April 2009 - Boost-users - lists.preview.boost.org

Help using math functions
by Mario Chacon 03 Apr '09

03 Apr '09

Hello: First at all I do not know about math, but I need to do some animations. I need to simulate a movement of a ball into a pipe. I have all the interface working, but now I have to do the best way to give it life..:D. My fists steps was giving X,Y coordinates but I do not like this way, so I need some tips to make it more professional way. How can I use boost math functions to make it? Thank you.. masch... **

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Re: [Boost-users] boost::transform_iterator, boost::array::iterator and category
by Hicham Mouline 03 Apr '09

03 Apr '09

Hello Following my previous post, the transformed iterator has input iterator tag (not forward, not bidir, not random) BOOST_STATIC_ASSERT(( boost::is_convertible< iteratorIntoFirst, std::input_iterator_tag >::value )); But it should be random_access... Is there anything extra I need to put in the Unary fct of transform_iterator? Rds,

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[Multi-Index] crash on invariant_() violation
by Neil Hunt 03 Apr '09

03 Apr '09

> > This is definitely going to break the container's invariants, yes. Key > modification has to be done via modify() so as to give the container a > chance to reindex elements. So if you are quite sure this is happening > try to remove the offending behavior; after this my bet is that the > invariant assertion will go away. Otherwise please get back here. > > Just weighing in here with a related question. But first to say: I find multi-index to be invaluable. So thanks for a great library. In my code, the objects I am indexing against are altered elsewhere, and then my index owning code is notified. At this point, the index owning code calls: index.modify( index_iterator, NoOperationFunctor() ); That is, on the assumption that the modify function has no knowledge of what changes the functor are making, it must re-evaluate all indices. Therefore, it doesn't matter if the change is made inside the modify function as long as modify is called. (So, this statement from above does not appear strictly true: "Key modification has to be done via modify() so as to give the container a chance to reindex elements.") Because (in my case) the change is made elsewhere, I am calling modify with a functor that does nothing. In my particular case, I can guarantee that change made elsewhere won't affect the index that I use to find the iterator to pass to modify. This may seem a weird scenario, but it also seems weird that I have to call modify with a no-op functor. Is it possible/desirable to add a simple update_indices( itor ) function? Neil

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question about using boost.function and boost.bind, V1.38
by Tan, Tom (Shanghai) 03 Apr '09

03 Apr '09

Can any one please explain to me why the former fails while the latter compilesThe definition: // usage in a ctor initialisation list ..., where m_button_monitor is of type ButtonMonitor, , m_button_monitor(boost::bind(boost::mem_fn(&CView::OnRun), this, ID_TOOLBUTTON_AUTO)) //definition 1 of ButtonMonitor that fails // the error message by MS VC9SP1: // error C2664: 'programmer_board::ButtonMonitor::ButtonMonitor(boost::function<Signatur e> &)' : //cannot convert parameter 1 from 'boost::_bi::bind_t<R,F,L>' to 'boost::function<Signature> &' // class ButtonMonitor { public: ButtonMonitor(boost::function<void()>& f) : m_f(f) { } void UpdateStatus(BUTTON_STATUS status) { m_f(); }; private: boost::function<void()>& m_f; }; //definition 2 of ButtonMonitor that works class ButtonMonitor { public: ButtonMonitor(const boost::function<void()>& f) : m_f(f) { } void UpdateStatus(BUTTON_STATUS status) { m_f(); }; private: const boost::function<void()>& m_f; }; Thanks,

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[Q] eliminating false memory leak reports
by V S P 03 Apr '09

03 Apr '09

Hello, I have a class (below), and MS memory leak detector reports a leak on ptr.reset I have redefined 'new' as follows: #define MYDEBUG_NEW new( _NORMAL_BLOCK, __FILE__, __LINE__) In another example, also below I have an _impl structure that is allocated and assign to typedef boost::shared_ptr<cmoney_impl_dtl> t_money_storage; My understanding is that it is a 'false' detection is that correct? In otherwords, in my thinking -- as long as I have assigned an object to boost::shared_ptr -- I do not have remember anything about it anymore. (using visual studio 2008, 32 bit) Another question, since I have all of my heap objects using boost::shared_ptr is there any free tool that I can use to verify that those things do not leak (as some of the are actually DB connections so it is important for them to get completely destroyed). Thank you in advance ---------------------------- template <typename TThrdData> struct CService_ThreadData:private boost::noncopyable { CService_ThreadData (void){}; ~CService_ThreadData (void){}; ///creates a new thread data object if does not exists //Call this from every thread to establish thread's data //manager object static TThrdData& getdata(void) { /* YES, using static variable in this case is safe, because it is in the 'global' scope and therefore is intialized before Main starts Otherwise, static variables are not thread safe */ if (ptr.get() == 0) { ptr.reset(new TThrdData()); } return (TThrdData&)(*ptr); } private: static boost::thread_specific_ptr<TThrdData> ptr; };//end of class -------------------------- cmoney_t::cmoney_t (void) :v(new cmoney_impl_dtl) { } -- V S P toreason(a)fastmail.fm -- http://www.fastmail.fm - Access your email from home and the web

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date_time question
by Amadeus W.M. 03 Apr '09

03 Apr '09

The program below reads a date from a string -> istringstream -> ptime. The string contains comma separated fields, the first of which is a date in the format %Y-%m-%d (without %H:%M:%S): 2009-04-03,12.34,56.78 If I define a facet with in the format %Y-%m-%d %H:%M:%S then the program outputs 2009-Apr-03 12:34:56 i.e. it interprets the numbers following the date as %H:%M:%S even though they are separated by commas and dots, rather than colons. Is this normal behaviour? Would it be possible to make it leave alone the fields following the date? That is, do not interpret 12.34,56.78 as %H:%M:%S. Thanks! // g++ -g -Wall -o dateIOSimgleFmt -I/usr/local/include/boost-1_38 dateIOSingleFmt.C #include <iostream> #include <sstream> #include <cstdlib> #include <string> #include <boost/date_time/posix_time/posix_time.hpp> using namespace std; using namespace boost::posix_time; int main(int argc, char * argv[]) { ptime pt(not_a_date_time); string datestr("2009-04-03,12.34,56.78"); const char * format="%Y-%m-%d %H:%M:%S"; istringstream INSTR(datestr); locale loc(INSTR.getloc(),new time_input_facet(format)); INSTR.imbue(loc); INSTR>>pt; cout << pt << endl; return 0; }

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[asio] Setting UDP Source Port
by Scott McMurray 03 Apr '09

03 Apr '09

I'm writing an application that makes use of the source port in the UDP header. The only way I've found that sets it is by setting the endpoint on construction of the udp::socket. The problem with that, however, is that I have 3 different components that want to use that port, one listening and two sending. Understandably, I cannot bind the same port for all three. (Incidentally, while binding with the udp::socket constructor works, the bind call gives a bad file descriptor exception. I'm using 1.35, though, so that may have been fixed.) Is there some way to set the source port without binding? Since there's no session state, it seems like I should be able to send packets from any number of sockets. (I can't just share a socket, as they're not shared-objects thread-safe, according to the documentation.) Thanks, ~ Scott McMurray

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Re: [Boost-users] [Multi-Index] crash on invariant_() violation
by Neil Hunt 03 Apr '09

03 Apr '09

> > ... it doesn't matter if the change is made inside the modify function > as long as modify is called. > > (So, this statement from above does not appear strictly true: > "Key modification has to be done via modify() so as to give the container a > chance to reindex elements.") > > Because (in my case) the change is made elsewhere, I am calling modify with > > a functor that does nothing. > I guess more generally, why is this paradigm implictly disallowed? index_itor->value++; index.update_indices( index_itor ); While I can see the benefit of tying the modification to the multi-index object via modify, there is no explicit reason that I can see why the above is invalid (as per my perfectly working code that uses this paradigm). And "forcing" the user to use a functor to modify can introduce annoying code overhead. Don't get me wrong, I think that using modify with a functor is very clear and helps prevent invalid indices. But, at the same time, it can be a pain to write a functor. (Here's to C++0x lambda's). But in my case, where the code that modifies the object is unaware of multi-indices on that object, it is not feasible to use modify() to make the change. Neil

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[serialization] Private default constructors
by Robert Dailey 03 Apr '09

03 Apr '09

I have a class that can be constructed statically in code, or constructed by data (this is where boost::serialization comes in). For example: class foo { public: foo() {} foo( std::string text ) : m_text( text ) {} private: template< class Archive > void serialize( Archive& archive, unsigned int version ) { archive & m_text; } std::string m_text; friend class boost::serialization::access; }; There is one problem with this, though. It is possible for a user of this class to create a "foo" with the default constructor, thus enabling them to have "zombie" objects. The only thing I want using the default constructor is boost::serialization, not the user. Is there a way I can make the default constructor private and still have boost::serialization access it? Keep in mind that this must work polymorphically too.

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[repost][filesystem][system] Linking errors with C++0X options on intel C++ 11.0
by jesseperla＠gmail.com 02 Apr '09

02 Apr '09

Sorry to repost, but I am at a loss and was hoping I have missed something. I am on Intel C++ 11.0 on windows. I built boost::filesystem and boost::system as static libraries with the following line in my userconfig.jam using intel-win : 11.0 : : <cxxflags>/Qstd:c++0x ; I am then compiling a project (that works with non-C++0x just fine) with /Qstd:c++0x in the command line. But when I try to link it with my calls to boost::filesystem header functions, I get the following link errors (it must be using auto linking) 1>etk_template.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_system_category(void)" (?get_system_category@system@boost@@YAABVerror_category@12@XZ) referenced in function _main 1>etk_template2.obj : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_system_category(void)" (?get_system_category@system@boost@@YAABVerror_category@12@XZ) 1>etk_template.obj : error LNK2019: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_generic_category(void)" (?get_generic_category@system@boost@@YAABVerror_category@12@XZ) referenced in function _main 1>etk_template2.obj : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::get_generic_category(void)" (?get_generic_category@system@boost@@YAABVerror_category@12@XZ) I am not changing any pre-compiler definitions for boost when I use /Qstd:c++0x. Should I be changing anything there? Am I out of luck? -Jesse

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