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

boost any_range
by tolik levchik 12 Jul '12

12 Jul '12

Is it possible the commented below condition. With regular ranges i make as many 'base()' calls as may adaptors i had applied. Obviously it's impossible with any_range. So what should i do ? #include <map> #define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 #include <boost/range/adaptors.hpp> #include <boost/range/algorithm.hpp> #include <boost/range/numeric.hpp> #include <boost/bind.hpp> #include <boost/range/any_range.hpp> struct foo{ int x, y; }; inline bool is_valid(int x){ return x > 0;} int main() { using namespace boost::adaptors; using boost::bind; typedef std::map<char, foo> map_t; typedef const int type; typedef boost::any_range< type, boost::forward_traversal_tag, typename boost::add_reference<type>::type, std::ptrdiff_t > forward_range_t; map_t m; forward_range_t rng = m | map_values | transformed(bind(&foo::x, _1)); // note: don't compile without BOOST_RANGE_ENABLE_CONCEPT_ASSERT defined as 0 forward_range_t::const_iterator found = boost::find_if(rng, is_valid); // found == boost::end(m); how to do it right ? }

2 1

serialization with templates
by Unger, Jörg F. 12 Jul '12

12 Jul '12

I'm trying to serialize a template class with multiple template parameters. In the header file, I declare something like template <int T1, int T2> class Node { private: std::array<double,T1> first; std::array<double,T2> second; } BOOST_CLASS_EXPORT_KEY(Node<1,1>) In a separate file, I would use the BOOST_CLASS_EXPORT_IMPLEMENT macro. However, when I'm using the BOOST_CLASS_EXPORT_KEY with a class that has more than one template parameter (as in the example above), I get an error message Error: macro "BOOST_CLASS_EXPORT_KEY" passed 2 arguments, but takes just 1 I'm using gcc 4.7.1 with boost 50 Any ideas, how to solve that problem? Jörg F.

3 2

Is there any interest in getting pseudo random number generation using preprocessor at compile time into the Preprocessor library?
by Alexander Stoyan 12 Jul '12

12 Jul '12

The complete code, approach and efficiency proofs I described in my blog: http://alexander-stoyan.blogspot.com/2012/07/getting-pseudo-random-numbers-a t.html Need your opinion regarding the relevance and the approach correctness of the feature. Thank you in advance.

1 0

[StateChart] Accessing machine and state members from within state constructor
by Andre Puschmann 12 Jul '12

12 Jul '12

Hello, I'd like to outsource some common functionality into a base state which needs to access some member variables from the state machine or from its direct context. I've managed to do exactly this in the constructor of the inherited class but not inside the constructor of the base class. I believe I am missing some bits here. Thanks in advance -Andre Code: #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> #include <iostream> namespace sc = boost::statechart; // event definition struct EvReset : sc::event< EvReset > {}; // forward definition struct Active; // starting state struct State1; // define FSM struct TestFsm : sc::state_machine< TestFsm, Active > { TestFsm() { std::cout << "Start TestFsm.\n"; fsmValue = 0; std::cout << "value: " << fsmValue << std::endl; } ~TestFsm() { std::cout << "Shut down TestFsm.\n"; } public: int fsmValue; }; struct Active : sc::state< Active, TestFsm, State1 > { Active(my_context ctx) : my_base( ctx ) { std::cout << "Start Active state!\n"; outermost_context().fsmValue++; stateValue = 0; std::cout << "value: " << outermost_context().fsmValue << std::endl; } ~Active() { std::cout << "Leave and desctruct Active state!\n"; } public: int stateValue; typedef sc::transition< EvReset, Active > reactions; }; template< class MostDerived, class Context > struct StateBase : sc::state< MostDerived, Context> { typedef sc::state< MostDerived, Context> base_type; typedef typename base_type::my_context my_context; typedef StateBase my_base; StateBase( my_context ctx ) : base_type( ctx ) { std::cout << "StateBase cst" << std::endl; // critical section outermost_context().fsmValue++; // access member of FSM (outermost context) ctx().stateValue++; // access member in direct context } }; struct State1 : StateBase< State1, Active > { State1(my_context ctx) : my_base( ctx ) { std::cout << "State1 cst" << std::endl; outermost_context().fsmValue++; std::cout << "value: " << outermost_context().fsmValue << std::endl; }; ~State1() {}; }; int main() { TestFsm myFSM; myFSM.initiate(); return 0; }

3 4

compilation problem and a couple of boost::variant questions
by Petros 12 Jul '12

12 Jul '12

Hi, I am trying to write some operator that multiplies two variants, each one containing a vector a zero and a unit, where I am trying to use the fact that I know the outcome for multiplying by 0 or by 1. The code (very bare bones) below describes how this is done, by: _ defining dummy structures of Variant-1, 2 _ defining a class that contains the instruction for multiplication _ defining a class (derived from variant) that contains possible outcomes of the multiplication _ defining the operator (only a few of the possible outcomes are shown) Compiling with msvc2010 (intel has similar issues) on win7: First here is the code: #include <boost/variant.hpp> using boost::variant; struct Zero1{ double operator[]( const size_t i ) const { return 0L ; } }; struct One1{ double operator[]( const size_t i ) const { return 1L ; } }; struct Zero2{ double operator[]( const size_t i ) const { return 0L ; } }; struct One2{ double operator[]( const size_t i ) const { return 1L ; } }; struct Vector1{ double operator[]( const size_t i ) const {return double( i ) ; } }; struct Vector2{ double operator[]( const size_t i ) const {return double( 2*i ) ; } }; struct subscript_operator:public boost::static_visitor<double>{ const size_t i_; subscript_operator( const size_t i ):i_(i){} template<typename _v> double operator()( _v const & v ) const { return v[i] ; } }; template <typename _V, typename _Z, typename _U> class VariantT :public variant< _V, _Z, _U > { public: typedef typename _Z zero_type ; typedef typename _U unit_type ; typedef typename VariantT<_V, _Z, _U> self_type ; typedef typename variant< _V, _Z, _U > variant_type ; template < typename _V> explicit VariantT( _V const & v ) :variant_type(v) {} VariantT() {} VariantT( self_type const & v ) :variant_type(static_cast<const variant_type&>(v)) {} template < typename _V> VariantT & operator = ( _V const & v ) { *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v); return(*this); } VariantT & operator = ( self_type const & v ) { *static_cast<variant_type*>(this) = v; return(*this); } double operator[]( const size_t i ) const { boost::apply_visitor( subscript_operator(i) , *this ) ; } bool isZero() const { return which() == 1 ; } bool isUnit() const { return which() == 2 ; } private: }; template < typename _V1, typename _V2 > class MultVarVar{ public: MultVarVar( _V1 const & v1, _V2 const & v2 ) :v1_(v1),v2_(v2) {} ~MultVarVar() {} typedef typename _V1::zero_type zero_type ; typedef typename _V1::unit_type unit_type ; double operator[]( const size_t i ) const { return boost::apply_visitor ( elementwise_visitor( i ), v1, v2 ) ; } private: _V1 const & v1_ ; _V2 const & v2_ ; struct elementwise_visitor : public boost::static_visitor< double > { const size_t & i_; public: elementwise_visitor( const size_t & i ) :i_(i) {} template <typename _V1, typename _V2 > double operator()( _V1 const & v1, _V2 const & v2) const { return v1[i_] * v2[i_] ; } }; }; template < typename _V1, typename _V2 > class MultVarVarResult :public variant<typename MultVarVar<_V1, _V2>, typename MultVarVar<_V1,_V2>::zero_type, typename MultVarVar<_V1,_V2>::unit_type, _V1, _V2 > { public: typedef typename variant< typename MultVarVar<_V1, _V2 > , typename MultVarVar<_V1,_V2>::zero_type, typename MultVarVar<_V1,_V2>::unit_type, _V1, _V2 > variant_type; typedef typename MultVarVarResult<_V1, _V2> self_type ; typedef typename _V1::zero_type zero_type ; typedef typename _V1::unit_type unit_type ; template<typename _V> /*explicit*/ MultVarVarResult( _V const & v ) :variant_type(v) {} MultVarVarResult( self_type const & v ) :variant_type(static_cast<const variant_type&>(v)) {} template < typename _V> MultVarVarResult & operator = ( _V const & v ) { *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v); return(*this); } MultVarVarResult & operator = ( self_type const & v ) { *static_cast<variant_type*>(this) = v; return(*this); } double operator[]( const size_t i ) const { boost::apply_visitor( subscript_operator(i), *this ) ; } private: }; template <typename _V1, typename _V2> MultVarVarResult<_V1, _V2> operator * ( _V1 const & v1, _V2 const & v2 ) { if ( v1.isZero() || v2.isZero() ) return MultVarVarResult<_V1, _V2>( typename MultVarVar<_V1,_V2>::zero_type() ) ; if ( v1.isUnit() ) return MultVarVarResult<_V1, _V2>( v2 ); if ( v2.isUnit() ) return v1 ; else return MultVarVarResult<_V1, _V2>( MultVarVar<_V1, _V2>( v1, v2 ) ) ; } typedef VariantT< Vector1, Zero1, One1 > Variant1; typedef VariantT< Vector2, Zero2, One2 > Variant2; int main(){ Variant1 v1; v1 = Zero1() ; Variant2 v2; v2 = One2() ; auto x = v1 * v2 ; return x[0] == double(0) ; } And here is one of the errors : boost_1_49_0\boost\variant\variant.hpp(1399): error C2666: 'boost::variant<T0_,T1,T2,T3,T4>::convert_construct' : 2 overloads have similar conversions 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2 1> ] 1> c:\_petros\_otc\ext\boost_1_49_0\boost\variant\variant.hpp(1384): could be 'void boost::variant<T0_,T1,T2,T3,T4>::convert_construct<_V,_Z,_U,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_>(const boost::variant<_V,T1,T2> &,long)' 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> _V=Vector1, 1> _Z=Zero1, 1> _U=One1 1> ] 1> c:\_petros\_otc\ext\boost_1_49_0\boost\variant\variant.hpp(1315): or 'void boost::variant<T0_,T1,T2,T3,T4>::convert_construct<const T>(T &,int,boost::mpl::false_)' 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> T=Variant1 1> ] 1> while trying to match the argument list '(const Variant1, long)' 1> c:\_petros\_otc\tests\variant\variant\main.cpp(120) : see reference to function template instantiation 'boost::variant<T0_,T1,T2,T3,T4>::variant<_V>(const T &)' being compiled 1> with 1> [ 1> T0_=MultVarVar<Variant1,Variant2>, 1> T1=Zero1, 1> T2=One1, 1> T3=Variant1, 1> T4=Variant2, 1> _V=Variant1, 1> T=Variant1 1> ] 1> c:\_petros\_otc\tests\variant\variant\main.cpp(151) : see reference to function template instantiation 'MultVarVarResult<_V1,_V2>::MultVarVarResult<_V1>(const _V &)' being compiled 1> with 1> [ 1> _V1=Variant1, 1> _V2=Variant2, 1> _V=Variant1 1> ] 1> Any help on this will be greatly appreciated! And the questions: What happens if a variant contains two identical template arguments ? when I create a (variant) object from one of the two identicals, how does it know which template argument I need ? Do I have to write the same code for the specialization of identical _V1 and _V2? Also, am I correct to assume that all this syntax ( element-wise static_visitor’s etc) will be optimized away at a release build ? TVMIA Petros

3 10

Boost 1.49 Locale Conversion failed
by NtVisigoth 12 Jul '12

12 Jul '12

Hello, everyone! I have already answred here: http://lists.boost.org/boost-users/2012/07/75097.php But previous latter badly typed. When using boost::locale with the russian language of the string in UTF-8 encoding I get an error while getting the locale. An exception with the message e.what(): "Conversion failed" is thrown My code is not very different from that in the examples: #define TR(S) boost::locale::translate(S).str() const std::string strDefaultLangId( "en" ); int main( int argc, char * argv[] ) { using namespace std; using namespace boost::locale; int exitCode = EXIT_SUCCESS; try { generator gen; gen.add_messages_path("g:\\source\\boost_locale\\languages\\"); gen.add_messages_domain("messages"); std::string language( argc == 2 ? argv[1] : strDefaultLangId.c_str() ); std::locale loc = gen( language ); locale::global( loc ); std::wstring s = TR(L"hello world"); wcout << s << endl; } catch( exception& e ) { cout << "Error : " << e.what() << endl; exitCode = EXIT_FAILURE; } catch( ... ) { cout << "Unknown error" << endl; exitCode = EXIT_FAILURE; } return exitCode; } The path to the file with the russian language: "g:\source\boost_locale\languages\ru\LC_MESSAGES\messages.mo" What could be wrong? * Is it necessary to use the backends? * Is it yet necessary to call imbue on the stream? But I'd like avoid it because I am going to write the log using glog. Compillers : Microsoft Visual Studio 2008 and 2010 Boost version : 1.49

4 7

Dealing with resistance to Boost
by hano botha 12 Jul '12

12 Jul '12

I am trying to get my organisation to use Boost. I have managed to get it included in source control and we have permission to use it in our unit testing. The main objection to using it in our production code is that it could be a potential security risk. I suggested that we restrict the usage of boost to the template\ headers only libraries. I don't see how the templates in boost can cause more of a security risk than what we have currently with the STL. My question is: How is vulnerabilities in the library dealt with? How is new vulnerabilities communicated to the user's community? I would also like to know historically, how many and how often were vulnerabilities discovered? Any good references would be great. Thanks,

3 2

boost range question
by tolik levchik 12 Jul '12

12 Jul '12

Why min_element give me errors without BOOST_RANGE_ENABLE_CONCEPT_ASSERT defined 0? Is it uses only for make error messages more readable? Is it safe to define it to 0? #include <vector> //#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0 #include <boost/range.hpp> #include <boost/range/adaptors.hpp> #include <boost/range/algorithm.hpp> #include <boost/range/numeric.hpp> #include <boost/bind.hpp> struct foo{ int x; }; int main() { using namespace boost::adaptors; using boost::bind; std::vector<foo> vec; auto rng = vec | transformed(bind(&foo::x, _1)); boost::accumulate(rng, 0); // ok boost::min_element(rng); // error }

2 1

Re: [Boost-users] Boost 1.49 msm problems with events
by Kamel Zaarouri, Mr 11 Jul '12

11 Jul '12

Hi, I am having problems with my transition table and events. Let me explain the fake design that illustrates the problem: I have a state machine (myStateMachine) containing 2 states (s0 and s1) and 1 substatemachine (subm1). the substatemachine subm1 contains an initial state 'sub0' and also s1 (the same state as in myStateMachine). this is the main transition table: s0->s1 on event 'ES1' s0->s2 on event 'ES2' s0->subm1 on event 'ESUB' this is the submachine transition table: sub0->s1 on event ES1 now, assume that state s1 is using the event that triggered it to extract some information i.e. struct s1 : public msm::front::state<> { template <class Event,class FSM> void on_entry(Event const& evt,FSM& fsm) { evt.getEventData(); } } so every event that could transition to s1 needs to implement getEventData() method. ->this is normal! now my problem is that ESUB does NOT implement getEventData() but apparently it should. And I don't get why. I am not using ESUB to transition to s1 but I am using ESUB to transition to subm1 and subm1 contains s1 but I don't access it at that point. I hope this is clear. Thank you.

3 2

[asio] asynchronous reading/writing to the tcp stream
by Ovanes Markarian 11 Jul '12

11 Jul '12

Hello *, I go through the ASIO docs, but somehow do not get if I can implement the following scenario: In one thread I would like to send lot's of commands to the server via a tcp connection. In the other thread I would like to start reading the commands being already handled and returned by the server. The commands are parsed by Spirit.QI. My idea was to use a tcp::iostream asynchronously so that I just pass the begin iterator to the output stream to QI and receive parsed data. If there is no output from the server the iterator should block and wait for it. This is a producer-consumer problem, but I would like to solve it with tcp::iostream and without explicit synchronization on my side. Is it possible? If yes, than how? I understand that I can introduce some storage, read bytes to it and notify my hand-crafter iterator, that there is some data that can be read again, but is there a better approach? Thanks, Ovanes

4 6