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The sieve of eratosthenes

OCaml

(* Sieve of Eratosthenes in OCaml
 * Written by Rob Hoelz
 *)

open Arg
open List

let rec genList start stop =
    if start = stop then
        [start]
    else
        start :: (genList (start + 1) stop)

class sieve lim =
    let pri = genList 2 lim in
    object
        val mutable primes = pri
        val limit = lim
        method generate =
            let rec gen' = function
                | [] -> []
                | (h::t) ->
                    if (h * h) <= limit then
                        h :: gen' (filter (fun x -> (x mod h) <> 0) t)
                    else
                        (h::t) in
            primes <- gen' primes
        method print_primes =
            let rec print_primes' = function
                | [] -> ()
                | (h::t) -> print_int h; print_string " "; print_primes' t in
            print_primes' primes;
            print_newline ();
    end

let main =
    let argref = (ref "") in
    parse [] (fun y -> argref := y) "Syntax error";
    let s = new sieve (int_of_string !argref) in
    s#generate;
    s#print_primes;;

let _ = main

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