Added decorator example.

README.md

@@ -1228,7 +1228,131 @@ classes with unique areas of concern.
 
 #### Programmatic Example
 
-TODO
+Lets take coffee for example. First of all we have a simple coffee implementing
+the coffee class
+
+```cpp
+class Coffee
+{
+  public:
+    typedef std::shared_ptr<Coffee> ptr_t;
+    virtual float getPrice(void) = 0;
+    virtual std::string getDescription(void) = 0;
+};
+
+class SimpleCoffee : public Coffee
+{
+  public:
+    float getPrice(void)
+    {
+      return 3;
+    }
+
+    std::string getDescription(void)
+    {
+      return "Simple coffee";
+    }
+};
+```
+
+We want to make the code extensible to allow options to modify it if required.
+Lets make some add-ons (decorators)
+
+```cpp
+class MilkCoffee : public Coffee
+{
+  public:
+    MilkCoffee(Coffee::ptr_t coffee)
+        : coffee_(coffee)
+    {
+    }
+
+    float getPrice(void)
+    {
+      return coffee_->getPrice() + 0.5;
+    }
+
+    std::string getDescription(void)
+    {
+      return coffee_->getDescription() + ", milk";
+    }
+
+  private:
+    Coffee::ptr_t coffee_;
+};
+
+class WhipCoffee : public Coffee
+{
+  public:
+    WhipCoffee(Coffee::ptr_t coffee)
+        : coffee_(coffee)
+    {
+    }
+
+    float getPrice(void)
+    {
+      return coffee_->getPrice() + 2;
+    }
+
+    std::string getDescription(void)
+    {
+      return coffee_->getDescription() + ", whip";
+    }
+
+  private:
+    Coffee::ptr_t coffee_;
+};
+
+class VanillaCoffee : public Coffee
+{
+  public:
+    VanillaCoffee(Coffee::ptr_t coffee)
+        : coffee_(coffee)
+    {
+    }
+
+    float getPrice(void)
+    {
+      return coffee_->getPrice() + 1;
+    }
+
+    std::string getDescription(void)
+    {
+      return coffee_->getDescription() + ", vanilla";
+    }
+
+  private:
+    Coffee::ptr_t coffee_;
+};
+```
+
+Here is how this can be used:
+
+```cpp
+Coffee::ptr_t simple = std::make_shared<SimpleCoffee>();
+// Output: 3
+std::cout << simple->getPrice() << std::endl;
+// Output: Simple coffee
+std::cout << simple->getDescription() << std::endl;
+
+Coffee::ptr_t milk = std::make_shared<MilkCoffee>(simple);
+// Output: 3.5
+std::cout << milk->getPrice() << std::endl;
+// Output: Simple coffee, milk
+std::cout << milk->getDescription() << std::endl;
+
+Coffee::ptr_t whip = std::make_shared<WhipCoffee>(milk);
+// Output: 5.5
+std::cout << whip->getPrice() << std::endl;
+// Output: Simple coffee, milk, whip
+std::cout << whip->getDescription() << std::endl;
+
+Coffee::ptr_t vanilla = std::make_shared<VanillaCoffee>(whip);
+// Output: 6.5
+std::cout << vanilla->getPrice() << std::endl;
+// Output: Simple coffee, milk, whip, vanilla
+std::cout << vanilla->getDescription() << std::endl;
+```
 
 #### When To Use