Enums

Enumerations (enum) allow defining a set of named values. By default, each value takes a consecutive integer starting from 0.

Classic enum

enum Color { RED, GREEN, BLUE }; // RED=0, GREEN=1, BLUE=2
enum Day { MONDAY=1, TUESDAY=2, WEDNESDAY=3 }; // MONDAY=1, TUESDAY=2, WEDNESDAY=3
Color background = RED;

Note

enum values automatically take consecutive integers (0, 1, 2, …), but you can assign them explicit values like in Day.

enum class (C++11)

enum class is the recommended form in modern C++: its values live in their own scope and are not implicitly converted to integers.

enum class Color { RED, GREEN, BLUE };
enum class NewColor { RED, GREEN }; // Names can be repeated without conflict
 
Color c = Color::RED; // The Color:: prefix must be used

Warning

Unlike the classic enum, enum class is not implicitly converted to int. If you need the number, do an explicit cast: static_cast<int>(Color::GREEN).

Note

It is advisable to use enum class to avoid name conflicts between multiple enums and to avoid accidental implicit conversions to integer.

Using the integer value

int value = static_cast<int>(Color::BLUE); // Explicitly converts to int

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