Sieve

/**
 * Unless overriden, any Sieve is a trivial one, letting through any element.
 * @author kuksenok
 */
public class Sieve<T> implements Function<T,Boolean>{

    @Override
    public Boolean eval(T in) {
        return true;
    }

}

/**
 * This represents a very generic function from something of the type S to something of the type T.
 * @author katie
 */
public interface Function<S,T> {
    public T eval(S in);
}