February 2009 - Boost-users

[Bind] Representing a member function as C function pointer?
by Roland Bock 02 Feb '09

02 Feb '09

Hi, maybe this is stupid, but I wonder if my code could become more elegant. I am using expat for XML parsing, which is working fine, but could be nicer: I have a class (XmlParser) which provides all the handlers for SAX parsing required by expat, but I can't figure out how to use them directly? When initializing expat, I give it a pointer to an XmlParser object and then register handlers: -------------------------- static void expatStartElementHandler (void* pUserData, const char* element, const char** attr) { XmlParser* xmlParser = reinterpret_cast<XmlParser*>(pUserData); xmlParser->startElement (element, attr); } static void expatEndElementHandler (void* pUserData, const char* element) { XmlParser* xmlParser = reinterpret_cast<XmlParser*>(pUserData); xmlParser->endElement (element); } void XmlParser::init() { parser_ = XML_ParserCreate ("UTF-8"); XML_SetUserData (parser_, this); XML_SetElementHandler (parser_, expatStartElementHandler, expatEndElementHandler); //... } ------------------------- I would prefer to get rid of those static non-member functions and their reinterpret_cast and do something like // does not work XML_SetElementHandler (parser_, boost::bind(&XmlParser::startElement, this, _2, _3), boost::bind(&XmlParser::endElement, this, _2)); Is there a nice way to do this with bind? Regards, Roland

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passing a boost.array to a c function, and boost.System
by Sean Farrow 02 Feb '09

02 Feb '09

Hi list: I have a c function EnumProcesses in windows, and waswondering: 1. How can I pass a boost.array to this function, I need to pass the undedrlying array, not the boost.array class. 2. Does boost.system suppor the retrieval of operating system process in an stl-complient way, i.e using stl containers and allowing boost.Foreach to iterate over them. Cheers Sean.

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linking query
by Sean Farrow 01 Feb '09

01 Feb '09

Hi: I've now got boost libraries compiled. The only other query I have is I have my visual studio project set up to use multi-threaded debug dll but when I build with boost filesystem it links the code in by default. How can I tell boost to use the dll version for debug and lib (static) for release? Sean.

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[Smart Ptr] intrusive_ptr_add_ref(T * & p)
by Alexader 01 Feb '09

01 Feb '09

Looks like it is possible to define intrusive_ptr_add_ref as void intrusive_ptr_add_ref(T * & p) not as void intrusive_ptr_add_ref(T * p) Then, it is possilbe either to increase reference count as usually or to clone the object if it is in non-shareable state. Would this work ? Is it know use case, maintained by Smart Pointers library ?

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error linking the boost.filesystem library
by Sean Farrow 01 Feb '09

01 Feb '09

Hi: When trying to build a probram with the boost.filesystem library, I get an lnk1104 using visual studio 8 (2005). The boost include and lib paths c:\program files\boost and c:\program files\boost\bin.v2 are in the default vc include and library paths respectively, the archive bit is set--this shouldn't make a difference as far as I know! Any one know why this error is ocuring? Cheers Sean.

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[Fusion] Sequence adapter
by Joel Falcou 01 Feb '09

01 Feb '09

Fusion provides supprot for thing like boost::tuple or boost::array to be treated as fusion sequence in runtime algorithm. Is there any meta-function that gives me the compile-time conversion or should I build them myself ? eg as_vector< array<int,6> >::type == vector<int,int,int,int,int,int> Thanks in advance -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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Calling a function in a defined time intervall
by Olivier Tournaire 01 Feb '09

01 Feb '09

Hi all, I would like to know how can I call a member function each x miliseconds, during a given time. Can any boost library help me for this task ? Regards, Olivier -- Olivier Tournaire MATIS - Institut Géographique National 73, Ave de Paris 94165 St Mandé cedex, France tel: (+33) 1 43 98 80 00 - 71 25 fax: (+33) 1 43 98 85 81

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date-time library and checked iterators 2
by gast128 01 Feb '09

01 Feb '09

Dear all, I post half year ago about a problem in the Boost.DateTime library but never got an answer. So I try again: 'the date_facet::do_put_tm' fct. contains an illegal dereferncing in '&*a_format.begin()'. If the a_format string is empty VS2008 complains (and terminates) about illegal iterator dereference. I suspect though that VS2008 is right. Is it possible that this gets attention, or is something else wrong? Wkr, me

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Cosmetic warning in gcc 4.3
by Joel Falcou 01 Feb '09

01 Feb '09

I foudn that the following lines int he following files generates a huge amount of spurious warning in gcc 4.3 with -Wall : /boost/math/special_functions/gamma.hpp line 1264: tgamma1pm1(T z, const Policy& /* pol */) /boost/function_types/detail/pp_retag_default_cc/preprocessed.hpp line 18 BOOST_STATIC_CONSTANT(bits_t, value = ( (::boost::function_types::detail::bits<Tag> ::value & 0x00008000 ) |( ::boost::function_types::detail::bits<RefTag> ::value & 802) )); /boost/function_types/detail/pp_tags/preprocessed.hpp line 56 BOOST_STATIC_CONSTANT(bits_t, combined_bits = (LHS_bits & ~RHS_mask) | RHS_bits ); The later was signaled as a ticket in trac but I wanted to know if it was fixed/merged in the upcoming 1.38. -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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Do "entire range" standard algorithms already exist
by Kirk Korver 01 Feb '09

01 Feb '09

Group, I recently found the boost::range library. It seems very useful. An annoyance that I have with STL algorithms is that they are very verbose. Most of the time I need to do something over the entire range. I'm sure I'm not alone here. At any rate, I can easily do this: template< typename Range, typename Pred > inline typename boost::range_iterator<Range>::type find_if( Range& c, Pred pred ) { return std::find_if( boost::begin( c ), boost::end( c ), pred ); } Which then allows me to do this: void foo() { typedef std::vector <int> V_INT; V_INT v; v.push_back(1); v.push_back(2); v.push_back(3); V_INT::iterator it = find_if(v, std::bind2nd(std::equal_to<int>(), 2)); } Perfect. Exactly what I want. Search the entire vector, and I give it a predicate. I could easily create these functions for copy_if, erase_if, find_if, and for_each. My question: Do I need to go ahead and create the tiny wrapper functions, or do they already exist somewhere in Boost? If they exist already, I prefer to use those. Thank you in advance, Kirk

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