Making shingles

This is starting to get a little boring, it seems that all of my Haskell work consists of recombining lists and folding them, but either way yet another piece of the puzzle is now in place, I can now generate shingles


makeShingle :: [[a]]->[[a]]
makeShingle [] = []
makeShingle zs 
  | length zs >= 4 = (foldl(\acc z -> (acc ++ z)) [] (take 4 zs)) : (makeShingle $ drop 1 zs)
  | otherwise = []



makeShingle $ filter(/="") $ genericRev $ otherTok "this, is a string.  it is a string, like many other.  but i like it, i like it a lot!" standard_delim
["thisisastring","isastringit","astringitis","stringitisa","itisastring","isastringlike","astringlikemany","stringlikemanyother","likemanyotherbut","manyotherbuti","otherbutilike","butilikeit","ilikeiti","likeitilike","itilikeit","ilikeita","likeitalot"]