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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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Re: [boost] Re: [Poll] New look-n-feel for Boost documentation
by brangdon＠cix.compulink.co.uk 13 Oct '04

13 Oct '04

In-Reply-To: <415CBB84.1050608(a)boost-consulting.com> joel(a)boost-consulting.com (Joel) wrote (abridged): > <http://tinyurl.com/5emyz> > > Serif or sans serif? > For continuous reading in print, serif fonts are generally more > readable than sans serif. However, on the web, the opposite is true. > Serifs are tiny, subtle strokes which, on screen in a small size, > become a rather crude series of little square bitmaps. Their absence > makes the font more readable. On my 1280x1024 desktop machine, the serif on the middle bar of my default Times New Roman 'F' is drawn with 12 pixels and 4 different colours. Maybe the studies you cite were done before anti-aliasing was common? Regardless, I think it should be up to the user. -- Dave Harris, Nottingham, UK

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[scoped_ptr] Invalid example in the documentation.
by Jurko Gospodneti� 13 Oct '04

13 Oct '04

Hi all. The example at the bottom of http://www.boost.org/libs/smart_ptr/scoped_ptr.htm specifies void as the return type for main() which is not valid C++. Could someone please fix this? Thanks, Jurko Gospodnetiæ

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[filesystem] Failures on FAT32
by Stefan Slapeta 12 Oct '04

12 Oct '04

Hi all, there are two failures reported for the intel-win32-8.1 toolset (both in operations_test): http://tinyurl.com/5dbla After some investigation I've found out now that the tests fail only because they are run on a FAT32 disk! It was just coincidence that the failures popped up in the Intel 8.1 tests (...and it's quite amusing to say that we would need another toolset dimension for the filesystem :) ) Anyway, here some analysis (the second failure seems to be a general design problem!): First failure: operations_test.cpp(287): test time_diff >= 0.0 && time_diff < 60.0 failed --> the actual difference is -2! Second failure: std::exception: boost::filesystem::last_write_time ("wrong parameter") last_write_time contains this code: ::utimbuf buf; buf.actime = std::time_t(); ^^^^^^^^^^^^^ buf.modtime = new_time; This means that the last access (!) time is set to 1970-01-01-... when the last write time is changed by this call! IMO that's absolutely incorrect because it's a side effect which I'm sure the user wouldn't expect to happen! Furthermore - a nice coincidence again - it seems not to be allowed to set this early access time for FAT32. I didn't investigate too much, but what I can say for sure is that it works to set an access time of this year, but not for 1970 (-> results in an error "wrong parameter"). Stefan

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