Optional<T> is a sealed class () used to represent situations where an instance/value of T may not be present. It has two sub-classes: None<T>, which is an object class (#?) used to represent no value, and Some<T>, which is a class used to represent some T value.
For ergonomics, Silicon has T? as shorthand for Optional<T> and the keyword none for None<T>. Additionally, Some<T> implements Box<T> (#19 ), so it can be treated as an instance of T due to implicit boxing and unboxing.
main {
const noneFoo : Foo? = none
const someFoo : Foo? = new Foo()
print(noneFoo is none) // Prints 'true'
print(noneFoo is Foo) // Prints 'false'
print(someFoo is Foo) // Prints 'true'
}
Overview
Optional<T>is a sealed class () used to represent situations where an instance/value ofTmay not be present. It has two sub-classes:None<T>, which is an object class (#?) used to represent no value, andSome<T>, which is a class used to represent someTvalue.For ergonomics, Silicon has
T?as shorthand forOptional<T>and the keywordnoneforNone<T>. Additionally,Some<T>implementsBox<T>(#19 ), so it can be treated as an instance ofTdue to implicit boxing and unboxing.