C Ternary Operator

Summary: in this tutorial, you’ll learn how to use the C ternary operator to make the code more concise.

Introduction to the C ternary operator

The ternary operator is shorthand of an if...else and return statements. The ternary operator has the following syntax:

expression ? value_if_true : value_if_false
Code language: C++ (cpp)

In this syntax, the ternary operator evaluates the expression first. If the result is true (not zero), the ternary operator returns value_if_true. Otherwise, the ternary operator returns the value_if_false.

The ternary operator is equivalent to the following:

if(codition) 
    return value_if_true;
else 
    return value_if_false;
Code language: C++ (cpp)

C Ternary operator examples

Let’s take some examples of using the ternary operator.

1) A simple C ternary operator example

The following example use an if..else statement to display a string true or false based on the value of the is_active variable:

#include <stdio.h>
#include <stdbool.h>

int main()
{
    bool is_active = true;

    if (is_active)
    {
        printf("true");
    }
    else
    {
        printf("false");
    }

    return 0;
}
Code language: C++ (cpp)

The code is quite verbose. To make it more concise, you can use the ternary operator as follows:

#include <stdio.h>
#include <stdbool.h>

int main()
{
    bool is_active = true;

    printf( is_active ? "true" : false);

    return 0;
}
Code language: C++ (cpp)

The five lines of code that uses an if...else statement is replaced by one line of code that uses the ternary operator (:?).

2) Using the ternary operator example

The following program uses an if...else statement to determine the discount of tickets based on age:

#include <stdio.h>

int main()
{
    int age = 10;             // age
    float ticket_price = 100, // ticket price
        discount;             // discount

    // determine the discount based on age
    if (age < 5)
    {
        discount = 0.5;
    }
    else
    {
        discount = 0.15;
    }
    // get the ticket price
    ticket_price = ticket_price * (1 - discount);

    printf("Ticket price is %f\n", ticket_price);
    return 0;
}
Code language: C++ (cpp)

In this example, if the age is less thatn 5, the discount is 50%. Otherwise, the discount is 15%.

The following example is the same as above but use the ternary operator instead:

#include <stdio.h>

int main()
{
    int age = 10;             // age
    float ticket_price = 100; // ticket price
    float discount = age < 5 ? 0.5 : 0.15;
    // get the ticket price
    ticket_price = ticket_price * (1 - discount);

    printf("Ticket price is %f\n", ticket_price);

    return 0;
}
Code language: C++ (cpp)

Summary

• C ternary operator is expression ? value_if_true : value_if_false.
• Use the ternary operator to make the code more concise.