Question

Find the error(s) in the following code: class mystery //Line 1 \\{ friend operator+(mystery); //Line 2 //overload binary + . . . };

Short answer

The class keyword should be capitalized.

Step-by-step solution

Error 1: Incorrect Class Declaration

The class declaration should begin with a capital letter 'class' in C++. On line 1, the code incorrectly uses lowercase 'class.'

Key concepts

C++ Syntax

Understanding C++ syntax is the foundation of becoming proficient in C++ programming. Syntax refers to the set of rules that defines the combinations of symbols that are considered to be a correctly structured program in a given language.

In C++, a class declaration should always start with the capitalized keyword `class`, followed by the class name. This is crucial, as lowercase `class` would lead to a compilation error. For example, the statement should be written as:

• class Mystery { ... };

Other fundamental syntax rules include ending statements with a semicolon and correctly matching braces for class and function bodies. Proper use of syntax ensures that your C++ code is readable and understandable to the compiler. Therefore, always pay close attention to these details when writing or reviewing C++ code.

Friend Functions in C++

Friend functions in C++ provide a way to access private and protected members of a class from outside the class. Normally, private members of a class cannot be accessed directly from outside functions or other classes.

To declare a friend function, you use the keyword `friend` within the class, placed before the function declaration. This grants the function special access privileges. However, friend functions are not part of the class' own member functions, and therefore, have some unique characteristics:

• Friend functions are not called using the object of the class.
• They can be declared in any part of the class, private or public.
• Friend functions typically operate on two or more objects.

Use friend functions when you want an external function to have the privilege of accessing the internals of a class without being a member of that class. This can be beneficial for operator overloading and when requiring access to multiple class instances at once.

Operator Overloading in C++

Operator overloading allows C++ operators to be redefined and used where one or both of the operands is of a user-defined class. This enhances the ability of objects to behave like built-in types, making the class easier to use and more intuitive.

Operators can be overloaded as member functions or non-member functions. If overloading through a member function, the left-hand operand must be an object of the class. Overloading operators as global functions, often requires making them friends of the class. Here are a few important aspects to consider:

• Not all operators can be overloaded, such as ::, ?, and sizeof.
• The syntax for a friend function operator overload involves the `friend` keyword followed by the operator keyword and function parameters.
• To overload the binary `+` operator, the function should accept more than one argument, representing both operands.

In the code from the exercise, the friend function operator overloading syntax is incorrect, as the operator function lacks a return type and needs parameters to accept operands. Operator overloading can make your code more intuitive and the operations performed on classes simpler, which is helpful in code maintenance and readability.