Optional Types

A type which can contain a value (Some) or no value (None). The type of the value is specified after optional, e.g. optional int. The literal expressions for optionals are None and Some(❮expression❯).

// declare an optional field
effect Foo {
     a string,
     b optional int,
}

// initialize an optional
// type of these player variables is `optional string`
let player1 = Some("George")
let player2 = None

// access inner value
// type of `winner` is `string`
let winner = unwrap player1
// This will terminate execution with a runtime exception
let winner = unwrap player2