• Some("some value") creates an Option[string] that has a value.

• None[string]() creates a value of the same type, but without a value.

• var foo: Option[string] has a value of None[String](). In other words, foo == None[String]().

• Some[string](nil) is invalid: the value inside a Some[ref T] is required to never be nil. This is only validated in debug mode, the check is disabled in release mode unless assertions are enabled.

isNone(Option[T]): bool

returns true if the Option[T] is None, otherwise returns false.

isSome(Option[T]): bool

returns not isNone(…​)

get(Option[T], [default: T]): T

Gets the value from the Option[T]. If the Option[T] is None, it raises an exception unless default is passed, in which case it returns default.

unsafeGet(Option[T]): T

Gets the value inside the Option[T], behavior is undefined if it is None. You probably don’t need this, the C optimizer is pretty good. Worry about the humans, not the computer.

map(Option[T], proc(T): R): R

If the Option[T] is not None, the passed procedure is executed with it’s value as a parameter, otherwise a None is returned without executing the passed procedure.

if myOptionT: …​

The if condition evaluates to true if the value is Some, otherwise it evaluates to false.

$ and == work as expected.

Note: If optional_t.nonstrict is imported, then all Option[T] s are automatically unpacked where necessary. This uses a converter, so the laziness might lead to odd errors.