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Using boost::serialization in real-time without allocating memory
by Peter Soetens 22 Sep '09

22 Sep '09

Hi, I'm trying to find out if boost::serialization can be used in real-time applications to stream data into a fifo to another process. It is mandatory that no memory allocations happen during the serialization. I tested this with a std::vector<double> of 10 elements in combination with the boost::iostreams library. The aim is that all memory allocations happen during construction of the archive object, while the serialisation itself causes none. <code> #include <boost/archive/binary_oarchive.hpp> #include <boost/serialization/vector.hpp> #include <boost/iostreams/stream.hpp> #include <boost/iostreams/device/array.hpp> namespace io = boost::iostreams; int main(int argc, char *argv[]) { vector<double> d(10, 1.1); char sink[1000]; memset( sink, 0, 1000); io::stream<io::array_sink> out(sink,1000); boost::archive::binary_oarchive oa(out); //oa << d; // should not allocate return 0; } </code> The setup code does 10 memory allocations according to valgrind: ==12995== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 8 from 1) ==12995== malloc/free: in use at exit: 0 bytes in 0 blocks. ==12995== malloc/free: 10 allocs, 10 frees, 913 bytes allocated. ==12995== For counts of detected errors, rerun with: -v ==12995== All heap blocks were freed -- no leaks are possible. If we uncomment 'oa << d' we get 2 more (unwanted) allocations: ==13010== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 8 from 1) ==13010== malloc/free: in use at exit: 0 bytes in 0 blocks. ==13010== malloc/free: 12 allocs, 12 frees, 1,001 bytes allocated. ==13010== For counts of detected errors, rerun with: -v ==13010== All heap blocks were freed -- no leaks are possible I'm guessing that the 2 allocations in the serialisation path come from a temporay std::string object, when writing the 'serialization::archive' string into the archive. Wouldn't it be possible to rewrite this library code as such that there are no allocations / strings created ? A similar pattern is observed for deserializing: 2 allocs in the serialisation path. Peter PS: I tried to find out who defines the macro BOOST_ARCHIVE_SIGNATURE() but I couldn't find the definition/#define !?

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typelist using mpl::list
by noman javed 22 Sep '09

22 Sep '09

Hi I want to implement typelist concept through mpl::list or mpl::vector. The idea is that for every call to some functor i want to store its type in a mpl::list e.g suppose we have struct A { }; A callA() {}; struct B {}; B callB() {}; main() { callA(); callB(); } this program should create a compile time mpl::list containing {B,A}. How can I implement this concept using mpl::list or mpl::vector ? Thanks in advance Regards Noman

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[program_options] vector parameters not working.
by aiooua 22 Sep '09

22 Sep '09

hello, I recently picked up boost to make use of the various libraries it includes. Unfortunately, I got stuck with the very first one (program_options) I used in my code. Any help would be appreciated very much. I want an option "bunch" which goes along with a bunch of numbers. I thought the following code would do the job: --------------------------------------------------------------------------------------- #include <iostream> #include <string> #include <vector> #include <boost/program_options.hpp> using namespace std; namespace po = boost::program_options; int main(int argc, char* argv[]) { try { vector<int> numbers; po::options_description params("parameters"); po::variables_map options; params.add_options() ("bunch,b", po::value< vector<int> >(&numbers), "a bunch of numbers"); po::store(po::parse_command_line(argc, argv, params), options); po::notify(options); if(options.count("bunch")!=0) { copy (numbers.begin(), numbers.end(), std::ostream_iterator<int>(cout, "\n")); } } catch(exception & e) { cerr << e.what() << endl; } return 0; }; --------------------------------------------------------------------------------------- However, it doesn't seem to work as it should. When I run this as follows: --------------------------------------------------------------------------------------- > test --bunch 4 2 42 4 --------------------------------------------------------------------------------------- It is just printing the first value - Am I doing something wrong here? I'm using 'boost_1_40_0' which I compiled using MS Visual Studio 2005. thanks,

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Status inquiry on Boost.Move
by Phil Deets 22 Sep '09

22 Sep '09

Hello, I am looking for a way to support move semantics with a few of my classes in a personal project I am working on. As soon as Visual C++ 2010 Express Edition comes out, I plan to convert the code to use R-value references, but I would prefer to have move semantics now so I can avoid needless expensive copies now. The Boost.Move code in the sandbox (http://svn.boost.org/svn/boost/sandbox/move/) seems to meet my needs, but I have not tried it yet; so I do not know whether it is stable or not. Does anyone know the status of this implementation. Is it relatively bug-free or should I not use it right now? If there is another move library that you would recommend, feel free to let me know. Thanks, Phil Deets II -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

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Re: [Boost-users] Usingboost::serializationinreal-timewithoutallocating memory
by Brian Wood 22 Sep '09

22 Sep '09

Stefan Strasser writes: > that's the same approach. > code seems to be written by an external code generator instead of a c++ > compiler, but there is no difference beyond that, is there? > .NET for example implements serialization based on its reflection mechanism. > it iterates at runtime through the (reflected) fields of a class and extracts > the data. > I don't think an external code generator is "cleaner". I don't claim that an external code generator is cleaner, but that the Ebenezer approach is cleaner, since it (usually) writes marshalling functions at build time. C++ compilers should have been able to do that for 10 years now, but for whatever reason that isn't being developed. Regards, Brian Wood http://webEbenezer.net <http://webebenezer.net/> "Then Samuel took a rock and set it up between Mizpah and Shen. He named it Ebenezer [Rock of Help] and said, 'Until now the L-RD has helped us.'"

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Re: [Boost-users] Usingboost::serializationinreal-timewithoutallocating memory
by Brian Wood 22 Sep '09

22 Sep '09

Stefan Strasser writes: > sure, it's the best serialization solution I know and the template > technique trumps any reflection based solution (even if c++ had > reflection). In what way? The "Usage" section of this page, http://webEbenezer.net/comparison.html<http://webebenezer.net/comparison.html>, gives an example of how it's possible to produce a cleaner solution than that afforded by the Boost Serialization library. The Ebenezer approach to the bus_stop example is twelve lines less than the Boost Serialization approach. Regards, Brian Wood www.webEbenezer.net <http://www.webebenezer.net/> "Then Samuel took a rock and set it up between Mizpah and Shen. He named it Ebenezer [Rock of Help] and said, 'Until now the L-RD has helped us.'"

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boost::proto user guide - compile error creating a lazy function
by Tom Babbin 21 Sep '09

21 Sep '09

Hi, I am going through proto user guide. I am getting compiling error for the following piece code (it's pretty much copy and pasted from the guide). I used 1.40 and gcc. #include <iostream> #include <boost/mpl/int.hpp> #include <boost/proto/core.hpp> #include <boost/proto/context.hpp> #include <boost/proto/debug.hpp> #include <cmath> #include <vector> namespace proto = boost::proto; template<int I> struct placeholder {}; // Define some placeholders proto::terminal< placeholder< 1 > >::type const _1 = {{}}; proto::terminal< placeholder< 2 > >::type const _2 = {{}}; struct calculator_context : proto::callable_context< calculator_context const > { // Values to replace the placeholders std::vector<double> args; // Define the result type of the calculator. // (This makes the calculator_context "callable".) typedef double result_type; // Handle the placeholders: template<int I> double operator()(proto::tag::terminal, placeholder) const { return this->args[I]; } }; // Define a pow_fun function object template<int Exp> struct pow_fun { typedef double result_type; double operator()(double d) const { return std::pow(d, Exp); } }; // Define a lazy pow() function for the calculator DSEL. // Can be used as: pow< 2 >(_1) template<int Exp, typename Arg> typename proto::function< typename proto::terminal<pow_fun<Exp> >::type , Arg const & >::type pow1(Arg const &arg) { typedef typename proto::function< typename proto::terminal<pow_fun<Exp> >::type , Arg const & >::type result_type; result_type result = {{{}}, arg}; return result; } int main() { calculator_context ctx; ctx.args.push_back(3); std::cout << boost::proto::eval( pow1<2>( _1 ), ctx ); return 0; } The error says: calc2.cpp: In function 'int main()': calc2.cpp:116: error: no matching function for call to 'eval(boost::proto::exprns_::expr<boost::proto::tag::function, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<pow_fun<2> >, 0l>, const boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1> >, 0l>&>, 2l>, calculator_context&)' /auto/cigprod/spg/lx86_64/opt/boost_1_40_0/boost/proto/eval.hpp:91: note: candidates are: typename boost::proto::result_of::eval<Expr, Context>::type boost::proto::eval(Expr&, Context&) [with Expr = boost::proto::exprns_::expr<boost::proto::tag::function, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<pow_fun<2> >, 0l>, const boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1> >, 0l>&>, 2l>, Context = calculator_context] /auto/cigprod/spg/lx86_64/opt/boost_1_40_0/boost/proto/eval.hpp:100: note: typename boost::proto::result_of::eval<Expr, Context>::type boost::proto::eval(Expr&, const Context&) [with Expr = boost::proto::exprns_::expr<boost::proto::tag::function, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<pow_fun<2> >, 0l>, const boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<placeholder<1> >, 0l>&>, 2l>, Context = calculator_context] Thanks. -- View this message in context: http://www.nabble.com/boost%3A%3Aproto-user-guide---compile-error-creating-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[graph] : newbie question on brandes_betweenness_centrality
by Matthew Walker 21 Sep '09

21 Sep '09

Hi, I am very much a newbie at this and would greatly appreciate some help on how I could get the brandes_betweenness_centrality function to work for me. I have the following code that compiles without error, but seg faults when I run it: #include <map> #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/graph_utility.hpp> #include <boost/graph/betweenness_centrality.hpp> #include <boost/graph/exterior_property.hpp> int main() { ... // I am reading a network from a file and storing it into lEdges and lNumVertices typedef adjacency_list<vecS, vecS, undirectedS > Graph; Graph g(lEdges.begin(), lEdges.end(), lNumVertices); typedef boost::exterior_vertex_property<Graph, float> BetweennessProperty; typedef BetweennessProperty::map_type BetweennessMap; BetweennessMap lMap; brandes_betweenness_centrality(g, lMap); } If I could get this to work, I then have aspirations that the helper function central_point_dominance(g, lMap) might give me the betweenness centralization measure that I'm after. Thanks in advance for your help! Matthew

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Hierarchical enumeration?
by Archie14 21 Sep '09

21 Sep '09

Does boost (or any other lib in C++) have facility to support smth that resembles hierarchical enumeration? I would like to have something like the following: enum Hierarchy { Store::Clothing = 1 Store::Electronics, Building::Residential, Building::Commercial } ... Hierarchy h = Hierarchy::Building::Commercial; ... if (h == Hierarchy::Store) { if (h == Hierarchy::Store::Clothing) std::cout<<"clothing"; } ...

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ASIO newbie: Passing parameters from a TCP client to a server
by Ramon F Herrera 21 Sep '09

21 Sep '09

Hello all, I have studying the ASIO examples, and experimenting with them. Still, I could benefit from the guidance of experienced programmers. This is my first client-server set of apps. I need the client to pass a few arguments to the server, lets say four. Should I pass them in 4 different lines? Being synchronous I suppose the client blocks until the server performs a read? (that seems to be what I am seeing now). I heard that there are ways to attach the debugger (gdb) to a server process when it starts? (that feat seems to be major wizardry). Sample code would be very appreciated. TIA, -Ramon

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[fusion] transform a heterogeneous vector
by Jean-Louis Leroy 20 Sep '09

20 Sep '09

In the example from the documentation : struct triple { typedef int result_type; int operator()(int t) const { return t * 3; }; }; ... assert(transform(make_vector(1,2,3), triple()) == make_vector(3,6,9)); ...all the elements have the same type. How can it work with heterogeneous vectors ? What would be typedef'ed to result_type ? Jean-Louis

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Can Regex callback function arguments be modified?
by Ramon F Herrera 20 Sep '09

20 Sep '09

I am having some trouble with the Regex callback architecture. Fist of all for, for a variable number of matches, the only way to code is with a callback function and for_each iterator, correct? To make it more interesting, I have a callback calling another callback. This could obviously go deeper and deeper. Due to the inflexibility (perhaps by me perceived?) of the callback architecture, I am forced to use a lot of global variables. To be fair, this is highly manageable within my current application, but I am concerned that this "implicit number and types of parameters" restriction may become a stumbling block in future code. At this stage, what I am trying to determine whether I should base my program(s) on (from simplest to more complex): - Regex - eXpressive - Spirit So far, I prefer Regex because it is much more stable than Spirit. The latter seems to have great potential, but when when I find that I am unable to even build the test examples properly, and the specs vary from one version to the next, I conclude that it is best to allow the good people of Spirit ("spirited people"? :-) time to deliver a more polished product. Don't know anything about eXpressive yet. Regards, -Ramon

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[Test] How to treat memory leaks as errors?
by Василий Старостин 19 Sep '09

19 Sep '09

Hi! I use Boost.Test as testing facility and get "memory leak detected" messages every time this happens. And this is good. However, Boost.Test doesn't return non-zero error code when leaks detected (as it does this when tests fail). How can I make my testing program to return non-zero error code if memory leaked? WBR, Vasily

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How to find Boost 1.40.0 with cmake 2.6?
by Ingolf Steinbach 19 Sep '09

19 Sep '09

Hi, maybe this is a bit off-topic as it is probably a cmake problem, but it could turn out that the correct solution also involves suitable invocation of bjam. As there seems to be no Windows/VC9.0 installer for Boost 1.40.0 (yet), I have built and installed the libraries myself as follows: ...\boost_1_40_0> bootstrap ...\boost_1_40_0> .\bjam --prefix=C:\Programme\boost\boost_1_40_0 ...\boost_1_40_0> .\bjam --prefix=C:\Programme\boost\boost_1_40_0 install Now, there is the following tree in C:\Programme\boost: C:\Programme\boost +-boost_1_40_0 +-include | +-boost-1_40 | +-boost | +.... +-lib +-libboost....-vc90-mt-1_40.lib +-... What is the correct way to teach the FindBoost module in cmake where to search for the boost installation? I have found that I need to at least set(Boost_ADDITIONAL_VERSIONS "1.40" "1.40.0") However, cmake does not yet find Boost. According to the debugging output of the module, the situation seems to improve slightly when I additionally specify set(BOOST_ROOT C:/Programme/boost) Now, cmake reports "Boost version: 1.40.0" but does not find any libraries. Would I have to supply different options to bjam in order to find the libraries? Is it possible to avoid having to specify BOOST_ROOT in the CMakeLists.txt file? TIA for your support! Ingolf

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Mersenne twister problem
by ruya 19 Sep '09

19 Sep '09

Hello I've built a meta-heuristics library in which I use the boost random library. I am using several independent generators through the application. The problem is in the core of my library. The tricky part is that I have three different algorithms using the core, all of them using the class where a segmentation fault happens, but only one of them crashes when it tries to use the class, the others run as expected. Gdb points to the boost library, as you can see in the snippet bellow. I couldn't find any information on this issue, and I cannot see something wrong with my code (the relevant part is bellow). The parent class where generators are declared: template< class SType, typename MemP > class SearchFunctor{ (...) public: virtual SPtr operator()( SPtr s, int iter ) = 0; SearchFunctor(){ (...) //This is how I initialize teh generators, being MASTER SEED 666 generator1 = base_generator_type(MASTER_SEED*13); uni_dist1 = boost::uniform_real<>(0,1); uniEmp = new GeneratorI(generator1, uni_dist1); generator2 = base_generator_type(MASTER_SEED*17); uni_dist2 = boost::uniform_real<>(0,1); uniRes = new GeneratorI(generator2, uni_dist2); } protected: base_generator_type generator1, generator2; boost::uniform_real<> uni_dist1, uni_dist2; GeneratorI* uniEmp; GeneratorI* uniRes; }; The derived class using the generators: template< class SType, typename MemP > struct SwapSearch : public SearchFunctor<SType,MemP>{ typedef SearchFunctor<SType,MemP> Parent; (...) SPtr operator()( SPtr s, int iter ){ assert(s != NULL); assert(s->GetDomain()!= NULL); assert(s->GetDomain()->GetTotalEntities()>1); (...) d1 = (*Parent::uniEmp)() * (s->GetDomain()->GetTotalEntities()-1); d2 = (*Parent::uniEmp)() * (s->GetDomain()->GetTotalEntities()-1); (...) return 0; } }; The output of the debugger has a lot of lines because of meta-programming but starts and finishes with this: #0 0x08071a57 in brickheuristics::SwapSearch (...) (...) at /usr/include/boost/random/mersenne_twister.hpp:279 279 UIntType z = x[i]; Thanks -- View this message in context: http://www.nabble.com/Mersenne-twister-problem-tp25382114p25382114.html Sent from the Boost - Users mailing list archive at Nabble.com.

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[units] CODATA constant for electron charge?
by Manoj Rajagopalan 19 Sep '09

19 Sep '09

Hi developers, Could you please include the electron charge in the codata constants? Right now it has to calculated using codata::e_over_m_e*codata::m_e or set using quantity<electric_charge>::from_value() which is inconvenient. thanks, Manoj

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[Interprocess] deadlocking race condition in emulation interprocess_condition.hpp
by Young, Zachariah L 18 Sep '09

18 Sep '09

This appears related to the discussion found here: http://lists.boost.org/boost-users/2009/03/46051.php Bug: There is a set of conditions where a process can manage to enter do_timed_wait, increment m_num_waiters, and exit without decrementing it. Boost 1.39.0 Sequence of events: We join our hero, Process A (P_A), in boost/interprocess/sync/emulation/interprocess_condition.hpp. P_A is executing a do_timed_wait(true, lock, abs_time) call, and is spinning at the while loop at line 124. tout_enabled == true, and abs_time is a microsecond in the future (about to expire but hasn't yet). Process B, P_A's trusty sidekick, sends a notify_all on the conditional, breaking P_A out of the while loop at line 124. abs_time arrives (ie, P_A got to line 149 with microsec_clock::universal_time() >= abs_time and timed_out = false). With these conditions, P_A gets to line 163 and calls the constructor for scoped_lock. P_A jumps to boost/interprocess/sync/scoped_lock.hpp line 114. P_A executes mp_mutex->timed_lock(abs_time) at line 115. P_A jumps to boost/interprocess/sync/emulation/interprocess_condition.hpp line 49. P_A takes a reading of now at line 56. P_A finds that (now >= abs_time) at line 58 and is sent packing with a return value of false. P_A arrives back in boost/interprocess/sync/emulation/interprocess_condition.hpp on line 163. P_A gets to line 171 and finds lock is false. He panics! He sets timed_out to true and unlock_enter_mut to true, but in his haste to break out of evil Dr. while(1)'s clutches, he forgot to atomically decrement m_num_waiters! Manic laughter can be heard behind him as he tries in vein to acquire the lock on line 214. "You fool! You fell into my trap!", shouts Dr. while(1). "Process B grabbed that very lock and attempted to free you again! He is at line 56 of this very header file, waiting for a call from you that will never come, and he's holding your precious lock! Your deadlock is complete! HAHAHAHAHAHAH!!" Ahem. I do not know the proper way to fix this problem. My straightforward idea is to add the following line at line 172 of boost/interprocess/sync/emulation/interprocess_condition.hpp: if(!lock){ detail::atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters)); timed_out = true; unlock_enter_mut = true; break; } However, the commment inlcuded with the block in question: //Notification occurred, we will lock the checking interprocess_mutex so that //if a notify_one notification occurs, only one thread can exit ...makes me wary. One thing seems certain to me: there's something not quite right here. I could increase my timeout window to lower the chances of this occurring, but that is not a solution. That is masking a problem. Anyone got a take on this? Am I missing something obvious? That whole block with the comment really makes me suspicious.

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Using Boost Mutex
by Wesley Bland 18 Sep '09

18 Sep '09

This is firmly in n00b territory. I'm trying to use a boost::mutex to lock a STL queue. The mutex is stored in a class in a map. When I pass the mutex to the boost::mutex::scoped_lock constructor, I get this error: /usr/local/include/boost/noncopyable.hpp: In copy constructor ‘boost::mutex::mutex(const boost::mutex&)’: /usr/local/include/boost/thread/pthread/mutex.hpp:31: instantiated from ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = int, _Tp = boost::mutex, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, boost::mutex> >]’ SwitchBox.cpp:15: instantiated from here /usr/local/include/boost/noncopyable.hpp:27: error: ‘boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)’ is private /usr/local/include/boost/thread/pthread/mutex.hpp:31: error: within this context /usr/include/c++/4.2.1/bits/stl_map.h: In member function ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = int, _Tp = boost::mutex, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, boost::mutex> >]’: /usr/include/c++/4.2.1/bits/stl_map.h:350: note: synthesized method ‘boost::mutex::mutex(const boost::mutex&)’ first required here This appears to be complaining about me passing the mutex into the scoped_lock. Can anyone give me some help here? I've included a much shortened version of the code that otherwise compiles. Thanks for your help, Wesley SwitchBox.hpp ----- #include <map> #include <queue> #include <boost/thread/mutex.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; using namespace std; namespace Network { typedef struct Message { int type; unsigned long sender; unsigned long destination; int size; void *body; char *PackHeader(); void UnpackHeader(char *); } Message; class SwitchBox { protected: unsigned long myID; int headerSize; map< int, queue< Message > > sendQueues; map< int, boost::mutex > sendMutexes; bool Initialize(); void SendThread(unsigned long id, tcp::socket sock); }; } SwitchBox.cpp ------ #include "Switchbox.hpp" using namespace Network; bool SwitchBox::Initialize() { myID = 0; headerSize = sizeof(int) + sizeof(unsigned long) * 2 + sizeof(int); return true; } void SwitchBox::SendThread(unsigned long id, tcp::socket sock) { // Set up the lock so it can be locked and unlocked as we need boost::mutex::scoped_lock sendLock(sendMutexes[id], boost::defer_lock); while (true) { // First get the message off of the message queue // Lock the message queue so nothing is moved unexpectedly sendLock.lock(); Message m = sendQueues[id].front(); sendQueues[id].pop(); // Unlock the message queue so everyone else can get to it now sendLock.unlock(); // Next send the message through the socket boost::asio::write(sock, boost::asio::buffer(m.PackHeader(), headerSize)); boost::asio::write(sock, boost::asio::buffer((char *) m.body, m.size)); } }

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Can the Regex code be placed into a class?
by Ramon F Herrera 18 Sep '09

18 Sep '09

The following sample program comes with the Boost Regex distribution. It compiles and runs fine. Its purpose is to count the number of classes in the input text file. http://patriot.net/~ramon/regex_iterator_example.cpp.txt I am having a real hard time trying to convert the code to a class (named "Pairs"). The compilation problem occurs in this statement: std::for_each(m1, m2, &regex_callback); The compiler suggests to use this statement, which does not compile either: std::for_each(m1, m2, &Pairs::regex_callback); Thanks, -Ramon http://www.parashift.com/c++-faq-lite/pointers-to-members.html

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boost::function typename Signature
by veerus 18 Sep '09

18 Sep '09

How to extract the return type and the argument type list from the type Signature in boost::function<Signature> ? More specifically if I have a object of type boost::function< int ( double) >, the thing "int (double)" is matched with a type. What type is that ? Where can I find it? Thanks -- View this message in context: http://www.nabble.com/boost%3A%3Afunction-typename-Signature-tp25507953p255… Sent from the Boost - Users mailing list archive at Nabble.com.

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[Regex] Which sub-expression did participate in a partial match?
by Kay-Michael Wuerzner 18 Sep '09

18 Sep '09

Hello, I wonder if it is possible to find out which sub-expression of a regex is responsible for a partial match? Consider the following example: int main ( int argc, char** argv ) { std::string input ( argv[1] ); boost::regex test ( "((?:Apple )?iPhone)|(Sony Vaio)" ); boost::sregex_iterator it ( input.begin(), input.end (), test, boost::match_default | boost::match_partial ); boost::sregex_iterator none; if ( it != none ) { std::cout << (*it).size () << std::endl; if ( (*it)[0].matched ) std::cout << "full match\n"; else std::cout << "partial match\n"; for ( unsigned int i = 1; i < (*it).size (); ++i ) { if ( (*it)[i].matched ) // this should in principle also be true for partial matches std::cout << i << " " << (*it).position () << std::endl; } } return 0; } The problem is that the if-condition in the for loop is not met in case of a partial match on the sub-expression: $> ./regex_test "Apple" partial match $> ./regex_test "iPhone" full match 1 0 In the first case I would expect the output of the sub-expression and the position of the match. Are you aware of any method to achieve this behavior? Many thanks in advance, Kay

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shared_ptr and pass by value
by Marat Abrarov 18 Sep '09

18 Sep '09

Dear Boost C++ Libraries Developers, According to http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/ why Boost use this (not the only example): ~~~~~~~~~~~~~~~~~~~ shared_ptr & operator=( shared_ptr const & r ) { this_type(r).swap(*this); return *this; } ~~~~~~~~~~~~~~~~~~~ and not such: ~~~~~~~~~~~~~~~~~~~ shared_ptr & operator=( shared_ptr r ) { r.swap(*this); return *this; } ~~~~~~~~~~~~~~~~~~~ Regards, Marat.

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[format] compilation error
by Johan Råde 18 Sep '09

18 Sep '09

Hi, I'm using Boost 1.38 and Visual Studio 2008. The following code #include <boost/format.hpp> #include <ostream> #include <vector> using boost::format; using std::ostream; using std::vector; ostream& operator<<(ostream& os, const vector<int>& v) { os << '['; for(size_t i = 0; i < v.size(); ++i) { if(i > 0) os << ' '; os << v[i]; } os << ']'; return os; } void f() { vector<int> v; str(format("%1%") % v); } fails to compile with the error message 1>c:\libraries\boost\boost_1_38_0\boost\format\feed_args.hpp(100) : error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const std::vector<_Ty>' (or there is no acceptable conversion) 1> with 1> [ 1> _Ty=int 1> ] Why? How do I fix this? Thank you, Johan Råde

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[Math] Bug in example code / doc (Binomial Distr.)
by Ralf M. 18 Sep '09

18 Sep '09

On p.66 (Binomial distribution, "Binomial Quiz Example") of the Math Toolkit pdf-file, and also at http://www.boost.org/doc/libs/1_40_0/libs/math/doc/sf_and_dist/html/math_to… it is written: "Probability of getting exactly 11 answers right by chance is 2.32831e-010" I think this is wrong. It rather should be one of these below: "Probability of getting exactly 11 answers right by chance is 0.000247132" or "Probability of getting exactly 16 answers right by chance is 2.32831e-010" I have'n checked the underlying source code of this yet; ie. maybe it is only a doc error... And this code there seems IMHO to be problematic too: " int questions = 16; // All the questions in the quiz. int answers = 4; // Possible answers to each question. double success_fraction = (double)answers / (double)questions; // If a random guess. // Caution: = answers / questions would be zero (because they are integers)! binomial quiz(questions, success_fraction); " Shouldn't the second param not simply be the constant p of each item, ie. here 0.25, even if # of questions is set to a different value, for example 32 ? Because 32 / 4, as done above, wouldn't be 0.25 anymore...

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Parallel BGL status in Boost
by Mathieu Malaterre 18 Sep '09

18 Sep '09

Hi there, I am getting lost with the status of PBGL in boost. Is it officially in Boost now ? I am reading some documentation such as: http://charm.cs.uiuc.edu/charmWorkshop/slides/2009_PBGL_Lumsdaine.pptx And it appears there are multiple implementations (see slide #54), namely 'the Parallel BGL' (is there only one?) and the (Parallel) BGL-VTK. Documentation links to : http://www.osl.iu.edu/research/pbgl but this page has not been updated in years, and recent commit AFAIK did happen directly within boost, right ? Is there some threads I am missing, I have been following boost users list but could not find any thread relevant. Basically all I am interested in is how do you provide an iterator interface in a parallel environment where vertex/edge are not local to the machine. Thanks -- Mathieu

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