import testing.*;

abstract class FamilyList {

  //To add the contents of names to this FamilyList
  abstract FamilyList append( FamilyList names );
}

class EmptyFL extends FamilyList {
  EmptyFL() { }

  //new EmptyFL().append( new EmptyFL() ) -> new EmptyFL()
  //new EmptyFL().append( new LargerFL( "Fred", new EmptyFL() ) ) ->
  //     new LargerFL( "Fred", new EmptyFL() )
  //To add the contents of names to this EmptyFL
  FamilyList append( FamilyList names ) {
    // ... names ...
    return names ;
  }
}

class LargerFL extends FamilyList {
  String front;
  FamilyList rest;

  LargerFL( String front, FamilyList rest ) {
    this.front = front;
    this.rest = rest;
  }

  //new LargerFL( "Fred", new EmptyFL() ).append( new LargerFL( "Betty", new EmptyFL()) )
  //   --> new LargerFL( "Fred", new LargerFL( "Betty", new EmptyFL() ))
  //new LargerFL( "Bob", new LargerFL("JOhn", new EmptyFL())).append( new LargerFL("Lauren", new LargerFL("Monaca", new EmptyFL()))) 
  //   --> new LargerFL( "Bob", new LargerFL( "JOhn", new LargerFL( "Lauren", new LargerFL("Monaca", new EmptyFL()))))
  //new LargerFL( "Fred", new EmptyFL()).append(new EmptyFL() ) -> new LargerFL("Fred",new EmptyFL())
  //To add the contents of names to this LargerFL
  FamilyList append( FamilyList names ) {
    // ... this.front ... this.rest.FamilyListMethod() ... names
    return new LargerFL( this.front, this.rest.append( names ) );
  }

}

class FamilyListTests extends Test {
  FamilyListTests() { }

  FamilyList mt = new EmptyFL();
  FamilyList one = new LargerFL("Sarah", this.mt);

  TestResult testAppendMT() {
    return this.compareObjects(this.mt.append(this.mt), this.mt);
  }

  TestResult testAppendMTNon() {
    return this.compareObjects(this.mt.append(this.one), this.one);
  }

  TestResult testAppendOne() {
    return this.compareObjects(this.one.append(this.mt), this.one);
  }

  TestResult testAppendOneOne() {
    return this.compareObjects(this.one.append(this.one), new LargerFL("Sarah",this.one));
  }

}