Solution.nim

#[
    # Driver code in the solution file
    # Definition for singly-linked list.
    type
    Node[int] = ref object
        value: int
        next: Node[int]

    SinglyLinkedList[T] = object
        head, tail: Node[T]
]#

# More efficient code churning ...
proc addTwoNumbers(l1: var SinglyLinkedList, l2: var SinglyLinkedList): SinglyLinkedList[int] =
  var
    aggregate: SinglyLinkedList
    psum: seq[char]
    temp_la, temp_lb: seq[int]

  while not l1.head.isNil:
    temp_la.add(l1.head.value)
    l1.head = l1.head.next

  while not l2.head.isNil:
    temp_lb.add(l2.head.value)
    l2.head = l2.head.next

  psum = reversed($(reversed(temp_la).join("").parseInt() + reversed(temp_lb).join("").parseInt()))
  for i in psum: aggregate.append(($i).parseInt())

  result = aggregate