Untitled

type
  TDoublyLinkedListNode[T] = object
    head, tail: TDoublyLinkedListNode[T]
    value: T
  PDoublyLinkedListNode[T] = ref TDoublyLinkedListNode[T]

proc newDoublyLinkedListNode[T](value: T): PDoublyLinkedListNode[T] =
  new(result)
  result.value = value

proc fist[T](list: var PDoublyLinkedListNode[T]): PDoublyLinkedListNode[T] =
  var head = list.head
  if head:
    return head.first()
  else:
    list

proc addFirst[T](list: var PDoublyLinkedListNode[T], value: T) =
  var first = list.first
  var node = newDoublyLinkedList(value)
  node.tail = first
  first.head = node

var list: PDoublyLinkedListNode[string]
newDoublyLinkedListNode("first")
list.addFirst("before")
echo list