Enumeration

Enumerations can make a program easier to read.

enum Color {RED, GREEN, BLUE, YELLOW, WHITE};

All an enumeration does is assign names to integer values. The only difference between an enum and a variable is that an enumeration creates its own datatype (in the above example, the enumeration creates a Color datatype). When the program is compiled, the enum is converted to a plain integer.

Note

Becuase all enum does is map words to an integer value, you can also assign specific values to enumerations.

enum Distance {
    TOO_CLOSE = 10,
    TOO_FAR = 20
};

Because they are easy to read and do not slow down the code, enumerations are great for switch statements.

Example

//This program performs actions based on user input, which can be a very good appliation for enumerations.

#include <iostream>
using namespace std;

enum Distance {
    TOO_CLOSE = 10,
    TOO_FAR = 20,
    OK
};

Distance checkDistance(int input);
bool userDone();

int main() {
    Distance checked;
    do {
        int input;
        cout << "Enter a distance: ";
        cin >> input;
        checked = checkDistance(input);
        switch (checked) {
        case OK:
            cout << "You chose wisely.\n";
            break;
        case TOO_FAR:
            cout << "You chose poorly: too far.\n";
            break;
        case TOO_CLOSE:
            cout << "You chose poorly: too close.\n";
        }
    } while (checked != OK && !userDone());
    cout << "Goodbye.\n";
}

Distance checkDistance(int input) {
    if (input <= TOO_CLOSE) //comparing an `int` and a `Distance`
        return TOO_CLOSE;
    else if (input >= TOO_FAR)
        return TOO_FAR;
    else //OK does not have an associated value.
        return OK;
}

bool userDone() {
    char input;
    cout << "Are you done? [y/n] ";
    cin >> input;
    cout << endl;
    if (input == 'y')
        return true;
    else
        return false;
}

Example Input/Output

In order to demonstrate the capabilities of cin, I am going to run the above program.

Note

If you give cin too much data, it will save the extra values and use them in future inputs.

Enter a distance: 10
You chose poorly: too close.
Are you done? [y/n] n

Enter a distance: 20
You chose poorly: too far.
Are you done? [y/n] n

Enter a distance: 15
You chose wisely.
Goodbye.

This method, while not always apparent to the user, can be very useful for those who do know about it. You are actually able to provide a valid input set at the beginning of the program.

Enter a distance: 10 n 20 n 15
You chose poorly: too close.
Are you done? [y/n] 
Enter a distance: You chose poorly: too far.
Are you done? [y/n] 
Enter a distance: You chose wisely.
Goodbye.