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Re: An Oops! in Level 2 text

On 10/19/2012 12:06 PM, John Pryce wrote:

Vladik, P1788

Really someone should have pulled me up short about wid(xx) (width of an interval) in the Level 2 draft text.

   Shame on us.

I had written

    wid(xx) returns the same value as 2 ∗ rad(xx)

This is quite wrong, e.g. in 3-digit decimal, if xx = [.234,.235] then mid(xx), if we follow the

  roundTiesToEven rule of motion 37, will be m=.234, and rad(xx) will be .00100.
  My recipe above gives width w=.00200 but surely the only sensible result is .00100, the actual width.


So IMO the correct recipe is
    wid(xx) returns the smallest F-number ≥ the mathematical width xhi-xlo.


   That is also my opinion (speaking as an ordinary member).


Vladik: what is the Level 2 width of Empty? I would be happy with

   NaN, on the grounds that it is genuinely undefined;
or
   -oo, on the grounds that wid(xx) = (sup xx) - (inf xx), and when
        xx=Empty, one has sup xx = -oo and inf xx = +oo.



    That's a good question.  Is this one of the things that
    can't be decided purely from logical deduction?

Best regards,

Baker

--

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Ralph Baker Kearfott,   rbk@xxxxxxxxxxxxx   (337) 482-5346 (fax)
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