Navigate from a node to its Nth child or return Option.none if it has no
Nth child.
Negative indexes are handled as offsets from the final tree in the forest so
that focusing on index -1 focuses on the last tree in the forest, -2 on
the tree before that and so on.
Navigate from a node to its Nth child or return
Option.noneif it has no Nth child.Negative indexes are handled as offsets from the final tree in the forest so that focusing on index
-1focuses on the last tree in the forest,-2on the tree before that and so on.See at for an unsafe version.
Type Param: A
The underlying type of the tree.
Param: self
The zipper that will be navigated.
Param: n
Index of child that will be the new zipper focus.
Returns
An updated zipper pointing at a new focus or
Option.none()if the node is a leaf or the given index is out-of-bounds.