>
> It is possible for bbox->low.x to be NaN when circle->center.x is and
> circle->radius are both +Infinity.
>
What is rationale behind this circle?
It seems to me that any circle with radius of any Infinity should become a
[-Infinity .. Infinity, -Infinity .. Infinity] box. Then you won't have
NaNs, and index structure shouldn't be broken.
If it happens because NaN > Infinity, then the check should be not for
isnan, but for if (low>high){swap(high, low)}. It probably should be a part
of box, not a part of circle, maths.
