On Mon, Nov 02, 2009 at 11:22:00AM +0000, Jasen Betts wrote: > On 2009-10-27, Sam Mason <sam@xxxxxxxxxxxxx> wrote: > > On Tue, Oct 27, 2009 at 03:25:02PM +0000, Sam Mason wrote: > >> If the absolute value of an interval was defined to strip out all the > >> negation signs you'd get the "wrong" answers out. > > > > Oops, forgot another reason! For maths to work (n) and (-(-n)) should > > evaluate to the same value. Inverting all the signs, as negation does, > > will ensure that these semantics remain. Hum, I'm not entirely sure what I was thinking when I wrote the above. it's got nothing to do with taking absolute values! > There not requrement in mathematics that > > z be a member of the set { abs(z) , -abs(z) } > > consider the case of z=sqrt(-1) That said, I don't follow your point at all. -- Sam http://samason.me.uk/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general