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extending boost::io
by Israel Fdez. Cabrera 14 Oct '04

14 Oct '04

Hi, I'm working with the boost's IOStream library adding compression/decompression methods others than zip, gzip and bzip2. I'm working too adding support to OLE Compound Documents to the same library, I'd like to "extract" a containt OLE Document using boost::io stream interface. The problem is I'm not sure how to "return or extract" more than one document or compressed file from a stream. All boost examples boost::io::copy() a whole stream to another but not just part of it. I'll appreciate any help, best regards and thank you for such a helpful library Israel

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[tuple] regression with borland-5_6_4
by Joaquín Mª López Muñoz 14 Oct '04

14 Oct '04

Hi, I've noted that tuple_test_bench is marked as a regression for BCB 564: http://tinyurl.com/62plc However, in the the following page listing Boost 1.31 issues, this test seems to appear as a failure: http://tinyurl.com/6j68r The problem seems to be related with BCB having a hard time with specializations on const types. So my questions are: 1. Is this really a regression or an expected failure as it seems to be present back in Boost 1.31? 2. Scanning the list, some folks claim that the problem goes away with BCB 5.6.4, yet what we have have does not indicate so. Anyone knows the status of this problem wrt to the version of the Borland compiler? 3. tuple already has an alternative implementation for those compilers without PTS, driven by BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION (line 26 of boost/tuple/tuple.hpp). Could someone with local access to the Borland compiler try to apply the alternative implementation by replacing that line with the following? #if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)|| defined(BOOST_BCB_PARTIAL_SPECIALIZATION_BUG) (I don't know if BOOST_BCB_PARTIAL_SPECIALIZATION_BUG really relates to this particular problem, but its name fits perfectly well.) Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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BLL on a vector of tuples
by Brian Riis 14 Oct '04

14 Oct '04

Hi list, I have a situation where I need to find a tuple from a vector based on the value of one of the tuple's values. vector<tuple<string, int, int> > v; Basically I need the last int, and all I'm supplied is the first int. I thought of using lambda expressions for this, and dug into the documentation for that (so, this is my first real experience with BLL...and any lambda expressions for that matter). After some experimentation, I ended up with something akin to this. typedef boost::tuple<std::string, int, int> myTuple; std::vector<myTuple> v; ... using namespace boost::lambda; int id = <the value for the first int, that I need to find> std::vector<myTuple>::iterator iter = std::find_if(v.begin(), v.end(), (bind(&myTuple::get<1>, _1) == id)); My compiler (MinGW-3.4.2) gives me an error message on that last line: "error: cannot resolve overloaded function `get' based on conversion to type `SOCKET'" I'm sure it's trying to tell me where I've messed up, but I can really see it. (no doubt it's due to lack of experience with BLL, or lack of intelligence; quite possibly both :)) Am I totally out to sea here? If so, I'd be joyous if someone would light a beacon for me! :) TIA -- /Brian Riis

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TR1 library extensions in libstdc++ - SmartPtr
by Jonathan Wakely 14 Oct '04

14 Oct '04

Hi, The libstdc++ developers are starting to implement the library extensions from TR1, including Boost-like smart ptrs, regex etc. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1687.pdf I have volunteered to look into modifying the Boost smart pointers to match the TR1 specs and the libstdc++ coding standards. I realise I can modify the files and include them under the terms of the Boost licence, but the last Boost code to be used in libstdc++ (the concept checks) were licensed under the GPL. I believe that was something Jeremy Siek (as copyright holder) allowed specially: http://gcc.gnu.org/ml/libstdc++/2001-04/msg00050.html Would the SmartPtr authors (Peter, Greg, Beman, Daniel, Howard, Multi Media Ltd ...) consider allowing modified versions of shared_ptr.hpp, weak_ptr.hpp, shared_count.hpp and (maybe) checked_delete.hpp to be included in the GCC sources? It would probably require licensing them as GPL, which is where I imagine some people might have reservations. That wouldn't affect the copies in the Boost tree, of course. Allowing this would greatly speed up the process of adding TR1 features to libstdc++ and tracking the draft TR as it evolves. I am prepared to rewrite the smart pointers without using Boost code if necessary, but would obviously prefer not to, when the Boost implementations are the reference ones that were used for the TR1. I eagerly await responses, as whether I have to rewrite the classes or not will have quite an impact on my free time :-) jon -- "The following story is true. By which I mean false. It's all lies. But they're entertaining lies. And in the end, isn't that the real truth. The answer, is no." - Leonard Nimoy, in "The Simpsons"

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bug in boost/date/time/date_parsing.hpp - wrong wchar_t -> char conversion
by Vyacheslav E. Andrejev 14 Oct '04

14 Oct '04

Hi there, I've found wrong usage of std::stringstream::narrow in date_parsing.hpp template<class date_type, class iterator_type> inline date_type from_stream_type(iterator_type& beg, iterator_type& end, wchar_t) { std::stringstream ss(""); while(beg != end) { ss << ss.narrow(*beg++, 'X'); // 'X' will cause exception to be thrown } return parse_date<date_type>(ss.str()); } In the code above ss.narrow does nothing, because the argument of narrow function already has type char, not wchar_t at all. I think, that the right code should be like this: template<class date_type, class iterator_type> inline date_type from_stream_type(iterator_type& beg, iterator_type& end, wchar_t) { std::stringstream ss(""); while(beg != end) { ss << std::use_facet<std::ctype<wchar_t> >(std::locale()).narrow(*beg++, 'X'); } return parse_date<date_type>(ss.str()); } -- ______________________________ Vyacheslav E. Andrejev System Architect, Excelsior, LLC E-mail: vandrejev(a)excelsior-usa.com ICQ: 7152604

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bug in boost/date_time/time_system_split.hpp - wrong static_cast
by Vyacheslav E. Andrejev 14 Oct '04

14 Oct '04

Hi there I've found a minor bug in time_system_split.hpp. In the following code date_duration_type day_overflow(static_cast<int_type>(doff)); int_type is __int64 if BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG is on. But date_duration_type contructor expects int_adaptor<long> instead. So static_cast is useless here. I think, that right code should look like this: date_duration_type day_overflow(static_cast<date_duration_type::duration_rep_type>(doff)); Proposed patch's attached to this post. -- ______________________________ Vyacheslav E. Andrejev System Architect Excelsior, LLC E-mail: vandrejev(a)excelsior-usa.com ICQ: 7152604

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Redmond Meeting
by Jonathan Turkanis 14 Oct '04

14 Oct '04

Hi All, I'd post this to comp.std.c++ but I'll be traveling soon and hope to get an answer faster here. I'll be in the Seattle area next week and hope to attend the standard committee meeting as a 'technical expert' (no giggling please). I don't see anything on the boost site (http://www.boost.org/more/cpp_committee_meetings.html) or the C++ Standard Committee site about registering advance for meetings. May I assume that it is not necessary? Jonathan

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mpl apply_if.hpp question
by Robert Ramey 14 Oct '04

14 Oct '04

Would someone have a fit if something like this were added to boost/mpl ? Robert Ramey //-------------------------------------------------------------------------- --- // boost/mpl/apply_if.hpp header file // See http://www.boost.org for updates, documentation, and revision history. //-------------------------------------------------------------------------- --- // // Copyright (c) 2004 // Robert Ramey // // Permission to use, copy, modify, distribute and sell this software // and its documentation for any purpose is hereby granted without fee, // provided that the above copyright notice appears in all copies and // that both the copyright notice and this permission notice appear in // supporting documentation. No representations are made about the // suitability of this software for any purpose. It is provided "as is" // without express or implied warranty. // apply_if is deprecated. Use eval_if instead. This is only included // to support older code like spirit 1.6 #ifndef BOOST_MPL_APPLY_IF_HPP_INCLUDED #define BOOST_MPL_APPLY_IF_HPP_INCLUDED #include "boost/mpl/eval_if.hpp" namespace boost { namespace mpl { template< typename C , typename F1 , typename F2 > struct apply_if { typedef BOOST_DEDUCED_TYPENAME eval_if<C,F1,F2>::type type; }; // (almost) copy & paste in order to save one more // recursively nested template instantiation to user template< bool C , typename F1 , typename F2 > struct apply_if_c { typedef BOOST_DEDUCED_TYPENAME eval_if_c<C,F1,F2>::type type; }; } // namespace mpl } // namespace boost #endif // BOOST_MPL_APPLY_IF_HPP_INCLUDED

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Proposed specialization of algorithm/minmax_element
by Robert Minsk 13 Oct '04

13 Oct '04

I would like to propose to specialize algorithm/minmax_element for random access iterators. The inner loop for a random access iterator would have one less compare and does not have the "potential_min" special case. I have included a sample implementation without all the support functions. template <typename RandomAccessIter, typename Compare> std::pair<RandomAccessIter, RandomAccessIter> basic_minmax_element(RandomAccessIter first, RandomAccessIter last, Compare comp, std::random_access_iterator_tag) { if (first == last) return std::make_pair(first, first); RandomAccessIter min(first), max(first), second(first + 1); // Even or odd number of elements if (std::distance(first, last) & 0x01) { // Odd - swap the first and second so first will equal last somewhere down // the line std::swap(first, second); } else { // Even - so treat first pair separately (only one comparison for first two // elements) if (comp(first, second)) max = second; else min = second; first += 2; } // Each element by pairs, with at most 3 comparison per pair while (first != last) { second += 2; if (comp(first, second)) { if (comp(first, min)) min = first; if (comp(max, second)) max = second; } else { if (comp(second, min)) min = second; if (comp(max, first)) max = first; } first += 2; } return std::make_pair(min, max); } template <typename Iter> std::pair<Iter, Iter> minmax_element(Iter first, Iter last) { typedef typename std::iterator_traits<Iter>::iterator_category IterType; return detail::basic_minmax_element(first, last, detail::less_over_iter<Iter>(), IterType()); } template <typename Iter, class _BinaryPred> std::pair<Iter, Iter> minmax_element(Iter first, Iter last, _BinaryPred comp) { typedef typename std::iterator_traits<Iter>::iterator_category IterType; return detail::basic_minmax_element(first, last, detail::binary_pred_over_iter<Iter, _BinaryPred>(comp), IterType()); }

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Mpl Set
by Jaap Suter 13 Oct '04

13 Oct '04

Hi, I noticed that there is a boost/mpl/set directory with some files in them (CVS from circa one week ago). Is this work-in-progress or can I actually start using it in some way? Do you need any help in writing these? I'm in dire need for a compile time set. Regards, Jaap Suter

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