March 2012 - Boost-users - lists.preview.boost.org

[code] multi_array serialization
by Andriy Gapon 28 Mar '12

28 Mar '12

I needed to serialize some multi_array objects in my project and came up with the following code. How does it look? It's probably missing serialization of the "quirks" like memory layout, dimension bases and similar. template<typename Archive, typename T, std::size_t N> inline void save(Archive & ar, const boost::multi_array<T, N> & t, const unsigned int file_version) { ar << boost::serialization::make_nvp("dimensions", boost::serialization::make_array(t.shape(), N)); ar << boost::serialization::make_nvp("data", boost::serialization::make_array(t.data(), t.num_elements())); } template<typename Archive, typename T, std::size_t N> inline void load(Archive & ar, boost::multi_array<T, N> & t, const unsigned int file_version) { typedef typename boost::multi_array<T, N>::size_type size_type; boost::array<size_type, N> dimensions; ar >> boost::serialization::make_nvp("dimensions", boost::serialization::make_array(dimensions.c_array(), N)); t.resize(dimensions); ar >> boost::serialization::make_nvp("data", boost::serialization::make_array(t.data(), t.num_elements())); } template<typename Archive, typename T, std::size_t N> inline void serialize(Archive & ar, boost::multi_array<T, N>& t, const unsigned int file_version) { split_free(ar, t, file_version); } -- Andriy Gapon

1 0

[Bind] Understanding protect
by Robert Jones 28 Mar '12

28 Mar '12

Hi All I'd appreciate some helpful words about Boost.Bind protect, 'cos I'm not quite understanding it! I thought its purpose was allow binding, but not evaluating, of a function object. So that this should work. #include <iostream> #include <boost/bind.hpp> #include <boost/bind/protect.hpp> void f( int i ) { std::cout << i << std::endl; } template <typename NullaryCallable> void g( const NullaryCallable & callable ) { callable( ); } int main( ) { g( protect( bind( f, _1 ) )( 1 ) ); } But it doesn't, and instead thinks I'm calling g() with the return type of f(), just as if I'd not used protect at all. Is it possible to have bind generate a fully bound, nullary callable object? TIA, - Rob.

4 12

[shared_ptr] Multiple enable_shared_from_this in inheritance tree
by Edward Diener 28 Mar '12

28 Mar '12

There was a Code Project article (http://www.codeproject.com/Articles/286304/Solution-for-multiple-enable_sha…) about a problem using multiple enable_shared_from_this derivations in an inheritance tree. Does this problem actually exist in the current Boost implementation ? If so, should there not be some documentation regarding it ?

2 5

[random] number of seed values required to seed engine
by Thomas Mang 27 Mar '12

27 Mar '12

Hi, Consider the mersenne_twister_engine<...> member function seeding a engine with an iterator range of seed values: template<typename It> void mersenne_twister_engine<...>::seed(It &, It); Is there some nice way to figure out how many seed values this function will need? I have used mt19937 and had to inspect the code to figure out it needs 624. I would find it very useful if this information is somewhere readily provided through some organized interface, e.g. a member function or a static class member stating that value. Same for other engine types. BTW, I find it surprising that the first parameter is a reference to an iterator, and hence the input argument itself will be altered. Is that by design? If so what's the rationale? I think it's fairly odd behaviour, giving rise to unnecessary dangerousness and should become documented more clearly (big warning in bold flashing red letters etc. :) ). Thanks Thomas

2 1

[ptr_container] Disable indirection interface
by Philipp Moeller 27 Mar '12

27 Mar '12

I have an API that expects iterators to pointers and using it with ptr_container would simplify some code. But the indirection interface of ptr_container prevents this. I can of course add an iterator adapter on top of the ptr_vector but that seems like overkill to me. -- Philipp Moeller GeometryFactory

2 1

[Boost.Locale] [Boost.Iostreams] Example with code converter does not work with clang
by Jesse Beder 27 Mar '12

27 Mar '12

I'm trying the example on the "Character Set Conversions" page of the Boost.Locale documentation: http://www.boost.org/doc/libs/1_49_0/libs/locale/doc/html/charset_handling.… (the full code I'm running is at the end of this message). When compiling with gcc: g++ -o test -lboost_locale test.cpp It run correctly - it prints "שלום" to standard output. However, when compiling with clang: clang++ -o test -lboost_locale test.cpp It produces, as far as I can tell, gibberish - it prints "×©××" to standard output. The hex values of the output are: 0xc3 0x97 0xc2 0xa9 0xc3 0x97 0xc2 0x9c 0xc3 0x97 0xc2 0x95 0xc3 0x97 0xc2 0x9d -------- What I'd like is to have a stream that accepts wide strings in the current locale and produces narrow strings in UTF-8 - am I completely off the track? If so, what should I do instead, and if not, what am I doing wrong? Thanks! - Jesse Beder ------- (code follows) #include <boost/iostreams/stream.hpp> #include <boost/iostreams/categories.hpp> #include <boost/iostreams/code_converter.hpp> #include <boost/locale.hpp> #include <iostream> namespace io = boost::iostreams; class consumer { public: typedef char char_type; typedef io::sink_tag category; std::streamsize write(const char* s, std::streamsize n) { std::cout.write(s,n); return n; } }; int main() { typedef io::code_converter<consumer> converter_device; typedef io::stream<converter_device> converter_stream; consumer cons; converter_device dev; boost::locale::generator gen; dev.imbue(gen("en_US.UTF-8")); dev.open(cons); converter_stream stream; stream.open(dev); stream << L"שלום"; return 0; }

2 1

[Boost.Serialization] Documentation about the archive file formats
by Júlio Hoffimann 27 Mar '12

27 Mar '12

Dear all, I'm trying to debug an application and would be helpful to know how the contents of the archives should look like. I read the entire Boost.S11n documentation, but can't find any explanation about the archive file formats. Do you have some technical material? I'm having an annoying (and famous) "input stream error": http://stackoverflow.com/questions/5178321/boost-serialization-problem-in-w…. The link describes exactly the same problem, the "author's solution" isn't satisfactory at all. Best regards, Júlio.

2 4

[Signals2] Signal memory overhead
by Sean Buckheister 26 Mar '12

26 Mar '12

Hello, I've been using the Signals2 library for a while now, and I'm very happy with it. But lately I have noticed that the library seems to have a rather large overhead in terms of memory consumption. My measurements indicate 233 bytes per signal<>, and an additional 128 bytes of overhead per connected slot. Connections themselves are lightweight at 24 bytes, as expected. I've been measuring on Linux 64bit, by creating a class with one signal and a number of active connections to that signal. This class is instantiated on the heap and the pointer is discarded. When run under Valgrind, I get the numbers mentioned above. All measurements have been done with threading support disabled (using boost::signals2::dummy_mutex). Since I don't need most of the features (my signals have one active connection most of time, seldomly more), I hacked together a small replacement that fits my needs as well. That code measures at 32 bytes per signal, 32 bytes per slot and 16 bytes per connection. Of course it provides nothing except connect/disconnect and operator(). Am I using the library incorrectly? Does my measurement method skew results? -- Sean

3 7

Multiple definition error with boost::icl
by Rajalakshmi Iyer 26 Mar '12

26 Mar '12

Hello, I have the following code structure: Range.h: ------------ #ifndef __RANGE_H__ #define __RANGE_H__ #include <boost/icl/interval_map.hpp> #include <boost/icl/gregorian.hpp> using namespace boost::gregorian; using namespace boost::icl; class Range { public: Range() ; ~Range() ; private: interval_map< date, int > m_mapRange }; #endif // __CAMPAIGNS_BY_RANGE_H__ Range.cpp ---------------- #include "Range.h" Range::Range() { } Range::~Range() { } main.cpp -------------- #include "Range.h" int main() { return 0; } When I build this code, I see the following errors: main.o: In function `boost::icl::operator++(boost::gregorian::date&)': main.cpp:(.text+0x0): multiple definition of `boost::icl::operator++(boost::gregorian::date&)' Range.o:Range.cpp:(.text+0x0): first defined here main.o: In function `boost::icl::operator--(boost::gregorian::date&)': main.cpp:(.text+0x2d): multiple definition of `boost::icl::operator--(boost::gregorian::date&)' Range.o:Range.cpp:(.text+0x2d): first defined here main.o: In function `boost::icl::operator++(boost::gregorian::date_duration&)': main.cpp:(.text+0x5a): multiple definition of `boost::icl::operator++(boost::gregorian::date_duration&)' Range.o:Range.cpp:(.text+0x5a): first defined here main.o: In function `boost::icl::operator--(boost::gregorian::date_duration&)': main.cpp:(.text+0xa1): multiple definition of `boost::icl::operator--(boost::gregorian::date_duration&)' Range.o:Range.cpp:(.text+0xa1): first defined here collect2: ld returned 1 exit status make: *** [rangetest] Error 1 Any ideas on how to resolve this would be greatly appreciated. Thanks! -- Twitter: @Blismobile <http://twitter.com/#!/blismobile> BlisMobile Media 32 Percy Street, London W1T 2DE www.blismobile.com [image: BlisMobile] <http://www.blismobile.com/>[image: Follow on Twitter]<http://twitter.com/#!/blismobile>[image: Blis Website] <http://www.blismobile.com/> This communication is from BlisMobile Media, which is a trading name of Breeze Tech (UK) Ltd, a company registered in England and Wales with registered number 06455773. Its registered office is 32 Percy Street, London W1T 2DE, United Kingdom. This communication contains information that is confidential and may also be privileged. It is for the exclusive use of the intended recipient(s). If you are not the intended recipient(s), please (1) notify info(a)blismobile.com by forwarding this email and delete all copies from your system and (2) note that disclosure, distribution, copying or use of this communication is strictly prohibited. Email communications cannot be guaranteed to be secure or free from error or viruses. All emails sent to or from a Blismobile email account are securely archived and stored by an external supplier. This email does not constitute a contractual agreement; such agreements are in specified contractual or Insertion Order (IO) form only and exclusively contain all the terms to which Breeze Tech )UK) Ltd will be bound. To the extent permitted by law, Breeze Tech (UK) Ltd does not accept any liability for use of or reliance on the contents of this email by any person save by the intended recipient(s) to the extent agreed in a contract or Insertion Order. Opinions, conclusions and other information in this email which have not been delivered by way of the business of Breeze Tech (UK) Ltd are neither given nor endorsed by it.

2 1

[mpl] how can I pattern-match a 'built' mpl::vector?
by Rob Desbois 26 Mar '12

26 Mar '12

I have an mpl::vector that is built by a series of push_back ops, and want to traverse at runtime using mpl::for_each<v>( do_sth() ) A member type may also be an mpl::vector, and in this case I wish to specialise do_sth::operator() for that case. I'm having trouble doing that, since the result of push_back is not an mpl::vector type, so how do I go about matching this? TIA -- rob -- Rob Desbois http://theotherbranch.wordpress.com/ "I disapprove of what you say, but I’ll defend to the death your right to say it", Voltaire

2 2