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C language provides a special kind of operator called - conditional operator. It is also called ternary operator because it has three operands, such as -

• Boolean-condition.
• First expression.
• Second expression.

Syntax of conditional operator -

boolean-condition ? first expression : second expression;

Rules of conditional operator -



• If the result of boolean-condition is true, first expression will be executed and its value is returned.
• If the result of boolean-condition is false, second expression will be executed and its value is returned.
• First expression and second expression must result in a value.

Conditional operator example.

/* Conditional Operator Example */

#include<stdio.h>

int main()
{
int a=10, b=20;


int result =a>b ? 10 : 20;
printf("Result1 is %d \n", result);


result = a>b ? 10 : 100.50;
printf("Result2 is %d \n", result);


char ch = a>b ? 'y' : 'n';
printf("Result3 is %c \n", ch);


result = 100>=99 ? 100 : 99;
printf("Result4 is %d \n", result);

return 0;
}

Output

Result1 is 20
Result2 is 100
Result3 is n
Result4 is 100

The first expression of a conditional operator can be left blank

#include<stdio.h>

int main()
{
int a=10, b=20;

int result = a>b ? 0 : 10;
printf("Result1 is %d \n", result);

char ch = a < b ? : 'n'; 	/* Intentionally leaving the first expression */
printf("Result2 is %c \n", ch);

return 0;
}

Output-

Result1 is 10
Result2 is ☺

In the last code, we have intentionally left out the first expression and the program has still compiled and executed successfully.

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The second expression of a conditional operator cannot be left blank

#include<stdio.h>

int main()
{
result = 9<2 ? 9 : ;
printf("Result2 is %d \n", result);
}

Output-

func41.c:5:20: error: expected expression before ';' token
 result = 9<2 ? 9 : ;
                    ^

In the last code, we have intentionally left out the second expression and the compiler has thrown an error, complaining that the second expression is expected before semicolon.

An expression of a conditional operator can be a method call.

Any expression of a conditional operator could even be a call to a function but this function must return a value.

#include<stdio.h>

int main()
{
char fun(); /* function prototype declaration*/

char result = 100>99? fun() : 'n'; /* Calling function fun() in the first expression */
printf("Result is %c ", result);

return 0;
}


char fun()
{
return 'y';
}

Output-

Result is y

In the last code, the first expression of the conditional operator is a call to a function fun(), which has returned us a char y.

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