Issue 260 - [Typed objects] Implement type inheritance

lib/typedObjects.js

Index: lib/typedObjects.js
===================================================================
--- a/lib/typedObjects.js
+++ b/lib/typedObjects.js
@@ -53,16 +53,50 @@
  * ---------------------------
  *
  *    var point = Point2D(5, 10);
  *    point.rotate(10);
  *    Console.log(point.x + ", " + point.y);
  *
  * The parameters 5 and 10 will be passed to the constructor function defined
  * for this type.
+ *
+ * Type inheritance
+ * ----------------
+ *
+ *    var Point3D = Point2D.extend({
+ *      z: uint32
+ *    }, {
+ *      constructor: function(super_, x, y, z)
+ *      {
+ *        super_(x, y);
+ *        ...
+ *      }
+ *    });
+ *
+ * Extended types can be used wherever their base type is required. The
+ * parameters taken by type.extend() are the same as parameters of
+ * new ObjectType(), the only difference is that properties and methods
+ * of the original type are taken over. Methods and constructors can be
+ * overwritten, they will then get superclass method/constructor as the first
+ * parameter and can call it.
+ *
+ * Common object methods
+ * ---------------------
+ *
+ * All objects inherit from ObjectBase type implicitly and share its methods.
+ * In particular, object.equals() can be used to compare objects:
+ *
+ *    var point1 = Point2D(5, 10);
+ *    var point2 = Point2D(6, 12);
+ *    console.log(point1.equals(point2)); // false
+ *    console.log(point1.equals(point1)); // true
+ *
+ * Note that JavaScript comparison operators == and != won't always produce
+ * correct results for typed objects.
  */
 
 function forwardExports(module)
 {
   let moduleExports = require(module);
   for (let key in moduleExports)
     exports[key] = moduleExports[key];
 }