On 05/03/07, Jon Harrop <jon@ffconsultancy.com> wrote:
> # let rec transpose list =
>     try map hd list :: transpose (map tl list) with _ -> [];;

Here is a slightly different version that raises an exception if the
given list is not quadratic:

let rec transpose xs =
  if for_all ((=) []) xs then [] else
    map hd xs :: transpose (map tl xs);;

-- 
http://www.lix.polytechnique.fr/~zumkeller/