January 2008 - Boost-users - lists.preview.boost.org

Switch library review extended to Sunday, Jan 13th
by Stjepan Rajko 09 Jan '08

09 Jan '08

The review for the Switch library has been extended to Sunday, January 13th. I hope that the extended period will provide an opportunity for more reviewers to submit their vote, and give enough time for the discussion on design to resolve. As this library is both small and seen as very useful, it seems preferable to take advantage of the momentum of the ongoing discussion between very knowledgeable reviewers and a very knowledgeable author, and get this ironed out now. Stjepan

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(no subject)
by Lars Schouw 09 Jan '08

09 Jan '08

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Re: [Boost-users] [multi_index] range selection over composit_key problem
by Joaquín Mª López Muñoz 09 Jan '08

09 Jan '08

Hi Oliver, "Kowalke Oliver (QD IT PA AS)" ha escrito: > Hello, > I want to do an range selection over an composit key but I get compiler errors like: [...] > std::pair< > idx_type::iterator, > idx_type::iterator > > p( > idx.range( > boost::make_tuple( mi::unbounded, true), > boost::make_tuple( > boost::lambda::_1 >= 0., > true) ) ); I think there's a misunderstanding here about the usage of composite keys with range(): note that the composite key-based index sorts the elements of p according to a lexicographical order on (descending function, descending active); for instance, the values you insert in your example get sorted as follows: (1.1,false),(1,true),(0,true),(-1,true),(-1,false),(-1.1,true). Now, a fundamental limitation (or chararacteristic, if you wish) of range() is that it can only retrieve *contiguous* ranges, no matter whether the key used is simple, composite, custom or whatever . Your (syntactically incorrect) invocation to idx.range() suggests that you're trying to get the values with function>=0 and active==true, but the set of matching values is not contiguous (it is so by chance with the particular set of values you're using in oyur example, but it wouldn't be if for instance you inserted an additional (1,false) ). In order to do that you'd need to retrieve some larger range and filter out the "undesirable" elements, for example like this: // get all elements with function>=0 and arbitrary active: these do always form // a range. std::pair< idx_type::iterator, idx_type::iterator > p( idx.begin(), idx.upper_bound( boost::make_tuple(0.0) ) ); // filter out the elements with !active for ( ; p.first != p.second; ++p.first) if(p.first->active) std::cout << p.first->function << " " << std::boolalpha << p.first->active << std::endl; Hope this helps, please come back if something's still not clear. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Can i build boost under cygwin?
by Steven Woody 09 Jan '08

09 Jan '08

hi, the building process failed. it reported the libraries was not fully build properly. does boost support cygwin? thanks. -- woody then sun rose thinly from the sea and the old man could see the other boats, low on the water and well in toward the shore, spread out across the current.

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boost::asio - reason for asio_handler_invoke
by mikpol 08 Jan '08

08 Jan '08

Hi, I've been trying to understand the reasons to have asio_handler_invoke function, and so far I am unable to understand why it is needed. It is used to override invocation policy for a function-like object based on the handler. boost::asio gives one example with using io_service::strand: template<typename F> void asio_handler_invoke(F fun, MyHandler* h) { h->strand.invoke(fun); } My question is why is it needed to make this function templatized on ANY function object, and not just MyHandler? Why can't we just define MyHandler::operator() in terms of strand like this: struct MyHandler { io_service::strand strand. void operator()() { strand.invoke(boost::bind(&MyHandler::private_invoke, this)); } void private_invoke() { // do stuff... } } Thanks for any help. -- View this message in context: http://www.nabble.com/boost%3A%3Aasio---reason-for-asio_handler_invoke-tp14… Sent from the Boost - Users mailing list archive at Nabble.com.

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[multi_index] range selection over composit_key problem
by Kowalke Oliver (QD IT PA AS) 08 Jan '08

08 Jan '08

Hello, I want to do an range selection over an composit key but I get compiler errors like: /home/kowalke/Projects/test_multi_index/src/test_multi_index.cpp:85: instantiated from here /opt/boost/include/boost-1_34/boost/multi_index/ordered_index.hpp:978: error: no match for call to '(boost::tuples::tuple<boost::multi_index::detail::unbounded_type, bool, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>) (boost::multi_index::composite_key_result<boost::multi_index::composite_key<item, boost::multi_index::member<item, double, &item::function>, boost::multi_index::member<item, bool, &item::active>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> >)' I've appended a test app. Thanks for advice! regards, Oliver #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <algorithm> #include <iostream> #include <utility> #include <cstdlib> #include <stdexcept> #include <string> #include <boost/foreach.hpp> #include <boost/multi_index_container.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/composite_key.hpp> #include <boost/lambda/lambda.hpp> namespace mi = boost::multi_index; struct item { double function; bool active; item( double function_, bool active_) : function( function_), active( active_) {} }; struct idx_tag {}; typedef mi::multi_index_container< item, mi::indexed_by< mi::ordered_unique< mi::tag< idx_tag >, mi::composite_key< item, mi::member< item, double, & item::function >, mi::member< item, bool, & item::active > >, mi::composite_key_compare< std::greater< double >, std::greater< bool > > > > > table; typedef table::index< idx_tag >::type idx_type; int main( int argc, char *argv[]) { try { table tbl; tbl.insert( item( -1.1, true) ); tbl.insert( item( 1., true) ); tbl.insert( item( 0., true) ); tbl.insert( item( 1.1, false) ); tbl.insert( item( -1., true) ); tbl.insert( item( -1., false) ); idx_type & idx( tbl.get< idx_tag >() ); std::pair< idx_type::iterator, idx_type::iterator > p( idx.range( boost::make_tuple( mi::unbounded, true), boost::make_tuple( boost::lambda::_1 >= 0., true) ) ); for ( ; p.first != p.second; ++p.first) std::cout << p.first->function << " " << std::boolalpha << p.first->active << std::endl; return EXIT_SUCCESS; } catch ( std::exception const& e) { std::cerr << e.what() << std::endl; } catch ( ... ) { std::cerr << "unhandled exception" << std::endl; } return EXIT_FAILURE; }

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Re: [Boost-users] [boost] upcoming Switch library review Jan 5th - Jan 9th
by Stjepan Rajko 07 Jan '08

07 Jan '08

On Jan 6, 2008 7:34 AM, Tobias Schwinger <tschwinger(a)isonews2.com> wrote: > Steven Watanabe wrote: > > Tobias Schwinger <tschwinger <at> isonews2.com> writes: > >> Of course there are no pointers to templates, so using a function > >> pointer for anything but the default is pretty pointless. So is trying > >> to handle varying result types -- maybe the result type should be passed > >> in with another template parameter? > > > > I'd rather leave it as result_of<F()>::type. > > Actually 'result_of<F()>::type' determines the result of the nullary > call to F. I don't think I like this sort of "result_of abuse"... The > correct usage would be 'result_of<F(MPLConstant)>::type' but it's > pointless since 'MPLConstant' varies and so may the whole type expression. > > So, if you insist on deducing the result type from the function object > (instead of having it specified explicitly) my vote is 'F::result_type', > however, I still find another template parameter more appropriate for > the following good reasons: > > o The function object can work fine with result_of in a non-'switch_' > context. The cases can return different things as long as they are > convertible to the result of 'switch_', and > > o there is no way to determine this type with 'result_of. > > The current implementation seems to use result_type - is it planned to change to use result_of? I agree that result_of<F()>::type is slightly abusive, since that's not what actually gets called. Would using result_of<F(boost::mpl::front<Cases>::type)> be an option for a non-empty case sequence? As long as the order of the cases doesn't matter (btw, does it?), the user could put the desired type in the front of the Cases sequence if the return type differs for different MPLConstant types. Stjepan

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Which library my program linked?
by Lizheng 07 Jan '08

07 Jan '08

I download the precompiled static boost librarys from boost-consulting website,I found there is more than one "lib" files for a boost library,for example "regex" library,there exist below ".lib" files: - libboost_regex-vc80-mt-1_34_1.lib; - libboost_regex-vc80-mt-gd-1_34_1.lib; - libboost_regex-vc80-mt-s-1_34_1.lib; - libboost_regex-vc80-mt-sgd-1_34_1.lib; - libboost_regex-vc80-s-1_34_1.lib; - libboost_regex-vc80-sgd-1_34_1.lib; so what is the function of the files?I most use VC8 and MFC to write my program,so which ".lib" file my program linked?If I want my program to link with a boost dll library,how can I do?

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thread strange
by Chameleon 07 Jan '08

07 Jan '08

I have a strange problem with the code below. >From outside the function operator()(), I can have the pointer to thread object 'thread'. >From inside operator()() 'thread' is always 0. Why does this happen? ------------------------------------------------------------------ #include <cstdio> #include <boost/thread/thread.hpp> class A { boost::thread *thread; public: A() : thread(0) {} ~A() { join(); } void createThread() { thread = new boost::thread(*this); } void operator()() { printf("Starting thread with pointer: %d\n", thread); //<<<<<<<<<<<<<<HERE! delete thread; thread = 0; } void join() { if (thread) thread->join(); } }; int main(int, char**) { A a; a.createThread(); a.join(); return 0; } ------------------------------------------------------------------

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MSVC2005/icc10.1 boost::date_time std::max 1.34.1
by Hicham Mouline 07 Jan '08

07 Jan '08

hello, #include <iostream> #include <algorithm> int main() { const double d = std::max(5.0, 6.0); return 0; } This works fine. <algorithm> is supposed to be included to use the max algorithm. <algorithm> comes with VisualC++ headers, which intel uses. The strange thing is that when adding #include <boost/date_time/posix_time/posix_time.hpp> before or after <algorithm> #include <iostream> #include <algorithm> #include <boost/date_time/posix_time/posix_time.hpp> int main() { const double d = std::max(5.0, 6.0); return 0; } 1>.\main.cpp(9): error: expected an identifier 1> const double d = std::max(5.0, 6.0); 1> ^ 1> 1>.\main.cpp(9): error: expected an identifier 1> const double d = std::max(5.0, 6.0); Inclusing of that header seems somehow to damage "max". Gcc4.1/boost doesn't have this problem. any ideas, rds,

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