C++ return Keyword

The return keyword in C++ is used to exit a function and optionally pass a value back to the caller. It indicates the end of the function’s execution and can be used with or without a value, depending on the function’s return type.

If a function is declared with a return type other than void, the return statement must include a value of the corresponding type. For void functions, the return keyword is optional and does not include a value.

Syntax

</>
Copy
// For non-void functions
return value;

// For void functions
return;
value
The value to be returned to the caller. This is required for functions with a non-void return type.

Examples

Example 1: Returning a Value from a Function

In this example, we shall write a function that returns an integer value.

</>
Copy
#include <iostream>
using namespace std;

int add(int a, int b) {
    return a + b; // Return the sum of a and b
}

int main() {
    int result = add(5, 3); // Call the function and store the return value
    cout << "Sum: " << result << endl;
    return 0;
}

Output:

Sum: 8

Explanation:

  1. The add function takes two integers as arguments and returns their sum using the return statement.
  2. The main function calls add, and the returned value is stored in the variable result.
  3. The result is then printed to the console.

Example 2: Using return in a void Function

In this example, we shall see how return is used in a void function to exit early.

</>
Copy
#include <iostream>
using namespace std;

void checkNumber(int num) {
    if (num < 0) {
        cout << "Negative number detected!" << endl;
        return; // Exit the function early
    }
    cout << "Positive number: " << num << endl;
}

int main() {
    checkNumber(-5);
    checkNumber(10);
    return 0;
}

Output:

Negative number detected!
Positive number: 10

Explanation:

  1. The checkNumber function checks if the input number is negative.
  2. If the number is negative, the function prints a message and exits early using the return statement.
  3. If the number is positive, the function continues to execute and prints the positive number.

Example 3: Returning a Value from a Conditional Statement

In this example, we will return a value based on a condition.

</>
Copy
#include <iostream>
using namespace std;

string evaluateGrade(int score) {
    if (score >= 90) return "A";
    if (score >= 80) return "B";
    if (score >= 70) return "C";
    return "F"; // Default return value
}

int main() {
    int score = 85;
    cout << "Grade: " << evaluateGrade(score) << endl;
    return 0;
}

Output:

Grade: B

Explanation:

  1. The evaluateGrade function returns a grade based on the input score.
  2. The return statements inside the conditional blocks return the corresponding grade for each condition.
  3. If none of the conditions are met, the function returns the default grade "F".

Key Points to Remember about return Keyword

  1. The return keyword is used to exit a function and optionally return a value to the caller.
  2. For non-void functions, the return statement must include a value of the appropriate type.
  3. For void functions, return can be used to exit the function early without returning a value.
  4. If a return statement is omitted in a non-void function, the compiler may generate an error or warning.