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[DateTime] Daily Schedules
by John Rocha 07 Jan '11

07 Jan '11

I was looking at the DateTime library for a scheduling module in my application. I was very excited to see time periods (time_period) and its method contains(). I could set up a time_period for say 8:00-17:00, and then when something happened I could create a ptime and see if the time_period contains my ptime. (i.e. did my action happen between 8:00 and 17:00.) However, I realized that a time period is much more specific than I want. A time_period is tied to a specific date, i.e. 8:00-17:00 on Sep. 20 1999. I read the documentation, and I didn't see (or missed) anything that might be what I would call an hour period -- a range of time that is independent of the date. I don't think it's a duration, because I understood that to mean the amount of time between two time points (i.e. +/- 5 hours). I have some ideas on how I might extend this to achieve what I want, but before going that route, I wanted to double check if others have encountered this and if so how they resolved it. Was it done with a bit of the library that I'm overlooking? Or did you have to extend the class to achieve the desired results? Thanks in advance, -=John

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[boost][Serialization] - about macro BOOST_CLASS_VERSION
by girish hilage 07 Jan '11

07 Jan '11

Hi, I have a query regarding macro BOOST_CLASS_VERSION(). I am running following code : class testRep { friend std::ostream & operator<<(std::ostream &os, const testRep &tr); public : template<class Archive> void serialize(Archive &ar, const unsigned int version) { if(version >= 2) ar & BOOST_SERIALIZATION_NVP(Site); } private : string Site; }; BOOST_CLASS_VERSION(testRep, 2) std::ostream & operator<<(std::ostream &os, const testRep &tr) { return os << '\n' << tr.Site << endl; } void read_file (testRep &s, const char * filename) { std::ifstream ifs(filename); assert (ifs.good()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(s); } int main (void) { testRep tr; read_file (tr, "Test.xml"); cout << tr << endl; return 0; } This code runs fine. But, if I remove the statement : BOOST_CLASS_VERSION(testRep, 2) then I get following error : terminate called after throwing an instance of 'boost::archive::archive_exception' what(): class version Aborted (core dumped) So, want to ask if it is mandatory to declare a macro BOOST_CLASS_VERSION()? and if not then how do I prevent this runtime error from happening? Regards, Girish

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[Off topic] Strict Aliasing white paper redux
by Patrick Horgan 07 Jan '11

07 Jan '11

Some time ago, I posted a link here to my (then new) white paper on strict-aliasing. I wrote it because people keep posting, on this and on other lists, questions that show a basic misunderstanding of aliasing and what the rules in C and C++ standards on aliasing are intended to communicate. I got some great feedback and have posted a new revision, http://dbp-consulting.com/StrictAliasing.pdf. I'm hoping that people on this list will review the paper and tell me some more ways of improving it. My intention is to write a paper that will make it so that I won't have to keep answering the same questions over and over again;) I'll just point people at the paper. Best regards, Patrick

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1.45: thread/condition_variable.hpp: unused variable 'res' warning, gcc 4.2
by Hicham Mouline 06 Jan '11

06 Jan '11

hello, in Release build in Xcode, gcc 4.2.1, inline void condition_variable::wait(unique_lock<mutex>& m) { ... int const res = pthread_cond_wait(&cond, &internal_mutex); BOOST_ASSERT(!res); ... } Unused variable 'res' is gcc mistaken? regards,

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Re: [Boost-users] [FunctionTypes] function_arity for non-built-ins
by Hossein Haeri 06 Jan '11

06 Jan '11

Hi Roman, > This is actually possible in most cases. Check this nice article by Eric > Niebler: http://www.boost.org/doc/libs/1_45_0/doc/html/proto/appendices.html#boost_p… This is beautiful, thanks! :) So, from the description, it seems like this can_be_called guy (or its siblings) is in heavy use for Proto. Does Proto then also port this as a part of its toolbox? Or, is it only for internal use and I'll need to craft my own version of it? TIA, --Hossein

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Re: [Boost-users] [ asio ] how to determine if a server is overloaded ?
by Avi Bahra 06 Jan '11

06 Jan '11

ecyrb wrote> >Server overload does not come from network overload, but from service >overload. If you can't serve (compute) more requests/s than the network >load, your server is overloaded... >You can compute your server overload by queuing requests. If your queue >becomes too big, you can consider that your server is under heavy pressure >and take appropriate measures to circumvent the flow of requests (load >balancing etc...) Is there any asio example in the docs, which demostrate this Does the io_service expose the queue of request/connections as I have not seen such an api ? or do you mean that server should be structured to maintain its _own_ queue.( as apposed to the queue in io_service) Request are then handled from this internal queue? Best regards, Ta, Avi

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[Accumulators] Retract samples
by Alex Hagen-Zanker 06 Jan '11

06 Jan '11

Dear all, I am considering using Boost Accumulators for a moving window calculation. When a window would step from left to right, it should add the sample on the right side of the window and retract the sample on the left side on each step. For weighted accumulators, it might be possible to use negative weights. But, since the accumulators do not appear to be intended for this use, there may be implementation details that invalidate the use of negative weights. Is there a recommended way to retract samples in Boost Accumulators? Thanks, Alex p.s. the general idea: void movingwindowsum(const vector<double>& in, vector<double>& out, size_t radius ) { size_t n = in.size(); double sum = 0; // This should be an accumulator for(size_t i = 0; i < min(n, radius); ++i) { sum += in[i ]; // add sample } out.resize(n); for(size_t i = 0; i < n; ++i) { size_t left = i - radius - 1; size_t right = i + radius; if (left >= 0) sum -= in[left]; // retract sample if (right < n) sum += in[right]; // add sample out[i] = sum; }

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boost::signals2 connection management
by frares＠gmail.com 06 Jan '11

06 Jan '11

Hi, all If I have one only signal that can be connected at different times to several different slots, then I create several boost::signals2::connection, one for each slot but for that same only signal, if I disconnect one of the connections, will all connections be disconnected or just that particular slot? If this is not the way to disconnect specific individual signal/slot connections, how do I do it? I have to use "boost::bind" for the connections are from signals and slots of different classes, and I cannot use scoped connections because asynchronous tasks are being performed (and signaled). Thanks Francisco

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streaming of tuples - adjusting field widths?
by Christian Meesters 06 Jan '11

06 Jan '11

Hi, Having the following code (where 'out' is a std::ostream): out << boost::tuples::set_open('[') << boost::tuples::set_close(']') << boost::tuples::set_delimiter(',') << std::setw(21) << std::right << get_some_tuple(); I expected to see the tuple in a column of 21 spaces, adjusted to the right. Instead, the tuple is appended on 21 spaces. Any hint on what my mistake is? TIA Christian

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regex linker issue/
by John Hendrix 06 Jan '11

06 Jan '11

Hi all, I just downloaded boost and I am attempting to create a trivial program. This my first attempt to develop boost on Fedora. Here is what I did: 1) downloaded boost_1_45_0 2) ./bootstrap.sh 3) ./bjam toolset=gcc variant=debug link=static --address-model=64 --with-regex All of these step ran uneventfully I then created a "hello world" regex program: // regex-test.cpp #include <string> #include <iostream> #include <boost/regex.hpp> int main( int argc, char * argv[] ) { // boost::regex pattern ("b.lug",boost::regex_constants::icase|boost::regex_constants::perl); std::string stringa ("Searching for bolug"); std::string replace ("BgLug"); std::string newString; // newString = boost::regex_replace (stringa, pattern, replace); printf("The new string is: |%s|\n",newString.c_str()); return 0; } To compile and link: g++ -o regex-test -I../../boost/boost_1_45_0/ -L../../boost/boost_1_45_0/stage/lib/ -lboost_regex regex-test.cpp If all of the boost::whatever code is commented-out then it compiles and links fine. [root@fc5-virt64 upstream]# g++ -o regex-test -I../../boost/boost_1_45_0/ -L../../boost/boost_1_45_0/stage/lib/ -lboost_regex regex-test.cpp [root@fc5-virt64 upstream]# ./regex-test The new string is: || [root@fc5-virt64 upstream]# However, if I, say, uncomment-out the first line of code I get: [root@fc5-virt64 upstream]# g++ -o regex-test -I../../boost/boost_1_45_0/ -L../../boost/boost_1_45_0/stage/lib/ -lboost_regex regex-test.cpp /tmp/ccDG8tmV.o: In function `boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::assign(char const*, char const*, unsigned int)': regex-test.cpp:(.text._ZN5boost11basic_regexIcNS_12regex_traitsIcNS_16cpp_regex_traitsIcEEEEE6assignEPKcS7_j[boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::assign(char const*, char const*, unsigned int)]+0x27): undefined reference to `boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::do_assign(char const*, char const*, unsigned int)' collect2: ld returned 1 exit status [root@fc5-virt64 upstream]# Does anyone have any suggestions? johnh

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