Adds the given object as a left child of the specified parent.
If the parent already had a left child the link to that node
(and possibly many others) is lost.
Adds the given tree as the left subtree of the specified parent.
If the parent already had a left child the link to that node
(and possibly many others) is lost.
Adds the given object as a right child of the specified parent.
If the parent already had a right child the link to that node
(and possibly many others) is lost.
Adds the given tree as the right subtree of the specified parent.
If the parent already had a right child the link to that node
(and possibly many others) is lost.