In C++, the ternary operator is a concise, inline method used to execute one of two expressions based on a condition. It is also called the conditional operator.
Ternary Operator in C++
A ternary operator evaluates the test condition and executes an expression out of two based on the result of the condition.
Syntax
condition ? expression1 : expression2;
Here, condition is evaluated and
- if
conditionistrue,expression1is executed. - if
conditionisfalse,expression2is 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.
Note: We should only use the ternary operator if the resulting statement is short.
1. Ternary Operator for Concise Code
The ternary operator is best for simple, inline conditional assignments where readability is not compromised. For example,
int age = 20;
string status;
status = (age >= 18) ? "Adult" : "Minor";
In this example, the condition age >= 18 is evaluated. If it's true, Adult is assigned to status; if it's false, Minor is assigned.
This is much more concise than using a full if...else statement, which would look like this:
int age = 20;
string status;
if (age >= 18) {
status = "Adult";
} else {
status = "Minor";
}
Here, the if...else statement takes up more lines and can clutter code when used for many simple conditional assignments.
2. if...else for Clarity in Complex Conditions
The if...else statement is better suited for complex decision-making processes and when clarity and readability are prioritized over brevity.
Suppose you need to categorize weather based on multiple conditions. Using a ternary operator with multiple conditional statements would be cumbersome and hard to read. In such cases, we use if...else.
Let's look at an example.
int temperature = 25;
string category;
if (temperature < 10) {
category = "Cold";
} else if (temperature <= 25) {
category = "Moderate";
} else if (temperature > 25) {
category = "Hot";
} else {
category = "Inhabitable";
}
3. Ternary Operator Implicitly Returns a Value
Let's look at an example to justify this point.
int number = -4;
string result;
// ternary operator assigns value directly
result = (number > 0) ? "Positive Number" : "Negative Number";
Here, the ternary operator returns the value based on the condition (number>0). The returned value is stored in the result variable.
In contrast, if...else does not inherently return a value. Thus, assignment to a variable is explicit.
int number = -4;
string result;
// explicit assignment with if...else
if (number > 0)
result = "Positive Number";
else
result = "Negative Number";
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 isfalse.
Note: It is not recommended to use nested ternary operators. This is because it makes our code more complex.