February 2012 - Boost-users

Boost.Interprocess containers question
by Davidson, Josh 02 Mar '12

02 Mar '12

I have an object that I'm storing in shared memory that contains a map data member whose values are lists. The processes that interact with this object don't have direct access to the map data structure. Instead, the object is accessed and modified through its public interface. The issue I am running into is how to handle new key, value insertions. I would prefer to leave the fact that the object is in shared memory an implementation detail, but in order to construct a new list to insert in the map, the list needs to be initialized with an allocator using the segment manger. Unless I pass that segment manager into every method that might add a new list to the map, I'm struggling how to get it working. I can't simply store a pointer to the managed shared memory or segment manager within the class since the address would only be valid in the process that constructed it. The only possible implementations I can think of would be to require passing in the segment manager into all of the methods and then create a simple wrapper class that contains a pointer to this object along with a pointer to the segment manager. The wrapper class would essentially "duplicate" each of the methods in the wrapped class but drop the segement manager parameter since it has it as a member. Processes that "find" this object in shared memory would then be responsible for wrapping it in an object of the wrapper class. The other possible implementation would be to always open the shared memory segment by name before modifying the map. Josh

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Graph: writing graph properties to graphml file
by Juerg Tschirren 01 Mar '12

01 Mar '12

I wrote the code below to construct a directed graph with internal properties (for vertices, edges, and the graph itself) and write everything to a graphml file. The code compiles and works as it is, but my two questions are: 1. What dynamic property do I have to add to write the graph properties out to the graphml file as well? So far I could only figure out how to write vertex and edge properties. 2. Does everything else look good? Specifically, is it O.K. to define the properties the way I did in the first typedef line (without using boost::property<>), and is it O.K. to access the properties the way I do it? Juerg //--- start of example code typedef boost::adjacency_list<boost::listS, boost::vecS, boost::directedS, std::string, std::string, std::string> Graph; typedef boost::graph_traits<Graph>::vertex_descriptor vertex_t; typedef boost::graph_traits<Graph>::edge_descriptor edge_t; Graph g; vertex_t u = boost::add_vertex(g); vertex_t v = boost::add_vertex(g); edge_t e; bool b; boost::tie(e,b) = boost::add_edge(u,v,g); g[u] = "a_vertex_name"; g[v] = "an_other_vertex_name"; g[e] = "an_edge_name"; boost::get_property(g) = "the_graph"; boost::dynamic_properties dp; dp.property("vertex_data", boost::get(boost::vertex_bundle, g)); dp.property("edge_data", boost::get(boost::edge_bundle, g)); std::ofstream graphmlOutFile("graph.xml"); boost::write_graphml(graphmlOutFile, g, dp, true); graphmlOutFile.close();

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zip_iterator.hpp / boost::tuple requires a using namespace std!
by mark pashley 01 Mar '12

01 Mar '12

Hi, I have been using zip iterators with a BOOST::Test to check that maps contain expected values. After moving some templated code to a header file I found that the code would not compie unless I place a *'using namespace std;' * declaration within one of functions. The compiler is gcc 4.6.2 and 4.4.2. The version of boost is 1.47 and 1.49 The minimum code snippet is as follows: * using namespace std; // without this the next line does not compile!* The error from gcc is: -- View this message in context: http://boost.2283326.n4.nabble.com/zip-iterator-hpp-boost-tuple-requires-a-… Sent from the Boost - Users mailing list archive at Nabble.com.

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embedding
by Andreas Fabri 01 Mar '12

01 Mar '12

Hello I am wondering if there is ongoing work around the notion of embeddings of the Boost Graph Library. In the CGAL project which deals with geometric data structures we have written specializations of the graph_traits for the polyhedral surface, the halfedge datastructure, 2D triangulations, and arrangements. This allows to run BGL algorithms directly on CGAL data structures. http://www.cgal.org/Pkg/BGL. As these graphs are always embedded, that is as there is a circular order of edges we introduced a HalfedgeGraph concept http://www.cgal.org/Manual/latest/doc_html/cgal_manual/BGL_ref/Concept_Half… where one has global functions in order to walk along the border of a face, and go from an outgoing edge via the opposite incoming edge to a neighbor face. Would any of these ideas be interesting for the maintainers of the BGL. best regards, andreas -- Andreas Fabri, PhD Chief Officer, GeometryFactory Editor, The CGAL Project phone: +33.492.954.912 skype: andreas.fabri

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[PREDEF] Review for the Boost.Predef library by Rene Riviera
by Joel Falcou 29 Feb '12

29 Feb '12

The review of BOOST.PREDEF by Rene Riviera is scheduled between Monday, February 20th to February 29th. ================ Contents & Scope ================ BOOST.PREDEF defines a set of compiler, architecture, operating system, and library version numbers from the information it can gather of C++ predefined macros or those defined in generally available headers. The idea for this library grew out of a proposal to extend the Boost Config library to provide more, and consistent, information than the feature definitions it supports. What follows is an edited version of that brief proposal. =============== How to get it ? =============== Sources and documentation can be retrieved from http://tinyurl.com/73n6a3k ================ Writing a Review ================ The reviews and all comments should be submitted to the developers list, and the email should have "[PREDEF] 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.

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PP: commas issues
by MM 29 Feb '12

29 Feb '12

Hi, I am trying to generate a list of instances of the same template with different pairs of args, to populate a mpl container, with PP so, mpl::vector< tmpl<A::x,A::y>, tmpl<B::x,B::y>, tmpl<C::x, C::y> > i'm having trouble with the commas. I successfully generate the pp sequence (tmpl<A::x,A::y>)(tmpl<B::x,B::y>) (tmpl<C::x, C::y>) but from this to get the enumeration, it's impossible using SEQ_ENUM, because the sequence contains commas MM

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[multi_array] How to specify degenerate at runtime?
by Anton Daneyko 29 Feb '12

29 Feb '12

Greetings to Boosters, I have a 3D multi_array and I would like to make 2D slices using dimensions specified at runtime. I know the index of degenerate dimension and an index of slice, that I want to extract in that degenerate dimension. Currently the ugly workaround looks like that: if (0 == degenerate_dimension) { Slice slice = input_array[boost::indices[slice_index][range()][range()]]; } else if (1 == degenerate_dimension) { Slice slice = input_array[boost::indices[range()][slice_index][range()]]; } else if (2 == degenerate_dimension) { Slice slice = input_array[boost::indices[range()][range()][slice_index]]; } Is there a more beautiful way to construct index_gen object? Something like that: var slicer; for(int i = 0; i < 3; ++i) { if (degenerate_dimension == i) slicer = boost::indices[slice_index]; else slicer = boost::indices[range()]; } Slice slice = input_array[slicer]; It seems each subsequent call to boost::indices::operator[] returns a different type depending on the dimensionality, so there's no way to use a single variable, that can hold the temporary index_gen object.

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iterator_facade with incomplete type as Value argument
by Philipp Moeller 29 Feb '12

29 Feb '12

I've tried writing an iterator with iterator_facade that returns itself as the result of dereference, but the Value template argument requires a complete type because it tries to make a difference between returning by value or reference if Value is_pod (as far as I understand). #include <boost/iterator/iterator_facade.hpp> class iter : public boost::iterator_facade< iter, iter, boost::forward_traversal_tag > { public: void fancy_non_iterator_member(); private: friend class boost::iterator_core_access; void increment() { } bool equal(iter const& other) const { return true; } iter& dereference() const { return const_cast<Derived&>(static_cast<const Derived&>(*this)); } }; Is this the intended behavior of iterator_facade? Is there some workaround? Would such an iterator actually be conforming? -- Philipp Moeller GeometryFactory

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boost python & context manager/with statement
by Avi Bahra 29 Feb '12

29 Feb '12

Does boost python support context management using the with statement? In my case I need to manage __enter__/__exit__ on the c++ side. Could not find any examples for this in the documentation. Any help appreciated. Best regards, Ta, Avi

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Using boost with PathScale v4.x under Linux
by Roberto Fichera 29 Feb '12

29 Feb '12

Hi there, I've compiled the last boost v1.49 against PathScale v4.x compiler under 64bit linux distribution, but when compiling certain library that uses the boost/numeric/interval/rounded_transc.hpp include file, I end up on getting some error regarding asinh(), acosh() and atanh() which were searched in the std namespace. Compiling the same library against g++ or MSVC goes pretty straight without problems. /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:42: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:42: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:43: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:43: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:44: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_exact<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:44: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:77: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:77: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:78: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:78: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:79: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_std<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:79: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::asinh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:122: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::asinh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:122: error: 'std::asinh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::atanh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:123: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::atanh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:123: error: 'std::atanh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::acosh_down(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:132: error: 'std::acosh' has not been declared /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp: In member function 'T boost::numeric::interval_lib::rounded_transc_opp<T, Rounding>::acosh_up(const T&)': /TempData/boost_1_49_0_pathscale/boost/numeric/interval/rounded_transc.hpp:132: error: 'std::acosh' has not been declared Thus, I had a look in the boost include file boost/numeric/interval/detail/bugs.hpp and look like that apply the patch below fixes the compilation error: --- numeric/interval/detail/bugs.hpp.orig 2012-02-29 10:44:06.876597264 +0100 +++ numeric/interval/detail/bugs.hpp 2012-02-29 10:18:42.831581398 +0100 @@ -25,7 +25,7 @@ #else # define BOOST_NUMERIC_INTERVAL_using_math(a) using std::a # if defined(BOOST_HAS_INV_HYPERBOLIC) -# if defined(__GLIBCPP__) || defined(__GLIBCXX__) +# if defined(__GLIBCPP__) || defined(__GLIBCXX__) || defined(__GLIBC__) # define BOOST_NUMERIC_INTERVAL_using_ahyp(a) using ::a # else # define BOOST_NUMERIC_INTERVAL_using_ahyp(a) using std::a does anyone can comment? Thanks in advance, Roberto Fichera.

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