(* Async workflows sample (parallel CPU and I/O tasks) *)

(* A very naive prime number detector *)
let isPrime (n:int) =
   let bound = int (System.Math.Sqrt(float n))
   seq {2 .. bound} |> Seq.exists (fun x -> n % x = 0) |> not

(* We are using async workflows *)
let primeAsync n =
    async { return (n, isPrime n) }

(* Return primes between m and n using multiple threads *)
let primes m n =
    seq {m .. n}
        |> Seq.map primeAsync
        |> Async.Parallel
        |> Async.RunSynchronously
        |> Array.filter snd
        |> Array.map fst

(* Run a test *)
primes 1000000 1002000
    |> Array.iter (printfn "%d")