package fj.demo;
import fj.F1Functions;
import fj.P1;
import static fj.data.Enumerator.naturalEnumerator;
import fj.Show;
import fj.data.Natural;
import static fj.data.Natural.*;
import fj.data.Stream;
import static fj.data.Stream.*;
import static fj.Ord.naturalOrd;
import static fj.Show.naturalShow;
import static fj.Show.streamShow;
import java.math.BigInteger;
/**
* Prints all primes less than n
*/
public class Primes2 {
// Finds primes in a given stream.
public static Stream<Natural> sieve(final Stream<Natural> xs) {
return cons(xs.head(), new P1<Stream<Natural>>() {
public Stream<Natural> _1() {
return sieve(xs.tail()._1().removeAll(F1Functions.o(naturalOrd.equal().eq(ZERO), mod.f(xs.head()))));
}
});
}
// A stream of all primes less than n.
public static Stream<Natural> primes(final Natural n) {
return sieve(forever(naturalEnumerator, natural(2).some())).takeWhile(naturalOrd.isLessThan(n));
}
public static void main(final String[] a) {
final Natural n = natural(new BigInteger(a[0])).some();
final Show<Stream<Natural>> s = streamShow(naturalShow);
s.println(primes(n));
}
}