11 -> 10(-1)

gistfile1.hs

trans2NegForm :: Integer -> [Int]
trans2NegForm x = loop x "init" []
    where
        trans 0 "init" = (0, "init")
        trans 1 "init" = (-1, "trans")
        trans 1 "trans" = (0, "trans")
        trans 0 "trans" = (1, "init")
        loop 0 "trans" ans = 1:ans
        loop 0 "init" ans = ans
        loop i status ans = loop (i `shiftR` 1) newStatus (newBit:ans)
            where (newBit, newStatus) = trans (i .&. 1) status