D Recurrences

[Timon Gehr]

Steve Schveighoffer wrote:
> On Thu, 09 Jun 2011 14:45:49 -0400, Andrej Mitrovic
> <andrej.mitrovich at gmail.com> wrote:
>
> > I never understood why it's called "open" interval. What does it 'open'?
>
> Look at the terminology section of
> http://en.wikipedia.org/wiki/Interval_(mathematics)
>
> No clue as to the "why" :)
>
> -Steve

Actually it does not make too much sense to use the terms open or closed on
integer intervals in a strict mathematical sense. If your universe is the
integers, all subsets of the integers are neither open nor closed, with the
exception of the empty set and the set of all integers, which are both open and
closed. :o)


Timon