C++ Ternary Operator

In C++, the ternary operator (also known as the conditional operator) can be used to replace if...else in certain scenarios.

Ternary Operator in C++

A ternary operator evaluates the test condition and executes a block of code based on the result of the condition.

Its syntax is

condition ? expression1 : expression2;

Here, condition is evaluated and

• if condition is true, expression1 is executed.
• And, if condition is false, expression2 is executed.

The ternary operator takes 3 operands (condition, expression1 and expression2). Hence, the name ternary operator.

Example : C++ Ternary Operator

#include <iostream>
#include <string>
using namespace std;

int main() {
  double marks;

  // take input from users
  cout << "Enter your marks: ";
  cin >> marks;

  // ternary operator checks if
  // marks is greater than 40
  string result = (marks >= 40) ? "passed" : "failed";

  cout << "You " << result << " the exam.";

  return 0;
}

Output 1

Enter your marks: 80
You passed the exam.

Suppose the user enters 80. Then, the condition marks >= 40 evaluates to true. Hence, the first expression "passed" is assigned to result.

Output 2

Enter your marks: 39.5
You failed the exam.

Now, suppose the user enters 39.5. Then, the condition marks >= 40 evaluates to false. Hence, the second expression "failed" is assigned to result.

When to use a Ternary Operator?

In C++, the ternary operator can be used to replace certain types of if...else statements.

For example, we can replace this code

#include <iostream>
using namespace std;

int main() {
  // Create a variable
  int number = -4;

  if (number > 0)
    cout << "Positive Number";
  else
    cout << "Negative Number!";

  return 0;
}

with

#include <iostream>
#include <string>
using namespace std;

int main() {
  int number = -4;
  string result;

  // Using ternary operator
  result = (number > 0) ? "Positive Number!" : "Negative Number!";

  cout << result << endl;

  return 0;
}

Output

Negative Number!

Here, both programs give the same output. However, the use of the ternary operator makes our code more readable and clean.

Note: We should only use the ternary operator if the resulting statement is short.

Nested Ternary Operators

It is also possible to use one ternary operator inside another ternary operator. It is called the nested ternary operator in C++.

Here's a program to find whether a number is positive, negative, or zero using the nested ternary operator.

#include <iostream>
#include <string>
using namespace std;

int main() {
  int number = 0;
  string result;

  // nested ternary operator to find whether
  // number is positive, negative, or zero
  result = (number == 0) ? "Zero" : ((number > 0) ? "Positive" : "Negative");

  cout << "Number is " << result;

  return 0;
}

Output

Number is Zero

In the above example, notice the use of ternary operators,

(number == 0) ? "Zero" : ((number > 0) ? "Positive" : "Negative");

Here,

• (number == 0) is the first test condition that checks if number is 0 or not. If it is, then it assigns the string value "Zero" to result.
• Else, the second test condition (number > 0) is evaluated if the first condition is false.

Note: It is not recommended to use nested ternary operators. This is because it makes our code more complex.