October 2004 - Boost - lists.preview.boost.org

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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New Library Proposals
by Lemings, Eric B. 13 Oct '04

13 Oct '04

Hi, I'd like to solicit interest in the following brief proposals for inclusion in the Boost library. cla (Command-Line Arguments) - A generic C++ framework for parsing command-line arguments. The library design would be based on the popt (http://www.rpm.org/dark_corners/popt/) library. uom (Units Of Measure) - A generic C++ framework for arithmetic calculations and conversions between different units of measure. The library design would be based on The Units Of Measure Library (http://tuoml.sourceforge.net/) Questions and comments welcomed. Thanks, Eric.

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[array] bug, interface change and more
by Joao Abecasis 13 Oct '04

13 Oct '04

Hi all! 1) I want to report that array::at throws range_error when it should throw out_of_range to comply to Sequence requirements. After I decided to report this issue I learned that Nicolai Josuttis maintains a parallel version boost/array.hpp on his website that corrects this and has a few other changes. Namely, an overload for 0-sized arrays was added and c_array has been renamed to data. I believe these changes were made after discussion for proposed inclusion in TR1. 2) Now I'm wondering if c_array should be renamed to data before the next release, to avoid having to change the interface later. 3) Could get<Index> functions be added to array, in order to mimick tuple? There are probably other things that can be done to make boost::array behave like a tuple. I think array could also be considered for inclusion in fusion. 4) On a side note, I wrote an initialized_array class that is very much like array but provides the constructors (and thus cannot provide aggregate initialization syntax): * default element construction * default array construction (boost::array provides this) * initialized_array<T, N>(T const & val) // elements initialized to val * initialized_array<T, N>(T const (&vals)[ N2 ]) // elements initialized with array. If N2 < N remaining elements are default constructed * initialized_array<T, N>(InputIterator start, InputIterator finish) // similar to previous but with iterators Exception behaviour is the same as for arrays (accomplished with a linear hierarchy of base classes) and each element is initialized exactly once (except with default array construction). Is there any interest in this class? br, João Abecasis

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signals: vc7.1 warning in named_slot_map.hpp
by Eric Niebler 13 Oct '04

13 Oct '04

This is actually an error for me since I have "warnings as errors" turned on. For the Dinkumware lib, type_info::operator== and operator!= return int instead of bool. This causes problems with the any_bridge_compare class in named_slot_map.hpp template<typename Compare, typename Key> class any_bridge_compare { ... bool operator()(const any& k1, const any& k2) const { if (k1.type() == typeid(front_type)) return k2.type() != typeid(front_type); -------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This results in warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning) I recommend changing the line in question to: return !(k2.type() == typeid(front_type)); -- Eric Niebler Boost Consulting www.boost-consulting.com

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Need more Boost.Build files for CodeWarrior?
by Daryle Walker 13 Oct '04

13 Oct '04

I noticed that there are *.jam files for CodeWarrior 8.3, 9.2, and 9.3. I also noticed that there are separate *.jam files for the Linux and Windows-32 versions of Intel's compiler. But CodeWarrior also comes for multiple platforms (Windows and Mac). Shouldn't the CodeWarrior *.jam files be split up as well? (Unless we're certain that CW reacts exactly the same way for the two platforms.) -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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