i think this goes back to the discussion about whether it was necessary to have all the different kinds of intervals (half-open, closed and open) within joda. i argued at the time that we'd eventually have difficulties unless they were all allowed.
so for instance, i don't think the interval [9:00, 9:00) is well defined to begin with. it has to be [9:00, 9:00] to make sense. i think [9:00, 9:00) is illegal, there should be no way to construct or calculate it. once you allow all the interval types, i think all these relationships are clearer. so for instance [9:00, 10:00) does contain, abut and overlap [9:00, 9:00] [9:00, 10:00) does not contain [10:00, 10:00] [9:00, 10:00) does abut [10:00, 10:00], and depending on the definition of abut, may or may not abut (10:00, 11:00] [9:00, 10:00) does not overlap [10:00, 10:00] of course, if you allow all interval types, you have to careful about defining operations like concatenation and equality. for instance are you allowed to concatenate [9:00, 9:30) and (9:30, 10:00]? IMO no, it doesn't make sense, and it isn't necessary. is [9:00, 10:00] equal to [9:00, 10:00). again no. are their lengths equal? yes. i believe introducing all the interval types is the only solution that's going to cover all the exotic cases, present and future. regards, al Stephen Colebourne wrote: > In case anyone is wondering, I've been trying to tidy up loose ends to > finally get this out. > > The first loose end was the 'find next' concept. This sounded easy, but > is in fact very hard. The problem is with DST shifts, where the same > time appears twice in quick succession. For now, I've shelved this work. > > The second loose end is trying to work out if a previous bug fix for > empty intervals was valid. Are there any mathematicians present? > > > Consider an interval from 09:00 to 10:00. Its half-open - [09:00,10:00). > > Does this interval contain an empty interval [09:00,09:00) ? > Does this interval abut an empty interval [09:00,09:00) ? > Does this interval overlap an empty interval [09:00,09:00) ? > > As far as I can tell, there is no 'right' answer to this as an empty > interval is rather ill-defined. Do you consider it as a point on the > timeline (thus it is contained and abuts). Or do you consider it as > starting at and excluding 09:00 (thus it is not contained as it excludes > 09:00, but does abut) > > Any of this make any sense? Anyone know interval theory? > > Stephen > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Joda-interest mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/joda-interest > > Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Joda-interest mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/joda-interest
