Enums

An enumeration is a programmer-defined data type that can take on a finite set of user-specified values. The values that an enumerated type can hold are all stored as integer values. However, they are generally specified in the program by the more user-friendly names given in the type definition.

The default integer value of the first enumerated value is 0 and the value for any other is 1 more than the previous value. However, the programmer can specify any integer values that he would like, including repeated values and formulas that use prior values.

 

Examples


Example 1

// We can define an enum to represent boolean values.
// In this case, keFalse = 0 and keTrue = 1.
enum EBool {keFalse, keTrue};
// Create an instance of the type and assign it the value keTrue.
EBool eMyBool = keTrue;

Example 2

// We can define an enum to represent colors.
// In this case, keRed = 0, keBlue = 1, keYellow = 2.
enum EColor {keRed, keBlue, keYellow};
// Create an instance of the type and assign it the value keRed.
EColor eMyColor = keRed;

Example 3

// We can define an enum to represent some prime numbers.
// Unspecified values are one more than the previous value.
// In this case, keTwo = 2, keThree = 3, keFive = 5, keSeven = 7.
enum EPrimeNum {keTwo = 2, keThree, keFive = 5, keSeven = 7};
// Create an instance of the type and assign it the value keThree.
EPrimeNum eMyPrime = keThree;

Example 4

// We can define an enum to represent bits.
// We can use formulas and the previous values to assign new values.
// Here, we use the bit shift to set keZero = 1, keOne = 2, keTwo = 4.
enum EBit {keZero = 1, keOne = keZero << 1, keTwo = keOne << 1};
// Create an instance of the type and assign it the value keTwo.
EBit eMyBit = keTwo;

Example 5

// We can define an enum to represent numbers of a Fibonacci sequence.
// We can use formulas and the previous values to assign new values.
// In this case, keF1 = 1, keF2 = 1, keF3 = 2, keF4 = 3.
enum EFibonacci {keF1 = 1, keF2 = keF1, keF3, keF4 = keF2 + keF3};
// Create an instance of the type and assign it the value keF4.
EFibonacci eMyFib(keF4);