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Re: [boost] [fusion] random access views?
by dan marsden 31 Oct '06

31 Oct '06

Eric Niebler wrote: >A fusion transform_view of a random access sequence should itself be a >random access sequence, and its category is random access, but it >doesn't seem to implement the complete interface. For instance: > >struct plus1 >{ > template<typename T> struct result { typedef T type; }; > template<typename T> T operator ()(T const &t) const > { > return t + 1; > } >}; > >template<typename V> >void bar(V const &v) >{ > boost::fusion::at_c<1>(v); // OK > boost::fusion::transform_view<V const, plus1> view(v, plus1()); > boost::fusion::at_c<1>(view); // ERROR >} > >int main() >{ > bar(boost::fusion::make_vector(1,2,3)); > return 0; >} > > >I can't randomly access elements of a transformed fusion::vector. Bug? The at_impl had been completed omitted. I've fixed this in the cvs, and added covering tests. Thanks for spotting this. Cheers Dan ___________________________________________________________ Try the all-new Yahoo! Mail. "The New Version is radically easier to use" – The Wall Street Journal http://uk.docs.yahoo.com/nowyoucan.html

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Simulating log{10}(2)
by Daryle Walker 31 Oct '06

31 Oct '06

Our code that deals with determining how many characters are needed to express an integer in decimal form, based on the number of bits, use a conversion factor like: #digits <= 2 + #bits * log{10}(2) where "log{10}(2)" is the logarithm of 2 for base 10. This can be calculated from "ln(2) / ln(10)", where "ln" is the natural logarithm function. Since the conversion factor is used in compile-time integer contexts, the constant is expressed as an integer multiply followed by an integer divide. The decimal expansion of the constant is approximately 0.30102999566.... Our code uses cut-off versions of that expansion for the constant: static int const digits10 = 2 + digits * 301 / 1000; I've also seen "30103 / 100000" being used. Couldn't there be better approximate fractions to use? Based on various web calculators, like Google's and "Contfrac" at <http://wims.unice.fr/wims/wims.cgi?session=B75AF6A950.2&+lang=en&+module=to ol%2Fnumber%2Fcontfrac.en>, I've found a continued fraction representation of the constant. An irrational number has an infinitely long c.f. expansion, but the convergents off that expansion are usually the best rational approximations of an irrational value. Let's compare expansions: 1. ln 2 / ln 10 = [0; 3, 3, 9, 2, 2, 4, 6, 2, 1, 1, 3, 1, 18, 1, 6, 1,...] 2. 0.301 = [0; 3, 3, 9, 1, 2, 3] 3. 0.30103 = [0; 3, 3, 9, 2, 2, 4, 5, 1, 1, 1, 2] where [a0; a1, a2,...] = a0 + 1/(a1 + 1/(a2 + ...)). The common approximation 0.301 differs from the actual expansion at a4 = 2. The convergent there is 59/196. The absolute differences between those values and the actual value are: |log{10}(2) - 0.301| = 2.9995664e-5 |log{10}(2) - 59/196| = 9.58750072e-6 The convergent is 3.1 times closer to the actual value than the common approximation. Using 0.30103 versus the convergent 4004/13301 at the point of differing a7 = 6 gives the convergent an improvement factor of 2.1. The convergents have smaller numerators and denominators than their common approximations, making them easier to calculate without worry of overflow. Conversely, if you know that you have more leeway in multiplications, then using higher convergent fractions instead of the decimal expansion are a better bet. -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com

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[GIL] Asking for help for vc2003 compiler bug
by Christian Henning 31 Oct '06

31 Oct '06

Hi there, taking the latest GIL source from their site is exposing a tedious compiler bug with VC2003. I have been trying to find an easy wokaround but failed. It fails in channel.hpp when trying to define specializations for channel_min_value() and channel_max_value. Here is the code: template <typename T> typename channel_traits<T>::value_type inline channel_min_value() { return std::numeric_limits<typename channel_traits<T>::value_type>::min(); } template <typename T> typename channel_traits<T>::value_type inline channel_max_value() { return std::numeric_limits<typename channel_traits<T>::value_type>::max(); } template<> inline bits8 channel_min_value<bits8>() { return 0; } template<> inline bits8 channel_max_value<bits8>() { return 255; } template<> inline bits16 channel_min_value<bits16>() { return 0; } template<> inline bits16 channel_max_value<bits16>() { return 32768; } template<> inline bits32f channel_min_value<bits32f>() { return 0.0f; } template<> inline bits32f channel_max_value<bits32f>() { return 1.0f; } Here is the compiler error messages: c:\gil\gil\core\channel.hpp(95) : error C2785: 'channel_traits<T>::value_type gil::channel_min_value(void)' and 'gil::bits8 gil::channel_min_value(void)' have different return types c:\gil\gil\core\channel.hpp(90) : see declaration of 'gil::channel_min_value' c:\gil\gil\core\channel.hpp(95) : see declaration of 'gil::channel_min_value' c:\gil\gil\core\channel.hpp(95) : error C2912: explicit specialization; 'gil::bits8 gil::channel_min_value<gil::bits8>(void)' is not a specialization of a function template c:\gil\gil\core\channel.hpp(95) : fatal error C1903: unable to recover from previous error(s); stopping compilation I have been trying to find a workaround reading some news groups entry. But all I could find are conformations that this is a bug and that VC2005 is compiling. Not very helpful. Does anyone here at boost know a workaround? I have realized that this request is offtopic. Please, ignore when feeling that my request is inappropriate. Thanks, Christian

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Boost inspection notification (2006-10-31/RC_1_34_0) *X*
by Rene Rivera 31 Oct '06

31 Oct '06

Boost Inspection Report Run Date: 17:04:25 UTC, Tuesday 31 October 2006 An inspection program <http://www.boost.org/tools/inspect/index.html> checks each file in the current Boost CVS for various problems, generating this as output. Problems detected include tabs in files, missing copyrights, broken URL's, and similar misdemeanors. Totals: 11675 files scanned 906 directories scanned (including root) 157 problems reported Problem counts: 0 files with invalid line endings 0 bookmarks with invalid characters 3 invalid urls 89 broken links 22 unlinked files 7 file/directory names issues 1 files with tabs 0 violations of the Boost min/max guidelines 35 usages of unnamed namespaces in headers (including .ipp files) Summary: archive (3) bind (1) boost-root (1) build (3) date_time (1) doc (2) filesystem (36) graph (3) iostreams (2) lambda (3) mpl (1) multi_array (2) parameter (2) ptr_container (1) regex (1) regression (13) serialization (1) signals (1) test (79) type_traits (1) Details: *R* invalid (cr only) line-ending *A* invalid bookmarks, invalid urls, broken links, unlinked files *N* file/directory names issues *T* tabs in file *M* uses of min or max that have not been protected from the min/max macros, or unallowed #undef-s *U* unnamed namespace in header |archive| boost/archive/basic_streambuf_locale_saver.hpp: 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path.htm#normalize *A* broken link: path.htm#operator_eq *A* broken link: path.htm#synopsis libs/filesystem/doc/portability_guide.htm: *A* broken link: path.htm#name_check_typedef libs/filesystem/doc/tr2_proposal.html: *A* invalid URL (hardwired file): file:///C|/boost/site/libs/filesystem/doc/operations.htm#complete_note |graph| boost/graph/maximum_cardinality_matching.hpp: *N* name exceeds 31 characters libs/graph/doc/lengauer_tarjan_dominator_tree.htm: *N* name exceeds 31 characters libs/graph/doc/sorted_erdos_renyi_generator.html: *N* name exceeds 31 characters |iostreams| libs/iostreams/doc/acknowledgments.html: *A* unlinked file libs/iostreams/doc/concepts/multi-character.html: *A* unlinked file |lambda| boost/lambda/core.hpp: *U* unnamed namespace at line 62 boost/lambda/detail/lambda_functors.hpp: *U* unnamed namespace at line 25 boost/lambda/exceptions.hpp: *U* unnamed namespace at line 24 |mpl| boost/mpl/alias.hpp: *U* unnamed namespace at line 17 |multi_array| boost/multi_array/base.hpp: *U* unnamed namespace at line 69 libs/multi_array/test/generative_tests.hpp: *U* unnamed namespace at line 57 |parameter| libs/parameter/doc/html/python.html: *A* broken link: tag::x(int *A* broken link: tag::y*(int |ptr_container| libs/ptr_container/doc/tutorial_example.html: *A* unlinked file |regex| libs/regex/performance/input.html: *A* unlinked file |regression| regression/.htaccess: *N* leading character of ".htaccess" is not alphabetic tools/regression/xsl_reports/xsl/html/issues_legend.html: *A* unlinked file tools/regression/xsl_reports/xsl/html/library_developer_legend.html: *A* unlinked file tools/regression/xsl_reports/xsl/html/library_user_legend.html: *A* unlinked file tools/regression/xsl_reports/xsl/html/make_tinyurl.html: *A* unlinked file tools/regression/xsl_reports/xsl/html/summary_developer_legend.html: *A* unlinked file tools/regression/xsl_reports/xsl/html/summary_user_legend.html: *A* unlinked file 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Boost Timer Update
by Philippe Vaucher 31 Oct '06

31 Oct '06

Hello guys, I've been quite away from home in the last months so I wasn't able to work on the timer, but now I'm back so I'd have some time now. Today I've implemented Gennaro's device idea for QueryPerformanceCounter() / timeGetTime(). As the vault's down, you can find it at http://www.unitedsoft.ch/boost/timer_2006_10_29.zip. Are you guys still using QuickBook for the documentation ? Before going away I started using it but it was quite painful. Philippe Vaucher

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[result_of] problems on MSVC
by Eric Niebler 31 Oct '06

31 Oct '06

(CC'ing Doug, who has the unfortunate distinction of having his name in result_of.hpp.) Has anybody else noticed inexplicable compile failures with MSVC 7.1, and sometimes even MSVC 8.0, when using boost::result_of? It happens with functors that have a nested result<> template, like struct unary { template<typename Sig> struct result; template<typename This, typename Arg> struct result<This(Arg)> { typedef void type; }; ... }; And when instantiating boost::result_of<unary(int)>::type, I'll sometimes get an error like: "struct unary::result<F> is undefined, with F=unary(int)." In some contexts, it seems, MSVC is unable to find the correct partial specialization. The same code will compile fine with GCC. I have yet to find a suitable work-around. As my work relies more and more heavily on result_of, this has become a real pain point for me. I can provide a repro to anybody interested, but it's large so I can't post it here. I haven't found a simple repro yet. -- Eric Niebler Boost Consulting www.boost-consulting.com

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current cvs broken?
by Neal Becker 30 Oct '06

30 Oct '06

don't know how to make <@boost!libs!python!build>../src/indexing/indexing_slice.cpp don't know how to make <@boost!libs!python!build>../src/indexing/python_iterator.cpp

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Any interest in a separate Boost.TR1 release/download?
by John Maddock 30 Oct '06

30 Oct '06

I wonder if people would find a separate download for the Boost TR1 components useful ? At present this is vapourware: I'm not sure how easy it will be to sort out documentation and build issues when extracting the TR1 subset, but I'm prepared to put together a preliminary (alpha) release of such a beast if there's demand, and from there we can at least see how viable releasing such a Boost subset would be. Thought? Thanks, John.

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Visual Studio 2005: C4103 Warnings
by Edward Lam 30 Oct '06

30 Oct '06

Hi, I've found that when using Boost on Visual Studio 2005, I get warning C4103 when including any boost header which end up including abi_{prefix,suffix}.hpp (eg. iostreams/filter/zlib.hpp) or which manually performs a #include BOOST_ABI_{PREFIX,SUFFIX} (eg. regex/v4/regex_traits_defaults.hpp). An explanation for the warning can be found here: http://windowssdk.msdn.microsoft.com/en-us/library/t4d0762d.aspx What is happening is that config/abi/msvc_{prefix,suffix}.hpp performs "#pragma pack(push,8)" (in msvc_prefix.hpp) and then performs a "#pragma pack(pop)" (in msvc_suffix.hpp). This leads the compiler to think that the packing alignment has erroneously changed, generating unnecessary warnings. Could something be done to fix this? I think the warning needs to be disabled prior to including BOOST_ABI_{PREFIX,SUFFIX}. Thanks, -Edward

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[serialization][test] Last few serialization regressions with VC6
by John Maddock 30 Oct '06

30 Oct '06

Looking through the serialization regressions, there are a few spurious ones, then these errors http://tinyurl.com/y3qpqf seem to be caused by Boost.Test, I have two questions: 1) How do I run the serialization tests with bbv2 and an earlier version of Spirit? There's code in the bbv1 Jamfile, but not the v2 version? 2) Is there a particular reason why the problem template (equal_impl_frwd in test_tools.hpp) is marked as exported, when it contains only inline functions? I realise it shouldn't make any difference either which way, and if it's used by classes that do need to be exported then it suppresses a whole lot of warnings so I guess that's the reason ? :-) Thanks, John.

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