# Perform left rotation on `node`
#
+ # ~~~raw
# N Y
# / \ > / \
# a Y N c
# / \ < / \
# b c a b
+ # ~~~
#
protected fun rotate_left(node: N) do
var y = node.right
# Perform right rotation on `node`
#
+ # ~~~raw
# N Y
# / \ > / \
# a Y N c
# / \ < / \
# b c a b
+ # ~~~
#
protected fun rotate_right(node: N) do
var y = node.left