Enumeration

Similar to structure, enumeration declaration can be

Enumeration names form a separate namespace
```
enum ENUM {
  member1 [= integer],
  member2 [= integer]
};
```
usage in declarations and definitions requires keyword enum in C (recommended to C++ too)
```
enum ENUM e;
```
typedef can be used to shorten declarations and definitions
```
typedef enum ENUM Enum;
Enum e;
```

typedef and enum declarations can be combined into one construct

typedef enum ENUM {
  member1 [= integer],
  member2 [= integer]
} Enum;

Typically, inner enum declaration needs no name

typedef enum {
  member1 [= integer],
  member2 [= integer]
} Enum;

In C++, typedef is optional.

enum Enum {
  member1 [= integer],
  member2 [= integer]
};
Enum e;

In C, the type of an enumerator is int. In C++, the type of an enumerator is its enumeration. C++ objects of enumeration type can only be assigned values of the same enumeration type.

enum Color {
  Red,
  Blue,
  Green
} c = 1;	// valid C, invalid C++

When necessary, however, an enumeration type is automatically promoted to an arithmetic type. For example

Enum e = member1;
const int array_size = 1024;
int chunk_size = array_size * e; // promoted to int

In C++, iterate over the values using the enumerators is not allowed, as there is no support for moving backward or forward from one enumerator value to a succeeding or preceding one.

for (Enum e=member1; e!=member2; e++) // not supported
  // ...

To print the actual enumerator names, define an array of strings indexed by the value of the enumerator.

const char *EnumName[] = { "member1", "member2" };
Enum e = member1;
cout << EnumName[e] << endl;
e = member2;
cout << EnumName[e] << endl;

Index