C++ Enumeration

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Introduction

In C++, an enumeration (or enum) is a user-defined data type that consists of a set of named integer constants. Enumerations are used to make programs more readable by replacing numeric constants with meaningful names.

By using enum, you can define a variable that can take one of the values from a predefined set of constants. Enumerations are useful when you have a set of related values (such as days of the week, months of the year, or statuses in a process) and want to improve code readability and maintainability.

In this guide, we will learn how to define and use enumerations in C++.

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1. What is an Enumeration in C++?

An enum in C++ is a data type that allows you to define a set of named integer constants. The syntax of an enum is straightforward:

Syntax for Defining an Enumeration:

enum EnumName {
    CONSTANT1,
    CONSTANT2,
    CONSTANT3,
    // ...
};

• EnumName: The name of the enumeration.
• CONSTANT1, CONSTANT2, CONSTANT3: The named constants within the enumeration.

By default, the constants in an enum are assigned integer values starting from 0 unless explicitly specified.

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2. Basic Example: Defining and Using an Enumeration

Here’s a basic example of how to define and use an enum in C++:

#include <iostream>
using namespace std;

// Define an enumeration for days of the week
enum Day {
    Sunday,    // 0
    Monday,    // 1
    Tuesday,   // 2
    Wednesday, // 3
    Thursday,  // 4
    Friday,    // 5
    Saturday   // 6
};

int main() {
    // Declare a variable of type Day
    Day today = Wednesday;

    // Output the integer value corresponding to Wednesday
    cout << "Integer value of Wednesday: " << today << endl;

    return 0;
}

Output:

Integer value of Wednesday: 3

Explanation:

• We defined an enum called Day with days of the week as constants.
• The constants automatically start with the value 0 (for Sunday), and the subsequent days are assigned increasing integer values (1 for Monday, 2 for Tuesday, etc.).
• We declared a variable today of type Day and assigned it the value Wednesday.
• The today variable holds the integer value 3, as Wednesday is the third constant in the enumeration.

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3. Specifying Custom Values in an Enumeration

You can also assign custom integer values to the constants in an enumeration. This allows more control over the values used.

Example: Custom Values in Enumeration

#include <iostream>
using namespace std;

// Define an enumeration with custom values
enum Day {
    Sunday = 1,    // Custom value 1
    Monday = 2,    // Custom value 2
    Tuesday = 3,   // Custom value 3
    Wednesday = 4, // Custom value 4
    Thursday = 5,  // Custom value 5
    Friday = 6,    // Custom value 6
    Saturday = 7   // Custom value 7
};

int main() {
    // Declare a variable of type Day
    Day today = Friday;

    // Output the integer value corresponding to Friday
    cout << "Integer value of Friday: " << today << endl;

    return 0;
}

Output:

Integer value of Friday: 6

Explanation:

• We explicitly specified custom values for each day of the week.
• In this case, Sunday starts at 1, and the values increment accordingly. Friday will have the value 6.

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4. Enum with Non-Sequential Values

Sometimes, you may want to have non-sequential values for your enumeration constants. This is also possible by manually assigning specific values to each constant.

Example: Non-sequential Values in Enumeration

#include <iostream>
using namespace std;

// Define an enumeration with non-sequential values
enum Day {
    Sunday = 1,    // Custom value 1
    Monday = 10,   // Custom value 10
    Tuesday = 20,  // Custom value 20
    Wednesday = 30, // Custom value 30
    Thursday = 40,  // Custom value 40
    Friday = 50,    // Custom value 50
    Saturday = 60   // Custom value 60
};

int main() {
    // Declare a variable of type Day
    Day today = Tuesday;

    // Output the integer value corresponding to Tuesday
    cout << "Integer value of Tuesday: " << today << endl;

    return 0;
}

Output:

Integer value of Tuesday: 20

Explanation:

• We assigned specific, non-sequential values to the constants in the Day enumeration.
• Tuesday now holds the value 20 instead of 2 or another default value.

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5. Enum as a Type

You can use an enumeration type to declare variables, as shown in the previous examples. Enums provide better readability and organization compared to using plain integer constants.

Example: Enum as a Type

#include <iostream>
using namespace std;

// Define an enumeration for status codes
enum StatusCode {
    OK = 200,       // Successful request
    NotFound = 404, // Resource not found
    Forbidden = 403, // Forbidden access
    InternalError = 500 // Server error
};

int main() {
    // Declare a variable of type StatusCode
    StatusCode status = NotFound;

    // Check the status code
    if (status == NotFound) {
        cout << "Error: Resource not found" << endl;
    }

    return 0;
}

Output:

Error: Resource not found

Explanation:

• We defined an enum called StatusCode to represent HTTP status codes.
• By using enums, the code is more readable and easier to maintain, as we don't need to rely on magic numbers like 404.

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6. Using Enum with Switch Statements

Enums work well with switch statements, which makes it easier to handle different cases based on the enum value.

Example: Using Enum with Switch Statement

#include <iostream>
using namespace std;

// Define an enumeration for seasons
enum Season {
    Spring = 1,
    Summer,
    Autumn,
    Winter
};

int main() {
    // Declare a variable of type Season
    Season currentSeason = Winter;

    // Use switch-case to handle different seasons
    switch (currentSeason) {
        case Spring:
            cout << "It's Spring!" << endl;
            break;
        case Summer:
            cout << "It's Summer!" << endl;
            break;
        case Autumn:
            cout << "It's Autumn!" << endl;
            break;
        case Winter:
            cout << "It's Winter!" << endl;
            break;
        default:
            cout << "Invalid season!" << endl;
    }

    return 0;
}

Output:

It's Winter!

Explanation:

• We use the Season enum to declare the current season and use a switch statement to print a message based on the season.

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