RE: Comments on decoration ill, intersection and union
Vincent Lefevre wrote:
> On 2012-12-13 16:29:52 -0600, Nathan T. Hayes wrote:
> > If we evaluate the range of the intersection of X and Y, then
> > g([0,1] intersect [2,3])
> > = g(([0,1],DAC) intersect ([2,3],DAC))
> > = g((Empty,DAC)) // Empty input!!!
> > = (Empty,DAC)
>
> But the initial input is [0,1], which is not empty ([2,3] can be
> seen as a constant or another input, depending on the context).
> One gets Empty only after the intersect operation, and since this
> is after an operation, Empty cannot be an input.
Precisely. This is why the (Empty,DAC) result is not meaningless: it may
imply the input was nonempty even though the result is empty.
Nate