Examples of conditional expressions

The following expression determines which variable has the greater value, y or z, and assigns the greater value to the variable x:

x = (y > z) ? y : z;

The following is an equivalent statement:

if (y > z)
   x = y;
   x = z;

The following expression calls the function printf, which receives the value of the variable c, if c evaluates to a digit. Otherwise, printf receives the character constant 'x'.

printf(" c = %c\n", isdigit(c) ? c : 'x');

If the last operand of a conditional expression contains an assignment operator, use parentheses to ensure the expression evaluates properly. For example, the = operator has higher precedence than the ?: operator in the following expression:

int i,j,k;
(i == 7) ? j ++ : k = j;

The compiler will interpret this expression as if it were parenthesized this way:

int i,j,k;
((i == 7) ? j ++ : k) = j;

That is, k is treated as the third operand, not the entire assignment expression k = j.

To assign the value of j to k when i == 7 is false, enclose the last operand in parentheses:

int i,j,k;
(i == 7) ? j ++ : (k = j);