Comparator that compares lists lexicographically.

lexicographicOrder.kt

/**
 * Returns a comparator that compares lists _lexicographically_ using the given [elementComparator].
 */
internal fun <T> lexicographicOrder(elementComparator: Comparator<T>): Comparator<List<T>> =
    object : Comparator<List<T>> {
        override fun compare(listA: List<T>, listB: List<T>): Int {
            val iteratorA = listA.iterator()
            val iteratorB = listB.iterator()
            while (iteratorA.hasNext() && iteratorB.hasNext()) {
                val elementA = iteratorA.next()
                val elementB = iteratorB.next()
                val ordering = elementComparator.compare(elementA, elementB)
                if (ordering != 0) {
                    return ordering
                }
            }
            return listA.size compareTo listB.size
        }
    }

/** Returns a comparator that compares lists _lexicographically_. */
internal fun <T : Comparable<T>> lexicographicOrder(): Comparator<List<T>> =
    lexicographicOrder(naturalOrder())