October 2010 - Boost-users - lists.preview.boost.org

Proto domains shenanigans
by joel falcou 13 Oct '10

13 Oct '10

OK, I have a situation in which proto domain/subdomain could help me but i can't wrap my head around a proper solution. Here is the deal, i have various sub EDSL that goes like: - constants EDSL provides named consatnts (like zero_, one_, pi_ etc) that are meant to be terminal usable in any other EDSL en provide a type based way to know which constant is beging used and provide optimization in came it helps (e.g detecting x < zero_ in SIMD EDSL to replace with the SSSE3 corresponding fused operation) - a SIMD vector EDSL - various container based EDSL : table (multidim array), vector, matrix and tensor, polynom and rigid_transform. The rules I want to have is : - constant can mix with any other EDSL - SIMD don't mix with anybody - table mix with every other container and make them evaluates as table (e.g matrix * table == elementwise product and not matrix product) - vector, matrix, tensor can mix - polynom can mix with table but not with vector, matrix, tensor - rigid_transform van mix with table and matrix However i can't find any combination of domain definition that satisfy all. Is there some systematic methodologies to not fail at that ?

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[asio] DNS query
by for-gmane 13 Oct '10

13 Oct '10

Hi, is it possible to do DNS queries with asio? (for example getting the MX record(s) of a domain)

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[units] quantities with system abstraction "any<length>"
by alfC 13 Oct '10

13 Oct '10

Hi, In order to avoid reinventing the wheel I was wondering if there is any effort or there was any attempt to further abstract boost::units::quantities from its unit system but with a given dimension. That is, an object that can hold any boost::units::quantity<unit<Dimension, System> > with a given Dimension fir any System. For example (names are not ideal) any<length_dimension> a1 = 2.*si::meter; // RHS is type quantity<si::length> any<length_dimension> a2 = 2.*cgs::centimeter; //RHS is type quantity<cgs::length> any<length_dimension> b1 = 2.3 * si::second; // ERROR. or can hold any other quantity with length dimension (from any system). A sort of boost::variant<quantity<Dimension, system1> , quantity<Dimension, system2>, ... >, (but since the list is of type is not well defined maybe variant is not an options.) I know that there are some unresolved issues, for example, what is the result of a1 + a2, for which I have some solutions in mind. Anyway I just was wondering if this was tried before. And if not, what would be the best way to achieve it (boost::any? boost::variant?). (Note that all quantity<Unit> types has always the sizeof a double.) Alfredo

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Boost serialization through base class
by Joe Drumm 13 Oct '10

13 Oct '10

Hi, I've tried using the most basic example I can find in the documentation to serialize a class using a pointer to a polymorphic base. However, it only serializes the base class. I'm currently on 1.34.1. Am I missing something obvious? Sample code below: class base { public: friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int) { } }; class derived : public base { public: derived() : foo(5) { } friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int) { boost::serialization::base_object<base>(*this); ar & BOOST_SERIALIZATION_NVP(foo); } int foo; }; BOOST_CLASS_EXPORT_GUID(base, "base") BOOST_CLASS_EXPORT_GUID(derived, "derived") TEST(OMSTestSuite, BasicDeserializeTest) { std::ofstream ofs("test.out"); boost::archive::xml_oarchive toa(ofs); base *b = new derived; toa & BOOST_SERIALIZATION_NVP(b); }

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[String algo] Breaking change between 1.41 and 1.44 in split
by Christophe Henry 13 Oct '10

13 Oct '10

Hi, I noticed a breaking change in the split function when the input string is empty. Consider the following example: #include <string> #include <vector> #include <iostream> #include <boost/algorithm/string/split.hpp> #include <boost/algorithm/string/classification.hpp> int main() { std::vector<std::string> result; std::string empty_string; boost::algorithm::split( result, empty_string,boost::algorithm::is_any_of( "\t" ),boost::algorithm::token_compress_off); std::cout << "result size: " << result.size() << std::endl; return 0; } With boost 1.41 I get: result_size: 1 With 1.44 I get: result_size: 0 Meaning that splitting an empty string now has a new meaning. All I found to this subject was that 1 seems to be the correct answer (http://lists.boost.org/Archives/boost/2005/07/90266.php) Furthermore, there has been, according to the release notes, no change to string algo since the 1.41. This brings me to the question, before I start updating my code, is this change a design decision or an accident? Thanks, Christophe

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[Accumulators] How to define the initial value ?
by Adrien Todeschini 13 Oct '10

13 Oct '10

Hi everyone, As the code of weighted_sum_impl constructor is [ in header <boost/accumulators/statistics/weighted_sum.hpp> ] template<typename Args> weighted_sum_impl(Args const &args) : weighted_sum_( args[parameter::keyword<Tag>::get() | Sample()] * numeric::one<Weight>::value ) { } and the template parameter Tag is defined as tag::sample namespace tag { struct weighted_sum : depends_on<> { typedef accumulators::impl::weighted_sum_impl<mpl::_1, mpl::_2, tag::sample> impl; }; } How can I define this tagged argument when initializing the accumulator_set ? ( Indeed, weighted_sum_impl constructor is called at this point ) Thanks in advance for your help. Adrien

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[serialization] Deserialization of a float whose value is infinite throws an archive_exception ("stream error")
by Luca 12 Oct '10

12 Oct '10

Hello, using the Boost.Serialization library version 1.43, I saved to an XML archive a float number which has a value of infinite; then loading that XML file leads to a boost::archive::archive_exception, exception.what() return "stream error". The source code to reproduce the problem is the following: #include <boost/serialization/serialization.hpp> #include <sstream> #include <boost/archive/xml_woarchive.hpp> #include <boost/archive/xml_wiarchive.hpp> #include <iostream> struct XXX { friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(mValue); } float mValue; };//struct int main() { std::wstringstream lSS; boost::archive::xml_woarchive oa(lSS); XXX xxx; float zero = 0.f; xxx.mValue = 1 / zero; oa << BOOST_SERIALIZATION_NVP(xxx); std::wcout<<"saved:"<<lSS.str() << std::endl; boost::archive::xml_wiarchive ia(lSS); ia >> BOOST_SERIALIZATION_NVP(xxx); std::wcout<<"loaded:"<<lSS.str() << std::endl; return 0; } Using gcc 4.4.4 on Linux/Debian the mValue member is saved as: <mValue>inf</mValue> while on Visual Studio 2005 on Windows XP sp2 the mValue member is saved as: <mValue>1.#INF</mValue> I see that the value of infinite has a different representation, (and this could be the main motivation behind the choice to not support them), but this lead to a situation in which a properly saved archive is not loadable by the library itself. As far I can see, the issue is at this line 209 of \libs\serialization\src\basic_xml_grammar.ipp parse_info<BOOST_DEDUCED_TYPENAME std::basic_string<CharType>::iterator> result = boost::spirit::parse(arg.begin(), arg.end(), rule_); return result.hit; where the parse function fails since result.hit is equal to false. I resolved the issue by checking all the data preventing accurately any infinite value before it is saved to an xml archive, but I wonder if this problem belongs to the library itself or not. Greetings, Luca

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[asio]How to insure async handles not be called after calling deadline_timer::cancel()?
by 鑫炜廖 12 Oct '10

12 Oct '10

The document says, If the timer has already expired when cancel() is called, then the handlers for asynchronous wait operations will: have already been invoked; or have been queued for invocation in the near future. These handlers can no longer be cancelled, and therefore are passed an error code that indicates the successful completion of the wait operation. Does this mean that async handlers may be called after calling deadline_timer::cancel() (say, the second curcumstance) ? If yes, it seems make things unintuitive, eg. delete the resources that associate with handlers after cancel(). Is there any way to suppress or identify these handlers? thx.

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Re: [Boost-users] boost 1.44.0 undefined reference to boost::filesystem2::no_check
by Asif Fayyaz 12 Oct '10

12 Oct '10

No, that issue is a bit different and I have already included <boost/filesystem.hpp> I am again posting the code: --------------------------------Sample application source: #include <stdio.h> #include <boost/filesystem.hpp> int main() { std::string m_FileName(boost::filesystem::path("testfile1.txt", boost::filesystem::no_check).native_file_string()); printf("Testboost.....%s\n", m_FileName.c_str()); return 0; } -------------------------------- Asif ---------- Replied message ---------- From: Igor R <boost.li...(a)gmail.com> Date: Oct 11, 5:57 pm Subject: boost 1.44.0 undefined reference to boost::filesystem2::no_check To: BOOST Archives > Any one?? > any idea? > Waiting for response in this regard. There was a similar issues here: http://permalink.gmane.org/gmane.comp.lib.boost.user/62789 Doesn't it apply your case? do you include <boost/filesystem.hpp>? _______________________________________________ Boost-users mailing list Boost-us...@lists.boost.orghttp:// lists.boost.org/mailman/listinfo.cgi/boost-users

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Distance/size of boost ranges for std::set.
by Matthew Gwynne 12 Oct '10

12 Oct '10

Hi, I'm working within a C++ library which makes extensive use of the range concept, and also of boost::size. The current version of the library makes use of boost 1_38, however, updating to the newer versions of boost, I've had to replace boost::size with boost::distance as some of the ranges involved, such as std::set don't have random access iterators. However, this presents a problem - it's not really acceptable within our application to have linear time complexity for the size operation on sets when the size member function of the set container is constant time, so I'm looking for some advice. Are we misusing the range concept here and should be using something else? Everything other than this matches up nicely, and it's only the time complexity with regards to boost::distance that will cause problems. Should we simply be extending the boost::size function with additional overloaded versions specific to std::set if we wish to use it in this way (is this reasonable?)? Thanks in advance! Matthew Gwynne

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