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boost::trim throwing std::bad_cast exeption with custom basic_string
by Arash Abghari 24 Jan '11

24 Jan '11

Hi, I have a custom basic_string as follows: typedef basic_string<unsigned int> ustring; so if I pass an instance of ustring to boost:trim it throws an std::bad_cast exception. ustring str; boost::trim(str); The exception comes from here: include/boost/algorithm/string/detail/classification.hpp:45 return std::use_facet< std::ctype<CharT> >(m_Locale).is( m_Type, Ch ); It does not matter what character type I use for basic_string, It throws the exception for anything but char and wchar_t. Document mentions "A string is not restricted to std::basic_string and character does not have to be char or wchar_t, although these are most common candidates", So I assume, It must work with unsigned int or other types. Here is the system spec: boost: 1.40 gcc: 4.3.4 OS: Debian Lenny 64bit Thanks

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Re: [Boost-users] [Fusion] Building parameter list for fusion::invoke
by Vivek 23 Jan '11

23 Jan '11

> > 2011/1/22 Vivek <vivek_at_[hidden]> > Or alternatively, is there a direct way to initialize a fusion vector? IIUC, its ctor just do the job, not? The problem is I don't know the arity or parameter types of the function being called. I just have a source of data (which can be simplified to TYPE data = data_source<TYPE>().pop();) and arbitrary functions being passed in. One alternative is to code-generate template specializations for a bunch of arity and use the constructor like you suggested. But I feel the "arity code generation" thing has been done so many times and so much better in boost that I should be able to use a transform or invoke function to take advantage of that. That's why I started trying to use fusion.

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Re: [Boost-users] [Preprocessor] Relative Addresses in BOOST_PP_FILENAME_1
by Hossein Haeri 23 Jan '11

23 Jan '11

Hi TONGARI, > > #define BOOST_PP_FILENAME_1 "./Header.hpp" //1 > > #define BOOST_PP_FILENAME_1 ".\Header.hpp" //2 > > #define BOOST_PP_FILENAME_1 "Header.hpp" //3 > I have the same problem with you, I also use GCC 4.5.1, while <> works > fine but "" not. Strangely enough, <> doesn't work in my GCC either. (And, I'm not writing a precompiled header anyway.) Are you also using GCC under MinGW32? TIA, --Hossein

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Help me out from boost.log
by Steven Woody 23 Jan '11

23 Jan '11

Hi, I want to use boost.log and I succeeded in building it with bjam with Visual Studio 2005. But I quickly found I cannot use it. Below code are from the tutorial, #include <boost/log/core.hpp> #include <boost/log/trivial.hpp> #include <boost/log/filters.hpp> logging::core::init_log_to_file( keywords::file_name = "dsttest_%N.log", keywords::rotation_size = 10 * 1024 * 1024, keywords::time_based_rotation = sinks::file::rotation_at_time_point(0, 0, 0), keywords::format = "[%TimeStamp%]: %_%" ); logging::core::get()->set_filter( flt::attr<logging::trivial::severity_level>("Severity") >= loggin::trivial::debug ); but the compiler (vc++ 8.0) just complains: error C2653: 'logging' : is not a class or namespace name error C2653: 'keywords' : is not a class or namespace name ... I tried to use boost::log::logging, but it did not help. Then I decided to try the most simple code: BOOST_LOG_TRIVIAL(debug) << "hello boost.log"; it passed the compiler but not the linker: libboost_log-vc80-mt-gd-1_45.lib(trivial.obj) : error LNK2019: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) referenced in function "void __cdecl boost::system::`dynamic initializer for 'posix_category''(void)" (??__Eposix_category@system@boost@@YAXXZ) .... Please help me! Thanks in advance. -- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer narke public key at http://subkeys.pgp.net:11371 (narkewoody(a)gmail.com)

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troubles with boost filtering streams
by Daniel Oberhoff 23 Jan '11

23 Jan '11

Hi, I am working on a matlab file reader/writer. Since matlab uses zip to compress variables I was thinking I could use the boost filtering streams with the zip filter to handle that. The use case is that there are zipped blocks inside the file, i.e. not the whole file is zipped but just parts. I am not sure how to handle that with boost, since I would need to start/stop zipping/unzipping at almost arbitrary points in the file. Also I have trouble working with filtering streams at all. As a baseline test I started substituting the fstream I was reading from with a boost filtering istream onto which I pushed the fstream. Reading works fine for a while and then breaks. What I noted is that the fstream tellg always lags behind the actual number of bytes read. also using the fitlering streams tellg breaks the whole stream. also seeking does not seem to work with the filtering stream. I need to seek quite often. seeking only happens when not unzipping. I tried seeking on the fstream instead. that worked up to some point(as stated above). I fear the seeking on the fstream breaks the filtering stream, but seeking on the filtering stream doesn't work. If anyone has pointers that would be great. Best Daniel

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Random permutations using boost::random_number_generator and std::random_shuffle.
by Matthew Gwynne 23 Jan '11

23 Jan '11

Hi, We need the ability to randomly permute some range, and we already have this functionality available in the computer algebra system Maxima. We use Maxima for numerous things, often implementing basic algorithms in it, then later writing more efficient versions in C++. The problem we have is that we'd like to be able to make sure that any function we write to randomly shuffle a range, matches up with the Maxima "random_permutation" function. We believe it uses the Mersenne twister (boost::mt19937) and Knuth shuffle algorithms, and so we thought to implement these in C++ using boost::uniform_distribution, boost:variate_generator etc. However, we have two questions (open problems): 1) How does boost::variate_generator interact with mt19937, and the distribution? Is this documented somewhere? In the attached code, it seems we can construct boost::uniform_distribution with any maximum value, and still the number generator returns values outside of that range? Is this really right? 2) What algorithm does std::random_shuffle implement? (Not boost related specifically but hopefully someone will know) Is this defined by the C++ standard? It doesn't seem to be the simple Knuth shuffle algorithm (starting from top of range to bottom or vice versa) as we implement in the attached code. If anyone could point me in the right direction, I'd very much appreciate it. Thanks Matthew Gwynne http://cs.swan.ac.uk/~csmg/ Code: #include <vector> #include <iostream> #include <algorithm> #include <iterator> #include <cassert> #include <boost/lexical_cast.hpp> #include <boost/random/mersenne_twister.hpp> #include <boost/random/uniform_int.hpp> #include <boost/random/variate_generator.hpp> #include <boost/random/random_number_generator.hpp> namespace { enum { errcode_parameter = 1 }; const std::string program = "RandomShuffle"; const std::string err = "ERROR[" + program + "]: "; const std::string version = "0.0.3"; const int default_seed = 1; typedef boost::mt19937 base_generator_type; base_generator_type base_rand_gen; inline void set_random(const int seed) { assert(seed >= 1); base_rand_gen.seed(seed); } const unsigned int default_N = 10; typedef std::vector<int> vec_t; inline void initialise(vec_t& a) { for (unsigned int i = 0; i < a.size(); ++i) a[i] = i+1; } inline void output(const vec_t& a) { for (unsigned int i = 0; i < a.size(); ++i) std::cout << a[i] << " "; std::cout << "\n"; } template <class RandomAccessIterator, class RandomNumberGenerator> inline void random_shuffle(const RandomAccessIterator first, const RandomAccessIterator last, RandomNumberGenerator& rand) { typedef typename std::iterator_traits<RandomAccessIterator>::difference_type difference_type; difference_type n = last - first; assert(n >= 0); if (n <= 1) return; for (RandomAccessIterator i = first; i != last-1; ++i,--n) { const difference_type r = rand(n); assert(r >= 0); assert(r < n); std::iter_swap(i, i+r); } assert(n == 1); } } int main(const int argc, const char* const argv[]) { if (argc > 3) { std::cerr << err << "\n At most two arguments are allowed " "(the seed for the random-number generator and the number of elements).\n"; return errcode_parameter; } const int seed = (argc == 1) ? default_seed : boost::lexical_cast<int>(argv[1]); const unsigned int N = (argc < 3) ? default_N : boost::lexical_cast<unsigned int>(argv[2]); vec_t V(N); typedef boost::uniform_int<> uniform_distribution_type; uniform_distribution_type uniform_distribution(0,std::numeric_limits<int>::max()); // is this correct??? typedef boost::variate_generator<base_generator_type&, uniform_distribution_type> generator_type; generator_type rand_gen(base_rand_gen, uniform_distribution); typedef boost::random_number_generator<generator_type> RandomNumberGenerator; RandomNumberGenerator rg(rand_gen); set_random(seed); std::cout << "Underlying random sequence:\n"; for (long n = V.size(); n > 1; --n) std::cout << rg(n) << " "; std::cout << "\n\n"; initialise(V); set_random(seed); std::random_shuffle(V.begin(), V.end(), rg); std::cout << "std::random_shuffle:\n"; output(V); initialise(V); set_random(seed); ::random_shuffle(V.begin(), V.end(), rg); std::cout << "::random_shuffle:\n"; output(V); }

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[Boost 1.34] Unsatisfied symbol "boost::thread::~thread()
by Alexander Vinokur 23 Jan '11

23 Jan '11

Hi, I have the following problem. Boost 1.34 HP-UX B.11.23 U ia64 aCC: HP C/aC++ B3910B A.06.25.01 [May 16 2010] // ------ vvv1.cpp ------ #include <boost/thread.hpp> void tproc() {} int main() { boost::thread t(tproc); t.join(); return 0; } // ----------------------- Compilation-1. > aCC +DD64 -AA -mt -I$BOOST_HOME vvv1.cpp ld: Unsatisfied symbol "boost::thread::~thread()(complete)" in file vvv1.o ld: Unsatisfied symbol "boost::thread::thread(boost::function0<void,std::allocator<boost::function_base> > const&)(complete)" in file vvv1.o ld: Unsatisfied symbol "boost::thread::join()" in file vvv1.o 3 errors. Compilation-2. > aCC +DD64 -AA -mt -lboost_thread-mt -I$BOOST_HOME vvv1.cpp ld: Can't find library for -lboost_thread-mt Fatal error. What is wrong? Thanks Alex Vinokur This message and the information contained herein is proprietary and confidential and subject to the Amdocs policy statement, you may review at http://www.amdocs.com/email_disclaimer.asp

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serialization binary file backwards compatibility issue 1.42 -> 1.45
by Jake Brownson 22 Jan '11

22 Jan '11

I see in the changelog (http://www.boost.org/doc/libs/1_45_0/libs/serialization/doc/release.html) that files serialized with 1.42's binary serialization will have problems opening in 1.45. This is exactly what I'm experiencing. Luckily we have only used 1.42 in our project up to this point when we are testing for a release including boost 1.45, so we know all of our previous files were saved using 1.42. We should be able to automatically apply the fix_six fix when loading old files (I can tell by the filename when it's an old one). However I'm confused because fix_six bumps the version from 6 to 7, but in my copy of boost 1.42 serialization is already saving files w/ a library version of 7. Did 1.42 get patched to fix this issue already, or am I misunderstanding something? I found a recent thread where Robert Ramey asked someone to try trunk. I just did this and without the fix_six fix the files seem to be loading properly. Thanks, Jake

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[Fusion] Building parameter list for fusion::invoke
by Vivek 22 Jan '11

22 Jan '11

I am building a library in which users pass in function pointers of any type. I would like the library to determine the function's signature (using function_types), build a fusion vector for the function's arguments, populate the vector with data from a particular source, and then invoke the function using fusion::invoke. The kicker is that the argument types may not be default constructible. Therefore I need a way of initializing a fusion vector from a source as it is being created. For example, the following won't work namespace ft = ::boost::function_types; namespace bf = ::boost::fusion; struct non_def_type { private: non_def_type(); }; void my_func(non_def_type); template <typename FPTR> void my_invoker(FPTR f) { typedef typename ft::parameter_types<FPTR>::type parameter_types; typedef typename bf::result_of::as_vector<parameter_types>::type parameter_vector; parameter_vector params; // error if FPTR contains a parameter_type that is not default-constructible // // ... do something to populate params from data source // bf::invoke(f, params); } int main() { my_invoker(my_func); } Any idea how I might initialize the fusion vector as it is being created? I feel like there might be a way to transform parameter_types into a version in which each type is wrapped in a default-constructible wrapper, then transform that list into the final boost fusion list while at the same time populating it with data, but I can't seem to get the functors to work. E.g.: template <typename T> struct type_wrapper { type_wrapper() {} }; template <typename T> struct wrap { typedef type_wrapper<T> type; }; // Metafunction to unwrap types, and function to populate data // (data should never need to be default-constructible) struct fill { template <typename SIG> struct result; template <typename T> struct result<fill(const type_wrapper<T>&)> { typedef T type; }; // Reference type needed for bf::transform_view template <typename T> struct result<fill(type_wrapper<T>&)> { typedef T type; }; // Non-reference type needed for bf::vector template <typename T> struct result<fill(type_wrapper<T>)> { typedef T type; }; template <typename T> T operator()(const type_wrapper<T>&) const {return data_source<T>().pop();} }; template <typename FPTR> void my_invoker(FPTR f) { typedef typename ft::parameter_types<FPTR>::type parameter_types; // Conversion 1: create a fusion vector with types wrapped in a // default-constructible wrapper typedef mpl::transform<parameter_types, wrap<mpl::_1>, mpl::back_inserter<mpl::vector<> > >::type wrapped_parameter_types; typedef typename bf::result_of::as_vector<wrapped_parameter_types>::type wrapped_parameter_vector; // Conversion 2: create a fusion vector with the unwrapped types // that is also populated with the data from the data_source // (without having to ever default_construct any of the parameter_types) typedef typename bf::result_of::transform<const wrapped_params, fill>::type params_view; typedef typename bf::result_of::as_vector<const params_view>::type params_t; // Finally: invoke the function with arguments bf::invoke(f, bf::as_vector(bf::transform(params_view(), fill()))); } I can't seem to get the meta-function calls or the 'fill' metafunction itself quite right, instead getting vast reams of compiler complaints. Am I missing something? Or alternatively, is there a direct way to initialize a fusion vector? Many thanks, Vivek

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[boost.thread] function call and functor in thread creation: performance
by Boost lzw 22 Jan '11

22 Jan '11

Hi, everyone, A new thread can be created using boost thread either from a function or a functor as the entry point of the new thread, as: void thread_function(); boost::thread thrd(&function); class functor { public: inline void operator()(); }; functor f; boost::thread thrd(f); Is there a performance difference between these two? In an ordinary C++ program, can I claim that calling f() 1000 times gives better performance than calling thread_function() 1000 times, because the functor is hinted "inline" even the hint is igored by my compiler? Is f() the same as a function call in term of performance? Thanks in advance. Robert

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