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[phoenix][lambda] lambda to phoenix translation: get arguments from expression
by alfC 29 May '10

29 May '10

Hi I have a phoenix expression of type actor< composite< divides_eval, vector< LambdaExp, composite< minus_eval, vector< argument<0>, value<double> > > > > > f_expr with boost.lambda I could extract the different components (Lambda and the actual value stored by value<double>) from f_expr as: get<0>(f_expr.args) //for lambda and get<1>(get<1>(f_expr.args).args) //for lambda what is the equivalent for Boost.phoenix?, it seems that the phoenix actor doesn't have the member "args". something like at_c<1>(at_c<1>(f_expr)) seems to be in the right direction but it returns something of type value<double> from which I don't know how to extract the value in the same way at_c<1>(f_expr) returns the denominator, but it is not an actor, so it is not a lambda expression. the corresponding lambda type was: lambda_functor<lambda_functor_base< arithmetic_action<divide_action>, tuple< lambda_functor<// LambdaExp >,// lambda_functor<lambda_functor_base< arithmetic_action<minus_action>, tuple< lambda_functor< placeholder<1> >, double const // <-- attention adds const to avoid unreadable errors > > > > > > f_expr Thank you, Alfredo

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[lambda] helping lambda to deduce return type and then avoid 'ret<T>'
by alfC 29 May '10

29 May '10

Hi, the lambda manual says: "The return type deduction system may not be able to deduce the return types of some user defined operators or bind expressions with class objects. A special lambda expression type is provided for stating the return type explicitly and overriding the deduction system. To state that the return type of the lambda functor defined by the lambda expression e is T, you can write:" and indeed for even very simple arithmetic user-defined classes (for example boost.units quantities) the lambda expression is poluted with many many ret<T> statements, for example _1*_1/(_1+x)/(_1-x) becomes ret<anothertype>(ret<usertype>(_1*_1)/ ret<othertype>(ret<usertype>(_1+x)/ret<usertype>(_1-x))); the question is, is there a way to help lambda library to help deducing the return type to avoid the repeated use of ret<T>. Thank you, Alfredo

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spirit and property_tree headers conflict
by Artem Kozlov 28 May '10

28 May '10

Hello, When attempting to compile a program which includes the following headers (at once): #include <boost/property_tree/json_parser.hpp> #include <boost/spirit/include/qi.hpp> , I get a lot of error messages. Is there any way to resolve this conflict and compile the program without dividing it into several translation units? Thanks in advance, Artem

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[Chrono] How to report problems?
by Roland Bock 28 May '10

28 May '10

Hi, after having received a push in the right direction by Howard yesterday, everything works fine so far, except for for the following two details: a) I get some warnings about unused parameters when using the stopclock. For instance: include/boost/chrono/stopwatch_reporter.hpp:81: warning: unused parameter ‘ec’ The fixes are trivial in all cases I encountered. b) The thread_clock part of the tutorial looks pretty broken. Not sure if more things will come up, but if so, where should I send them? Maybe this information would be a nice addition to the FAQ until chrono makes it into boost? Thanks for this cool library! Regards, Roland

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Exposing C++ Instances to Python
by Leonhard Weber 28 May '10

28 May '10

Hello, I'm in the same bind this topic describes: http://lists.boost.org/boost-users/2009/02/44749.php Unfortunately the subject didn't tell about the resolution or approach he took to succeed. Can anyone help me? Basically: I want to expose a C++ Instance to Python at runtime. I have a pointer to the Instance and need to expose that instance to Python. Thankful for any help, Best regards, ~lwk

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[interprocess] user application can't attach shared memory created by Windows service
by Rui Pedro Fernandes 28 May '10

28 May '10

Hi, I'm using version 1.41 in a Windows Server 2008 host. If I run an application as a service (in fact launching it with srvany) that creates a named managed_windows_shared_memory and then execute a user application that tries to attach the shm, the later cannot succeed to attach - error is: "The system cannot find the file specified". On the other hand, if the shared memory is of type managed_shared_memory then all runs fine. Couldn't this indicate that in the windows approach the file mapping object should be created with more global security and access rights? Thanks, Rui

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Re: [Boost-users] Exception on windows::stream_handle!
by Lloyd 28 May '10

28 May '10

I would like to post the reason for this exception, may it will be useful for someone else :) The create file was not created with the "Overlapped IO attribute" It should look like this CreateFile(("MyFile",GENERIC_WRITE,0,NULL,CREATE_NEW,FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED,NULL); ----- Original Message ----- From: Lloyd To: boost-users(a)lists.boost.org Sent: Wednesday, May 26, 2010 2:35 PM Subject: Exception on windows::stream_handle! Hello, We are trying to create a "windows::stream_handle" from a native Windows HANDLE. But it throws an exception with "The parameter is incorrect". The code is given below. What could be the reason? (Another IOservice is already running in the system) HANDLE FileHandle=CreateFile("MyFile",FILE_WRITE_DATA,0,NULL,CREATE_NEW,FILE_ATTRIBUTE_NORMAL,NULL); if(FileHandle==INVALID_HANDLE_VALUE) { return; } try { io_service ios; windows::stream_handle StreamHandle(ios,FileHandle); ... ... } catch(std::exception& e) { Log(e.what()); //The parameter is incorrect } Thanks, Lloyd ______________________________________ Scanned and protected by Email scanner

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simple serialization of boost::variant
by Archie14 28 May '10

28 May '10

I use std::istream and std::ostream for binary serialization ( can't use boost::serialization) and can't find a way to serialize boost::variant<int, double, std::string>. I'll appreciate a code sample or link to the documentation. Thanks.

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[units] User-defined vector class template won't compile
by Terry Golubiewski 28 May '10

28 May '10

I'm trying to make a "simple" cartesian vector class. It should be similar to the quaternion example that you give in the docs, but I can't get it to compile. I've attached a complete program. Here are the error I get when I try to compile it. Lets just focus on fixing the first few errors about no binary '*'. When I understand that, perhaps I'll be able to fix the rest. Thanks, terry try.cpp using native typeof C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2678: binary '*' : no operator found which takes a left-hand operand of type 'double' (or there is no acceptable conversion) C:/boost/boost_1_43_0\boost/units/detail/one.hpp(47): could be 'T boost::units::operator *<T>(const boost::units::one &,const T &)' with [ T=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/detail/one.hpp(53): or 'T boost::units::operator *<double>(const T &,const boost::units::one &)' with [ T=double ] C:/boost/boost_1_43_0\boost/units/detail/one.hpp(58): or 'boost::units::one boost::units::operator *(const boost::units::one &,const boost::units::one &)' while trying to match the argument list '(double, rci::cartesian::vector<Dim,Rep>)' with [ Dim=3, Rep=double ] C:/boost/boost_1_43_0\boost/units/operators.hpp(75) : see reference to class template instantiation 'boost::units::multiply_typeof_helper<X,Y>::nested' being compiled with [ X=double, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/quantity.hpp(690) : see reference to class template instantiation 'boost::units::multiply_typeof_helper<X,Y>' being compiled with [ X=double, Y=rci::cartesian::vector<3,double> ] try.cpp(255) : see reference to class template instantiation 'boost::units::multiply_typeof_helper<X,Y>' being compiled with [ X=boost::units::quantity<boost::units::si::length>, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2866: 'boost::units::multiply_typeof_helper<X,Y>::nested::_typeof_register_value' : a const static data member of a managed type must be initialized at the point of declaration with [ X=double, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2027: use of undefined type 'boost::type_of::msvc_extract_type<ID>::id2type_impl<__formal>' with [ ID=boost::units::multiply_typeof_helper<double,rci::cartesian::vector<3,double>>::nested ] and [ __formal=true ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2146: syntax error : missing ';' before identifier 'type' C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2602: 'boost::units::multiply_typeof_helper<X,Y>::nested::type' is not a member of a base class of 'boost::units::multiply_typeof_helper<X,Y>::nested' with [ X=double, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : see declaration of 'boost::units::multiply_typeof_helper<X,Y>::nested::type' with [ X=double, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : see declaration of 'boost::units::multiply_typeof_helper<X,Y>::nested' with [ X=double, Y=rci::cartesian::vector<3,double> ] C:/boost/boost_1_43_0\boost/units/operators.hpp(74) : error C2868: 'boost::units::multiply_typeof_helper<X,Y>::nested::type' : illegal syntax for using-declaration; expected qualified-name with [ X=double, Y=rci::cartesian::vector<3,double> ] try.cpp(255) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'boost::units::quantity<Unit,Y>' (or there is no acceptable conversion) with [ Unit=boost::units::unit<boost::units::length_dimension,boost::units::si::system>, Y=int ] try.cpp(28): could be 'rci::cartesian::vector<Dim,Rep> &rci::cartesian::vector<Dim,Rep>::operator =(const rci::cartesian::vector<Dim,Rep> &)' with [ Dim=3, Rep=boost::units::quantity<boost::units::si::length> ] while trying to match the argument list '(rci::cartesian::vector<Dim,Rep>, boost::units::quantity<Unit,Y>)' with [ Dim=3, Rep=boost::units::quantity<boost::units::si::length> ] and [ Unit=boost::units::unit<boost::units::length_dimension,boost::units::si::system>, Y=int ]

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Boost and ARM like processor
by joel falcou 27 May '10

27 May '10

Is there any return of experience to actually compiles and use Boost on ARM platform (CORTEX 9 or similar). We're currently trying to look at such machien and pondered about the state of C++ compiler on them. More down to earth question, has anybody use tricky template stuff with ARM tool set and were there any problem ? thanks

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