July 2011 - Boost-users - lists.preview.boost.org

[wave] Trace output lines with single underscore
by Edward Diener 19 Jul '11

19 Jul '11

Many of the rescanning lines in the Wave trace output for a macro I am tracing show either just a single underscore ( _ ), where the output is empty, or a number and and underscore ( 1_ ) where it is actually just the number which is being output. What is the reason for the underscore ?

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[accumulator] median absolute deviation
by Phil Bouchard 19 Jul '11

19 Jul '11

Hi, I see the median absolute deviation (MAD) is not provided by the accumulator library. Perhaps this is a feature that could be added. Thanks, -Phil

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More on my result_type problem
by John M. Dlugosz 19 Jul '11

19 Jul '11

I see from the source code that the transform range is calling make_transform_iterator which takes two arguments, and that "If Reference is use_default then the reference member of transform_iterator is result_of<UnaryFunction(iterator_traits<Iterator>::reference)>::type." The documentation for result_of explains the need, and shows how to use a result template instead of a result_type simple type in this case. My code follow from the example: struct ASCII_lower { // tell details to result_of template, since VS8 doesn't support decltype keyword. template <typename> struct result; template<typename F, typename T> struct result<F(T)> { typedef T type; }; template< typename CharT > CharT operator() (const CharT& ch) const { if (ch >= 'A' && ch <= 'Z') return ch+0x20; return ch; // unchanged } }; But, I still get an error that result_type is not found! B:\boost/iterator/transform_iterator.hpp(42) : error C2039: 'result_type' : is not a member of 'vst::internal::ASCII_lower' B:\boost/mpl/eval_if.hpp(41) : see reference to class template instantiation 'boost::detail::function_object_result<UnaryFunc>' being compiled with [ UnaryFunc=vst::internal::ASCII_lower ] B:\boost/iterator/iterator_adaptor.hpp(172) : see reference to class template instantiation 'boost::mpl::eval_if<C,F1,F2>' being compiled with [ C=boost::is_same<boost::use_default,boost::use_default>, F1=boost::detail::function_object_result<vst::internal::ASCII_lower>, F2=boost::mpl::identity<boost::use_default> ] It appears to be using function_object_result, not result_of as documented. And that is: template <class UnaryFunc> struct function_object_result { typedef typename UnaryFunc::result_type type; }; which simply turns result_type into type to make eval_if happy, and doesn't do anything fancier. So, it doesn't work as documented, and neither provides another way of passing the parameter in (exposing more arguments from the underlying transform_iterator). Is that a bug, or what? —John

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[Preprocessor] Is it possible to expand recursively?
by TONGARI 19 Jul '11

19 Jul '11

Hello, I'd like to have a macro like: BUILD_HIERARCHY (a, (b,) (c, (d,) (e,) ) ) which should expand to: struct a {}; struct b: a {}; struct c: a {}; struct d: c {}; struct e: c {}; Is this possible at all? I have tried but with no luck, if this is impossible, please tell me so. TIA

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[spirit] warnings after upgrade to 1.47
by Diederick C. Niehorster 19 Jul '11

19 Jul '11

Dear all, After upgrading to boost 1.47, I got the attached enormous warning, ironically saying that names are too long, for a very simple use of boost.spirit. Code: #include <string> #include <vector> using namespace std; #include <boost/spirit/include/karma.hpp> namespace bsk = boost::spirit::karma; namespace bsa = boost::spirit::ascii; vector<string> vUnrecog; //... bsk::generate(ostream_iterator<char>(cout), "Init file options not recognized:\n" << (" \"" << bsa::string << '"' << bsk::eol) % "", vUnrecog); Is there something I am doing suboptimally or in an old way? (The code has been around for about 2 years now). Thanks and best, Dee

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Asio 1.6: compile error in signal_set_service with MSVC10
by Norbert Wenzel 19 Jul '11

19 Jul '11

Hi, I was just updating Boost from 1.46.1 to 1.47 and encountered a compile error inside Asio. Since there is no major outcry on this list I guess I've made an error anywhere in the upgrade process or my code. When compiling my static library that contains the networking code with (our only compiler) Visual Studio 2010 I get compile errors in asio/detail/impl/signal_set_service.ipp in line 74 saying 'boost::signal': use of class template requires template argument list As a remedy I simply defined BOOST_ASIO_DISABLE_SIGNAL, the code compiles fine and I did not recognize any problems at a first short test. I tried to make a simple example showing the error, but I was not able to reproduce this easily. So I thougt I ask what disabling signals means for Asio and if this is a valid workaround, or if I really should try to get this compile error fixed before working with 1.47. thanks, Norbert

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[fusion] adapt std::tuple to be a fusion sequence?
by Nathan Ridge 19 Jul '11

19 Jul '11

Hello, Is it possible to adapt std::tuple to be a fusion sequence? I'm thinking it may be possible to do it for a specific number of elements using BOOST_FUSION_ADAPT_TPL_ADT, but I haven't tried. Is there some functionality like this already in fusion? Thanks, Nate.

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Boost::Asio SSL Handshake - Payload in TDS package
by Andi Clemens 19 Jul '11

19 Jul '11

Hi, I need to parse TDS packages that contain SSL as their payload. For example the TDS package type 0x12 (PreLogin) will have the SSL handshake as its payload. Can I extract this payload and somehow tell Boost::Asio to use this data for an SSL handshake (async_handshake)? Andi

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What result_type ? And why?
by John M. Dlugosz 19 Jul '11

19 Jul '11

I wrote the following functor: struct ASCII_lower { template< typename CharT > CharT operator() (const CharT& ch) const { if (ch >= 'A' && ch <= 'Z') return ch+0x20; return ch; // unchanged } }; and when I used it to create a transformed_range, I get an error that it doesn't find result_type in ASCII_lower. Since the return type depends on the argument, how could I declare a result_type? And why do I need it? Lambda functions don't have it, and I thought it was fairly old fashioned and optional for helping figure out the result type if necessary.

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invalid conversion from 'bool
by Eric Lin 19 Jul '11

19 Jul '11

Dear Advanced c/g++ on boost programers: I have copied and testd a simple (Copy a file with Boost) program from page 372, Example10-10, book(C++ cookbook) but I got compile error ----------------------------- eric@eric-laptop:~/cppcookbook/ch10$ g++ Example10-10.cpp Example10-10.cpp: In function ‘int main(int, char**)’: Example10-10.cpp:17:47: error: invalid conversion from ‘bool (*)(const std::string&)’ to ‘boost::enable_if_c<true, void>::type*’ Example10-10.cpp:17:47: error: initializing argument 2 of ‘boost::filesystem3::path::path(const Source&, typename boost::enable_if<boost::filesystem3::path_traits::is_pathable<typename boost::decay<Source>::type> >::type*) [with Source = char*, typename boost::enable_if<boost::filesystem3::path_traits::is_pathable<typename boost::decay<Source>::type> >::type = void]’ Example10-10.cpp:18:47: error: invalid conversion from ‘bool (*)(const std::string&)’ to ‘boost::enable_if_c<true, void>::type*’ Example10-10.cpp:18:47: error: initializing argument 2 of ‘boost::filesystem3::path::path(const Source&, typename boost::enable_if<boost::filesystem3::path_traits::is_pathable<typename boost::decay<Source>::type> >::type*) [with Source = char*, typename boost::enable_if<boost::filesystem3::path_traits::is_pathable<typename boost::decay<Source>::type> >::type = void]’ Example10-10.cpp:18:48: error: expected ‘)’ before ‘;’ token ----------------------------- This is my program, you can download and test by your self from http://examples.oreilly.com/9780596007614/ ----------------------------------------------------- // Example 10-10. Copying a file with Boost #include <iostream> #include <string> #include <boost/filesystem/operations.hpp> #include <boost/filesystem/fstream.hpp> #include <boost/filesystem/path.hpp> using namespace std; using namespace boost::filesystem; int main(int argc, char** argv) { // Parameter checking... try { // Turn the args into absolute paths using native formatting path src = complete(path(argv[1], native)); path dst = complete(path(argv[2], native); copy_file(src, dst); } catch (exception& e) { cerr << e.what() << endl; } return(EXIT_SUCCESS); } ---------------------------------------------------------------------------- I ever check around web, there is some suggestion ask me to get rid native, but in my test/system, it only generate more errors. my boost version probably is 1.46.1 and I am on g++ 4.5.2 and Ubuntu10.04/linuxKernel2.6.35-25 Need and thanks your help a lot in advance, Eric

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