4.7. The Conditional Operator

The conditional operator (the ?: operator) lets us embed simple if-else logic inside an expression. The conditional operator has the following form:

cond  ? expr1  : expr2;

where cond is an expression that is used as a condition and expr1 and expr2 are expressions of the same type (or types that can be converted to a common type). This operator executes by evaluating cond. If the condition is true, then expr1 is evaluated; otherwise, expr2 is evaluated. As one example, we can use a conditional operator to determine whether a grade is pass or fail:

string finalgrade = (grade < 60) ? "fail" : "pass";

The condition checks whether grade is less than 60. If so, the result of the expression is "fail"; otherwise the result is "pass". Like the logical AND and logical OR (&& and ||) operators, the conditional operator guarantees that only one of expr1 or expr2 is evaluated.

That result of the conditional operator is an lvalue if both expressions are lvalues or if they convert to a common lvalue type. Otherwise the result is an rvalue.