?: (elvis)

Evaluates the truthiness of the first expression, and returns its value if that value is truthy. If the value of the first expression is not truthy, it returns the value of the second expression.

condition ?: ifFalse

• condition - the conditional expression to be evaluated for truthiness.
• ifFalse - the expression to be evaluated if condition is not found to be truthy.

name.pref ?: name.first returns someone's preferred first name if available, otherwise returns their formal first name.

• = (equals)
• != (not-equals)
• ? (ternary)