[Haskell-cafe] How to devide matrix into small blocks

[Henning Thielemann]

On Wed, 13 Jun 2007, L.Guo wrote:

> I already have one matrix of type [[a]] to store one image.
>
> What I want to do is to devide the image into severial small blocks in same size.
>
> To do that, I wrote this tool function.
>
> chop      :: Int -> [a] -> [[a]]
> chop _ [] = []
> chop n ls = take n ls : chop n (drop n ls)

I assume that it is more efficient to use 'splitAt' instead of 'take' and
'drop'.

> But I do not know how to use it to write the function.

chop blockHeight (map (chop blockWidth) image)