C++ Inline Functions

In C++, we can declare a function as inline. This copies the function to the location of the function call in compile-time and may make the program execution faster.

Before following this tutorial, be sure to visit the C++ Functions.

Inline Functions

To create an inline function, we use the inline keyword. For example,

inline returnType functionName(parameters) {
    // code
}

Notice the use of keyword inline before the function definition.

C++ Inline Function

#include <iostream>
using namespace std;

inline void displayNum(int num) {
    cout << num << endl;
}

int main() {
    // first function call
    displayNum(5);

    // second function call
    displayNum(8);

    // third function call
    displayNum(666);

    return 0;
}

Output

5
8
666

Here is how this program works:

Here, we created an inline function named displayNum() that takes a single integer as a parameter.

We then called the function 3 times in the main() function with different arguments. Each time displayNum() is called, the compiler copies the code of the function to that call location.