(*
Sieve of Eratosthenes.
*)

let generatePrimes limit =
    let candidates = set [ 2 .. limit ]
    let bases = [| 2 .. (limit / 2 + 1) |]

    let nonPrimes =
        bases
        |> Array.map (fun b -> set [ (b * 2) .. b .. limit ])
        |> Array.reduce (+)

    candidates - nonPrimes