A language feature worth understanding

15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.

Use the language note below to explain this example’s state changes. Identify what is copied, what is shared, what can fail, and what is released. Only some of those questions apply to this particular program: say which ones. Make one deliberate change, predict the effect, and compare it with the actual result. A familiar-looking operator in another language may obey a different rule.

:= declares a value. Add mut only when it must change. !int describes a result that may fail; the caller handles the failure with an or block. Standard V examples do not import the Agila SDK.

fn checked_score(value int) !int {
    if value < 0 || value > 100 { return error('Invalid score') }
    return value
}
fn main() {
    result := checked_score(101) or {
        println('Practice')
        return
    }
    println(result)
}

Expected result: Practice

Practice and evidence

Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.

Language reference