October 2005 - Boost - lists.boost.org

Review Request: pimpl
by Asger Mangaard 19 Dec '05

19 Dec '05

I would like to submit the pimpl library for a formal review. The suggested library can be found in the sandbox's root. Regards, Asger Mangaard

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[ANN] Phoenix-2 Preview
by Joel de Guzman 01 Dec '05

01 Dec '05

Hi, Hi. Here's a preview of Phoenix V2. This will probably be the last release of the library. Phoenix V2 will be the basis of the Phoenix and Boost.Lambda merger. You can get it here: http://spirit.sourceforge.net/dl_more/phoenix-2.zip You can browse the draft docs here: http://tinyurl.com/6crgp What's new? A lot. This is a total rewrite based on earlier discussions with Jaakko Jarvi. The library's is built on top of Fusion and of course MPL. Of particular interest are local variables and lambda-lambda scopes: http://tinyurl.com/3mn6w There is also a set of lazy functions that work on STL sequences (e.g. push_back etc.): http://tinyurl.com/46bbm and pretty soon, a final TODO item (built on top of scopes/ lambda), lazy STL algorithms (e.g. find_if, etc). The scopes section (link provided above) in the docs illustrates how to write lazy functions that accept higher order functions (e.g. for_each). Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net

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Boost.Python: patch for gcc 3.2
by Graham Bennett 28 Nov '05

28 Nov '05

Hi all, Attached is a small patch that I applied to get Boost.Python in 1.33 to build correctly with gcc 3.2. It works around a bug mentioned here: http://lists.debian.org/debian-gcc/2003/09/msg00055.html, where a type is used before it is declared in cxxabi.h. The problem seems to be fixed in gcc 3.4. cheers, Graham. -- Graham Bennett

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VC++ compiler error with boost graph library
by Chris Alvers 19 Nov '05

19 Nov '05

Hi, I tried to do a depth_first_search with the following graph type and visitor: struct CycleDetector : public boost::default_dfs_visitor { CycleDetector( bool& cycle ) : m_hasCycle(cycle) {}; void back_edge( T_Edge, const T_Graph& ) { m_hasCycle = true; } bool& m_hasCycle; }; typedef boost::adjacency_list< boost::setS, boost::listS, boost::bidirectionalS> T_Graph; bool hasCycle(false); CycleDetector cd(hasCycle); boost::depth_first_search(m_graph, visitor(cd)); Compiling this on VC++ 7.1.3 (.NET Framework 1.1) results in the following error message: \boost\boost\property_map.hpp(349): error C2678: binary '+' : no operator found which takes a left-hand operand of type 'const std::vector<_Ty>::iterator' (or there is no acceptable conversion) with [ _Ty=boost::default_color_type ] ---------------------- Changing the graph type definition to: typedef boost::adjacency_list< boost::setS, boost::vecS, boost::bidirectionalS> T_Graph; (i.e. replacing the listS by vecS) works perfectly. Is this a known restriction of the library ? Best regards Alex ___________________________________________________________ Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos - Hier anmelden: http://mail.yahoo.de

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[MPL.Math] updates for double
by Cromwell Enage 11 Nov '05

11 Nov '05

I've now added a BOOST_MPL_CFC_NO_MATH_DOUBLE macro that is defined in <boost/mpl/aux_/config/math_double.hpp> when it is known that BOOST_MPL_MATH_DOUBLE won't compile. Please send me your compiler-platform configuration if BOOST_MPL_MATH_DOUBLE doesn't work for you. Peder, The double_::aux::get_value function still returns a number 2^16 times too big on MSVC 7.1 when the input is a whole number. Cromwell D. Enage __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

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Re: [boost] New boost webpage
by Janusz Piwowarski 11 Nov '05

11 Nov '05

Rene Rivera <grafik.list_at_[hidden]> writes: > Sam Partington wrote: >> You also need to add this to httpd.conf, otherwise IE will just keep >> on downloading images, over and over and over again, even when they've >> been loaded at page load time. >> >> #this stops background-image flicker in IE >> BrowserMatch "MSIE" brokenvary=1 >> BrowserMatch "Mozilla/4.[0-9]{2}" brokenvary=1 >> BrowserMatch "Opera" !brokenvary >> SetEnvIf brokenvary 1 force-no-vary >> ExpiresActive On >> ExpiresByType image/gif A2592000 >> ExpiresByType image/jpeg A2592000 >> ExpiresByType image/png A2592000 > > Unfortunately that level of server setup is beyond our control. We can > only hope that SF has such configuration already present on their servers. I see background image flickering is still a problem. I've discovered that you can put above lines to .htaccess file. Regards, Janusz

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[database]
by Brock Peabody 10 Nov '05

10 Nov '05

Hi, I've added the code for the database project to the sandbox. I've also made the following changes based on feedback from Caleb and Jonathan: 1) fixed <: digraphs 2) added transaction functions to the abstract interface. Added a reference_counted_transaction_manager class for use in implementations that don't support nested transactions. 3) made the interface support null field detection via boost.optional 4) iteration supports BiDirectional model instead of RandomAccess 5) added a transaction class for scoped transaction management on the to-do list: 1) documentation - this is going to be a word document or something at first since I know nothing about html. 2) make .jam files 3) test cases - I'm not sure how these are going to work. 4) investigate possibility of supporting a prepare_statement function

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alignment trouble with boost::optional
by Michael Shepanski 10 Nov '05

10 Nov '05

The code below fails a compile-time assertion in boost 1.32.0 on MSVC 7.1. This is because, internally, boost::optional uses boost::alignment_of, which produces the number 12, which is then passed as a template parameter to boost::type_with_alignment, which won't accept 12. Not sure where the blame lies. Is it with boost::alignment_of, for producing 12 in the first place? Perhaps not, since 12 is a multiple of 4, and the doco says boost::alignment_of is allowed to produce any multiple of the actual alignment value. So is the fault with boost::type_with_alignment, for not accepting 12? Or is there something wrong with the app? #include <boost/optional.hpp> class D { virtual ~D(); }; class E : virtual public D { virtual ~E(); unsigned long long m_i; }; boost::optional<E> s_optE; Cheers, --- Michael Shepanski

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[type_map] Interest in container indexed by type?
by Tony D 08 Nov '05

08 Nov '05

Hi people, A couple years ago I wrote a container indexed by type, which I've come to consider a basic building block for reusable code. Effectively, code can use "type_maps" to handle an arbitrary structure, without needing to know member identifiers, and gets the speed benefit of compile-time access resolution. A simple implementation follows: namespace NS { namespace Private { class no_type2 { }; class no_type3 { }; class no_type4 { }; class no_type5 { }; template <typename T> class type_map_base { public: void operator=(const T& t) { t_ = t; } operator const T&() const { return t_; } private: T t_; }; template<> class type_map_base<no_type2> { }; template<> class type_map_base<no_type3> { }; template<> class type_map_base<no_type4> { }; template<> class type_map_base<no_type5> { }; } template <typename T1, typename T2 = Private::no_type2, typename T3 = Private::no_type3, typename T4 = Private::no_type4, typename T5 = Private::no_type5> class type_map : public Private::type_map_base<T1>, public Private::type_map_base<T2>, public Private::type_map_base<T3>, public Private::type_map_base<T4>, public Private::type_map_base<T5> { public: using Private::type_map_base<T1>::operator=; using Private::type_map_base<T2>::operator=; using Private::type_map_base<T3>::operator=; using Private::type_map_base<T4>::operator=; using Private::type_map_base<T5>::operator=; }; } // sample usage... #include <iostream> #include <string> using namespace std; int main() { NS::type_map<int, string> tmid; tmid = 3; tmid = "hello"; string s = tmid; cout << (int)tmid << ' ' << (string)tmid << ' ' << s << endl; cout << sizeof(tmid) << " vs " << sizeof(int) << '+' << sizeof(string) << endl; } I've found typemaps useful for writing things like a logging system that allows arbitrary criterion for cataloging errors. To store several data items of the same type, simply wrap each instance in a distinct class (possibly using the template w/ unique number idiom). Implementation note: the empty base class optimisation makes it practical to have a single template, avoiding typelists (mpl sequences), preprocessing etc.. Cheers, Tony ___________________________________________________________ How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com

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[iostreams] Why devices must be copy-constructible?
by Alberto Ganesh Barbati 07 Nov '05

07 Nov '05

Hi, I started using the iostreams library for a pet project. I thinks it's a great piece of software. However, I immediately stumbled in what I think it may be a defect. Consider this simple source device: #include <boost/iostreams/stream.hpp> struct Source : boost::noncopyable { typedef char char_type; typedef boost::iostreams::source_tag category; Source(int); // ctor std::streamsize read(char* s, std::streamsize n) { // implementation here } private: /* ... private members here */ }; int main() { boost::iostreams::stream<Source> s(0); } the boost::noncopyable up there has been put because the device keeps handles to OS resources whose duplication can be very expensive. I was amazed that the code above doesn't compile. This is the error message reported by VC7.1: C:\lib\Boost\include\boost-1_33\boost\iostreams\detail\wrap_unwrap.hpp(52) : error C2558: struct 'Source' : no copy constructor available or copy constructor is declared 'explicit' (full error message is very long and is reported, for reference, at the end of the message) It seems that a device must be copy-constructibile. In particular, the code above makes at least three short-lived copies of the device. Question is: why? I believe this requirement is unintended and not due to a conscious design choice, my arguments are: 1) it's not documented, there is no mention of such requirement in http://www.boost.org/libs/iostreams/doc/concepts/device.html 2) it's unnatural and I believe my case (where copying the device could be expensive) occurs more often in practice than the opposite case 3) from the error messages it seems that a copy is only required as a side-effect of the template machinery used in BOOST_IOSTREAMS_FORWARD. In fact, the offending line detail\wrap_unwrap.hpp(52) is: inline T wrap(const T& t BOOST_IOSTREAMS_DISABLE_IF_STREAM(T)) { return t; } that requires T to be copy-constructible. Am I missing something? Thanks in advance, Ganesh ----- full error messaage follows C:\lib\Boost\include\boost-1_33\boost\iostreams\detail\wrap_unwrap.hpp(52) : error C2558: struct 'Source' : no copy constructor available or copy constructor is declared 'explicit' C:\lib\Boost\include\boost-1_33\boost\iostreams\stream_buffer.hpp(90) : see reference to function template instantiation 'T boost::iostreams::detail::wrap<T>(const T &,boost::disable_if_c<B,void>::type *)' being compiled with [ T=Source, B=false ] C:\lib\Boost\include\boost-1_33\boost\iostreams\stream_buffer.hpp(90) : while compiling class-template member function 'void boost::iostreams::stream_buffer<T,Tr,Alloc>::open(const T &,int,int)' with [ T=Source, Tr=std::char_traits<char>, Alloc=std::allocator<char> ] C:\lib\Boost\include\boost-1_33\boost\utility\base_from_member.hpp(69) : see reference to class template instantiation 'boost::iostreams::stream_buffer<T,Tr,Alloc>' being compiled with [ T=Source, Tr=std::char_traits<char>, Alloc=std::allocator<char> ] C:\lib\Boost\include\boost-1_33\boost\iostreams\stream.hpp(61) : see reference to class template instantiation 'boost::base_from_member<MemberType>' being compiled with [ MemberType=boost::iostreams::stream_buffer<Source,std::char_traits<char>,std::allocator<char>> ] C:\lib\Boost\include\boost-1_33\boost\iostreams\stream.hpp(98) : see reference to class template instantiation 'boost::iostreams::detail::stream_base<Device,Tr,Alloc>' being compiled with [ Device=Source, Tr=std::char_traits<char>, Alloc=std::allocator<char> ] TestVc2.cpp(26) : see reference to class template instantiation 'boost::iostreams::stream<Device>' being compiled with [ Device=Source ]

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