static bool IsGood(RealNumber cand, RealNumber[] nums, bool disableIrrational)
{
var minLevel = nums.Select(n => (int)n.Type).Min();
return(cand.IsRational() ||
((int)cand.Type <= minLevel && !disableIrrational) ||
(cand.IsIrrational() && cand.Value == 0)); // TODO: make im:0 downcastable
}
