Conditional Expression Operator (?:)

Syntax

exp1 ? exp2 : exp3

Description

The conditional expression construction provides a shorthand way of coding an ifelse condition. The difference between the expression notation and an ifelse condition is that the ? : notation is an expression and therefore returns a value, while an ifelse condition is a statement and does not return a value. The syntax described above is equivalent to

if (exp1)
    exp2;
else
    exp3;

When a conditional expression is executed, exp1 is evaluated first. If it is true (that is, nonzero) exp2 is evaluated and its result is the value of the conditional expression. If exp1 is false, exp3 is evaluated and its result is the value of the conditional expression.

There is no requirement that you put parentheses around the exp1 portion of the conditional expression, but doing so will improve your code"s readability.

Both exp2 and exp3 must be assignment-compatible. If exp2 and exp3 are pointers to different types, then the compiler issues a warning. The value of a conditional expression is either exp2 or exp3, whichever is selected. The other expression is not evaluated. The type of the result is the type that would be produced if exp2 and exp3 were mixed in an expression. For instance, if exp2 is a char and exp3 is a double, the result type will be double regardless of whether exp2 or exp3 is selected.

Example

/*  Program name is "conditional_exp_op_example".
    This program uses the conditional expression to
    see if the user wants to continue adding
    numbers.  */
#include <stdio.h>
 
int main(void)
{
    int a, b, c, d, again, total;
    char answer;
 
    printf("\n");
    again = 1;
    while (again)
    {
        printf("Enter four numbers separated by spaces that\n");
        printf("you want added together: ");
        scanf("%d %d %d %d", &a, &b, &c, &d);
        fflush(stdin);
        total = a + b + c + d;
        printf("\nThe total is: %d\n", total);
        printf("Do you want to continue ? ");
        scanf("%c", &answer);
        again = (answer == "y" || answer == "Y") ? 1 : 0;
    } /*  end while  */
}

If you execute this program, you get the following output:

Enter four numbers  separated by spaces that
you want added together: 20 30 40 50
 
The total is: 140
Do you want to continue ? y
Enter four numbers  separated by spaces that
you want added together: 1 2 3 4
 
The total is: 10
Do you want to continue ? n