min< T> function
Returns the minimum value in i, according to the order specified by the
compare function, or null if i is empty.
The compare function must act as a Comparator. If compare is omitted,
Comparable.compare is used. If i contains null elements, an exception
will be thrown.
Implementation
T min<T>(Iterable<T> i, [Comparator<T> compare]) {
if (i.isEmpty) return null;
final Comparator<T> _compare = compare ?? Comparable.compare;
return i.isEmpty ? null : i.reduce((a, b) => _compare(a, b) < 0 ? a : b);
}