July 2010 - Boost-users - lists.boost.org

date-time separator
by Conoscenza Silente 15 Jul '10

15 Jul '10

H all I am using posix time to print the current timestamp into a string. boost::posix_time::ptime now( boost::posix_time::microsec_clock::local_time() ); std::string nowString = boost::posix_time::to_iso_extended_string( now ); The output is the following being T the date-time separator 2002-01-31T10:00:01,123456789 Is there any way to change the 'T' char separator with another character or string? I need a space instead of a 'T' Thanks AFG

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Second kind modified Bessel function with complex argument...
by Sedysen 15 Jul '10

15 Jul '10

Hi everybody, I desperatly trying to calculate the Second kind Modified Bessel functions with complex argument... My first question is: can BOOST library perform the task? and if not: does anyone know how can perform the calculation with c/c++ ?

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nested bind() does not compile
by Serguei Kolos 15 Jul '10

15 Jul '10

Hello I'm wondering why the attached code which is using nested boost::bind() does not compile on GCC ( I have tried 4.1 and 4.3). According to the "bind" package documentation nested bind() calls are allowed. To make it compile (and work!) it's necessary to add explicit cast to the result of the nested bind() call, like: boost::function<void ( void )> f = boost::bind( wrapper, a, (boost::function<bool (void)>)boost::bind( cb, p ), b ); But that is something which I don't like. Any ideas? Cheers, Sergei #include <boost/bind.hpp> #include <boost/function.hpp> typedef bool (*Callback)( void * ); void wrapper( int , boost::function<bool (void)> , int ) { } bool callback( void * ) { } void test( Callback c, void * p ) { int a,b; boost::function<void ( void )> f = boost::bind( wrapper, a, boost::bind( c, p ), b ); } int main() { test( callback, 0 ); return 0; }

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Error Installing Boost 1.38
by Amine ABOU MOUGHLBAY 15 Jul '10

15 Jul '10

Hello I am trying to install the Boost 1.38: I am on Ubuntu 10.04 LTS machine I get this error : /home/aaboumou/profiles/default/install/stable/boost_1_38_0/boost/accumulators/statistics_fwd.hpp: In function ?void example1()?: /home/aaboumou/profiles/default/install/stable/boost_1_38_0/boost/accumulators/statistics_fwd.hpp:87: error: ?template<int N> struct boost::accumulators::tag::moment? is not a function, /home/aaboumou/profiles/default/install/stable/boost_1_38_0/boost/accumulators/statistics/moment.hpp:104: error: conflict with ?template<int T2, class Arg1, class A0, class A1, class A2, class A3, class A4, class A5, class A6, class A7, class A8, class A9, class A10, class A11, class A12, class A13, class A14> typename boost::accumulators::detail::extractor_result<Arg1, boost::accumulators::tag::moment<T2> >::type boost::accumulators::extract::moment(const Arg1&, const A0&, const A1&, const A2&, const A3&, const A4&, const A5&, const A6&, const A7&, const A8&, const A9&, const A10&, const A11&, const A12&, const A13&, const A14&)? /home/aaboumou/profiles/default/install/stable/boost_1_38_0/libs/accumulators/example/main.cpp:63: error: in call to ?moment? make[2]: *** [libs/accumulators/example/CMakeFiles/accumulators-accumulators_example.dir/main.cpp.o] Erreur 1 make[1]: *** [libs/accumulators/example/CMakeFiles/accumulators-accumulators_example.dir/all] Erreur 2 make: *** [all] Erreur 2 Any one have ideas to resolve this error ? Thanks a lot for your help. Best Regards ---------------------------------------------------------------------------- Amine ABOU MOUGHLBAY Université Blaise Pascal Doctorant au LASMEA, UMR 6602 du CNRS Membre de l'équipe ROSACE du GRAVIR 24, Avenue des Landais - 63177 AUBIERE Cedex ----------------------------------------------------------------------------

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Storing boost as a 'vendor library' within svn and minimising it's size
by David Aldrich 15 Jul '10

15 Jul '10

Hi We wish to use boost.python in our project that runs on both Windows and Linux platforms. I think that the best way of making boost available to the developers, particularly under Windows, will be as a 'vendor library' within our project's subversion repository. That way, we can control the version of boost in use and make available pre-built binaries. My problem is that I want to minimise the size of that vendor library in order to minimise the time of checkouts and updates within Subversion. This is important as we have developers on the other side of the world, connected via low bandwidth links. First of all, I would welcome any experience or suggestion of how best to share boost, using a vendor library or whatever. Secondly, I have built just the boost.python shared libraries (v.1_43) and then executed 'boost install' to create a directory of just the header files and binaries. This will become the vendor library. Is this a sensible approach? Thirdly, the install directory is 48MB, which is large compared to the other directories in the svn project. I am considering deleting the header file directories not used by boost.python. But this is a trial and error process, as boost.python uses lots of boost header files. Any ideas on how best to do this? I will be very grateful for any advice. With best regards David

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Swap two columns of a matrix
by Alex34 15 Jul '10

15 Jul '10

Hi, I'm using a ublas matrix matrix <double> m_mat(2,2); and I need to swap two columns. Row-major by default I coult not use memcpy. How to do it?

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run-time integer log2
by Tim Blechmann 15 Jul '10

15 Jul '10

hi all, i am aware, that boost provides a compile-time integer log2 function. but what is the best way to compile an integer log2 at run-time? thanks, tim -- tim(a)klingt.org http://tim.klingt.org Silence is only frightening to people who are compulsively verbalizing. William S. Burroughs

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Bug in VC++ using templates and or my error
by Edward Diener 14 Jul '10

14 Jul '10

I realize this question may not belong here, but since the code in question uses Boost, I will ask here first and hope I may be forgiven for doing so. The following code does not fail with a compile time message from BOOST_MPL_ASSERT but it seems as if it should, with both VC9 and VC10: ---------------------------------------------------------------------- #include "stdafx.h" #include <boost/config.hpp> #include <boost/mpl/assert.hpp> struct test_default { }; namespace test_template1 { template < class T1, class P1_1, class P1_2 > char test(typename T1::template AMemberTemplate<P1_1,P1_2> *); template < class T1, class P1_1, class P1_2 > char (&test(...))[2]; } template < class T, class P1 = test_default, class P2 = test_default > struct test_template { typedef test_template type; BOOST_STATIC_CONSTANT(bool, value=sizeof(test_template1::test<T,P1,P2>(0))==1); }; namespace test_template2 { template < class T1, class P1_1 > char test(typename T1::template AMemberTemplate<P1_1> *); template < class T1, class P1_1 > char (&test(...))[2]; } template < class T, class P1 > struct test_template < T, P1, test_default > { typedef test_template type; BOOST_STATIC_CONSTANT(bool, value=sizeof(test_template2::test<T,P1>(0))==1); }; struct TType { template <class X> struct AMemberTemplate { }; }; void AFunction() { BOOST_MPL_ASSERT(( test_template<TType> )); } ------------------------------------------------------------------ It appears that the specialization of the 'test_template' template is being chosen instead of the main template itself but I do not see why this should be so. Is this my error or an actual bug in VC9 and VC10. If it is a VC bug, does Boost currently have a way to workaround it ?

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Boost.Ranges 2.0 algorithms accepting a const reference
by Stefano Peluchetti 14 Jul '10

14 Jul '10

Hi, the Boost.Ranges (v 1.43) documentation suggests that for each algorithm there is a version accepting a reference to a range and a version accepting a const reference to a range (which in my case would be useful for the "non-const reference to temporary object problem" when dealing for example with a boost::iterator_range<std::vector<double>::iterator> range). However the code (take for instance the reverse algorithm) does not seems to include the const reference version. Am I missing something, is the documentation incorrect, or it has been decided against the const reference version? Thank you in advance for your help. Stefano

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Annoying compiler warnings in asio/error.hpp
by Hite, Christopher 14 Jul '10

14 Jul '10

/fs/tools/L1/boost_1_43_0/boost/asio/error.hpp: At global scope: /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:353: warning: 'boost::asio::error::system_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:355: warning: 'boost::asio::error::netdb_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:357: warning: 'boost::asio::error::addrinfo_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:359: warning: 'boost::asio::error::misc_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:361: warning: 'boost::asio::error::ssl_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:208: warning: 'boost::system::system_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:209: warning: 'boost::system::generic_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:214: warning: 'boost::system::posix_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:215: warning: 'boost::system::errno_ecat' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:216: warning: 'boost::system::native_ecat' defined but not used Code defines static variables in header which is bad form. static const boost::system::error_category& system_category = boost::asio::error::get_system_category(); In gcc the warning could be disabled with -Wno-unused-variable, but that disables valuable warnings. Are these variables really needed? They theoretically create a word per compilation scope. A cleaner alternative would be to just call the function where needed. If you really need to define global variables in a header only library, you can define static members of a template class. It's a fancy trick (not sure if it has a name). Perhaps there are portablity issues with it. Chris

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