[std-interval] csets

[Ray Moore]

John and all,

The one thing that bothers me about the cset approach is 
returning a result like [0, 1] when feeding the argument 
[-4, 1] to the square root function. I mean there is a very useful extension of the square root function to complex values, for which the result would be something else, like
[0, 1] U [-2, 2] i.

I understand the difficulty of allowing complex values. To make it complete would be another huge project on top of all that is already underway.

However, otherwise it will necessary to explain the restriction to real results. Furthermore, things like
(sqrt [-4, 1])^4 would produce [0, 1] without including complex numbers, whereas it should produce [0, 16]
with complex numbers allowed. 

What is the proposal for dealing with such concerns ?

Ray Moore
 
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