Al Major wrote: > Garvelink, Barend wrote: >> Paraphrasing a colleague of mine: >> >> If the interval [09:00,09:00) can be considered the empty set in >> discrete maths, then >> - Every interval contains the empty interval (a set contains another >> set if it contains all the other set's elements) > > but that would imply that [11:00, 12:00) (or any other non-empty > interval) would contain [9:00, 9:00) (and _every_ other empty interval). > intuitively that doesn't sound correct.
This one is tricky: with some examples of how includes() is generally used, we can drive to a reasonable conclusion. >> - The empty interval does not overlap any other interval (two sets >> overlap if their intersection is non-empty) > > that would imply that [9:00, 9:00) does not overlap [8:00, 10:00), > which also seems intuitively wrong. Why? How can an empty interval overlap anything? The empty interval contains no instants. >> - No interval abuts the empty interval (a set abuts another set if the >> intersection of the two without the edge value is empty, and the >> intersection of the two with the edge value is non-empty) >> > > which would imply that [9:00, 9:00) does not abut [9:00, 10:00). this > seems strange though not necessarily "wrong". Again: if the empty interval contains no instants, then what can it abut? > i still think that the "real" solution requires "completing" the > interval types. Either stop empty intervals from being created, or be consistent with set theory. I'm not sure any other solution would be helpful to the masses. -- J. B. (Joe) Rainsberger :: http://www.jbrains.info Your guide to software craftsmanship JUnit Recipes: Practical Methods for Programmer Testing 2005 Gordon Pask Award for contribution Agile Software Practice 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
