Map sorting by index

[Varia]

@Wasabi375

As you might have noticed there are a few areas where the documentation of the kotlin stdlib is not perfect. I guess this is one of them

Actually, this behavior is documented. The documentation states that toSortedMap returns a java.util.SortedMap. Since that is not part of the Kotlin Standard Library, it links to the Java documentation, which tends to be quite comprehensive. In particular:

Note that the ordering maintained by a sorted map (whether or not an explicit comparator is provided) must be consistent with equals if the sorted map is to correctly implement the Map interface. (See the Comparable interface or Comparator interface for a precise definition of consistent with equals .) This is so because the Map interface is defined in terms of the equals operation, but a sorted map performs all key comparisons using its compareTo (or compare ) method, so two keys that are deemed equal by this method are, from the standpoint of the sorted map, equal. The behavior of a tree map is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.