The Sift Process

The Sift  reactive process is recursively defined. First, it outputs the first value v it receives, then it adds in front of itself a process which filters all multiple of v.

public class Sift extends ReactiveProcess
{
  private Channel in, out, intern;
  private int prime;
  private boolean first = true;

  public Sift(Channel in, Channel out)
  {
    this.in    = in;
    this.out   = out;
  }

  public Sift(NrpMachine machine,String in, String out)
  {
    this.in = machine.getChannel(in);
    this.out= machine.getChannel(out);
    machine.add(this);
  }

  final public String toString(){ 
    return "sift(" + prime + "," + out + "," + in + ")";
  }

  protected byte activation(Machine machine)
  {
    if (first){
      byte b = fix(in,machine);
      if (b == TERM){
        prime = ((Integer)in.get()).intValue();
        put(out,new Integer(prime),machine);
        first = false;
        return STOP;
      }
      return b;
    }else{
      intern = ((NrpMachine)machine).newChannel();
      machine.add(new Filter(in,intern,prime));
      machine.add(new Sift(intern,out));
      return TERM;
    }
  }
}