`Optional<T>`

Pebble 0.3.1 · all symbols on this page are stable.

A value that may be absent. Two constructors:

Constructor	Payload	Meaning
`Some{ value: T }`	`value: T`	The value is present.
`None{}`	—	The value is absent.

const maybe: Optional<int> = Some{ value: 42 };

match maybe {
    Some{ value }: trace(value),
    None{}: fail "missing"
}

Optional is returned by every "lookup-shaped" operation in the standard library: List.find, LinearMap.lookup, and so on.

Constructing

const present: Optional<int> = Some{ value: 7 };
const absent:  Optional<int> = None{};

match is the canonical way to consume an Optional:

match maybe {
    Some{ value }: doSomething(value),
    None{}:        defaultBehavior()
}

Bind the inner value with Some{ value } (or any field-rename syntax).

When you know statically that an Optional is Some, you can destructure directly:

const Some{ value: x } = maybe;

This compiles to an assertion: if maybe is None{} at runtime, the script fails.