BitSeq.hs

module BitSeq where

merge :: Int -> [a] -> [a] -> [a]
merge n xs ys = goXs n xs
  where
    goXs 0 zs     = goYs n ys zs
    goXs m (z:zs) = z:goXs (m - 1) zs
    goXs _ []     = error "unreachable"

    goYs 0 zs     r = merge (n + 1) r zs
    goYs m (z:zs) r = z:goYs (m - 1) zs r
    goYs _ []     _ = error "unreachable"

-- | 
--
-- >>> take 10 ns
-- [[],[0],[1],[0,0],[0,1],[1,0],[1,1],[0,0,0],[0,0,1],[0,1,0]]
--
ns :: [[Int]]
ns = let l = []:merge 1 [0:xs | xs <- l] [1:xs | xs <- l] in l