(* Whether there are any odd factors m of n such that m>=k.
   Requires: k>=3, n>=1 *)
fun noOddFactors(k,n) =
  k*k > n orelse n mod k <> 0 andalso noOddFactors(k+2,n)

(* Whether n is prime. Requires: n>=2 *)
fun isPrime(n) : bool =
  n = 2 orelse
  n mod 2 = 1 andalso
  noOddFactors(3,n)

fun nextPrime(n) : int =
  if isPrime(n+1) then n+1 else
    nextPrime(n+1)






(* Returns: the next number larger than p
   and indivisible by any number in l *)
fun sieve(p:int, l: int list) =
  if List.all (fn (n) => p mod n <> 0) l then p
    else sieve(p+1, l)

fun sieve_state(p:int, l:int list): int*int list =
  let val p' = sieve(p,l) in
    (p', p'::l)
  end





val s = Stream2.make((2,[2]), fn(p,l) => (p,sieve_state(p,l)));