For the following messages, map stands for an associative array or a reference to one.
Returns the first key within map, or Empty() if map has no keys. Note that keys are returned in lexicographical order.
Returns the implicit value of all absent keys, or Empty() if none has been set.
If no argument is provided, a list of all values within map is returned.
Returns the key following the given key within the map, or Empty() if map has no keys. Note that keys are returned in lexicographical order.