I'm stymied trying to figure out why the program below blows up with <<<loop>>> when I use "f 0" for building the array, but if I substitute g or h in place of f, they work fine. Is this a bug or am I overlooking something? I am using GHC 7.4.2. Thanks, Alex P.S. Forgive the seemingly pointless program; I distilled this test from a longer actual program that was exhibiting this behavior. -------- import Data.Array((!),Array,elems,listArray) import Data.List(intercalate) solve = let a :: Array Int Int a = listArray (0, 3) (0 : f 0) f k = if k > 0 then f (a!0) else 0 : f 1 g k = k : a!(k+1) : a!(k+1) : a!(k+2) : a!(k+3) : [] h k = a!k : h (k+1) in (intercalate " " . map show . elems) a main = putStrLn solve