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[boost::python] problems wrapping a base class
by Andy Falanga (afalanga) 10 Apr '12

10 Apr '12

HI, I'm working on exposing what should be a factory to create derived objects using the standard pattern for such a factory. In short, I have something like the following: Class Base { // some private member variables Public: Virtual void Func1() =0; Virtual void Func2(); }; Class Derv1 : public Base { // override Func1() // override Func2() }; Class BaseWrapper : public Base, boost::python::wrapper<Base> { Void Func1() { Get_override("Func1")(); } Void Func2() { If(boost::python::override func = get_override("Func2")) { Func(); Return; } Base::Func2(); } }; Base* Factory(int selector) { // return derived classes base on selector } BOOST_PYTHON_MODULE(myMod) { Class_<Derv1, bases<Base> >("Derived") .def("Func1", &Derived::Func1) .def("Func2", &Derived::Func2) ; Class_<BaseWrapper, boost::noncopyable>("BaseWrapper") .def("Func1", pure_virtual(&Base::Func1)) .def("Func2", &Base::Func2, &BaseWrapper::Func2) ; Def("Factory", Factory); } Everything compiles now but I'm getting the following error: RuntimeError: extension class wrapper for base class class Base has not been created yet This comes when I try to import this module into the python interpreter. What exactly am I missing? I'm following instructions from here: http://www.boost.org/doc/libs/1_48_0/libs/python/doc/tutorial/doc/html/pyth… Some references I've found from Google thus far suggest that the problem is with linking order. However, how to specify linking order when that is determined dynamically during build? (I'm using Visual Studio 2010) Any help is greatly appreciated. Thanks, Andy

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boost.multi_index & IPC
by 陈海峰 10 Apr '12

10 Apr '12

typedef managed_shared_memory::allocator<char>::type char_allocator; typedef basic_string<char, std::char_traits<char>, char_allocator>shm_string; struct quote { public: int market; int kind; shm_string seccode; shm_string secname; float price; float zf; quote(int market_, int kind_, const char* seccode_, const char_allocator& a, const char* secname_, const char_allocator& b, float price_, float zf_): market(market_),kind(kind_), seccode(seccode_, a), secname(secname_, b), price(price_), zf(zf_) {} }; typedef boost::multi_index::composite_key<quote, BOOST_MULTI_INDEX_MEMBER(quote, int, market), BOOST_MULTI_INDEX_MEMBER(quote, shm_string, seccode) >comp_key_search; typedef boost::multi_index::composite_key_compare< std::greater<int>, std::greater<shm_string> >comp_key_compare_search; typedef boost::multi_index::composite_key<quote, BOOST_MULTI_INDEX_MEMBER(quote, float, price), BOOST_MULTI_INDEX_MEMBER(quote, int, market), BOOST_MULTI_INDEX_MEMBER(quote, shm_string, seccode) >comp_key_sortbyprice; typedef boost::multi_index::composite_key_compare< std::greater<float>, std::greater<int>, std::greater<shm_string> >comp_key_compare_sortbyprice; typedef boost::multi_index::multi_index_container< quote, boost::multi_index::indexed_by< boost::multi_index::ordered_non_unique<comp_key_search, comp_key_compare_search>, boost::multi_index::ordered_non_unique<comp_key_sortbyprice, comp_key_compare_sortbyprice> >, managed_shared_memory::allocator<quote>::type >quote_mic; int main() { /* struct shm_remove { shm_remove() { shared_memory_object::remove("MySharedMemory"); } ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); } } remover; */ managed_shared_memory segment(open_only,"MySharedMemory"); quote_mic *quotes = segment.find_or_construct<quote_mic> ("My MultiIndex Container") //Container's name in shared memory ( quote_mic::ctor_args_list(), //, segment.get_allocator<quote>()); //Ctor parameters quote_mic::allocator_type(segment.get_segment_manager())); quote_mic::nth_index<0>::type& idx_search = quotes->get<0>(); quote_mic::nth_index<1>::type& idx_sortbyprice = quotes->get<1>(); int count = 0; char_allocator ca1(segment.get_allocator<char>()); // 查询股票实时行情 shm_string seccode("600000", ca1); count = idx_search.count(boost::tuples::make_tuple(1, seccode)); quote_mic::nth_index<0>::type::iterator it = idx_search.find(boost::tuples::make_tuple(1, seccode)); for (int i=0; i<count; i++) { std::cout << it->seccode << std::endl; it++; } std::vector<quote> result; BOOST_FOREACH(const quote& q, idx_sortbyprice) { int kind = q.kind; if (kind == 1 || kind == 11) { // std::cout << "市场" << q.market << ",类别" << q.kind << ", " << q.secname << ",最新价" << q.price << std::endl; result.push_back(q); this statement will compile error, why? how to write? } else { // std::cout << "过滤：市场" << q.market << ",类别" << q.kind << ", " << q.secname << ",最新价" << q.price << std::endl; } } return 0; }

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boost serialization skip a node
by ujoimro 10 Apr '12

10 Apr '12

Hello, I am working on a config file format, which is a collection of several xml "config file" classes. I would like to save them in a single file like this: oarchive << NVP(filters); oarchive << NVP(processor); oarchive << NVP(segmentation); However, it does make sense te use the "processor" class without the filters or the segmentation. Is there a simple way to skip some nodes in Boost.Serialization.XML? Or to refer to nodes by their name? iarchive >> NVP(processor); Thank You for Your help, LM

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Including Boost 1.48.0 "qi.hpp" header file
by devika R S 10 Apr '12

10 Apr '12

Hi All, This post is regarding the issue we saw on IBM compiler using BOOST 1.48 version. Here is the sample code where we are trying to just include the header file "boost/spirit/include/qi.hpp>". *********************************Example Code************************************* #include <iostream> #include <boost/spirit/include/qi.hpp> main() { using namespace std; std::cout<<"test"<<"\n"; } *********************************END************************************************** When we compile this code on IBM with the compiler* : IBM XL C/C++ for AIX, V11.1 (5724-X13) Version: 11.01.0000.0000 *we end up with below error: xlC -I /usr/include/boost/1_48_0 -o dump test_prog.cpp - *xlC: 1501-230 (S) Internal compiler error; please contact your Service Representative. For more information visit:* - *http://www.ibm.com/support/docview.wss?uid=swg21110810* But this code works absolutely fine on g++ Linux. Looks like the inclusion of this header file on IBM platform is causing the issue. Is this is a known bug ?Is any patch available ? Thanks, Abc

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problems with Boost.Thread on VS10
by John M. Dlugosz 10 Apr '12

10 Apr '12

I'm trying to use a packaged_task, and get an error on creation. template<typename R,typename F> struct task_object: task_base<R> { F f; task_object(F const& f_): // << refers to look here f(f_) {} #ifndef BOOST_NO_RVALUE_REFERENCES task_object(F&& f_): // <<<< Error here f(f_) {} E:\boost_1_49\boost/thread/future.hpp(1251): error C2535: 'boost::detail::task_object<R,F>::task_object(F)' : member function already defined or declared with [ R=size_t, F=std::tr1::_Bind<size_t,size_t,std::tr1::_Bind1<std::tr1::_Callable_fun<size_t (__cdecl *const )(std::string &),false>,const char *>> & ] E:\boost_1_49\boost/thread/future.hpp(1247) : see declaration of 'boost::detail::task_object<R,F>::task_object' with [ R=size_t, F=std::tr1::_Bind<size_t,size_t,std::tr1::_Bind1<std::tr1::_Callable_fun<size_t (__cdecl *const )(std::string &),false>,const char *>> & ] So I'm thinking that VS10 (Microsoft Visual Studio 2010) has problems overloading the constructor with (T const&) and (T&&) ? But shouldn't someone have noticed that long ago? Any ideas here? Thanks, —John

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[Boost.Thread] unique_future without && ?
by John M. Dlugosz 09 Apr '12

09 Apr '12

My code needs to be compatible with a platform that doesn't have rvalue references available, for the time being. I've avoided explicit uses of move and made my && arguments fall back to const&. But I'm not sure about returning a unique_future. I see that unique_future<T> has a special move-the-guts type, with an implicit conversion operator and a constructor. But do I need to do anything special to declare a function returning one, and likewise the return statement itself? The code in packaged_task ( unique_future<R> packaged_task<R>::get_future() ) is not conditionally compiled based on BOOST_NO_RVALUE_REFERENCES, so I'm supposing that it just works by itself. Is that correct? But maybe it only works by itself in some cases? In that code, the return statement names a constructor directly. return unique_future<R>(task); In my code, I'm returning a unique_future that I already made somewhere else (actually, the result of another function call) so it would be wanting to call the copy constructor, I would think. So if I write unique_future<int> foo(); unique_future<int> bar() { return foo(); } what _should_ happen is that the existing value uses a user-defined conversion to construct the "copy", right? So I should expect this to work correctly if the thing I'm returning is already exactly the right type, as well as when naming the constructor directly. —John

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split_iterator not working with a reference to const std::string
by asif saeed 09 Apr '12

09 Apr '12

Hi, Here is my code: struct CharIterator { CharIterator( const std::string &s, char_t const *delimiters) : s_(s), begin_(boost::algorithm::split_iterator<std::string::iterator>(s, boost::token_finder(boost::is_any_of(delimiters), boost::token_compress_off))), end_(boost::algorithm::split_iterator<std::string::iterator>()), i_(begin_) { } const std::string s_&; boost::algorithm::split_iterator<std::string::iterator> begin_, end_, i_; }; The compile gives me an error on parameter 1 of the above constructor. It compiles fine if I change "const std::string &s" to "std::string s" - that is, pass by value. I just want to store a reference to a string. Could you help me on this? Best regards, Asif

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Clang "blocks" and function<>
by John M. Dlugosz 08 Apr '12

08 Apr '12

I wonder if there is anything already in Boost's implementation of the function template (that is exposed as std::tr1::function if you use Boost.TR1) that allows Clang's lambda-like "blocks" to be assigned to a function? Or, has anyone already fiddled with that and willing to share? —John reference: http://clang.llvm.org/docs/BlockLanguageSpec.txt

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C++ Now! Early Bird Registration Ending Soon
by Jon Kalb 08 Apr '12

08 Apr '12

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mpl documentation question
by Robert Ramey 07 Apr '12

07 Apr '12

Documentation for mpl::less<T> has the following section: Expression semantics For any Integral Constants c1 and c2: typedef less<c1,c2>::type r; Return type:Integral Constant. Semantics:Equivalent to typedef bool_< (c1::value < c2::value) > r; typedef less<c1,c2> r; // a Return type:Integral Constant. Semantics:Equivalent to struct r : less<c1,c2>::type {}; //b if //a is used then the following yields bool_<true> is_same< less<c1, c2>, r> if // b is used then the following yields bool_<false> is_same< less<c1, c2>, r> So in what sense are //a and // b equivalent? Robert Ramey

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