(z) is really an expression that eventually can be used to construct either another complex number (as type) or a unit circle number (as type). But lets start slower than that, lets build an expression that can be used (potentially) to build a complex number instead. The concrete question of this post will be how to obtain the desired syntax by adding layers to the original posted code. This is what I have done so far: #include <boost/proto/core.hpp> namespace pretty{ namespace proto = boost::proto; struct i_tag{}; proto::terminal< i_tag >::type const i = {{}}; } int main(){ using namespace pretty; 4. + 5.*i; //this will be a complex number (in some sense) return 0; } of course this program does nothing, it is just to show that I can create a expression template with a symbol called "i", this symbol will have properties that will eventually make it equivalent to one of the roots of -1 (mathematically speaking) (but not yet). Note that I didn't define any so called "grammar" or "context" yet. Since the first concern is to be able to use the new code with old code at all intermediate steps in the development, duppose I want to use this kind of expression to construct (in the c++ sense) an existing type, namely std::complex<double>. i.e. I want to be able to write: std::complex<double> z = 4. + 5.*i; or std::complex<double> z(4. + 5.*i); (forget about alternative notations, like 5.*i + 4. or 4. + i*5) The only ways I see this is possible is by adding either a constructor to std::complex<double> or a cast operator of the "expression of type 4.+5.*i" to std::complex<double>. The question for this post, 1) is this true? 2) if yes, then that means that one of the 2 types (type complex or typeof(4.+5.*i) ), will have to be modified (or extendended) in other to accept this syntax. 3) if no , how can I allow this syntax? 4) if the std::complex type is not modifiable, what is the mechanism in proto to define a cast over a certain set of expressions, e.g. of the type of 4.+5.*i. 5) if not, is this syntax not possible at all? is it here where we need to introduce those "eval" functions such as std::complex<double> z = eval_as_complex(4. + 5.*i). The idea is that once I resolve this general questions about the library I will continue building up. (And excuse me for these naive questions along the way). (Note: I know that std::complex<double> had constructor std::complex<double>(4.,5.) and that should be the preferred use, but this post is all about "syntax" and how to use proto, these are just examples). Thank you, Alfredo

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issues with the latest boost numeric bindings
by Simon Mpasi 11 Jan '11

11 Jan '11

To boost users: Greetings! I do not know if this the correct format but here are the issues that I am running into: /boost/numeric/bindings/lapack/detail/ The file clapack.h includes itself causing an error /boost/numeric/bindings/blas/detail/ The file cblas.h includes itself causing an error I changed them to lapack.h and blas.h respectively but I got several errors. I checked out the latest version of numeric bindings from boost.svn this morning. I am using Microsoft Visual Studio 2008 without a Fortran compiler (I need to use clapack) The issues here are that the l lapack routines come with 2 underscores, i.e. _sgesvd_ instead of sgesvd_ I declared BOOST_NUMERIC_BINDINGS_USE_CLAPACK in my driver. Thank you very much in advance for your assistance. Simon N. Mpasi

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[Build] Mimicking my Fedora13 Boost installation.
by Robert Jones 11 Jan '11

11 Jan '11

I have Boost installed as part of my Fedora13/64-bit system, at Boost 1.41. I now want install Boost 1.45, but need to keep the original around for backwards compatibility issues, so I'm putting my 1.45 build somewhere else, and and I want it look as much like the original 1.41 build as possible, but be 1.45. So I built with this command > ./bjam --prefix=/usr/local/boost_1_45_0 threading=single --runtime-link=shared --link=shared --layout=tagged install then listing all the Boost regex (regex chosen at random) I find > find /usr -name 'libboost_regex*' 187532 0 lrwxrwxrwx 1 root root 24 Sep 21 16:25 /usr/lib64/libboost_regex.so -> libboost_regex.so.1.41.0 142821 972 -rwxr-xr-x 1 root root 994792 Jun 4 2010 /usr/lib64/libboost_regex.so.1.41.0 540038 2356 -rw-r--r-- 1 root root 2410606 Jan 11 11:56 /usr/local/boost_1_45_0/lib/libboost_regex.a 540030 1132 -rwxr-xr-x 1 root root 1156757 Jan 11 11:55 /usr/local/boost_1_45_0/lib/libboost_regex.so.1.45.0 540031 0 lrwxrwxrwx 1 root root 24 Jan 11 11:55 /usr/local/boost_1_45_0/lib/libboost_regex.so -> libboost_regex.so.1.45.0 which seems to show an extra .a compared to my Fedora 'default' installation. How come? Do I need it? Can I determine the bjam flags that Fedora used originally? Thx, - Rob.

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[Iterator] advance and random_access_traversal iterators
by Anthony Foglia 11 Jan '11

11 Jan '11

What happened to the patch to add a boost::advance function designed to work with Boost.Iterator's concepts? Three years ago there was a thread pointing out the problem with std::advance not treating random access traversal iterators as random access (because of the reference type). Sebastian Redl posted a patch to add a boost::advance (and boost::distance) function. <http://lists.boost.org/Archives/boost/2007/09/127785.php> I don't see any proof of this patch ever being applied. Someone filed a bug report two years ago to bring attention to the patch, and it still hasn't been applied. <https://svn.boost.org/trac/boost/ticket/2539> Is there a reason it hasn't been applied (the collision with the boost::distance supplied by Boost.Range?) or has it just fallen through the cracks? -- Anthony Foglia Princeton Consultants (609) 987-8787 x233

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Problem compiling under Codegear
by jose perez 10 Jan '11

10 Jan '11

Hello. I’m using CodeGear compiler with Boost 1.39 and Boost 1.45. In both of them I have found an error in mpl\base.hpp line 25 (typedef typename T::base type;) [BCC32 Error] base.hpp(25): E2404 Dependent type qualifier 'na' has no member type named 'base' The code is: namespace boost { namespace mpl { template< typename BOOST_MPL_AUX_NA_PARAM(T) // find in mpl\aux_\na_spec.hpp, line 152: #define BOOST_MPL_AUX_NA_PARAM(param) param = na > struct base { typedef typename T::base type; // <------- ERRORRR BOOST_MPL_AUX_LAMBDA_SUPPORT(1,base,(T)) }; BOOST_MPL_AUX_NA_SPEC(1, base) }} Help will be appreciated. Thanks!

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[mpl] resulting sequence limits
by Igor R 10 Jan '11

10 Jan '11

Hello, I've got 2 mpl::map's, both have less than 20 elements. I copy one to another, and the result has more than 20 elements. I thought that BOOST_MPL_LIMIT_MAP_SIZE macro affects only explicit definitions of maps, not result values of metafunctions, but it turns out that the above case doesn't compile -- until I #include <boost/mpl/map/map30.hpp> Is it behavior "by design", or is it a bug? Thanks.

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[Range] Adaptors
by Robert Jones 10 Jan '11

10 Jan '11

I might be asking for the impossible here, but given the lovely adaptor syntax, eg std::vector<int> vec; boost::copy( vec | boost::adaptors::reversed | boost::adaptors::uniqued, std::ostream_iterator<int>(std::cout) ); I notice it still uses the function call notation in the outermost operation( boost::copy() ), can it be written to eliminate function call syntax completely, say something like vec | boost::adaptors::reversed | boost::adaptors::uniqued | boost::adaptors::copy( std::ostream_iterator<int>(std::cout) ); or even vec | boost::adaptors::reversed | boost::adaptors::uniqued | std::ostream_iterator<int>(std::cout); Thx, - Rob.

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Boost.Regex compile error with gcc 4.6
by Nathan Ridge 10 Jan '11

10 Jan '11

Hello, boost/regex.hpp fails to compile with gcc 4.6, giving the following errors: In file included from /lib/boost/boost/regex/v4/perl_matcher.hpp:578:0, from /lib/boost/boost/regex/v4/regex.hpp:88, from /lib/boost/boost/regex.hpp:31, from test.cpp:1: /lib/boost/boost/regex/v4/perl_matcher_non_recursive.hpp: In member function ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::unwind_short_set_repeat(bool)’: /lib/boost/boost/regex/v4/perl_matcher_non_recursive.hpp:1394:85: error: invalid use of incomplete type ‘const struct boost::regex_traits_wrapper<traits>’ /lib/boost/boost/regex/v4/regex_traits.hpp:163:8: error: declaration of ‘const struct boost::regex_traits_wrapper<traits>’ /lib/boost/boost/regex/v4/perl_matcher_non_recursive.hpp:1394:85: error: invalid type argument of unary ‘*’ (have ‘BidiIterator’) It compiles fine with gcc 4.5. Is this an issue with boost or gcc? Should I report it as a bug? Thanks, Nate.

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[Proto] Storing an Expression Template as a Data Member
by Hossein Haeri 10 Jan '11

10 Jan '11

Dear all, Is there any way I can have classes with data members of type (proto) expression templates? Here is where I get stuck: template<typename T> class MyClass { ... T expression_; }; What type should T be? If you're wondering why on earth I might need that, here is an explanation: Instances of MyClass need to store the lazy calculation they will be performing later on when enough initialisation data is available. Each instance of MyClass has its own FORMULATION for the lazy calculation in terms of the initialisation data. They need to be fed with these formulations and I thought (proto) expression templates will perhaps do the job. But, then, I don't know how to store these formulations until it's time for them to perform... TIA, --Hossein

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multi_index_container: replace() modifies my iterator
by Nicolas Rannou 10 Jan '11

10 Jan '11

Hi all, I'm pretty new in boost and I am experimenting an issue I can't understand. It looks like the usage of "replace()" modifies the iterator I am iterating on: Here is a simple example: it iterates properly if I do: Iterator it2, it3; boost::tuples::tie(it2, it3) = m_Container.get< CollectionID >().equal_range( 30 ); while( it2!= it3 ) { int time = it2->TCoord; if( time < 500 ) // we want to change the collection ID in this case { Structure tempStructure(*it2); tempStructure.CollectionID = 40; * //m_Container.get< CollectionID >().replace(it2, tempStructure); comment this line* } ++it2; } whereas if I call "replace()" the iterator value changes to "it3" then it exists the loop: Iterator it2, it3; boost::tuples::tie(it2, it3) = m_Container.get< CollectionID >().equal_range( 30 ); while( it2!= it3 ) { int time = it2->TCoord; if( time < 500 ) // we want to change the collection ID in this case { Structure tempStructure(*it2); tempStructure.CollectionID = 40; * m_Container.get< CollectionID >().replace(it2, tempStructure);* } ++it2; } the replace() method returns true. I must be missing something but after reading the documentation and some researches on the web I couldn't find the answer. Any help/explanation would be greatly appreciated, Thanks, Nicolas

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using '\0' as separator in char_separator and tokenizer classes
by kmulla＠mail.com 10 Jan '11

10 Jan '11

Hi All, I am trying to use boost::tokenizer to tokenize a string containing embedded '\0' characters. I am using boost::char_separator to specify the separator. I am not getting correct tokens when I am using '\0' as the separator. Here I am curious to know, if it is indeed possible to use '\0' as separator in boost::char_separator class. I am pretty much using the code in the example given on below link. I know my code works since I am getting correct results with different separator values. http://www.boost.org/doc/libs/1_45_0/libs/tokenizer/char_separator.htm Best, K Mulla

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[boost][Serialization] - xml-stylesheet tag not recognized
by girish hilage 08 Jan '11

08 Jan '11

Hi, I am trying to learn how to read an XML file using boost-serialization. The code snippet of a sample program is as follows : void restore_schedule(bus_schedule &s, const char * filename) { // open the archive std::ifstream ifs(filename); assert(ifs.good()); boost::archive::xml_iarchive ia(ifs); // restore the schedule from the archive ia >> BOOST_SERIALIZATION_NVP(s); } First few lines of demo.xml are as follows : <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <?xml-stylesheet type="text/xsl" href="XSLTFile.xsl"?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="6"> But this gives me below error : $ ./a.out terminate called after throwing an instance of 'boost::archive::xml_archive_exception' what(): unrecognized XML syntax If I remove the line : <?xml-stylesheet type="text/xsl" href="XSLTFile.xsl"?> from demo.xml then it works fine. Can you please let me know if there is any workaround for this problem? Currently I am using Fedora Core 13 with boost-serialization-1.41.0-7.fc13.i686. Is this case handled in latest boost release? Regards, Girish

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[signals vs. signals2] Slot connecting another slot to invoking signal
by Boris Schaeling 08 Jan '11

08 Jan '11

The Boost.Signals2 documentation at http://www.boost.org/doc/libs/1_45_0/doc/html/signals2/thread-safety.html says: "Suppose a user writes a slot which connects another slot to the invoking signal. Will the newly connected slot be run during the same signal invocation in which the new connection was made? The answer is no." I'm trying to find out what Boost.Signals has to say about it. A quick test program shows that Boost.Signals does call the newly connected slot. I'm not sure though if this is undefined behavior as connecting another slot might invalidate the iterators used by the combiner? Boris

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[serialization] polymorphic archives in dlls and pointer to derived problems
by Kolb, Jeremy 07 Jan '11

07 Jan '11

I'm having a lot of trouble getting serialization of derived classes through a base pointer working across dlls. I have the following: DLL (data_types.dll) code: stdafx.h: #pragma once #include "targetver.h" #define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers // Windows Header Files: #include <windows.h> #pragma warning(disable: 4308) #include "boost/archive/polymorphic_iarchive.hpp" #include "boost/archive/polymorphic_oarchive.hpp" #include "boost/serialization/nvp.hpp" Base.h: #pragma once #include "boost/serialization/export.hpp" class __declspec(dllexport) Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Base() {} virtual ~Base() {} int i; }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(Base); // Doesn't make a difference. BOOST_CLASS_EXPORT_KEY(Base); Base.cpp: #include "stdafx.h" #include "Base.h" template<class Archive> void Base::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(i); } BOOST_CLASS_EXPORT_IMPLEMENT(Base); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); Derived.h: #include "Base.h" class __declspec(dllexport) Derived : public Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Derived() {} Derived(int num) : j(num) {} int j; }; BOOST_CLASS_EXPORT_KEY(Derived); Derived.cpp: #include "stdafx.h" #include "Derived.h" template<class Archive> void Derived::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base); ar & BOOST_SERIALIZATION_NVP(j); } BOOST_CLASS_EXPORT_IMPLEMENT(Derived); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); My exe links against the DLL and contains the following: #include "stdafx.h" #include "boost/archive/polymorphic_xml_iarchive.hpp" #include "boost/archive/polymorphic_xml_oarchive.hpp" #include "data_types/Derived.h" #include <fstream> int _tmain(int argc, _TCHAR* argv[]) { std::ofstream f("c:\\test.xml"); boost::archive::polymorphic_xml_oarchive xml(f); Base* b = new Derived(123); xml & BOOST_SERIALIZATION_NVP(b); delete b; return 0; } When serializing this fails with unregistered_class even though I export both Base and Derived. Jeremy

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How to get bug reports addressed
by Geoffrey Romer 07 Jan '11

07 Jan '11

I'm responsible for maintaining the local Boost install for a large group of developers, and I find myself spending an inordinate amount of time reapplying our local patches for Boost bugs every time a new version comes out, seemingly with no end in sight. One obvious example is https://svn.boost.org/trac/boost/ticket/3645: the report is clear and specific, documents a real bug, and provides a trivial patch which completely resolves the issue. It's everything one could possibly want in a bug report, and it has been utterly ignored for over a year. In my experience this has been the rule rather than the exception; other examples that I've been personally acquainted with include http://lists.boost.org/Archives/boost/2009/06/153214.php, https://svn.boost.org/trac/boost/ticket/4918, and https://svn.boost.org/trac/boost/ticket/4919. In every case the reporters have done everything they could to provide a useful bug report, up to and including providing patches, but have been met with profound silence. Does anyone have any suggestions for how to get action in these situations?

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[DateTime] Daily Schedules
by John Rocha 07 Jan '11

07 Jan '11

I was looking at the DateTime library for a scheduling module in my application. I was very excited to see time periods (time_period) and its method contains(). I could set up a time_period for say 8:00-17:00, and then when something happened I could create a ptime and see if the time_period contains my ptime. (i.e. did my action happen between 8:00 and 17:00.) However, I realized that a time period is much more specific than I want. A time_period is tied to a specific date, i.e. 8:00-17:00 on Sep. 20 1999. I read the documentation, and I didn't see (or missed) anything that might be what I would call an hour period -- a range of time that is independent of the date. I don't think it's a duration, because I understood that to mean the amount of time between two time points (i.e. +/- 5 hours). I have some ideas on how I might extend this to achieve what I want, but before going that route, I wanted to double check if others have encountered this and if so how they resolved it. Was it done with a bit of the library that I'm overlooking? Or did you have to extend the class to achieve the desired results? Thanks in advance, -=John

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[boost][Serialization] - about macro BOOST_CLASS_VERSION
by girish hilage 07 Jan '11

07 Jan '11

Hi, I have a query regarding macro BOOST_CLASS_VERSION(). I am running following code : class testRep { friend std::ostream & operator<<(std::ostream &os, const testRep &tr); public : template<class Archive> void serialize(Archive &ar, const unsigned int version) { if(version >= 2) ar & BOOST_SERIALIZATION_NVP(Site); } private : string Site; }; BOOST_CLASS_VERSION(testRep, 2) std::ostream & operator<<(std::ostream &os, const testRep &tr) { return os << '\n' << tr.Site << endl; } void read_file (testRep &s, const char * filename) { std::ifstream ifs(filename); assert (ifs.good()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(s); } int main (void) { testRep tr; read_file (tr, "Test.xml"); cout << tr << endl; return 0; } This code runs fine. But, if I remove the statement : BOOST_CLASS_VERSION(testRep, 2) then I get following error : terminate called after throwing an instance of 'boost::archive::archive_exception' what(): class version Aborted (core dumped) So, want to ask if it is mandatory to declare a macro BOOST_CLASS_VERSION()? and if not then how do I prevent this runtime error from happening? Regards, Girish

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[Off topic] Strict Aliasing white paper redux
by Patrick Horgan 07 Jan '11

07 Jan '11

Some time ago, I posted a link here to my (then new) white paper on strict-aliasing. I wrote it because people keep posting, on this and on other lists, questions that show a basic misunderstanding of aliasing and what the rules in C and C++ standards on aliasing are intended to communicate. I got some great feedback and have posted a new revision, http://dbp-consulting.com/StrictAliasing.pdf. I'm hoping that people on this list will review the paper and tell me some more ways of improving it. My intention is to write a paper that will make it so that I won't have to keep answering the same questions over and over again;) I'll just point people at the paper. Best regards, Patrick

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1.45: thread/condition_variable.hpp: unused variable 'res' warning, gcc 4.2
by Hicham Mouline 06 Jan '11

06 Jan '11

hello, in Release build in Xcode, gcc 4.2.1, inline void condition_variable::wait(unique_lock<mutex>& m) { ... int const res = pthread_cond_wait(&cond, &internal_mutex); BOOST_ASSERT(!res); ... } Unused variable 'res' is gcc mistaken? regards,

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Re: [Boost-users] [FunctionTypes] function_arity for non-built-ins
by Hossein Haeri 06 Jan '11

06 Jan '11

Hi Roman, > This is actually possible in most cases. Check this nice article by Eric > Niebler: http://www.boost.org/doc/libs/1_45_0/doc/html/proto/appendices.html#boost_p… This is beautiful, thanks! :) So, from the description, it seems like this can_be_called guy (or its siblings) is in heavy use for Proto. Does Proto then also port this as a part of its toolbox? Or, is it only for internal use and I'll need to craft my own version of it? TIA, --Hossein

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Re: [Boost-users] [ asio ] how to determine if a server is overloaded ?
by Avi Bahra 06 Jan '11

06 Jan '11

ecyrb wrote> >Server overload does not come from network overload, but from service >overload. If you can't serve (compute) more requests/s than the network >load, your server is overloaded... >You can compute your server overload by queuing requests. If your queue >becomes too big, you can consider that your server is under heavy pressure >and take appropriate measures to circumvent the flow of requests (load >balancing etc...) Is there any asio example in the docs, which demostrate this Does the io_service expose the queue of request/connections as I have not seen such an api ? or do you mean that server should be structured to maintain its _own_ queue.( as apposed to the queue in io_service) Request are then handled from this internal queue? Best regards, Ta, Avi

1 0

[Accumulators] Retract samples
by Alex Hagen-Zanker 06 Jan '11

06 Jan '11

Dear all, I am considering using Boost Accumulators for a moving window calculation. When a window would step from left to right, it should add the sample on the right side of the window and retract the sample on the left side on each step. For weighted accumulators, it might be possible to use negative weights. But, since the accumulators do not appear to be intended for this use, there may be implementation details that invalidate the use of negative weights. Is there a recommended way to retract samples in Boost Accumulators? Thanks, Alex p.s. the general idea: void movingwindowsum(const vector<double>& in, vector<double>& out, size_t radius ) { size_t n = in.size(); double sum = 0; // This should be an accumulator for(size_t i = 0; i < min(n, radius); ++i) { sum += in[i ]; // add sample } out.resize(n); for(size_t i = 0; i < n; ++i) { size_t left = i - radius - 1; size_t right = i + radius; if (left >= 0) sum -= in[left]; // retract sample if (right < n) sum += in[right]; // add sample out[i] = sum; }

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boost::signals2 connection management
by frares＠gmail.com 06 Jan '11

06 Jan '11

Hi, all If I have one only signal that can be connected at different times to several different slots, then I create several boost::signals2::connection, one for each slot but for that same only signal, if I disconnect one of the connections, will all connections be disconnected or just that particular slot? If this is not the way to disconnect specific individual signal/slot connections, how do I do it? I have to use "boost::bind" for the connections are from signals and slots of different classes, and I cannot use scoped connections because asynchronous tasks are being performed (and signaled). Thanks Francisco

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streaming of tuples - adjusting field widths?
by Christian Meesters 06 Jan '11

06 Jan '11

Hi, Having the following code (where 'out' is a std::ostream): out << boost::tuples::set_open('[') << boost::tuples::set_close(']') << boost::tuples::set_delimiter(',') << std::setw(21) << std::right << get_some_tuple(); I expected to see the tuple in a column of 21 spaces, adjusted to the right. Instead, the tuple is appended on 21 spaces. Any hint on what my mistake is? TIA Christian

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