December 2005 - Boost - lists.boost.org

Proposed addition to the iterator library for iterating over all tuples.
by Alex Mendes da Costa 19 Jun '09

19 Jun '09

Hi folks: I quite often have to write code to do the following: Given N sequences, generate all the N-tuples s.t. the i'th element in each tuple is drawn from the i'th sequence. For example, if sequence S1 is { 1, 2, 3 } and sequence S2 is { 10, 20 }, I need to generate these tuples: (1, 10), (2, 10), (1, 20), (2, 20). I think this problem could be solved elegantly with a iterator similar to zip_iterator. I have some questions: (1) Is there already a way to do this in boost? (2) If not, would this be a worthwhile addition to the iterator library? (3) If so, could I contribute code for this, or must the existing library owners write it? (4) If so, how would I go about getting my code added? Most of the docs seem to be about submitting entire libraries, rather than extensions to existing libraries. Thanks, Alex

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interest in pair projection iterators?
by Lewis Hyatt 22 Dec '06

22 Dec '06

Hi All, I am in the middle of writing a large body of numerical code for data analysis and have found the boost library very useful for a number of things. I do a lot of work with std::map and with containers of std::pair objects, and one thing I've always felt annoyed with is the difficulty of interfacing a value_type of std::pair with the STL algorithms. Frequently, for instance, it is nice to represent data as a std::list< std::pair<double,double> > and then to be able to work with the first and second coordinates independently and pass them to std::accumulate() or whatever. The SGI extensions select1st() and select2nd() are somewhat useful but also non-standard, and they frequently require memory-wasting buffers to store only the first or second elements. I have a relatively simple system for solving this problem and it strikes me as the kind of quick thing that might be worth including in boost. The idea is to define a template class, template<typename Iterator> class first_iterator_t { Iterator pair_iter; public: first_iterator_t(Iterator const&); /*...*/ }; which overloads operator*() and operator->() to access the element named "first" of the object returned by Iterator::operator*(). (With something analagous for second_iterator_t.) A function named first_iterator() provides a convenient creation function a-la std::make_pair(). That's it for the most part, the class only needs to provide the required iterator interface which mostly consists of just calls to Iterator::operator functions. There is also the need to define the appropriate iterator_traits typedefs. There is a small issue of deducing whether the iterator needs to be a const iterator or not, which can be solved with partial specialization of a second template class containing nested typedefs. The end result is that something like this is now conveniently available: map<int, double> m; m[1] = 0.1; m[2]=0.2; m[5]=0.5; //prints: 1 2 5 copy(first_iterator(m.begin()), first_iterator(m.end()), ostream_iterator<int>(cout, "\t")); //prints: 0.1 0.2 0.5 copy(second_iterator(m.begin()), second_iterator(m.end()), ostream_iterator<double>(cout, "\t")); I don't see a way to do this otherwise without resorting to something like select1st(), and that also requires the use of std::transform(), which I find distasteful since the required operation is really just a simple copy. So anyway do you think this is useful enough to possibly include in boost somewhere, or is it too trivial? I have what I believe to be correct code, which could be made boost-ready with little effort. Thanks for your advice! -Lewis

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[variant, MPL] Is there a variant -> mpl sequence metafunction ?
by Jaakko Järvi 13 Nov '06

13 Nov '06

make_variant_over<Seq>::type creates a variant type from an MPL Sequence. Is there an operation that would do the opposite, create an MPL sequence from a variant? I cannot just use the type parameter list as such because the types that stand for an empty type are different in both libraries: boost::detail::variant::void_ in variant, and something else in MPL. Best, Jaakko -- Jaakko Järvi, jarvi(a)cs.tamu.edu

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[jamboost] Boost.Build V2, Milestone 10 released
by Vladimir Prus 04 Nov '06

04 Nov '06

I'm pleased to announce that the next milestone release of Boost.Build V2 is available at http://prdownloads.sourceforge.net/boost/boost-build-2.0-m10.tar.bz2 http://prdownloads.sourceforge.net/boost/boost-build-2.0-m10.zip See also http://boost.org/boost-build2/ for online docs (a copy is included in distribution). Due to large number of improvements all users are encouraged to upgrade. Changes in this release: Many toolsets were added: Intel, Metrowerks, Comeau, aCC, vacpp. Documentation was converted to BoostBook and improved. Performance was improved. - Toolsets initialization syntax is much more uniform. Compiler and linker flags can now be specified. - The algorithm for computing build properties was improved. Conditional requirements can be chained, and a number of bugs were fixed. - Specific order of properties can be specified. - The main target rules can be called from everywhere, not necessary from Jamfile. - Check for "unused sources" removed. - The <library> feature affects only linking now. - The <file> feature now works only for libraries. - Simpler syntax for "searched" libraries was added. - New <dependency> feature. Unix: The right order of static libraries on Unix is automatically computed. The <hardcode-dll-paths> feature is the default. gcc: The -fPIC option is passed when creating shared libraries. Problems with distcc were solved. Sun: It's now possible to use the sun linker (as opposed to gnu), and to compile C files. Darwin: Shared libraries are now supported. MSVC: Before resource files compilation, the setup script is invoked. Options deprecated in 8.0 are not longer used. The following bugs were fixed: - The <unit-test> rule did not handle the <library> property. - Don't add "bin" to the build directory explicitly specified by the user. - Allow <include-type> to select staged targets, even with <traverse-dependencies>off. - Includes for the form '# include <whatever>" did not work. - (Qt) Add paths to all dependent libs to uic command line, which helps if the UI files uses plugins. - Using <toolset-msvc:version>xxx in requirements was broken. - Error message printed when target can be found is much more clear. - Inline targets in sources of 'stage' did not work. - Don't produce 'independent target' warnings on Windows - (gcc) The <link-runtime>static did not work. - (gcc) Suppress warnings from the 'ar' tool on some systems. - (gcc) Don't try to set soname on NT. Developer visible changes: - Generator priorities are gone, explicit overrides are used. - 'Active' features were removed - Support for VMS paths was added. Thanks to Christopher Currie, Pedro Ferreira, Philipp Frauenfelder, Andre Hentz, Jurgen Hunold, Toon Knapen, Johan Nilsson, Alexey Pakhunov, Brock Peabody, Michael Stevens and Zbynek Winkler who contributed code to this release. - Volodya

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[Python] Slice test fails on Intel 8.1 at runtime
by Stefan Slapeta 23 Oct '06

23 Oct '06

This is not a new failure, but the failure is reported for the first time. Please could anybody have a look at it? See http://tinyurl.com/4n2fx Thanks, Stefan

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TR2 and C++0x heads up
by Beman Dawes 23 Sep '06

23 Sep '06

The C++ standards committee's Library Working Group has proposed a schedule for library changes and extensions: * October 2005: cutoff date for C++0x major library proposals * October 2006: cutoff date for library TR2 proposals * April 2007: cutoff date for C++0x library clean-up papers The usual rule-of-thumb is that new library components go in TR2, while changes to existing components go in C++0x. The LWG will consider exceptions to the rule on a case-by-case basis. The LWG is planning to issue a "Call for Proposals" with details, but in the meantime Boost developers might want to start thinking about which Boost libraries they want to propose to the LWG. Because most proposals go through one or more revisions before being accepted, it helps a proposal's chances if it reaches the committee as many meetings as possible before the final cut-off. So far there are plans to propose Boost.Threads, Boost.Filesystem, and Boost.Signals. As well as proposals for some of the more major libraries, I personally hope someone will do a sweep through Boost looking at some of the smaller utilities and helpers for a possible "Small Additions" proposal. --Beman

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Boost regression notification (2005-10-26 [RC_1_33_0])
by Douglas Gregor 23 Aug '06

23 Aug '06

Boost regression test failures ------------------------------ Report time: 2005-10-26T14:54:08Z This report lists all regression test failures on release platforms. Detailed report: http://engineering.meta-comm.com/boost-regression/CVS-RC_1_33_0/developer/i… 82 failures in 3 libraries: parameter (1) range (3) serialization (78) |parameter| tutorial: gcc-2.95.3-linux |range| array: vc-6_5 vc-6_5-stlport vc-7_0 |serialization| test_class_info_load_binary_archive: borland-5_6_4 cw-8_3 cw-9_4 cw-9_5-darwin gcc-3_4_3-sunos mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_binary_archive_dll: borland-5_6_4 cw-9_4 cw-9_5-darwin gcc-3_4_3-sunos intel-win32-8_1 mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_text_archive: borland-5_6_4 cw-8_3 cw-9_4 gcc-3_4_3-sunos mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_text_archive_dll: borland-5_6_4 cw-9_4 gcc-3_4_3-sunos intel-win32-8_1 mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_text_warchive: borland-5_6_4 cw-8_3 cw-9_4 gcc-3_4_3-sunos vc-7_0 test_class_info_load_text_warchive_dll: borland-5_6_4 cw-9_4 gcc-3_4_3-sunos intel-win32-8_1 vc-7_0 test_class_info_load_xml_archive: borland-5_6_4 cw-8_3 cw-9_4 cw-9_5-darwin gcc-3_4_3-sunos mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_xml_archive_dll: borland-5_6_4 cw-9_4 cw-9_5-darwin gcc-3_4_3-sunos intel-win32-8_1 mingw-3_4_2 vc-6_5 vc-7_0 test_class_info_load_xml_warchive: borland-5_6_4 cw-8_3 cw-9_4 gcc-3_4_3-sunos vc-6_5 vc-7_0 test_class_info_load_xml_warchive_dll: borland-5_6_4 cw-9_4 gcc-3_4_3-sunos intel-win32-8_1 vc-6_5 vc-7_0 test_demo_xml_load: borland-5_6_4 gcc-3_4_3-sunos gcc-4_0-darwin intel-win32-8_1 mingw-3_4_2 test_demo_xml_load_dll: borland-5_6_4 gcc-3_4_3-sunos gcc-4_0-darwin mingw-3_4_2 test_shared_ptr_132_text_warchive: intel-win32-8_1

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New implementation of remove_xxx for vintage compilers
by Peder Holt 28 Mar '06

28 Mar '06

Hi. I have started implementing some of the missing type_traits functionality for vintage compilers using typeof. The following are complete, and seem to work flawlessly on VC 6.5 and 7.0: remove_pointer remove_reference remove_bounds The source is available at: http://groups.yahoo.com/group/boost/files/typeof_vintage.zip The use of typeof in this respect, makes remove_xxx much more flexible. Would it be possible to start using this scheme for compilers without partial template specialization support? #define BOOST_MAX_TYPEOF_SIZE 20 #include <boost/test/minimal.hpp> //Include typeof_define.hpp in all header files where new types are added to typeof. #include <boost/typeof/typeof_define.hpp> #include <complex> #include <boost/type_traits/remove_reference.hpp> #include <boost/type_traits/remove_pointer.hpp> #include <boost/type_traits/remove_bounds.hpp> #include <boost/type_traits/is_same.hpp> template<typename A0> struct X {}; template<typename A0,unsigned int A1> struct Y {}; template<typename A0,typename A1,long A2> struct Z {}; BOOST_TYPEOF_DEFINE_TEMPLATE(X,1,(typename)) BOOST_TYPEOF_DEFINE_TEMPLATE(Y,2,(typename,unsigned int)) BOOST_TYPEOF_DEFINE_TEMPLATE(Z,3,(typename,typename,long)) BOOST_TYPEOF_DEFINE_TEMPLATE(std::complex,1,(typename)) int test_main(int, char*[]) { BOOST_TEST((boost::is_same<X<int>* const[8][9],boost::remove_bounds<X<int>* const[5][8][9]>::type>::value)); BOOST_TEST((boost::is_same<Z<X<double&>,Y<bool[4][7],12324>,0>* const*,boost::remove_pointer<Z<X<double&>,Y<bool[4][7],12324>,0>* const**volatile>::type>::value)); //VC7.1 fails to compile remove_reference. BOOST_TEST((boost::is_same<Y<int,345>** const,boost::remove_reference<Y<int,345>** const&>::type>::value)); typedef BOOST_TYPEOF(5.+std::complex<double>(6,7)) result_type; BOOST_TEST((boost::is_same<result_type,std::complex<double> >::value)); return 0; } -- Peder Holt

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Filesystem I18n comments
by Martin 07 Feb '06

07 Feb '06

1. Why "directory_iterator->exists()" instead of "exists(directory_iterator)" 2. Any chance of having a non-throwing version of directory_iterator (similar to status). Since such a common error like not having access to a directory throws an exception, every directory_iterator construction needs a try/catch. The recursive_directory_iterator is kind of useless since it will stop as soon as you get an "access denied". (Maybe a portable can_be_iterated function can be added) 3. The documentation doesn't say how other_flag is supposed to work. If an implementation adds more flags, will other_flag be set for these? 4. A suggestion is to overload exists, is_directory etc for status flags and let the error condition be statusflags == 0. (or make status_flags a class with a bool conversion) In the code you could then write like if (status_flags s = status(path)) { if (!exists(s) || !is_directory(s)) cout << "bad directory"; } else cout << "error"; In the current implementation you need to remember if you should use == or & when checking the status flags. status_flags s = status(path); if (s == error_flag) // must test with == here cout << "error"; else if ((s & directory_flag) == 0) // must test with & here cout << "bad directory";

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Bind comparisons
by David Abrahams 03 Feb '06

03 Feb '06

Is it really true that I can write bind(f, _1) > _2 but can't write _1 > _2 ?? I can't imagine a good reason for that restriction, but I don't see any indication that the latter is supported in the docs. -- Dave Abrahams Boost Consulting www.boost-consulting.com

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