Re: (long) A new proposal for midpoint et al...

[Dan Zuras Intervals <intervals08@xxxxxxxxxxxxxx>]

> Date: Wed, 29 Feb 2012 14:17:11 +0100
> From: Vincent Lefevre <vincent@xxxxxxxxxx>
> To: stds-1788@xxxxxxxxxxxxxxxxx
> Subject: Re: (long) A new proposal for midpoint et al...
> 
> On 2012-02-21 08:51:43 -0800, Dan Zuras Intervals wrote:
> > > Date: Tue, 21 Feb 2012 14:17:02 +0100
> > > From: Vincent Lefevre <vincent@xxxxxxxxxx>
> > > To: stds-1788@xxxxxxxxxxxxxxxxx
> > > Subject: Re: (long) A new proposal for midpoint et al...
> > > 
> > > . . .
> > > 
> 
> > > See my opinion above. But if you choose 0, you should use the
> > > following definition:
> > > 
> > >   wid(X) = sup_Rbar+ { a - b | a in X, b in X }.
> > 
> > 	How is that different from sup(X) - inf(X)?
> 
> sup and inf are over Rbar. If you assume that wid(X) should return a
> value in Rbar+ (the nonnegative real numbers), then the sup should be
> taken over Rbar+.
> 
> > > >
> > > > . . .
> > > >
> 
> -- 
> Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>


	Vincent,

	Of all of your comments here, I find this one to be
	potentially the most useful.  If we define the 3
	functions mag, wid, & rad as taking arguments in
	IRbar & returning results in Rbar+, I think we get
	the desired behavior on Empty without confusing the
	users.

	I'll make that change.

	Thanks,

				Dan