Re: Range Types: empty ranges

Jan Wieck <JanWieck@Yahoo.com> wrote:
> Does ['15:15:00','15:15:00') make any more sense? Doesn't this 
> essentially mean
> 
>      >= '15:15:00' && < '15:15:00'
> 
> which again doesn't include a single point on the time line?
It defines a position in time with zero duration.
Some of the graphics programming I've done in the past was based on
a system where, at the pixel level, the coordinates referred to the
boundaries *between* the pixels.  If you were to have a number of
horizontal bars, for example, the size of which you would adjust to
represent fluctuating data, you might have an x coordinate of 20 for
the left edge, and [20,30) would paint 10 pixels.  I guess you
*could* destroy and recreate the object when the number dropped to
zero and came off it again; but the concept of [20,20) to draw zero
pixels but maintain the positional anchor can be convenient.  I see
parallel concepts for some data domains in a database.
-Kevin