main :: [sys_message]
main = [Stdout (lay [inp, show enc, dec])]
       where inp = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
             enc = rlencode inp
             dec = rldecode enc

rlencode :: [*]->[(num,*)]
rlencode xs = [(#p, hd p) | p <- chunk xs]

rldecode :: [(num,*)]->[*]
rldecode xs = concat [take n (repeat x) | (n,x) <- xs]

chunk :: [*]->[[*]]
chunk = f []
        where f acc     []     = [acc]
              f []      (a:as) = f [a] as
              f (a:acc) (a:as) = f (a:a:acc) as
              f acc     (a:as) = acc:f [a] as