Lesson 5.4. Ternary Operator ?:

In C, there is a ternary operator ?:

this is a conditional operator : it check a condition (as an if...else).
this is a ternary opérator because it takes 3 operands.

The general syntax of this operator is:

(test) ? expressionTrue : expressionFalse ;

If the test is true, the first expression is evaluated (and assigned).
If the test is false, the second expression is evaluated (and assigned).

This operator is mainly used when you want to assign different values depending on the test.

// If x not equal to 0, 10 is assigned to n. Otherwise, 20 is assigned to n
n = (x != 0) ? 10 : 20;

Example

The example below assigns the variable a to max if a is greater than b, otherwise, the variable b is assigned to max. This instruction can be summarized in one sentence:

The variable max will contain the largest value between a and b. :

max = (a > b) ? a : b;

This instruction can also be written with an if...else :

if (a>b)
   max = a;
else
   max = b;

Try online

Exercise

Write a program that asks the user to enter the number of kids. Then, the program displays : You have 7 kids. The word kid must be in the plural if the number entered is strictly greater than 1.

int nbKids;

// Get number of kids
printf ("How many kids? ");
scanf ("%d", &nbKids);

// Displays the number of kid(s)
printf ("You have %d kid%c.\n", nbKids, /* COMPLETE HERE */ );

Tip: ASCII code zero does not display anything.

Here is the expected output:

How many kids? 1
You have 1 kid.

How many kids? 7
You have 1 kids.

Do the exercise

Solution

Quiz

What does the following code display?

int n = (2>3) ? 0 : 1;
putchar ('%d', n);

Check

What does the following code display?

int n=(2<3)?0:1;
putchar ('%d', n);

Check

Which instruction is equivalent to the code below?

if (x%2)
    c = 'p';
else
    c = 'i';

(x%2) ? c='p' : c='i';

(x%2) ? c='i' : c='p';

c = (x%2) ? 'p' : 'i';

c = (x%2) ? 'i' : 'p';

Check

Lesson 5.3 Summary Lesson 5.5

Lesson 5.4. Ternary Operator ?:

Example

Exercise

Quiz

See also