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[multi_index] How to iterate by user selected index
by René Haber 03 Oct '06

03 Oct '06

Hello, I'm looking for an easy way to iterate over a set by a user selected index. A little example: [code] struct Person { std::string name; std::string city; }; struct city{}; struct name{}; typedef multi_index_container< Person, indexed_by< ordered_unique< tag<name>, member<Person, std::string, &Person::name> >, ordered_non_unique< tag<city>, member<Person, std::string, &Person::city> > > > person_set; typedef Person::index<name>::type Person_by_name; typedef Person::index<city>::type Person_by_city; person_set persons; for(Person_by_name::iterator it = persons.get<name>().begin(); .....) {...} [/code] This for loop is hard-coded to iterate over the set sorted by name. How can I dynamically change the iterator used in this loop to let the user decide the sort criteria? Greetings, René

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Boost 1.33.1: boost::regex() constructor is not threadsafe
by p.klotz＠icoserve.com 03 Oct '06

03 Oct '06

A simple multithreaded application using 100 threads where each thread executes the following loop results in exceptions thrown by the boost::regex() constructor: for (int i=0;i<1000;++i) boost::regex("[a-z]{1}"); The exceptions thrown are either "Invalid content of repeat range" or "Unmatched { or \{". Since the regular expression used is valid and does not throw when executed in a single threaded environment I expect some static variable to be used by BoostRegex internally. Should BoostRegex be threadsafe? We use Red Hat Enterprise Linux 3 (gcc 3.2.3) as our development platform. Remark: The problem disappears when the curly braces are escaped by \\ or when using a "std::string" instead of a "const char*" argument. Best regards, Peter.

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[xpressive] Two problems with nested_results
by David Jenkins 03 Oct '06

03 Oct '06

I've been using Xpressive and think it's great. But, I think the following program shows two problems. Problem 1: You get a runtime error if you uncomment the line "std::wcout << what2.position(0) << L'\n';" Problem 2: I think it should output: This is my face is my face But it actually outputs: This is is Note that if you replace the nested regular expression with the (commented out) non-nested one, it still outputs the wrong thing. It outputs "This is" instead of "This is my face." Here is the program. Thanks for your help. #include <iostream> #include <boost/xpressive/xpressive.hpp> using namespace boost::xpressive; int main() { std::wstring str( L"This is his face." ); // find a whole word wsregex subtokens = +alnum; wsregex token = as_xpr(L"This ") >> subtokens; // wsregex token = as_xpr(L"This ") >> +alnum; // Also outputs the wrong thing wsregex_iterator cur( str.begin(), str.end(), token ); wsregex_iterator end; for( ; cur != end; ++cur ) { wsmatch const &what = *cur; std::wcout << what.str(0) << L'\n'; wsmatch::nested_results_type::const_iterator cur2 = what.nested_results().begin(); wsmatch::nested_results_type::const_iterator end2 = what.nested_results().end(); for ( ; cur2 != end2; ++cur2) { wsmatch const &what2 = *cur2; std::wcout << what2.str(0) << L'\n'; // std::wcout << what2.position(0) << L'\n'; // CAUSES RUNTIME ERROR } } std::cout << "\n\n" << std::flush; return 0; }

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auto_link question
by Robert Ramey 03 Oct '06

03 Oct '06

When I build the serialization library I get two copies of the diagnostic message. I asked this before but now I can't find the answer. It seems that it was suggested that this was symptom of some sort of mistake that could/should be corrected. In studying this I've come upon the following scenario. library ab contains a.cpp - with interface in a.hpp b.cpp - with interface in b.hpp User programs might contain a.hpp or b.hpp or both depending on what they want to call. So each of a.hpp and b.hpp should contain auto-link to generate the pragma corresponding to the library ab. However if, it the user includes both a.hpp and b.hpp - which he gets two diagnostic messages - since auto_link.hpp has no include guard. If this is a mistake, where is it and who is making it? Robert Ramey

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[program_options] undefined reference using mingw
by Johan Simon Seland 03 Oct '06

03 Oct '06

Hello all. I am trying to port a C++ program developed on Linux/g++ to Windows using MinGW. Boost was a joy to compile using MinGW and bjam and my program compiles fine, but failes during linking. The offending function calls seem to be two calls to program_options::store: po::store(po::command_line_parser(argc, argv).options(desc).positional(p).run(), vm); po::store(po::parse_command_line(argc, argv, desc), vm); Commenting out these two lines makes my program compile, but without parsing the command line of course. This problem seems to be related to mingw lacking wchar support. Apparently, Valadimir Prus made some patches for this in 2004. http://aspn.activestate.com/ASPN/Mail/Message/boost/2082829 I have recompiled program_options with his patched, but to no avail. Is anyone successfully using program_options using mingw? "H:\Program Files\CMake 2.4\bin\cmake.exe" -P CMakeFiles\rewrite.dir\cmake_clean _target.cmake h:\mingw\bin\g++.exe -O3 -DNDEBUG "CMakeFiles/rewrite.dir/src/rewrite.obj" "CMakeFiles/rewrite.dir/src/DyadicTrianglesVBO.obj" "CMakeFiles/rewrite.dir/src /HistoPyramid.obj" "CMakeFiles/rewrite.dir/src/BasisFuncTexture.obj" "CMakeFiles /rewrite.dir/src/BasisFunctions.obj" "CMakeFiles/rewrite.dir/src/ShaderSource.ob j" "CMakeFiles/rewrite.dir/src/Utility.obj" "CMakeFiles/rewrite.dir/src/Animate. obj" "CMakeFiles/rewrite.dir/src/CubicBezierCoefficients.obj" "CMakeFiles/rewrit e.dir/src/DataStructures.obj" MakeFiles/rewrite.dir/src/ImportSff.obj" -o re write.exe -Lh:\DOCUME~1\JOHANS~1\WORKSP~1\shallows -Lh:\DOCUME~1\JOHANS~1\WORKS P~1\libdyk -Lh:\local\lib -Lh:\boost\lib -lshallows -ldyk -lglu32 -lopengl32 -lg lut32 -lglew32 -lboost_program_options-mgw -lboost_regex-mgw Info: resolving vtable for boost::program_options::validation_errorby linking to __imp___ZTVN5boost15program_options16validation_errorE (auto-import) Info: resolving boost::program_options::arg by linking to __imp___ZN5boost1 5program_options3argE (auto-import) Info: resolving vtable for boost::program_options::variables_mapby linking to __ imp___ZTVN5boost15program_options13variables_mapE (auto-import) Info: resolving boost::re_detail::cpp_regex_traits_implementation<char>::init(): :null_string by linking to __imp___ZZN5boost9re_detail31cpp_regex_traits_imple mentationIcE4initEvE11null_string (auto-import) Info: resolving boost::object_cache<boost::re_detail::cpp_regex_traits_base<char >, boost::re_detail::cpp_regex_traits_implementation<char> > >::do_get(boost::re_d etail::cpp_regex_traits_base<char> const&, unsigned int)::s_databy linking to __ imp___ZZN5boost12object_cacheINS_9re_detail21cpp_regex_traits_baseIcEENS1_31cpp_ regex_traits_implementationIcEEE6do_getERKS3_jE6s_data (auto-import) Info: resolving boost::cpp_regex_traits<char>::get_catalog_name_inst()::s_name by linking to __imp___ZZN5boost16cpp_regex_traitsIcE21get_catalog_name_instEvE 6s_name (auto-import) CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcE7optionsERKNS0_19options_descriptionE[boost::p rogram_options::basic_command_line_parser<char>::options(boost::program_options: :options_description const&)]+0x1a): undefined reference to `boost::program_opti ons::detail::cmdline::set_options_description(boost::program_options::options_de scription const&)' CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcE10positionalERKNS0_30positional_options_descri ptionE[boost::program_options::basic_command_line_parser<char>::positional(boost ::program_options::positional_options_description const&)]+0x15): undefined refe rence to `boost::program_options::detail::cmdline::set_positional_options(boost: :program_options::positional_options_description const&)' CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcE5styleEi[boost::program_options::basic_command _line_parser<char>::style(int)]+0x15): undefined reference to `boost::program_op tions::detail::cmdline::style(int)' CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcE12extra_parserENS_9function1ISt4pairISsSsERKSs SaINS_13function_baseEEEE[boost::program_options::basic_command_line_parser<char >::extra_parser(boost::function1<std::pair<std::basic_string<char, >std::char_tra its<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char >, std::allocator<char> > >, std::basic_string<char, std::char_traits<char>, >std ::allocator<char> > const&, std::allocator<boost::function_base> >)]+0x75): unde fined reference to `boost::program_options::detail::cmdline::set_additional_pars er(boost::function1<std::pair<std::string, std::string>, std::string const&, std ::allocator<boost::function_base> >)' CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcEC1EiPPc[boost::program_options::basic_command_ line_parser<char>::basic_command_line_parser(int, char**)]+0x91): undefined refe rence to `boost::program_options::detail::cmdline::cmdline(std::vector<std::stri ng, std::allocator<std::string> > const&)' CMakeFiles/rewrite.dir/src/rewrite.obj:rewrite.cpp:(.text$_ZN5boost15program_opt ions25basic_command_line_parserIcE3runEv[boost::program_options::basic_command_l ine_parser<char>::run()]+0x7c): undefined reference to `boost::program_options:: detail::cmdline::run()' collect2: ld returned 1 exit status mingw32-make[2]: *** [rewrite.exe] Error 1 mingw32-make[2]: Leaving directory `H:/Documents and Settings/Johan Simon Seland /workspace/gpusilhouette' mingw32-make[1]: *** [CMakeFiles/rewrite.dir/all] Error 2 mingw32-make[1]: Leaving directory `H:/Documents and Settings/Johan Simon Seland /workspace/gpusilhouette' mingw32-make: *** [all] Error 2

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Re: [Boost-users] bind/function: composition
by Johan Torp 03 Oct '06

03 Oct '06

Monday, October 2, 2006, 10:05:23 PM, you wrote: burlbo> Johan Torp wrote: >> I often tend to have interfaces which take a boost::function<void()> >> that is to be called when an event occurs. Quite often I need make two >> separate function calls as response to one event. In these cases I >> usually solve the problem using the following technique: >> >> void foo(); >> void bar(); >> >> void call_two(const boost::function<void ()>& one, const >> boost::function<void ()>& two) >> { one(); two(); } >> >> boost::function<void ()> on_event = boost::bind(&call_two, >> boost::bind(&foo), boost::bind(&bar)); burlbo> Why not just use Boost Signals to have a single signal just call your burlbo> two different slots of foo and bar ? It seems you are unnecessarily burlbo> trying to re-invent a wheel which has already been re-invented by the burlbo> signals library. Good point. Actually I have developed some classes which closely resemble the signals library which I had already used extensively when I found signals. Maybe I will switch to boost signals when some shortcoming of my "library" becomes appearent, but for now it works nicely and I prefer to not mix APIs. In this particular case, boost::lambda solved the problem. I have a strong functional programming background so doing things like this (higher order programming) is much more natural to me than having to think about concepts such as signals and slots. -- Best regards, Johan Torp mailto:johan.torp@touchtable.se

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Re: [Boost-users] [BGL] Boost poor performance (against LEDA)
by Sohail Somani 02 Oct '06

02 Oct '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Leandro Melo > Sent: Monday, October 02, 2006 3:38 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [BGL] Boost poor performance (against LEDA) > > Ok Sohail. I agree with that. So we may be all talking the same thing > but in different words. > The way you formulate your sentence is very nice. Hey thanks!! Usually I'm incomprehensible :)

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Re: [Boost-users] [BGL] Boost poor performance (against LEDA)
by Sohail Somani 02 Oct '06

02 Oct '06

> -----Original Message----- > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Leandro Melo > > Hi David. > I think there's a misunderstanding here. I believe that I know many of > the benefits of Generic Programming. But my poiny is that I don't > agree that algorithms implemented generically can be considered to be > faster just because of that. No, but its easier to make algorithms faster because of it. It ends up almost working like multiple dispatch. I'm speaking generically about generic programming, not specifically BGL. Eventually you hit an "aha" moment where runtime code can be moved to compile time through generic techniques. Atleast that's what I've found. I'm sure a true artist can skip the "aha" moment.

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Whitespace ins boost::filesystem::path
by shookie＠email.de 02 Oct '06

02 Oct '06

All I want to know is, wether there is a specific reason the path class can't deal with a normal space in any path. path p("a b"); throws filesystem errors. I'd like to point out, that this omission basically defeats the purpose of this library to be usabel cross-platform, since the two most used systems have directory names with spaces in it for very commonly used paths. Neither windows with "My Documents" or "Program Files" nor OS X with "Application Support" will allow to use the boost::filesystem::path class. And if you can't use it for those platforms, what is the point of using it if you still need to write platform specific code? Regards Jan Schukat

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bug in boost::multi_index::sequenced splice (patch)
by Hubert Schmid 02 Oct '06

02 Oct '06

Hi, I guess there is a bug in boost/multi_index/sequenced_index.hpp. The following program fails to compile, because there is no matching operator== for class C. But this operator shouldn't be required for splice. #include "boost/multi_index/sequenced_index.hpp" #include "boost/multi_index_container.hpp" struct C { }; int main() { using namespace boost; using namespace boost::multi_index; typedef multi_index_container<C, indexed_by<sequenced<> > > Cs; Cs cs; cs.push_back(C()); cs.splice(cs.end(), cs, cs.begin()); // XXX: compile error } The following program compiles, but both assertions fail at runtime: #include "boost/multi_index/sequenced_index.hpp" #include "boost/multi_index_container.hpp" int main() { using namespace boost; using namespace boost::multi_index; typedef multi_index_container<int, indexed_by<sequenced<> > > ints; ints foo; foo.push_back(42); ints bar; bar.push_back(42); foo.splice(foo.end(), bar, bar.begin()); assert(foo.size() == 2); assert(bar.size() == 0); } I have made both tests with the boost library in Debian/unstable (version 1.33.1-7). I have also compared the source file sequenced_index.hpp with the CVS-MAIN version (1.12). I guess the following patch should fix this bug: --- sequenced_index.hpp.orig 2006-09-29 11:38:06.000000000 +0200 +++ sequenced_index.hpp 2006-09-29 11:39:43.000000000 +0200 @@ -355,7 +355,7 @@ BOOST_MULTI_INDEX_CHECK_DEREFERENCEABLE_ITERATOR(i); BOOST_MULTI_INDEX_CHECK_IS_OWNER(i,x); BOOST_MULTI_INDEX_SEQ_INDEX_CHECK_INVARIANT; - if(x==*this){ + if(&x==this){ if(position!=i)relink(position.get_node(),i.get_node()); } else{ @@ -388,7 +388,7 @@ BOOST_MULTI_INDEX_CHECK_IS_OWNER(last,x); BOOST_MULTI_INDEX_CHECK_VALID_RANGE(first,last); BOOST_MULTI_INDEX_SEQ_INDEX_CHECK_INVARIANT; - if(x==*this){ + if(&x==this){ BOOST_MULTI_INDEX_CHECK_OUTSIDE_RANGE(position,first,last); if(position!=last)relink( position.get_node(),first.get_node(),last.get_node()); regards, Hubert

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