Untitled

Can a thunk be duplicated to improve memory performance?
let xs = [1..10000000]

bad = do
    print $ foldl1' (+) xs
    print $ length xs

good = do
    (xs1,xs2) <- copyThunk xs
    print $ foldl1' (+) xs1
    print $ length xs2

xsFunction :: () -> [Int]
xsFunction = const [1..10000000]

better = do
  print $ foldl1' (+) $ xsFunction ()
  print $ length $ xsFunction ()

let xs () = [1..1000000]

good = do
    print $ foldl1' (+) (xs ())
    print $ length (xs ())