September 2010 - Boost-users

[BGL] changes in graph => changes in filtered_graph?
by Adam Spargo 15 Sep '10

15 Sep '10

Hi, Just a simple question - if I have a filtered_graph fg, based on adjacency_list g, do changes to g automagically turn up in fg? Or do I need to make a new fg, once I have finished changing g? I know I could write a simple test to find out, which I am doing, but I'd be grateful if someone with more experience of BGL could let me know of any exceptions or potential pitfalls. Thanks in advance, Adam. -- Dr Adam Spargo High Performance Assembly Group email: aws(a)sanger.ac.uk Wellcome Trust Sanger Institute Tel: +44 (0)1223 834244 x7728 Hinxton, Cambridge CB10 1SA Fax: +44 (0)1223 494919 -- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE.

3 2

[Filesystem] v3: preferred() vs. make_preferred()
by PB 15 Sep '10

15 Sep '10

Hello, I have built up a path in which the underlying string has a mixture of slashes and backslashes. I'm passing my_path.string().c_str() to a Windows API function which is getting confused because the string is being provided verbatim. I'm therefore looking to convert the string. According to the Filesystem tutorial (http://www.boost.org/doc/libs/1_44_0/libs/filesystem/v3/doc/tutorial.html) I can use the preferred() observer method to get the string that is suitable for the current (Windows) platform. This sounds like quite a nice design. However, it seems the preferred() method doesn't exist (i.e. the tutorial is wrong). There is a make_preferred() method which is non-const because it *changes the underlying representation* to the format preferred by the operating system. >From my application developer point of view, the preferred() observer is neater/better. I don't care and don't need to know what the underlying path format is. I have no desire to change it. All I am bothered about is that I can store it to a string (perhaps in an external file), and reconstruct the path from the same string. There are a few points in the application however where I need to present the path in a particular way, and it'd be nice to just throw a call to preferred() there. e.g. listBox_.AddString(my_path.preferred().c_str()); I've now got to do: bfs::path pref = my_path; pref.make_preferred(); listBox_.AddString(pref.string().c_str()); because the function that does the rendering of the string to the list box accepts the path as a const boost::filesystem::path& and therefore cannot change it. Wanted to point out the mismatch between the tutorial and the source code, and am wondering on the rationale behind make_preferred() over preferred()? Always possible I'm missing something! Thanks, Pete

2 1

boost::bind correct way
by Kraus Philipp 15 Sep '10

15 Sep '10

Hi, I'm using boost::bind for creating a thread group. My code shows this way: boost::thread_group l_threadgroup; for(std::size_t i=0; i < boost::thread::hardware_concurrency(); ++i) l_threadgroup .create_thread( boost::bind( &ncd<T>::multithread_deflate_symmetric, this, i ) ); The code runs within the class method "symmetric" and should be called from the self object the multithread_deflate_symmetric. My class "ncd" is a template class. I debug the code on a amd64 Gentoo Linux with valgrind 3.5 and get a "data race condition". Valgrind shows this message: ==6914== Possible data race during read of size 8 at 0x7fefff6d0 by thread #1 ==6914== at 0x4C2B138: ??? (in /usr/lib64/valgrind/ vgpreload_helgrind-amd64-linux.so) ==6914== by 0x6152B10: boost::thread::start_thread() (in /opt/ library/Boost/1.44/lib/libboost_thread.so.1.44.0) ==6914== by 0x414B50: boost::thread::thread<boost::_bi::bind_t<void, boost::_mfi::mf1<void, ncd<double>, unsigned long const&>, boost::_bi::list2<boost::_bi::value<ncd<double>*>, boost::_bi::value<unsigned long> > > >(boost::_bi::bind_t<void, boost::_mfi::mf1<void, ncd<double>, unsigned long const&>, boost::_bi::list2<boost::_bi::value<ncd<double>*>, boost::_bi::value<unsigned long> > >, boost::disable_if<boost::is_convertible<boost::_bi::bind_t<void, boost::_mfi::mf1<void, ncd<double>, unsigned long const&>, boost::_bi::list2<boost::_bi::value<ncd<double>*>, boost::_bi::value<unsigned long> > >&, boost::detail::thread_move_t<boost::_bi::bind_t<void, boost::_mfi::mf1<void, ncd<double>, unsigned long const&>, boost::_bi::list2<boost::_bi::value<ncd<double>*>, boost::_bi::value<unsigned long> > > > >, boost::thread::dummy*>::type) (in main) ==6914== by 0x419F4D: ncd<double>::symmetric(std::vector<std::string, std::allocator<std::string> > const&, bool const&) (in main) ==6914== by 0x40B10F: main (in main) ==6914== This conflicts with a previous write of size 8 by thread #2 ==6914== at 0x4C2B263: ??? (in /usr/lib64/valgrind/ vgpreload_helgrind-amd64-linux.so) Do I use boost::bind in the correct way? Thanks Phil

2 1

Property Tree problem with equal range.
by Andrew Maclean 14 Sep '10

14 Sep '10

I am using Boost 1.43 and last line in the following code causes this error: /usr/local/include/boost/property_tree/detail/ptree_implementation.hpp:471: error: ‘class boost::multi_index::detail::bidir_node_iterator<boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::index_node_base<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::property_tree::basic_ptree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::property_tree::basic_ptree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > > > > > >’ has no member named ‘base’ Here is the code fragment. pt is the property tree. std::string key = "program.query"; std::size_t num = pt->count(key); std::cout << "Number = " << num << std::endl; typedef boost::property_tree::ptree::assoc_iterator assocIt; typedef std::pair< assocIt, assocIt > TRangeItPair; TRangeItPair er = pt->equal_range(key); The only fix I could see was here: http://lists.boost.org/boost-users/2010/02/55806.php But I cannot see how to apply it to the above code fragment. Any help is appreciated. Regards Andrew -- ___________________________________________ Andrew J. P. Maclean Centre for Autonomous Systems The Rose Street Building J04 The University of Sydney 2006 NSW AUSTRALIA Ph: +61 2 9351 3283 Fax: +61 2 9351 7474 URL: http://www.acfr.usyd.edu.au/ ___________________________________________

1 0

Why doesn't boost::function use get_pointer() ?
by Peter Soetens 14 Sep '10

14 Sep '10

When using boost::bind, I can write this: struct X { void foo(int) {} }; shared_ptr<X> x( new X ); // bind takes shared_ptr: bind(&X::foo, x, 3)(); But I can't write this: function<void(X*,int)> foo = &X::foo; // function refuses shared_ptr: foo(x,1); Why doesn't boost::function have the same get_pointer() trick ? Or how can I rewrite the function signature such that it does work with shared pointers ? Any chance it gets into C++0x ;-) ? Thanks, Peter

2 1

[Filesystem] query
by Sean Farrow 14 Sep '10

14 Sep '10

Hi: I have a path of the form: Drive\directory1\directory2, how would I go about retrieving the second directory only i.e in this example directory2? Is this the same code in filesystem 2 and 3? Regards Sean.

2 1

Building FileSystem Version 3 static libraries
by Bibbo, Joe 14 Sep '10

14 Sep '10

I have downloaded the boost v1.44 and would like to see if our usage of the FileSystem library is compatible with Version 3 of library. I am having trouble building the library. Using the command bjam toolset=msvc-9.0 variant=debug threading=multi link=static define=_BIND_TO_CURRENT_VCLIBS_VERSION define=BOOST_FILESYSTEM_VERSION=3 --with-filesystem I am seeing following error message " .. compile-c-c++ bin.v2\libs\system\build\msvc-9.0\debug\link-static\threading-multi\error_code.obj error_code.cpp msvc.archive bin.v2\libs\system\build\msvc-9.0\debug\link-static\threading-multi\libboost_system-vc90-mt-gd-1_44.lib common.copy stage\lib\libboost_system-vc90-mt-gd-1_44.lib bin.v2\libs\system\build\msvc-9.0\debug\link-static\threading-multi\libboost_system-vc90-mt-gd-1_44.lib 1 file(s) copied. compile-c-c++ bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_operations.obj v2_operations.cpp S:\sony4\boost\boost_1_44_0\boost/filesystem/v2/config.hpp(16) : fatal error C1189: #error : Compiling Filesystem version 2 file with BOOST_FILESYSTEM_VERSION defined != 2 call "G:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86 >nul cl /Zm800 -nologo @"bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_operations.obj.rsp" ...failed compile-c-c++ bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_operations.obj... compile-c-c++ bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_path.obj v2_path.cpp S:\sony4\boost\boost_1_44_0\boost/filesystem/v2/config.hpp(16) : fatal error C1189: #error : Compiling Filesystem version 2 file with BOOST_FILESYSTEM_VERSION defined != 2 call "G:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86 >nul cl /Zm800 -nologo @"bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_path.obj.rsp" ...failed compile-c-c++ bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_path.obj... compile-c-c++ bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_portability.obj v2_portability.cpp S:\sony4\boost\boost_1_44_0\boost/filesystem/v2/config.hpp(16) : fatal error C1189: #error : Compiling Filesystem version 2 file with BOOST_FILESYSTEM_VERSION defined != 2 call "G:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86 >nul cl /Zm800 -nologo @"bin.v2\libs\filesystem\build\msvc-9.0\debug\link-static\threading-multi\v2\src\v2_portability.obj.rsp" ... " Is there something else I need to configure to build this version of the library? Regards, Joe

4 4

[Unordered] size() != distance(begin(), end())
by Hossein Haeri 14 Sep '10

14 Sep '10

Dear all, I have an instance of boost::unordered_map<> somewhere in my codebase (GCC 4.5.1, MinGW, WinXP) with the following funny piece of test code: container_[id].insert(v); cout << "container insertion succesful" << endl; cout << "The container now contains " << container_.size() << " ids in it." << endl; cout << "distance from begin to end = " << distance(container_.begin(), container_.end()) << endl; Strangely enough, it happens sometimes that the output I get is: container insertion succesful The container now contains 2 ids in it. distance from begin to end = 1 I.e., size() != distance(begin(), end()) which is against the documentation: http://www.boost.org/doc/libs/1_44_0/doc/html/boost/unordered_map.html#id13… Am I missing anything? Or, is this a bug in the implementation of boost::unordered_map<>? TIA, --Hossein

2 2

Is there still a way to explicitly compose functors ?
by Timothy Madden 14 Sep '10

14 Sep '10

Hello I just do not like the ugly syntax with using the _1 placeholder (or _2, or whatever) used in bind and lambda; is there still some other way to compose functors ? Like with compose ? Thank you, Timothy Madden

2 3

How to use %e for the format of time_input_facet?
by xiada74＠sina.com 14 Sep '10

14 Sep '10

Hello,   I tried the below code: #include <boost/date_time.hpp> #include <boost/date_time/posix_time/ptime.hpp> #include <iostream> using namespace boost::posix_time; int main() { std::string _format1 = "%Y-%m-%d %H:%M:%S"; std::string _format2 = "%Y-%m-%e %H:%M:%S"; std::string teststring = "2010-09-10 10:01:01"; ptime time1, time2; time_input_facet facet1(_format1, 1); time_input_facet facet2(_format2, 1); std::stringstream ss1(teststring); std::stringstream ss2(teststring); ss1.imbue(std::locale(ss1.getloc(), &facet1)); ss1 >> time1; ss2.imbue(std::locale(ss2.getloc(), &facet2)); ss2 >> time2; std::cout << "Time1: " << time1 << std::endl; std::cout << "Time2: " << time2 << std::endl; return 0; } The output is: Time1: 2010-Sep-10 10:01:01 Time2: not-a-date-time   Howto fix the issue for the format using "%e"?   Thanks!

1 0