October 2007 - Boost-users - lists.boost.org

defining a function according to a signature given as template parameter
by Stefan Funck 09 Oct '07

09 Oct '07

Hi everybody, I'd like to have a generic wrapper that can be put "in between" a signal and a slot to provide some additional functionality to the slot. So where I normally have something like void myslot(int i) { std::cout << "slot(" << i << ")\n"; } int main(int argc, char *argv[]) { boost::signal<void (int)> sig; sig.connect(boost::bind(myslot, _1)); sig(123); return 0; } I want something like int main(int argc, char *argv[]) { boost::signal<void (int)> sig; SlotWrapper<void (int)> slotWrap(boost::bind(myslot, _1)); sig.connect(boost::bind(SlotWrapper<void (int)>::slot, &slotWrap, _1)); sig(123); return 0; } The signature of SlotWrapper<Signature>'s member function slot() is defined by Signature. slot()'s implementation should have some common functionality (that's what I want the wrapper for) and then call the actual slot that was given at construction (myslot() in the example above). Is that doable? So far I have two questions: 1) How can I define a member function according to the signature that is given as a template parameter to the class? 2) If I can do 1), how can I then bind the arguments given and call another function, i.e. the original slot? A skeleton of the wrapper might look like: template <typename Signature> class SlotWrapper { public: SlotWrapper(const typename boost::signal<Signature>::slot_function_type& slot) : m_slot(slot) {} // define a function according to Signature typename boost::signal<Signature>::result_type slot(...arguments...) { // do something common // call somehow the actual slot (m_slot) with the given ...arguments... } private: const typename boost::function<Signature> m_slot; }; How can I write the slot() function? Thanks for any help, Stefan

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boost::basic_match::size_type
by Bill Webster 09 Oct '07

09 Oct '07

The basic_match access methods have int index parameters, whereas basic_match::size() returns basic_match::size_type. This means that the following results in compiler warnings (under MSVC 8.0) - boost::smatch match; // ... for ( boost::smatch::size_type i = 0; i < match.size(); i++ ) { cout << match.str( i ).c_str() << endl; }

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Dimensional analysis
by Joel C. Salomon 09 Oct '07

09 Oct '07

Have the dimensional analysis templates suggested in <http://www.boost.org/libs/mpl/doc/tutorial/dimensional-analysis.html> ever been developed into readily usable form? --Joel

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serialization and object tracking question...
by Graham Reitz 09 Oct '07

09 Oct '07

I am having trouble wrapping my head around object tracking for serialization. I see how to change the default behavior: BOOST_CLASS_TRACKING(my_class, boost::serialization::track_never) ...but based on the error below how do I determine what kind of object tracking is needed? oserializer.hpp:566: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>' inline void save(Archive & ar, T &t){ // if your program traps here, it indicates taht your doing one of the following: // a) serializing an object of a type marked "track_never" through a pointer. // b) saving an non-const object of a type not markd "track_never) // Either of these conditions may be an indicator of an error usage of the // serialization library and should be double checked. See documentation on // object tracking. BOOST_STATIC_ASSERT(check_tracking<T>::value); The following is the class to be serialized: class client_i { private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & m_client; } clients m_client; public: client_i() {}; client_i(clients c) : m_client(c) {}; ~client_i() {}; }; clients is a mysql++ specialized sql structure that is created via one of the mysql++ macros, i.e. sql_create_N(). Any help understanding this would be greatly appreciated. Thanks, Graham

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thread creating just hangs
by Eyon Land 08 Oct '07

08 Oct '07

Hey folks, I'm new to boost. I've used pthread and wanted to try out boost::thread. After installing the latest release I found that creation of the thread instance simply hangs. I use CentOS 4.3 on a single CPU machine. Has this happened to anyone else? Thanks in advance! Eyon ____________________________________________________________________________________ Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/

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Threads, condition variables, and signals
by Scott Gifford 08 Oct '07

08 Oct '07

Hello, I'm writing a multithreaded server on Unix using boost::thread. The basic operation is fairly straightforward; a master thread starts up worker threads, and coordinates various management tasks using condition variables. As with most Unix servers, the server is shut down with an OS signal telling the server to shut down. The server catches this signal, then simply calls exit(1). Any important cleanup happens in the destructors of global variables, so it will happen properly no matter how the server exits. One object which is always cleaned up is the object for the master thread. The master thread sets a flag, then does a notify_all() on some condition variables to tell the other threads to shut down, The problem I'm having is that if the master thread is waiting on a condition variable when the signal arrives, and the destructor does a notify_all() on that condition variable, then the destructor for the boost::condition variable hangs. For example, if I run the included code and hit CTRL-C after a short bit, I get this output: Waiting... ^C Caught signal 2 Destroyed ThreadTest Running destructor 1 [ ... hangs ... ] Here is the program: #include <iostream> #include <signal.h> #include <boost/thread.hpp> #include <boost/thread/mutex.hpp> #include <boost/thread/condition.hpp> template<int n> struct PrintOnDestruct { ~PrintOnDestruct() { std::cout << "Running destructor " << n<< std::endl; } }; class ThreadTest { public: void doSomething() { boost::mutex::scoped_lock lock(myMutex); while(true) { std::cout << "Waiting..." << std::endl; myCond.wait(lock); } } ~ThreadTest() { boost::mutex::scoped_lock lock(myMutex); myCond.notify_all(); std::cout << "Destroyed ThreadTest" << std::endl; } private: PrintOnDestruct<2> d2; boost::mutex myMutex; boost::condition myCond; PrintOnDestruct<1> d1; }; // Exit properly on signal void sighandle(int sig) { std::cerr << "Caught signal " << sig << std::endl; exit(1); } ThreadTest tt; int main() { // Get ready to handle signals signal(SIGINT,sighandle); tt.doSomething(); } Does anybody have any suggestions for a straightforward way to handle this properly? Thanks! ----ScottG.

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[preprocessor] using __FILE__ with BOOST_PP_FILENAME_x
by Server Levent Yilmaz 08 Oct '07

08 Oct '07

Hi all, Please take a look as this trivial example of file iteration: // trivial.h #if !BOOST_PP_IS_ITERATING #ifndef TRIVIAL_H #define TRIVIAL_H #include <boost/preprocessor/iteration/iterate.hpp> #define BOOST_PP_FILENAME_1 "trivial.h" //!!! #define BOOST_PP_ITERATION_LIMITS (1, 3) ??=include BOOST_PP_ITERATE() #endif // TRIVIAL_H #else BOOST_PP_ITERATION() #endif Perhaps not so obvious many (wasn't to me), that #define BOOST_PP_FILENAME_1 __FILE__ doesn't work. One has to specify (kind of like hardcode) the file's name in there.. Is there some, possibly contrived, way to achieve automation of this? regards, - Levent PS: What an AMAZING library this Boost.Preprocessor is!? -- Server Levent Yilmaz Mechanical Engineering University of Pittsburgh

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exp functions with interval
by Mark Beinker 08 Oct '07

08 Oct '07

Hi, I was trying to use the boost interval class using g++ under cygwin and ubuntu, but unfortunately, I have trouble to use the exp function. The following code: #include <iostream> #include <cmath> #include <boost/numeric/interval.hpp> #define DOUBLE boost::numeric::interval<double> int main(int argc, char** argv) { DOUBLE x(4,5); std::cout.precision(19); DOUBLE res = exp(x); std::cout<<'['<<res.lower()<<", "<<res.upper()<<']'<<std::endl; return 0; } generates the following compile error: /usr/include/boost/numeric/interval/transc.hpp: In function `boost::numeric::interval<T, Policies> boost::numeric::exp(const boost::numeric::interval<T, Policies>&) [with T = double, Policies = boost::numeric::interval_lib::policies<boost::numeric::interval_lib::rounded_math<double>, boost::numeric::interval_lib::checking_strict<double> >]': itest.cpp:14: instantiated from here /usr/include/boost/numeric/interval/transc.hpp:34: error: 'struct boost::numeric::interval_lib::rounded_math<double>' has no member named 'exp_down' itest.cpp:14: instantiated from here /usr/include/boost/numeric/interval/transc.hpp:34: error: 'struct boost::numeric::interval_lib::rounded_math<double>' has no member named 'exp_up' I use boost version 1.34.1. Any idea why this doesn't work? Regards, Mark

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[string_algo] Case-insensitive keys in map with is_iless?
by Boris 07 Oct '07

07 Oct '07

Am I supposed to be able to use boost::algorithm::is_iless (see http://www.boost.org/doc/html/boost/algorithm/is_iless.html) to create a map with case-insensitive keys? I wonder as either it is broken in VS2005 or I do something wrong: #include <boost/algorithm/string.hpp> #include <string> #include <map> int main() { std::map<std::string, int, boost::algorithm::is_iless> m; m["test"] = 1; } C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale(583) : error C2440: 'type cast' : cannot convert from 'unsigned char' to 'std::basic_string<_Elem,_Traits,_Ax>' ... C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale(561) : error C2440: 'type cast' : cannot convert from 'std::basic_string<_Elem,_Traits,_Ax>' to 'unsigned char' The assignment causes the problem. If you use insert() you get the same compiler error. Without the assignment the code compiles fine. Boris

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"Missing" lib for 1_34_1 using MSVC-71
by Larry 07 Oct '07

07 Oct '07

I had a program that I had built with Boost 1_34 and it worked well (built with MSVC 7.1). I downloaded 1_34_1 and built 1_34_1 for VC8 and VC7.1 using bjam 3.1.14. bjam --toolset=msvc-7.1 install I switched the program build to use Boost 1_34_1 and the build fails looking for libboost_date_time-vc71-mt-sgd-1_34_1.lib as part of the link. Going back to the Boost build I find msvc.archive bin.v2\libs\date_time\build\msvc-71\debug\link-static\runtime-link-static\libboost_date_time-vc-sgd-1_34_1.lib common.copy C:\Boost\lib\libboost_date_time-vc-sgd-1_34_1.lib 1 file(s) copied. The only thing I changed was the include list entry from c:\boost\include\boost_1_34 to c:\boost\include\boost_1_34_1. The lib directory is the same in both cases. I didn't find anything looking through the boost.user group or in the doc but perhaps I looked at it and just didn't realize the answer was there. Perhaps I didn't do something I should have or did something I shouldn't have. Any ideas? I got surprised (probably again) when building Boost because I had run vcvars32.bat for MSVC 7.1 and then did bjam --toolset=msvc install and the surprise was it built for MSVC 8.0. The doc does say the build will find the VC compiler but I had sort of assumed it would use what was in the environment before searching elsewhere for a compiler version. But after that I ran bjam --toolset=msvc-71 install and it ran without complaint. I did several iterations of the 7.1 build including a build with -a and also did a --clean followed by a Boost build and neither altered the outcome of the Boost build (that I could see) and did not alter the outcome of the program build with VC 7.1. The program build was done via VS. Moving the include back to 1_34 works. Larry

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