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Re: A mid-rad interchange motion...

John Pryce wrote:

- Define an interval type to be an inf-sup or mid-rad type depending
 on its level 3 representation: An inf-sup interval type is one whose
 level 3 representation by floating-point numbers lets the lower and
 upper bound of each nonempty interval of that type be retrieved
exactly.
and
 A mid-rad interval type is one whose level 3 representation by
 floating-point numbers lets the midpoint and radius of each
 nonempty [add "bounded" here?] interval of that type be
 retrieved exactly.


John, et. al.
Interesting suggestion. In light of reading Motion 16, I began to think the same thing. 



Letting level 3 drive the definition looks perverse, but it seems to
me that's where the essence of the two kinds of type lies.
On the one hand, I don't see it is all that perverse, for the reason you mention (and in so many words we kind of do this already in Motion 14 for inf-sup intervals). On the other hand, perhaps someone can come up with Level 2 definitions? 

Nate