options

nimony/lib/std/options.nim

This module implements types which encapsulate an optional value.

A value of type Option[T] either contains a value x (represented as some(x)) or is empty (none(T)).

This is the Nimony port. Since exceptions are not yet wired up, get on an empty Option terminates the program (mirroring assert) rather than raising UnpackDefect. Equality is the compiler-provided structural comparison: an empty Option always stores the default value, so two empty Options compare equal and an empty one never equals a populated one.

type Option = object
  val: T
  has: bool

func some(val: sink T): Option[T]
Returns an Option that contains val.
func none(): Option[T]
Returns an empty Option (i.e. with no value).
func option(val: sink T): Option[T]
Wraps val in an Option; for value types this is simply some(val).
func isSome(self: Option[T]): bool
Returns true if self contains a value.
func isNone(self: Option[T]): bool
Returns true if self is empty.
func unsafeGet(self: Option[T]): T
Returns the contained value. Behaviour is undefined when self is empty; only use after checking isSome.
func get(self: Option[T]): T
Returns the contained value. Terminates the program if self is empty.
func get(self: Option[T]; otherwise: T): T
Returns the contained value, or otherwise if self is empty.
func $(self: Option[T]): string
Returns the string representation of self.
proc map(self: Option[T]; cb: proc (x: T): R): Option[R]
Applies cb to the contained value and wraps the result; empty stays empty.
proc filter(self: Option[T]; cb: proc (x: T): bool): Option[T]
Returns self if it holds a value satisfying cb, otherwise empty.
proc flatMap(self: Option[T]; cb: proc (x: T): Option[R]): Option[R]
Applies cb (which itself returns an Option) and flattens the result.
func flatten(self: Option[Option[T]]): Option[T]
Collapses a nested Option into a single one.