Enums

Enums

An enum (short for enumeration) turns a set of choices into named values for a variable. Instead of remembering which number stood for "LSpeed" or "High", you name them.

Introducing an enum

#include <iostream>
using namespace std;

enum Level {
  LOW,
  MEDIUM,
  HIGH
};

• enum starts the definition.
• Level is the name of the new type.
• LOW, MEDIUM, HIGH are the named values (enumerators).

Declaring an enum variable

int main() {
  Level myLevel = MEDIUM;
  // ...
  return 0;
}

myLevel can be any of the three values, and you can compare it later.

Switching on an enum

int main() {
  Level myLevel = MEDIUM;

  switch (myLevel) {
    case 0:
      cout << "Low Level" << endl;
      break;
    case 1:
      cout << "Medium Level" << endl;
      break;
    case 2:
      cout << "High Level" << endl;
      break;
  }
  return 0;
}

The default numbering

Unless you say otherwise, enumerators get the numbers 0, 1, 2, ... in the order you list them. So LOW = 0, MEDIUM = 1, HIGH = 2.

Explicit values

You can assign the numbers yourself:

enum Level {
  LOW = 25,
  MEDIUM = 50,
  HIGH = 75
};

Pick explicit numbers when the values must line up with data or settings from somewhere else.

TL;DR

• enum Name { value1, value2, ... }; defines a named set of values.
• Enumerators default to 0, 1, 2, ... in the order you list them.
• Use it in a switch, in comparisons, and in functions.
• You can override numbers by hand: LOW = 25.
• Enums turn magic numbers into readable names.