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

storing a boost::asio::io_service in a boost.tuple
by Sean Farrow 20 Mar '11

20 Mar '11

Hi: I need to store a boost::asio::io_service in a boost::tuple. Each boost::tuple needs an individual io_service. Given that io_service is noncopyable, and I'm working in a constructor what is the best way of doing this? Cheers Sean.

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[spirit][karma][range] Range adaptors not handled by karma?
by Ravi 20 Mar '11

20 Mar '11

Hi, Does spirit karma handle boost.range adaptors correctly? The following code compiles but fails at run-time as the end of the range is not seen by karma: --8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<-- #include <boost/range/adaptors.hpp> #include <boost/assign.hpp> #include <iostream> #include <vector> #include <boost/spirit/include/karma.hpp> int main(int argc, const char* argv[]) { using namespace boost::adaptors; using namespace boost::assign; std::vector<int> input; input += 1,2,3,4,5,6,7,8,9,10; std::ostream_iterator<char> os( std::cout ); using boost::spirit::karma::int_; using boost::spirit::karma::generate_delimited; using boost::spirit::ascii::space; //generate_delimited( os, int_ % ',', space, // input | strided(2) ); // <- works generate_delimited( os, int_ % ',', space, input | copied(1,6) | strided(2) ); std::cout << std::endl; return 0; } --8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<-- The tests were done with boost 1.45. Regards, Ravi

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using boost.asio with wx widgets
by Sean Farrow 20 Mar '11

20 Mar '11

Hi: I'm trying to use wx widgets with boost.asio. I'm including wx.h in the main header file-which is not being included in the header I'm concerned with now. Wx.h includes windows.h and therefore winsock.h. I'm getting the error 1189 #error : winsock.h has already been included. I've defined win32_lean_and_mean before including boost/asio.hpp. I've also tried including wx.h before asio.hpp in the header I'm dealing with now, this makes no difference I still get the same error. Has anyone got any other ideas? Any help appreciated. Regards Sean.

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traversing archive file (tar, zip) directories the boost way?
by Ákos Maróy 20 Mar '11

20 Mar '11

Hi, I wonder if there is a boost-friendly API to manage directory structures in archive file formats, like tar, zip & the like? In boost iostreams, there are filters for popular compression formats, like gzip, bzip2 and zip. but these only provide stream compression / decompression - and rightfully so. In boost filesystem, one has a portable API for traversing file system directory structures, which is very nice. But I'm not aware of a boost-friendly API that would allow traversing in & managing directory structure & multiple files in archive formats, such as tar & zip. of course there are C libraries, such as libtar or zlib, or ziplib, but these are all C libraries. What I would be looking for is a way to list files & directories in an archive, extract specific files from an archive, and put files into an archive, in a nice, boost-like C++ way. Is there something like this available? Akos

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About includes in numeric/ublas ....matrix.hpp and vector.hpp
by Bhushan Inamdar 20 Mar '11

20 Mar '11

Dear all, I believe, I have set the environment right for the boost libraries. I had done a program a while ago using shared pointers. And after mentioning the includes in the additional includes directories, it compiled. However, no matter what I am trying to do here, the compiler does not find matrix.hpp and vector.hpp in the attached project. I am using Boost version 1.44.0. I have checked the paths and the files do exist there. But, I do not know why my compiler keeps complaining about them being not found. The errors I am getting are as under: Error 1 fatal error C1083: Cannot open include file: 'boost/numeric/ublas/matrix.hpp': No such file or directory c:\users\user\documents\visual studio 2008\projects\dbscanalgo\dbscanalgo\clusters.h 5 DBScanAlgo Error 2 fatal error C1083: Cannot open include file: 'boost/numeric/ublas/matrix.hpp': No such file or directory c:\users\user\documents\visual studio 2008\projects\dbscanalgo\dbscanalgo\dbscan.h 5 DBScanAlgo Error 3 fatal error C1083: Cannot open include file: 'boost/numeric/ublas/matrix.hpp': No such file or directory c:\users\user\documents\visual studio 2008\projects\dbscanalgo\dbscanalgo\dbscan.h 5 DBScanAlgo Now, I have configured my paths as under: $(BOOST_ROOT) is ,....C:\Program Files\boost\boost_1_44_0 Then in VS 2008 IDE on main menu, Tools | Options | Projects and Solutions | VC++ directories... I have added... For Include Files : $(BOOST_ROOT)Boost For library files : $(BOOST_ROOT)stage\lib; $(BOOST_ROOT)\libs; $(BOOST_ROOT)bin.V2 Also, after having done this, I go to the project properties, I go to C/C++ Node and on the RHS pane in the "Additional Include Directories" option add the path to "C:\Program Files\boost\boost_1_44_0\boost\numeric\ublas". Even then, I am not able to get it working. Just for your information, I am running VS 2008 professional edition on Windows 7 OS. Please let me know if there is anything wrong here. Thanks, Bhushan

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function<double(double)> - cmath
by er 19 Mar '11

19 Mar '11

Simply bringing this to the attention of the function maintainer, in case it hasn't been mentioned before, and it has any relevance (I can live with it). #include <cmath> #include <boost/function.hpp> typedef function<double(double)> f_; // error C2440 with MSVC 2010. No such problems with GCC 4.2 f_ f = log10; typedef double(*fp)(double); f_ f = fp( log10 ); // clumsy, but solves it

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[context review] Review starts next Monday, Mars 21st
by Vicente BOTET 19 Mar '11

19 Mar '11

Hi all, The review of Oliver Kowalke Context library starts next Monday Mars 21st 2011, and will end on Mars 30th. Boost.Context is a basic building block library that is used for more higher abstractions. It is used by Boost.Fiber, Boost.Tasklet and Boost.Task from the same author. I really hope to see your vote and your participation in the discussions on the Boost DEVELOPMENT mailing lists! Please use [context review] as prefix of your post to make easier the review follow up. You can already download a frozen version for the review from the Vault, TinyURL: http://tinyurl.com/5r77rel or --------------------------------------------------- About the library: Boost.Context provides a possibility to switch between different user-level context and is intended to be the basis for a higher abstraction like coroutine and fiber. A user-level context represents the current execution state, including all registers and CPU flags, the instruction pointer, the stack pointer. boost::context encapsulates such a user-level context and is able to store/restore its associated user-level context. This allows multiple execution paths running on a single thread using a sort of cooperative scheduling (in contrast a thread is preemptively scheduled) - the running boost::context decides explicitly when its yields to allow another boost::context to run (user-level context switching). A context can only run on a single thread at any point in time but may be migrated between thread. A context switch between threads costs usually thousands of CPU cycles on x86 compared to a user-level context switch with few hundreds of cycles. Boost.Context differes to setjmp()/longjmp() in the fact that the C99 standard does not require that longjmp() preserves the current stack frame, e. g. jumping into a function which was exited via a call to longjmp() is undefined. Boost.Context allows to select the mechanism provided by the operating system (ucontext on UNIX, Windows Fibers on Windows) or a faster implementation provided by this library (fcontext using assembler). --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - 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? Regards Vicente Review Manager

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[BGL] Separating twin vertices
by Shaun Jackman 19 Mar '11

19 Mar '11

Hi, I have a directed graph where every vertex has a twin vertex. It is known ahead of time which pairs of vertices are twins. I want to remove as few vertices as possible from the graph such that no vertex and its twin is in the same connected component. Could someone suggest an appropriate algorithm? I've just started delving into the BGL. So far I'm suitably impressed! Cheers, Shaun

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boost::exception_detail::error_info_base does not have virtual destructor
by Jens Auer 19 Mar '11

19 Mar '11

Hi, I am compiling a project with a more strict warning set and got the following reports: Error 29 error C4265: 'boost::exception_detail::error_info_base' : class has virtual functions, but destructor is not virtual c:\work\svn\sandbox\externals\boost\include\boost-1_45\boost\exception\detail\error_info_impl.hpp 36 Error 30 error C4265: 'boost::error_info<Tag,T>' : class has virtual functions, but destructor is not virtual c:\work\svn\sandbox\externals\boost\include\boost-1_45\boost\exception\detail\error_info_impl.hpp 69 IMHO these classes should have a virtual destructor as they are intended to be used as base classes. Best wishes, Jens

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[boost::thread] interrupt a future get boost::unknown_exception
by 乔志强 18 Mar '11

18 Mar '11

[Windows XP, VC++ 10, boost 1.46] When interrupt a future, the future.get() throw boost::unknown_exception, Not boost::thread_interrupted. Class boost::thread_interrupted should have a base class for current_exception_impl() to catch it ? or use BOOST_THROW_EXCEPTION in interruptible_wait) ? /////////////// namespace boost { class thread_interrupted {}; } exception_ptr current_exception_impl() { try { throw; } catch( exception_detail::clone_base & e ) { return exception_ptr(e.clone()); } ................ catch( std::exception & e ) { return exception_detail::current_exception_unknown_std_exception(e); } catch( boost::exception & e ) { return exception_detail::current_exception_unknown_boost_exception(e); } catch( ... ) { return exception_detail::current_exception_unknown_exception(); } // unknown_exception////////////////// ERROR: Throw in function (unknown) Dynamic exception type: class boost::exception_detail::clone_impl<class boost::unknown_exception> std::exception::what: Unknown exception //code ///////////////////// #include <boost/thread.hpp> #include <boost/date_time/posix_time/posix_time_types.hpp> #include <boost/thread/future.hpp> using namespace boost::posix_time; using namespace boost; int main(int argc, char** argv) { boost::packaged_task<int> pt( [=]()->int { this_thread::sleep(seconds(1000)); return 0; } ); boost::unique_future<int> fi = pt.get_future(); boost::thread task(std::move(pt)); // launch task on a thread task.interrupt(); try { int v = fi.get(); } catch (boost::exception& exc) { std::cerr << "ERROR: " << boost::diagnostic_information(exc) << std::endl; } }

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