// A simple Demeter/Java program for computing averages

// traversal function
// unfortunately we have to commit to specific visitors and
// their types. But the benefit is that we can use the calling
// mechanism of Java to attach context objects to calls.
Container {
  traversal allWeights(
    CountingVisitor cV, 
    SummingVisitor sV, 
    AverageVisitor aV) {
    to Weight;}
// it would be nicer if we could write:
//  traversal allWeights(
//    AverageVisitor aV) {
//    to Weight;}
// assuming aV contains a cV and a sV.

  (@
// traverse while counting and summing
  float statistics() throws Exception {
    // adaptive specification of objects using parsing
    CountingVisitor cV = CountingVisitor.parse("0");
    SummingVisitor sV = SummingVisitor.parse("0");
    AverageVisitor aV = new AverageVisitor(cV,sV,new Float(0.0));
    this.allWeights(cV,sV,aV);
    // better this.allWeights(aV);
    return aV.get_current().floatValue();
  }
  @)
}
SummingVisitor {
  before Weight (@ System.out.println("sum"); total = new 
    Integer(total.intValue() + host.get_i().intValue()); @)
}
CountingVisitor {
  before Weight (@ System.out.println("count");
	      total = new Integer(total.intValue() + 1); @)
}

AverageVisitor {
  (@
    void update() { current = new Float(
      (float) this.get_sV().get_total().intValue()/
         (float) this.get_cV().get_total().intValue());
      System.out.println(current.floatValue() + " = partial result");
	 } ;
  @)
  before Weight (@ update(); @)
}


Main {
(@
  static public void main(String args[]) throws Exception {

    Runtime rt = Runtime.getRuntime();
    rt.traceMethodCalls(true);

    Container a = Container.parse(System.in);

    float r = a.statistics();

    System.out.println("done " + r);
  }
@)
}