base class Option<+T>

Represents an optional value, ie one that may or may not be present. Some(T) represents a value that is present and None() represents a missing value.

Option fulfills a similar role to nullable types in other languages, but in a type-safe way: the programmer must explicitly handle the case of a missing value.

Example:

maybeValue = map.maybeGet(key);
maybeValue match {
| Some(value) -> /* use value */
| None() -> /* key not found, fallback...*/
};

NOTE: As a NBE optimization this implementation is customized in native/FastOption.sk, and the APIs must be kept in sync.

Methods

fun sourcemap<T2>(f: (T) -> T2): Option<T2>

For Some() values, returns a new Option with the result of applying the mapping function to the contained value. Returns None() when this is None().

fun sourceflatMap<T2>(f: (T) -> Option<T2>): Option<T2>

For Some() values, returns the results of applying the mapping function to the contained value. Returns None() when this is None().

fun sourcemaybe<T2>(nothing: T2, mjust: (T) -> T2): T2

Returns the result of calling the lambda for a Some() value or nothing for None() values. Equivalent to option.map(mjust).default(nothing)

fun sourcedefault<T2>(x: T2): T2

Returns the contained value for Some(), otherwise returns the default value.

fun sourcetest(p: (T) -> Bool): Bool

For Some() values, returns the result of calling the predicate on the contained value. Returns false for None() values.

fun sourcefromSome(msg: String): T

fun sourceisSome(): Bool

fun sourceisNone(): Bool

fun sourcehash(): Int

fun sourceeach(f: (T) -> Void): Void

For Some() values, calls the lambda with the contained value. Does nothing for None() values.

untracked fun sourceeachUntracked(f: (T) -> Void): Void

fun source==<U: Equality>(other: Option<U>): Bool

fun source!=<U: Equality>(other: Option<U>): Bool

fun source<<U: Orderable>(other: Option<U>): Bool

fun source><U: Orderable>(other: Option<U>): Bool

fun source<=<U: Orderable>(other: Option<U>): Bool

fun source>=<U: Orderable>(other: Option<U>): Bool

fun sourcecompare<U: Orderable>(other: Option<U>): Order

None() is less than Some().

fun sourcetoString(): String

frozen fun sourcegenMap<U>(f: (T) ~> ^U): ^Option<U>

frozen fun sourcegenFilter(p: (T) ~> ^Bool): ^Option<T>

Inherited Methods

static fun sourcemeta<U, C: MetaClass<U>>(itemClass: C): OptionMetaClass<U, C>

static fun sourcegenerator<T2>(generator: QuickCheck.Generator<T2>): QuickCheck.Generator<Option<T2>>

fun sourceperturb(rng: mutable Random): Void

fun sourceshrink(firstShrink: Bool): mutable Iterator<Option<T>>