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| Copy constructors |  The easy way to program object copying is via copy constructors. 
                      A copy constructor takes a single parameter of the same type
                      as the surrounding class.  | 
 It is sometimes useful to have a constructor that creates an identical copy of an existing object  | 
 The use of copy constructors is particularly useful when we deal with mutable objects  | 
 Read more about Copy constructors in the text book version of this material.  |