ChunkGroupBy.hs

-- > chunkGroupBy (\x y -> x == y) 6 [0,0,0,0,1,1,1,2,2,2,2,2,3,3,3,3]
-- [[[0,0,0,0]],[[1,1,1]],[[2,2,2,2,2]],[[3,3,3,3]]]
--
-- > chunkGroupBy (\x y -> x == y) 7 [0,0,0,0,1,1,1,2,2,2,2,2,3,3,3,3]
-- [[[0,0,0,0],[1,1,1]],[[2,2,2,2,2]],[[3,3,3,3]]]
--
-- > chunkGroupBy (\x y -> x == y) 15 [0,0,0,0,1,1,1,2,2,2,2,2,3,3,3,3]
-- [[[0,0,0,0],[1,1,1],[2,2,2,2,2]],[[3,3,3,3]]]
--
-- > chunkGroupBy (\x y -> x == y) 16 [0,0,0,0,1,1,1,2,2,2,2,2,3,3,3,3]
-- [[[0,0,0,0],[1,1,1],[2,2,2,2,2],[3,3,3,3]]]
--
chunkGroupBy :: (Num n, Ord n) => (a -> a -> Bool) -> n -> [a] -> [[[a]]]
chunkGroupBy eq n as = chunk $ groupBy eq as
  where
    chunk [] = []
    chunk (x:xs) = (x:ys):chunk zs
      where (ys,zs) = spanOrd (len x) xs
    spanOrd _   xs@[] = (xs,xs)
    spanOrd cnt xs@(x:xs')
        | cnt' <= n = let (ys,zs) = spanOrd cnt' xs' in (x:ys,zs)
        | otherwise = ([],xs)
      where cnt' = cnt + len x
    len = genericLength