adding a multiple level inheritance example

lectures/26_inheritance/README.md

@@ -180,12 +180,14 @@ Create a class hierarchy of geometric objects, such as: triangle, isosceles tria
 rhombus, kite, trapezoid, circle, ellipse, etc. How should this hierarchy be arranged? What member variables and
 member functions should be in each class?
 
-## 26.10 Note: Multiple Inheritance
+## 26.10 Multiple Inheritance
 
 - When sketching a class hierarchy for geometric objects, you may have wanted to specify relationships that were more complex... in particular some objects may wish to inherit from more than one base class.
 - This is called multiple inheritance and can make many implementation details significantly more hairy. Different programming languages offer different variations of multiple inheritance.
 - See [example 1](multiple_inheritance1.cpp) and [example 2](multiple_inheritance2.cpp).
 
+- And see [example 3](multiple_level_inheritance.cpp) for a multiple level inheritance example.
+
 ## 26.11 Introduction to Polymorphism
 
 - Let’s consider a small class hierarchy version of polygonal objects:

lectures/26_inheritance/multiple_level_inheritance.cpp

@@ -1,3 +1,7 @@
+#include <iostream>
+
+// multiple-level inheritance
+
 class A
 {
 public:
@@ -20,9 +24,15 @@ public:
 class D:public C
 {
 public:
+	D(int a, int b, int c, int d):C(a,b,c),d(d){}
+	void print(){
+		std::cout << a << ":" << b << ":" << c << ":" << d << std::endl;
+	}
 	int d;
 };
 
 int main(){
+	D dObject(1,2,3,4);
+	dObject.print();
 	return 0;
 }