==== Haskell ==== data Option a = None | Some a ys = [fn x | x <- xs] where fn x = let h = if is_first_page x then generate_header else None b = generate_body x f = if is_last_page x then generate_footer else None in (h, b, f)
==== Python ==== ys = (Document.new(h,b,f) for x in xs for h in [generate_header() if x.is_first_page else None] for b in [generate_body(x)] for f in [generate_footer() if x.is_last_page else None])
