Lazy vs eager evaluation and double linked list building

Question

I can't sleep! :)

I've written small program building double linked list in Haskell. The basic language's property to make it was lazy evaluation (see the bunch of code below). And my question is can I do the same in a pure functional language with eager evaluation or not? In any case, what properties eager functional language must have to be able to build such structure (impurity?)?

import Data.List

data DLList a = DLNull |
    DLNode { prev :: DLList a
           , x :: a
           , next :: DLList a
           }
  deriving (Show)

walkDLList :: (DLList a -> DLList a) -> DLList a -> [a]
walkDLList _ DLNull = []
walkDLList f n@(DLNode _ x _)  = x : walkDLList f (f n)

-- Returns first and last items.
makeDLList :: [a] -> (DLList a, DLList a)
makeDLList xs = let (first, last) = step DLNull xs in (first, last)
  where
    step prev [] = (DLNull, prev)
                         -- Here I use laziness. 'next' is not built yet, it's a thunk.
    step prev (x : xs) = let this = DLNode prev x next 
                             (next, last) = step this xs
                         in (this, last)

testList :: [Int] -> IO ()
testList l = let
    (first, last) = makeDLList l
    byNext = walkDLList next first
    byPrev = walkDLList prev last
  in do
    putStrLn $ "Testing: " ++ show l
    print byNext
    print byPrev

main = do
  testList []
  testList [1, 2, 3, 4]

Answer 1

A doubly-linked list can be implemented in a purely functional way in an eager language as a zipper on a singly-linked list. See, for example, Rosetta Code > Doubly-linked list > OCaml > Functional.

Answer 2

As long as a language has something like closures, lambdas etc. you can always simulate lazyness. You could rewrite that code even in Java (without mutating variables etc), you just need to wrap every "lazy" operation in something like

interface Thunk<A> {
   A eval();  
}

Of course this would look terrible, but it is possible.