Hello, as suggested by Paul Bristow in his response to my proposal on interval containers I started to integrate boost::date_time into my library examples. To my surprise I discovered that boost::date_time does not provide operator ++ (--) for it's date and time template classes. So the boost date and time classes are not Incrementable (Decrementable). One could say: they lack a tic-tac ;-) Which is for *time* kind of a major omission. Now, Incrementability seems most fundamental to me. Therefore, in the design of interval containers in my library, I avoided to reqire Addability for interval template parameters. Requiring only In(De)crementability I enable a broader set of instances for intervals and interval containers. Iterators for instance provide incrementation and decrementation but no addability in general (some do). Incrementability seems also more fundamental to me than Addability. Which is to say that a concept or algebra that offers Addability almost certainly also has a Incrementability, but not the other way round. Take for instance the Peano Axioms of natural numbers, where Incrementability is given in the form of the fundamental successor function. Therefore I would strongly suggest, that a class template that implements Addability/Subtractability (operators +, +=, -, -=) also implements In(De)crementability (operators ++ and --). This should apply even more to classes that resemble in their basic characteristics an integral numeric type like date and time do. For boost::date_time I tried to completed the code in this respect. I added 6 lines of code: boost\date_time\time_system_counted.hpp(114): counted_time_rep& operator ++(){++time_count_; return *this;} counted_time_rep& operator --(){--time_count_; return *this;} boost\date_time\int_adapter.hpp(191): int_adapter& operator ++() {++value_; return *this;} int_adapter& operator --() {--value_; return *this;} boost\date_time\time.hpp(179): time_type operator ++() { ++time_; return time_type(time_); } time_type operator --() { --time_; return time_type(time_); } With these minor additions to the code the 'party' example from my interval template library works fine with boost::date_time: ----------------------------------------------------------------------- #include <stdio.h> #include <iostream> #include <itl/itl_value.hpp> #include <itl/string_set.hpp> #include <itl/split_interval_map.hpp> #include <boost/date_time.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using namespace std; using namespace boost::posix_time; using namespace itl; typedef itl::set<string> GuestSetT; typedef split_interval_map<ptime, GuestSetT> PartyAttendenceHistoryT; void boost_party() { GuestSetT mary_harry; mary_harry.insert("Mary"); mary_harry.insert("Harry"); GuestSetT diana_susan; diana_susan.insert("Diana"); diana_susan.insert("Susan"); GuestSetT peter; peter.insert("Peter"); PartyAttendenceHistoryT party; party.insert( make_pair( rightopen_interval<ptime>( time_from_string("2008-05-20 19:30:00.000"), time_from_string("2008-05-20 23:00:00.000")), mary_harry) ); party.insert( make_pair( rightopen_interval<ptime>( time_from_string("2008-05-20 20:10:00.000"), time_from_string("2008-05-21 00:00:00.000")), diana_susan) ); party.insert( make_pair( rightopen_interval<ptime>( time_from_string("2008-05-20 22:15:00.000"), time_from_string("2008-05-21 00:30:00.000")), peter) ); PartyAttendenceHistoryT::iterator it = party.begin(); while(it != party.end()) { interval<ptime> when = (*it).first; // Who is at the party within the time interval 'when' ? GuestSetT who = (*it++).second; cout << "[" << to_simple_string(when.first()) << " - " << to_simple_string(when.last()) << "]" << ": " << who.as_string() << endl; } } int main() { cout << ">> Interval Template Library: Sample boost_party.cpp <<\n"; cout << "-------------------------------------------------------\n"; boost_party(); return 0; } Program output:
Interval Template Library: Sample boost_party.cpp <<
[2008-May-20 19:30:00 - 2008-May-20 20:09:59.999999]: Harry Mary [2008-May-20 20:10:00 - 2008-May-20 22:14:59.999999]: Diana Harry Mary Susan [2008-May-20 22:15:00 - 2008-May-20 22:59:59.999999]: Diana Harry Mary Peter Susan [2008-May-20 23:00:00 - 2008-May-20 23:59:59.999999]: Diana Peter Susan [2008-May-21 00:00:00 - 2008-May-21 00:29:59.999999]: Peter cheers Joachim ----- Interval Template Library (ITL) download from http://www.sourceforge.net/projects/itl documentation http://www.herold-faulhaber.de/itl