C Language Enumerations Simple Enumeration
Example
An enumeration is a user-defined data type consists of integral constants and each integral constant is given a name. Keyword enum is used to define enumerated data type.
If you use enum instead of int or string/ char*, you increase compile-time checking and avoid errors from passing in invalid constants, and you document which values are legal to use.
Example 1
enum color{ RED, GREEN, BLUE };
void printColor(enum color chosenColor)
{
const char *color_name = "Invalid color";
switch (chosenColor)
{
case RED:
color_name = "RED";
break;
case GREEN:
color_name = "GREEN";
break;
case BLUE:
color_name = "BLUE";
break;
}
printf("%s\n", color_name);
}
With a main function defined as follows (for example):
int main(){
enum color chosenColor;
printf("Enter a number between 0 and 2");
scanf("%d", (int*)&chosenColor);
printColor(chosenColor);
return 0;
}
C99
Example 2
(This example uses designated initializers which are standardized since C99.)
enum week{ MON, TUE, WED, THU, FRI, SAT, SUN };
static const char* const dow[] = {
[MON] = "Mon", [TUE] = "Tue", [WED] = "Wed",
[THU] = "Thu", [FRI] = "Fri", [SAT] = "Sat", [SUN] = "Sun" };
void printDayOfWeek(enum week day)
{
printf("%s\n", dow[day]);
}
The same example using range checking:
enum week{ DOW_INVALID = -1,
MON, TUE, WED, THU, FRI, SAT, SUN,
DOW_MAX };
static const char* const dow[] = {
[MON] = "Mon", [TUE] = "Tue", [WED] = "Wed",
[THU] = "Thu", [FRI] = "Fri", [SAT] = "Sat", [SUN] = "Sun" };
void printDayOfWeek(enum week day)
{
assert(day > DOW_INVALID && day < DOW_MAX);
printf("%s\n", dow[day]);
}
