March 2007 - Boost-users - lists.preview.boost.org

ptime::from_iso_string() & time_from_string()
by Chris Webster 29 Mar '07

29 Mar '07

Neither of the functions I listed in the title seem to support a time of the format: 1999-12-17T15:15:15 (that is with the 'T' in it). From everything I've seen (wikipedia, w3.org) that is a valid ISO time stamp. Also how do I search the archives? I could get to the page, but no search feature seemed to be present... Thanks, Chris

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[boost::mpl::apply] compiler dependent behavior
by Samuel Charron 28 Mar '07

28 Mar '07

Hi, I'm currently using the apply metafunction, and I have two different behaviors depending on the used compiler. Here is the code : #include <boost/mpl/lambda.hpp> #include <boost/mpl/apply.hpp> #include <boost/mpl/placeholders.hpp> #include <tr1/unordered_set> using namespace boost; using namespace mpl; int main () { apply < std::tr1::unordered_set < _1 , std::equal_to < int>, std::tr1::hash <int>, std::allocator < int > >, int > ::type foo; } With g++ 4.1, there is no error. With g++ 4.2, icc 9.1, an error occurs: - g++ : no class template named 'apply' in 'class std::tr1::unordered_set<mpl_::arg<1>, std::equal_to<int>, std::tr1::hash<int>, std::allocator<int>, false>' - icc: class "std::tr1::unordered_set<boost::mpl::_1, std::equal_to<int>, std::tr1::hash<int>, std::allocator<int>, false>" has no member class "apply" : F::template apply<T1> With g++ 4.3, on some computers, it works, on others it does not. Can you give me some help to make this work ? Thanks, -- Samuel

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returning values in Boost.StateChart
by Federico J. Fernández 28 Mar '07

28 Mar '07

I'm using statechart for a project and I'm trying to do the following without success. I want to get a new event for the statechart when an event is processed. I mean, call process_event with an event and get another event as a result. We tried with different approaches. For example, modifying the passed event (but it's const) and trying to do a custom reaction that returns something (but I had problems too.. don't remember exactly now). The solution for now was to call an interface that it is implemented in all the states.. so I have to do two calls, one for process_event and other for this interface that returns the new event.... and the question is... Is there a better way to do this? Thanks!

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How to download 1.34 RC
by Johan Råde 28 Mar '07

28 Mar '07

I just downloaded and built CVSROOT:pserver:anonymous@boost.cvs.sourceforge.net:/cvsroot/boost. Now I wonder, is this Boost 1.34 RC or the head branch? It seems to me it is the head branch. Where do I find 1.34 RC? I have never used CVS before, so I'm still a bit uncertain exactly how things work. -- Johan Råde

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[mpl] Inheriting from each type in a sequence
by Scott Meyers 28 Mar '07

28 Mar '07

Given some base class, class Base { virtual ~Base(){} }; I want to be able to implement this: template<typename Seq> const Base& createObject() { // return an object that inherits from Base and every type in Seq } The problem is how to create the type of object I want. mpl::inherit is almost what I need, but it takes as template parameters each type to inherit from, and I don't have discrete types, I have a sequence of types. mpl::inherit_linearly takes a sequence and would work for my purposes (which is to create an object that I can later check via dynamic_cast to see if it inherits from a given type), but it works only with forward sequences, and I'll typically have an mpl::set. I could copy the contents of Seq into an mpl::vector and go from there, but that seems kind of gross. Is there a good way to solve this problem that I am overlooking? Thanks, Scott

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[Math Toolkit] MSVC 7.1 issue
by Johan Råde 28 Mar '07

28 Mar '07

I just downloaded the latest version of the Math Toolkit, and tried a simple example: #include <boost/math/distributions/students_t.hpp> boost::math::students_t_distribution<double>(5) dist; When I compile these two lines of code with MSVC 7.1 I get the following error messages: boost\math\special_functions\log1p.hpp(195) : error C2785: 'tools::promote_args<T>::type boost::math::log1p(T)' and 'double boost::math::log1p(double)' have different return types boost\math\special_functions\math_fwd.hpp(246) : see declaration of 'boost::math::log1p' boost\math\special_functions\log1p.hpp(182) : see declaration of 'boost::math::log1p' boost\math\special_functions\log1p.hpp(195) : error C2912: explicit specialization; 'double boost::math::log1p<double>(double)' is not a specialization of a function template boost\math\special_functions\log1p.hpp(183) : fatal error C1903: unable to recover from previous error(s); stopping compilation -- Johan Råde

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String Algo used with std algorithms
by Jason Ivey 28 Mar '07

28 Mar '07

Is there any way to use the string algorithm predicates and other facilities in conjunction with the standard algorithms (IE. for_each, find_if, etc.)? For example I am trying to make the following example work in MSVC8: typedef std::vector<std::string> Strs; Strs strs; strs.push_back("bob"); strs.push_back("lisa"); strs.push_back("eric"); Strs::const_iterator iter = find_if( strs.begin(), strs.end(), boost::bind( &istarts_with, _1, "B", std::locale() ) ); std::cout << "Found: " << std::boolalpha << ( iter == strs.end() ) << std::endl; I would be grateful for any comments or suggestions. Thanks, Jason

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[fusion] Accessing sequence elements at runtime
by Christian Henning 28 Mar '07

28 Mar '07

Hi there, is it somehow possible to access a sequence element at runtime? Just image you're reading some name value pairs from file and you would like them to assign them to a fusion sequences. This way I don't know they order the values are supplied. Is that possible? For example take the following code: #include <string> #include <algorithm> #include <functional> #include <vector> #include <boost/any.hpp> #include <boost/bind.hpp> #include <boost/fusion/sequence.hpp> using namespace std; using namespace boost; struct A {}; struct B {}; struct info { string name; any value_type; }; static info info_table[] = { { "A_Value", any( A() ) }, { "B_Value", any( B() ) } }; string& get_name( info& i ) { return i.name; } typedef fusion::map< fusion::pair< A , int > , fusion::pair< B , double > > seq_type; int _tmain(int argc, _TCHAR* argv[]) { // Image a file read has delivered the following name value pair. string name = "A_Value"; int a_value = 12; // Find the type of the supplied name info* p = find_if( &info_table[0] , &info_table[0] + 2 , bind( equal_to<string>() , bind( &get_name, _1 ) , name )); seq_type seq; // How to add the value to the supplied name?? } Christian

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[boost::pool] problem with allocation
by Seweryn Habdank-Wojewódzki 28 Mar '07

28 Mar '07

Hi! Below if small code for testing of pool_allocator. The program below is working quite good. But if I change 10`000 to 100`000 or more then program never ending. Regards. #include <list> #include <iostream> #include <algorithm> #include <iterator> #include <boost/pool/pool_alloc.hpp> int main() { using namespace std; //print_list(std::cout,primes::PrimesLE(10000000)); list<int,boost::pool_allocator<int> > p; for ( int i = 0; i < 10000; ++i ) p.push_back(i); //copy ( p.begin(), p.end(), ostream_iterator<int>(cout,"\n") ); //boost::singleton_pool<boost::pool_allocator_tag, sizeof(int)>::release_memory(); } -- |\/\/| Seweryn Habdank-Wojewódzki \/\/

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[Statechart] Reusing states
by Philippe DAVID 27 Mar '07

27 Mar '07

Hi, I would like to reuse a state in statechart at different places of the state machine (so it can be a sub-state of at least 2 other states) or in different state machines. Since the state class has a template parameter with the context I am a bit stuck here. Have you done that yet or have an idea about how to do it ? Thanks, Philippe

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