Question

When a member function’s body is written inside a class declaration, the function is _________.

Short answer

Answer: The term used for such a member function is "inline".

Step-by-step solution

Definition of the term

When a member function's body is written inside a class declaration, the function is said to be "inline". This means the function is automatically an inline function, and it can lead to some potential performance improvements when the compiler replaces the function calls with the function code.

Key concepts

Class Declaration

A class declaration is a blueprint for creating objects in programming. It specifies the attributes (data members) and behaviors (member functions) that the objects created from the class will have. Think of it as the architectural plan of a building; it does not construct the building but details everything about it.
In C++ programming, a class declaration establishes the structure of an object using the keyword `class` followed by the class name. Here's a simple example:

• class Car {
• public:
• int speed;
• void displaySpeed();
• };

Here, `Car` is the class name, `int speed` is an attribute, and `void displaySpeed()` is a member function. The declaration itself does not allocate memory or use resources until an object of that class is created.
The importance of a class declaration lies in defining clean, organized, and reusable code. It's like naming and defining variables and operations that will repeatedly occur in your program.

Member Function

In the context of object-oriented programming, a member function is a function that belongs to the class. It operates on the data contained within an object of the class.
Member functions are crucial because they define how data is accessed and modified by class objects. These functions are declared within the class body and can control access to the class’s attributes.
For example, within the body of a `Car` class, a member function `displaySpeed()` might be defined to display the car's speed:

• void Car::displaySpeed() {
• cout << "Speed is: " << speed;
• }

This function uses the `speed` data member of the class to print the current speed. Member functions can also be declared directly inside the class declaration, making them `inline` functions. Inline member functions are intended to improve performance by reducing the overhead of a function call.
In summary, member functions allow interactions with an object's internal state, making them integral components of a class.

Performance Improvement

One noteworthy advantage of inline functions is their potential to enhance performance. When a member function is defined directly within a class declaration, it is automatically treated as an inline function by the compiler. But what does it mean for performance?
The primary goal of inline functions is to increase the execution speed of a program. This is achieved by reducing the overhead associated with standard function calls. Typically, invoking a function involves saving the state, transferring control, and restoring the state, which can be costly.

• Inline functions replace a standard function call with a direct code substitution, minimizing overhead.
• This can lead to quicker program execution because the program no longer pauses to handle function call mechanisms.
• The caveat, however, is that excessive use of inline functions in large programs could increase the binary size (code bloat).

Keep in mind, the compiler decides whether to inline a function. Sometimes, even if declared inline, it may not execute as such due to constraints or optimizations.
In essence, inline functions are a powerful tool for performance improvement, but should be used judiciously to balance speed and code size.