Chapter 11: Problem 23

Explain why the parameter of a copy constructor must be a reference.

Short Answer

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**Answer:** The parameter of a copy constructor must be a reference to avoid an infinite loop caused by recursively calling the copy constructor, prevent unnecessary overhead, and maintain encapsulation in object-oriented programming. Using a reference allows for direct access to the existing object's memory location, ensuring that the new object is an exact copy of the original object's data.

Step by step solution

1. Definition of a copy constructor

A copy constructor is a special type of constructor in C++ that is used to create a new object as a copy of an existing object. The copy constructor initializes the new object with the values of the existing object and has the following syntax: ```cpp classname (const classname &object_to_copy); ``` Here, `classname` is the name of the class, and `object_to_copy` is a reference to the object that needs to be copied.

2. Definition of a reference

A reference in C++ is an alias for an existing variable, meaning it effectively acts as another name for the same variable. References are created using the `&` symbol and allow us to directly access the memory location of the variable they are referencing. This is particularly useful in C++ as it enables us to avoid passing large objects to functions or constructors as arguments.

3. Reason for using references in copy constructors

The parameter of a copy constructor must be a reference because it allows us to directly access the existing object's memory location, ensuring that the new object receives an exact copy of the original object's data. If we were to pass the object by value — instead of by reference — a new temporary object would be created, leading the copy constructor to be called recursively. This would lead to a never-ending chain of object creations that would ultimately cause a program to crash.

4. Potential problems if not using a reference

If the parameter of a copy constructor is not a reference, the following issues may arise: - The copy constructor would be called recursively, leading to an infinite loop and eventually crashing the program. - Creating a temporary object and then passing it by value would cause unnecessary overhead and make the program slower. - Modifying the copied object would inadvertently modify the original object, violating the concept of encapsulation in object-oriented programming. In summary, using a reference as a parameter in a copy constructor is essential to prevent program crashes, maintain encapsulation, and ensure that the new object is a true copy of the original object.

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Explain why the parameter of a copy constructor must be a reference.

Short Answer

Step by step solution

1. Definition of a copy constructor

2. Definition of a reference

3. Reason for using references in copy constructors

4. Potential problems if not using a reference

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