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Motion 7 NaI

hi
  here I propose the next motion:

Motion 7: NaI}


P 1788 provides a unique NaI (Not an Interval)-datum for each
abstract interval format.
The datum indicates that the construction of an interval did not  produce an
$\mathbb{F}$ interval.
It propagates through all interval operations. If at least
one of the operands is NaI, so is the result. All comparisons with NaI are
evaluated to false, with one exception, the result of isNaI(NaI) is true.
 NaI,
however, is never returned by an operation on $\mathbb{F}$ intervals.

motion text and rationale appended

cheers Juergen
--
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      o          Prof. Dr. J. Wolff v. Gudenberg,  Informatik 2
     / \         Univ. Wuerzburg,  Am Hubland,   D-97074 Wuerzburg
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