main :: [sys_message]
main = [Stdout (table 5 10 nums), Stdout countmsg]
       where nums = filter additive_prime [1..500]
             countmsg = "Found " ++ show (#nums) ++ " additive primes < 500\n"

table :: num->num->[num]->[char]
table w c ls = lay [concat (map (rjustify w . show) l) | l <- split c ls]

split :: num->[*]->[[*]]
split n ls = [ls], if #ls < n
           = take n ls:split n (drop n ls), otherwise

additive_prime :: num->bool
additive_prime n = prime (dsum n) & prime n

dsum :: num->num
dsum n = n, if n<10
       = n mod 10 + dsum (n div 10), otherwise

prime :: num->bool
prime n = n>=2 & #[d | d<-[2..entier (sqrt n)]; n mod d=0] = 0