Interface used by types that have an intrinsic ordering.

abstract class Comparable<T> {
 /**
  * Compares this object to another [Comparable]
  *
  * Returns a value like a [Comparator] when comparing [:this:] to [other].
  *
  * May throw an [ArgumentError] if [other] is of a type that
  * is not comparable to [:this:].
  */
 int compareTo(T other);

 /**
  * Compare one comparable to another.
  *
  * This utility function is used as the default comparator
  * for the [List] sort function.
  */
 static int compare(Comparable a, Comparable b) => a.compareTo(b);
}