conditional_operator.md

Conditional Operator

When the only operation being performed inside of an if and else pair is setting the initial value of a variable, you can use the "conditional operator"¹ to perform that assignment instead.

~void main() {
int age = 22;

String message = age < 25
    ? "You cannot rent a car!"
    : "You might be able to rent a car";

IO.println(message);
~}

You write a condition followed by a ?, a value to use when that condition evaluates to true, a :, and then a value to use when that condition evaluates to false.

CONDITION ? WHEN_TRUE : WHEN_FALSE

Just like multiple if else statements, we have the concept to "chain" ternary operators. If the first condition is not true, it goes to the next condition and so on.

~void main() {
int age = 22;

String message = age <= 0
    ? "You do not exist yet"
    : age > 100
    ? "Sorry, you are too old."
    : age < 25
    ? "You cannot rent a car!"
    : "You might be able to rent a car";

IO.println(message);
~}

It is same as before, you write a condition followed by a ?, a value to use when that condition evaluates to true, a :, and then chain another condition to use when that condition evaluates to false.

Finally, if no condition was true, it matches the value after the final :.

CONDITION ? WHEN_TRUE : CONDITION ? WHEN_TRUE : CONDITION ? WHEN_TRUE ... : WHEN_ALL_FALSE

Footnotes

1. Some people will call this a ternary expression. Ternary meaning "three things." Same idea as tres leches. ↩