Reverse a linked list using mutation

linked_list_mutation.rb

class LinkedListNode
  attr_accessor :value, :next_node

  def initialize(value, next_node = nil)
    @value = value
    @next_node = next_node
  end
end

def print_values(list_node)
  print "#{list_node.value} --> "
  if list_node.next_node.nil?
    print "nil\n"
    return
  else
    print_values(list_node.next_node)
  end
end

def reverse_list(list, previous = nil)
  previous = nil
  while list
    current_node = list
    next_node = current_node.next_node
    current_node.next_node = previous
    list = next_node
    previous = current_node
  end

  current_node
end

node1 = LinkedListNode.new(37)
node2 = LinkedListNode.new(99, node1)
node3 = LinkedListNode.new(12, node2)

print_values(node3)

revlist = reverse_list(node3)

print_values(revlist)