Interface used by types that have an intrinsic ordering.

abstract class Comparable {
  /**
   * 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:].
   */
  abstract int compareTo(Comparable 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);
}