Thanks - it does now make sense, but since (mercifully!) time is only 1-dimensional, I find the span suggestion more intuitive.
Paul PS This explanation could usefully be added to the interval library documentation. I was puzzled why the word 'hull' was used. | -----Original Message----- | From: [EMAIL PROTECTED] | [mailto:[EMAIL PROTECTED] Behalf Of Guillaume Melquiond | Sent: Monday, August 18, 2003 8:36 AM | To: Boost mailing list | Subject: RE: [boost] Re: Date iterators in Boost Date-Time | | | En réponse à "Paul A. Bristow" <[EMAIL PROTECTED]>: | | > But as Michael Caine said "Not a lot of people know that" - so I trust | > you will explain what it does too for the benefit of us mere | non-mathematical | > mortals! | > | > Paul | | I'm not sure to understand. Do you want me to explain what a convex hull is or | to explain what the function of the date-time library is supposed to do? I | suppose it's the first, since the second is what started this subthread. | | A connected set is a set for which each couple of points are | connected by a path | itself included in the set (all the points are reachable from all the | points). A | convex set is a connected set with linear paths (all the points can be reached | from all the other points by following a segment). The convex hull of a set is | the smallest convex superset of it. For example, given three points in the | plane, the convex hull is the filled triangle defined by these points. | | In the case of a 1-dimension space, connected and convex set are equals: they | are segments (or half-line or line or empty). Date manipulated by the | date-time | library are in a 1-dimension space (the real line) and periods are segments | (non-empty bounded convex sets). So when you have two periods, the smallest | period enclosing these two is also the convex hull of them. Hence the name I | suggested. | | I hope it makes sense. | | Regards, | | Guillaume | _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
