compareTo method
Compares two DoubleDouble objects numerically.
@return -1,0 or 1 depending on whether this value is less than, equal to or greater than the value of o
Implementation
int compareTo(dynamic o) {
DD other = o;
if (hi < other.hi) return -1;
if (hi > other.hi) return 1;
if (lo < other.lo) return -1;
if (lo > other.lo) return 1;
return 0;
}