This is a nontrivial opIndex operator on indizies of the tree. Given an index a range (!) is returned, which is,
either the range of elements in the tree build up by [predecessor(i) .. successor(i)] (i. e. excluding the
successor(i)), when the given index is not set. Or, if the given index is set, [member(i), successor(i)]. If an
index out of bounds is given, an empty array is returned. The tree must not be empty to use this function.
This is a nontrivial opIndex operator on indizies of the tree. Given an index a range (!) is returned, which is, either the range of elements in the tree build up by [predecessor(i) .. successor(i)] (i. e. excluding the successor(i)), when the given index is not set. Or, if the given index is set, [member(i), successor(i)]. If an index out of bounds is given, an empty array is returned. The tree must not be empty to use this function.