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[boost-users][exception] BOOST_THROW_EXCEPTION returns
by Igor R 24 Mar '09

24 Mar '09

Hello all, A function throws boost::exception as follows: //.... typedef boost::error_info<struct tag_action, std::string> action_name; BOOST_THROW_EXCEPTION(error() << action_name(name)); return 0; Both BOOST_NO_EXCEPTIONS and BOOST_EXCEPTION_DISABLE are *not* defined. The excpetion is not catched anywhere. However, the thread continues running! If I put breakpoint at "return 0;" it's hit, and I can continue stepping the code. I run the program under MSVC 9.0, in debug mode, and I see "First-chance exception" and "Unhandled exception" notifications issued by the debugger. Isn't it wrong behavior, or I miss something? Thanks, Igor'.

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BoostCon 2009 Schedule Now Live
by David Abrahams 24 Mar '09

24 Mar '09

The official schedule is now live at http://www.boostcon.com/program! A few highlights of the "mouth-watering content" (in the words of one enrollee) are: * A keynote address from Andrei Alexandrescu called "Iterators Must Go." It's sure to be provocative! * Troy Straszheim's presentations on how high-energy physicists are using Boost to process massive datasets as they go "Icefishing for Neutrinos" and on Kamasu, his library for offloading computation to your machine's GPU. * Two hands-on sessions where we'll start recoding parts of Boost for C++0x, applying rvalue references, variadic templates, decltype, and advanced SFINAE capabilities using the latest GCC. * "Practical C++ Test-Driven Development with Boost.Test and Bmock," by Asher Sterkin * A session on compiler construction using Boost.Spirit v2, from Hartmut Kaiser and Joel de Guzman The complete list of sessions covers a wide range of other Boost and C++-related topics. It is available at http://www.boostcon.com/program/sessions. Please have a look, and please, sign up for the conference! Remember, registration for the whole week is just $599 before April 1st. -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Find last modified date of file
by Thor Andreas Tangen 24 Mar '09

24 Mar '09

Hi Is it possible by using boost to find the last modified date of a file? I looked in filesystem, but could not find it there. Thanks Thor Andreas

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[boost-users][exception] BOOST_THROW_EXCEPTION returns
by Igor R 24 Mar '09

24 Mar '09

Hello all, A function throws boost::exception as follows: //.... typedef boost::error_info<struct tag_action, std::string> action_name; BOOST_THROW_EXCEPTION(error() << action_name(name)); return 0; Both BOOST_NO_EXCEPTIONS and BOOST_EXCEPTION_DISABLE are *not* defined. The excpetion is not catched anywhere. However, the thread continues running! If I put breakpoint at "return 0;" it's hit, and I can continue stepping the code. I run the program under MSVC 9.0, in debug mode, and I see "First-chance exception" and "Unhandled exception" notifications issued by the debugger. Isn't it wrong behavior, or I miss something? Thanks, Igor'.

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Integrating boost into project version control
by Kenneth Porter 24 Mar '09

24 Mar '09

I have an existing C++ project that uses a few 3rd party libraries. It's maintained in a Subversion repository and the libraries are imported into the repository using the Subversion "vendor branch" paradigm together with Subversion "externals". I want to add Boost to the project, and am looking for guidance from others who have a project in Subversion: Should I import Boost sources into my repo, rebuilding on each developer's system as part of the normal whole-project build, or should I install a binary distro of Boost on each developer's system? The former guarantees that the repo always contains the source used to build our binaries, but at the cost of longer build times to build Boost each time the project is built. I'm currently building with Visual Studio 2005 and 2008, and will eventually be cross-compiling for an embedded Linux system.

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[lambda] extending lambda functions
by alfC 24 Mar '09

24 Mar '09

For some application I need to sum the complex modulus of a collection of elements. In short, I want to be able to replace the lambda expression _1 + bind(&std::norm<double>, _2) by something more natural like _1 + llnorm(_2) For that I use std::accumulate and the lambda library, like in the next working example; #include<boost/lambda/lambda.hpp> #include<boost/lambda/bind.hpp> using namespace boost::lambda; int main(){ using boost::lambda::_1; using boost::lambda::_2; std::vector<std::complex<double> > v(3); v[0]=1.; v[1]=2.; v[2]=3.; double result=std::accumulate(v.begin(), v.end(), double(0.), _1 + bind(&std::norm<double>, _2)); std::cout<<result<<std::endl; return 0; } the question is what do I have to do to be able to use the following syntax instead _1 + llnorm(_2) where llnorm is something I have to define (globally) somewhere else. The question is, how do I have to define llnorm to have the desired effect? The ideal syntax for me would be to be able to say std::norm(_2) or std::norm<double>(_2), but that may not be possible due to name conflict, is it? I am clueless because I don't even know even what is the (C++) type of the argument that would be taken by llnorm. Thanks, Alfredo

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selecting a type (tag) based on a runtime enum value
by Hicham Mouline 24 Mar '09

24 Mar '09

Hello, I have a templated function Engine, that takes 3 template arguments, these are tags T1, T2, T3, T4. I have an typedef enum { e1, e2, e3, e4 } E to element ei corresponds the type Ti ... const E e // switch (e) { case e1: Engine< Metafct1<T1>::type, Metafct2<T1>::type, Metafct3<T1>::type >::Process( .... ); break; case e2: Engine< Metafct1<T2>::type, Metafct2<T2>::type, Metafct3<T2>::type >::Process( .... ); break; ... } Is there a shorter way of writing this... For now I only have 4 in the enum, but I may have more later? regards,

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Seg fault while adding 2nd edge to the graph
by Phani Deepak 24 Mar '09

24 Mar '09

hi, i started using BGL for my project. strangely all the examples i tried to learn BGL worked fine. But when i write the actual code for my project, it started giving me this error. Problem: While adding second edge to the boost graph using boost::add_edge(u,v,g) it is giving out a seg fault. Please help with this prob. Iam also attaching the code that's giving the error /*********Code that's giving this error****************/ #include<iostream> #include<vector> #include<string> #include<queue> #include<stdlib.h> #include<string> #include<sstream> #include<boost/graph/graph_traits.hpp> #include<boost/graph/adjacency_list.hpp> class Node{ public: std::string id; double Energy; Node() {} }; class EdgeProperties { public: int targetI; int sourceI; EdgeProperties(int s,int t):sourceI(s),targetI(t) { } }; typedef boost::adjacency_list<boost::listS,boost::listS,boost::bidirectionalS, Node *,EdgeProperties *> Graph; typedef boost::graph_traits<Graph> GraphTraits; typedef GraphTraits::vertex_descriptor Vertex; typedef GraphTraits::edge_descriptor Edge; namespace boost { Vertex getVertexbyId(std::string id,Graph g){ std::cout << "getVID called for " << id << std::endl; fflush(stdout); GraphTraits::vertex_iterator vstart,vend; for(boost::tie(vstart,vend) = boost::vertices(g); vstart!=vend; vstart++) { if(g[*vstart]->id == (id)) return *vstart; } std::cout << "Critical Error: |" << id << "| referencing node not present in graph " << std::endl; return NULL; } } int main(){ Graph g; // populate Graph with all the vertices and edges. std::cout << "* Populating graph with Vertices and Edges " << std::endl; fflush(stdout); Vertex v = boost::add_vertex(g); g[v] = new Node(); g[v]->id = "xor_1"; g[v]->Energy = 2.3; std::cout << "Inserted xor_1" << std::endl; fflush(stdout); v = boost::add_vertex(g); g[v] = (new Node()); g[v]->id = "and_1"; g[v]->Energy = 1.9; std::cout << "Inserted and_1" << std::endl; fflush(stdout); v = boost::add_vertex(g); g[v] = (new Node()); g[v]->id = "i_1"; std::cout << "Inserted i_1" << std::endl; fflush(stdout); // add Edges std::pair<Edge,bool> e; EdgeProperties *ep = new EdgeProperties(1,1); e = boost::add_edge(boost::getVertexbyId("i_1",g),boost::getVertexbyId("and_1",g),ep,g); std::cout << "Inserted Edge 1" << std::endl; fflush(stdout); ep = new EdgeProperties(1,2); e = boost::add_edge(boost::getVertexbyId("i_1",g),boost::getVertexbyId("xor_1",g),ep,g); std::cout << "Inserted Edge 2" << std::endl; fflush(stdout); } /*******************************************************/ - Phani.

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[Q] better 'typedef'
by V S P 24 Mar '09

24 Mar '09

I have read somewhere that boost provides a better typedef. Something that allows to use the 'underlying class' but it is not a macro for example I want to define typedef std::wstring cvarchar_t to use for ODBC/Unicode db access (on win32) and then specialize some templates for this type that would behave differently then wstring I cannot remember what that mechanism was called. Also, sorry, for mixing this question in: is UTF-8 a more 'standard' encoding if I want to interface from my C++/boost programs to ODBC and to Boost.Python on Windows and FreeBSD (I have problems figuring out how to support the difference between UTF-16 on windows/wstring and Unix UTF-32 wstring ... while the unicode ODBC drivers are all 2-byte strings) thanks in advance -- V S P toreason(a)fastmail.fm -- http://www.fastmail.fm - Same, same, but different...

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proper erasing from ptr_vector
by Archie14 23 Mar '09

23 Mar '09

I have ptr_vector<A> lst; When I need to erase element from this container - should I just do A* el; iterator it = std::find (lst.begin(), lst.end(), el); lst.erase(it); or A* el; iterator it = std::find (lst.begin(), lst.end(), el); delete lst.erase(el);

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