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Serializing boost::variant?
by Merrill Cornish 24 Nov '05

24 Nov '05

If I have a boost::variant data member I want to serialize, it looks like I'm going to have to use boost::static_visitor and boost::apply_visitor in the serialize() method. However, there is some black magic going on with the ar & dataMember; statements. Any pointers as to how I do it? Merrill

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Bind, lambda and how to chain relative function calls
by Kerner, Jacques 24 Nov '05

24 Nov '05

Hi, I would like to create a functor for calling functions in a chain like this : car.GetRigidBody().GetPosition().GetX() What is the best way to do that using bind (and lambda ?) The car.GetRigidBody() is easy : bind(&Car::GetRigidBody, &car) , but then I am a bit stuck. Note that I don't want to store the result of car.GetRigidBody(). I want the final functor to call all the functions everytime its operator() is called. So bind ( &Position::GetX, &bind ( &RigidBody::GetPosition, &bind ( &Car::GetRigidBody, &car )() )() ) would not be acceptable... Any help greatly appreciated Jacques Kerner

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Tuple operator==
by Josue Gomes 23 Nov '05

23 Nov '05

Hi, Take this code: #include <string> #include <boost/tuple/tuple.hpp> struct A {}; bool operator==(A, A) { return true; } int main() { using namespace boost; tuple<std::string, int, A> t1(std::string("same?"), 2, A()); tuple<std::string, long, A> t2(std::string("same?"), 2, A()); tuple<std::string, long, A> t3(std::string("different"), 3, A()); t1 == t2; // error: no match for operator== t1 == t3; // error: no match for operator== } This is similar to the example shown in Boost.Tuple docs. However the compiler(*) refuses to compile it. I tried it with versions 1.33.0 and 1.33.1 (Beta) Any ideas? Compiler outputs below: MSC C/C++ Compiler 13.10;3077 cl /GR /EHsc /IE:\projects\libraries\boost_1_33_1 tuple_error.cpp Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 13.10.3077 for 80x86 Copyright (C) Microsoft Corporation 1984-2002. All rights reserved. tuple_error.cpp tuple_error.cpp(17) : error C2678: binary '==' : no operator found which takes a left-hand operand of type 'boost::tuples::tuple<T0,T1,T2>' (or there is no acce ptable conversion) with [ T0=std::string, T1=int, T2=A ] tuple_error.cpp(18) : error C2678: binary '==' : no operator found which takes a left-hand operand of type 'boost::tuples::tuple<T0,T1,T2>' (or there is no acce ptable conversion) with [ T0=std::string, T1=int, T2=A ] gcc 3.4.4 g++ -I E:\projects\libraries\boost_1_33_1 tuple_error.cpp -o tuple_error_gcc.exe tuple_error.cpp: In function `int main()': tuple_error.cpp:17: error: no match for 'operator==' in 't1 == t2' tuple_error.cpp:7: note: candidates are: bool operator==(A, A) tuple_error.cpp:18: error: no match for 'operator==' in 't1 == t3' tuple_error.cpp:7: note: candidates are: bool operator==(A, A) Regards, Josue

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Re: [Boost-users] Collections of shared_ptr<Base> and shared_ptr<Derived>
by Keith Weintraub 23 Nov '05

23 Nov '05

Michael, Thanks for the reply. You are absolutely right. I'm coming back to C++ after years of Java and I haven't been careful enough about reading the stl docs. One quibble with your solution is that I am doing an upcast not a down cast, but your solution worked perfectly for me. Thanks all, KW ________________________________________________ Date: Mon, 21 Nov 2005 15:29:29 -0800 From: Michael Rickert <pandamojo(a)gmail.com> Subject: Re: [Boost-users] Collections of shared_ptr<Base> and shared_ptr<Derived> To: boost-users(a)lists.boost.org Message-ID: <561a17f20511211529l1a528314od7905edcc2aa2ab7(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 On 11/21/05, Keith Weintraub <Keith(a)archeuscap.com> wrote: > > > > Folks, > > I have come up with the following solution in template form. I would be ecstatic to receive any feedback on either my solution or original question. I am not an expert in these things and I can use all the help any generous soul could provide. > > > > Here is my solution: *snip* It would seem you're overengineering things. It'd be simpler just to use std::vector's iterator constructors: std::vector< boost::shared_ptr< derived > > data; ... std::vector< boost::shared_ptr< base > > downcast_data( data.begin() , data.end() ); If you wanted to go with your original version, I'd suggest returning a managed pointer of some sort (std::auto_ptr or boost::shared_ptr) to decrease the likelyhood of a leak - or having the user pass a nonconstant reference to a vector to fill. Sorry if this has allready been covered by the time this is recieved, my posts seem to still be awaiting moderator approval. -Mike

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[Announce] Boost Graph Library Python Bindings Version 0.9
by Douglas Gregor 23 Nov '05

23 Nov '05

Version 0.9 of the Boost Graph Library Python bindings has been released. The BGL-Python bindings provide access to many of the features of the C++ Boost Graph Library from Python, blending the rapid prototyping and application development capabilities of Python with the power and performance of C++. BGL-Python is the successor to the experimental Python bindings found in Boost 1.33.0, providing more algorithms, better data structures, and drastically improved documentation. The BGL-Python bindings are available at: http://www.osl.iu.edu/~dgregor/bgl-python/ Doug

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Re: [Boost-users] Compiling with Visual C++ 2005 Express Edition
by Keith Weintraub 23 Nov '05

23 Nov '05

Folks, Thanks for all the kind help. I solved my problem by doing something similar to what Mr Kozicki suggested. Only I did it on the command line. All works fine now. Thanks again, KW

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Newbie build problem
by Rob Marsden 23 Nov '05

23 Nov '05

I too am having similar problems to Keith Weintraub with regard to failed and skipped targets. I applied the suggested addition of the Platform SDK, to the include paths, but in the process I had to reboot my machine (for unrelated reasons). Since then, I get virtually nothing actually built (quite a leap backwards really :-) The symptom I get is related to expansion of the compiler name, as the messages are all of the type: '/Zm800' is not recognised as an internal command... etc or '/nologo' is not ... The environment is Win2K with VC6 and the Intel compiler v8.0 (9 on order). The command line is bjam "-sTOOLS=intel-win32" install Now there's a certain familiarity about this problem, but at my age, memory doesn't serve me all that well. So what's the answer? -- Rob Marsden Gistix (Northern) Limited

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boost.thread problem
by magazine.lihuiba 23 Nov '05

23 Nov '05

I'm a newbie to boost, and I'm trying to use boost.thread together with STLport in VC6. When I compile my project in debug version, I get a error message saying "fatal error C1189: #error : 'Build options aren't compatible with pre-built libraries'", the error code is in auto_link.hpp in boost directory: # if (defined(__SGI_STL_PORT) || defined(_STLPORT_VERSION)) && (defined(_STLP_OWN_IOSTREAMS) || defined(__STL_OWN_IOSTREAMS)) # if defined(_DEBUG) && (defined(__STL_DEBUG) || defined(_STLP_DEBUG)) # define BOOST_LIB_RT_OPT "-gdp" # elif defined(_DEBUG) # define BOOST_LIB_RT_OPT "-gdp" # pragma message("warning: STLPort debug versions are built with /D_STLP_DEBUG=1") # error "Build options aren't compatible with pre-built libraries" # else # define BOOST_LIB_RT_OPT "-p" # endif But I don't get this error message in release version. What can I do?

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[program_options] Finding out the type of the options
by Giuseppe Vacanti 23 Nov '05

23 Nov '05

Hello, I'm using program_options, and I want to be able to learn what the option type is by manipulating an options_description object. As I illustrate in the example below (boost 1.33), I can do this if the option has been given a default value. Could anyone suggest a wasy to this for options without a default? The story behind this question is that I would like to be able to build a simple GUI parameter dialog based on the options_description, and I want to map different types to different widgets. Thanks, Giuseppe #include <boost/program_options.hpp> #include <boost/filesystem/path.hpp> #include <iostream> #include <vector> #include <string> #include <algorithm> #include <iterator> template<typename T> bool type_is (const boost::any & v) { return v.type() == typeid(T); } struct MyType { MyType() : x(0) {} MyType(double d) : x(d) {} double x; }; std::ostream & operator<<(std::ostream & os, const MyType & mt) { os << mt.x; return os; } std::istream & operator>>(std::istream & is, MyType & mt) { is >> mt.x; return is; } using namespace std; namespace po = boost::program_options; int main(int ac, char * av[]) { typedef vector<string> type; po::options_description desc1("Allowed options 1"); desc1.add_options() ("switch", po::value<bool>(), " a boolean switch") ("numbers", po::value<type>(), "a list of numbers") ("number", po::value<double>()->default_value(42), "the number") ; po::options_description desc2("Allowed options 2"); desc2.add_options() ("mytype", po::value<MyType>()->default_value(MyType(123.4)), "my type") ; po::options_description cmdlinedesc; cmdlinedesc.add(desc1).add(desc2); po::variables_map vm; po::store(po::parse_command_line(ac, av, cmdlinedesc), vm); po::notify(vm); typedef std::vector< boost::shared_ptr<po::option_description> > VOD; const VOD & pk = cmdlinedesc.options(); for(VOD::const_iterator K = pk.begin(); K != pk.end(); ++K){ cout << " [ " << (*K)->long_name() << " - " << (*K)->description() << " ] "; boost::shared_ptr< const po::value_semantic > sem = (*K)->semantic(); boost::any default_store; bool has_default = sem->apply_default(default_store); if(has_default) cout << " has default "; if(type_is<double>(default_store)) cout << " = (double) " << boost::any_cast<double>(default_store); if(type_is<bool>(default_store)) cout << " = (bool) " << boost::any_cast<bool>(default_store); if(type_is<MyType>(default_store)){ MyType x = boost::any_cast<MyType>(default_store); cout << " = (MyType) " << x; } cout << endl; } }

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progress_timer, incorrect timing
by __PPS__ 23 Nov '05

23 Nov '05

I got strange results with boost::progress_timer - it shows timings like 1.45s whereas it took about 15 sec. to complete a routine. It used to work ok, but I have no idea why it just doesn't work anymore! I use freebsd 4.11 and clocks_per_sec is defined 128. sysconf(_SC_CLK_TCK) also returns 128, but clock counter is not correct completely. I wrote simple test class, to see what's wrong: struct Timer { clock_t t; time_t tt; Timer() : t(clock()), tt(time(0)){} ~Timer(){ std::cout << "Elapsed interval: " << (static_cast<double>(clock() -t))/CLOCKS_PER_SEC << "s " << (time(0)-tt) << "s\n" ; } }; this is the output: Elapsed interval: 1.52344s 33s 1.52 s <- output by boost::progress_timer. so, you may see that measured time is completely wrong. I rewrote it with microtime(...) and it works correctly now. any ideas what's wrong, why clock() doesn't work anymore? Wouldn't that be a good idea to use microtime for unices? thanks

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