Navigate from a node to its first child or return Option.none if the zipper is focused on a leaf.
Option.none
See head for an unsafe version.
This is like rewind except it will descend one tree level.
The underlying type of the tree.
An updated zipper pointing at a new focus or Option.none() if there is no first child.
Option.none()
Navigate from a node to its first child or return
Option.noneif the zipper is focused on a leaf.See head for an unsafe version.
This is like rewind except it will descend one tree level.