/** Visitor class for composite IntList ::= EmptyIntList | ConsIntList(int, IntList) */
interface IntListVisitor {
  Object forEmptyIntList(EmptyIntList host);  /* abstract modifier is implicit */
  Object forConsIntList(ConsIntList host);    /* abstract modifier is implicit */                 
}

class InsertVisitor implements IntListVisitor {
  int elt;
  IntList forEmptyIntList(EmptyIntList host) { return host.cons(elt); }
  IntList forConsIntList(ConsIntList host) {
    if (elt <= host.first()) return host.cons(elt);
    IntList insertedRest = (IntList) host.rest().accept(this);
    return insertedRest.cons(host.first());
  }                      
}

class SortVisitor implements IntListVisitor {
  static SortVisitor ONLY = new SortVisitor();
  private SortVisitor() { }
  IntList forEmptyIntList(EmptyIntList host) { return host; }
  IntList forConsIntList(ConsIntList host) {
    IntList sortedRest = (IntList) host.rest().accept(this);
    return (IntList) sortedRest.accept(new InsertVisitor(host.first()));
  }
}
 
class MaxVisitor implements IntListVisitor {
  static IntListVisitor ONLY = new MaxVisitor();
  private MaxVisitor() { }
  Integer forEmptyIntList(EmptyIntList host) { 
    throw new IllegalArgumentException("max cannot be applied to the EmptyIntList"); 
  }
  Integer forConsIntList(ConsIntList host) { 
    if (host.rest().equals(EmptyIntList.ONLY)) return host.first();
    return Math.max(host.first(), (Integer)(host.rest().accept(this))); }
}