oberonjs/doc/wiki/eberon-ternary-operator.md

Ternary operator can be used as a shortcut for the IF/ELSE statement.

Syntax

condition ? a : b

condition is a boolean expression.
a and b are expressions to evaluate.
The operator returns a when condition is TRUE and b when condition is FALSE. Ternary operator has lowest priority.

Example

PROCEDURE max(a, b: INTEGER): INTEGER;
VAR
    result: INTEGER;
BEGIN
    IF a > b THEN
        result := a;
    ELSE
        result := b;
    END;
    RETURN result;
END;

This code above may be rewritten in much shorter and cleaner manner using ternary operator:

PROCEDURE max(a, b: INTEGER): INTEGER;
    RETURN a > b ? a : b;
END;

Implicit Type Narrowing

Ternary operator supports [[Implicit Type Narrowing|eberon-implicit-type-narrowing]]:

TYPE
    Base = RECORD END;
    Derived = RECORD (Base) derivedField: INTEGER END;

PROCEDURE p(VAR b: Base): INTEGER;
    RETURN b IS Derived ? b.derivedField : 0
END;