Use enumerations to represent sets of related named constants

Reason

An enumeration shows the enumerators to be related and can be a named type.

Example

enum class Web_color { red = 0xFF0000, green = 0x00FF00, blue = 0x0000FF };

Note

Switching on an enumeration is common and the compiler can warn against unusual patterns of case labels. For example:

enum class Product_info { red = 0, purple = 1, blue = 2 };

void print(Product_info inf)
{
    switch (inf) {
    case Product_info::red: cout << "red"; break;
    case Product_info::purple: cout << "purple"; break;
    }
}

Such off-by-one switch-statements are often the results of an added enumerator and insufficient testing.

Enforcement

• Flag switch-statements where the cases cover most but not all enumerators of an enumeration.
• Flag switch-statements where the cases cover a few enumerators of an enumeration, but there is no default.