abstract class polygon {
    abstract function printCharacteristic();
  }

  class rectangle extends polygon {
    function printCharacteristic() {
      print("All my angles are 90 degrees and my opposite sides are equal");
    }
  }
  class square extends polygon {
    function printCharacteristic() {
      print("All my angles are 90 degrees and all my sides are equal");
    }
  }

  var shape1 : polygon = new rectangle;
  var shape2 : polygon = new square;

  shape1.printCharacteristics();
  shape2.printCharacteristics();

  All my angles are 90 degrees and my opposite sides are equal
  All my angles are 90 degrees and all my sides are equal

People who read this tip also read these tips:

• Calling Web Services from JavaScript
• Using "*/*" to Match Grandchildren in DOMDocument
• The Object Class
• Calling the EchoFloat Web Service
• Playing with the StockQuote Web Service