/mod.ts | optio@1.0.0

import * as optio from "https://deno.land/x/optio@1.0.0/mod.ts";

Optional values. Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not.

Operators overview

Option provides a wide variety of different operators.

Querying the variant

The isSome and isNone return true if the Option is Some or None, respectively.

Extracting the contained value

Extract the contained value in an Option<T> when it is the Some.

If the Option is None:

expect throws with a provided custom message
unwrap throws with generic message
unwrapOr returns the provided default value
unwrapOrElse returns the result of evaluating the provided function

Transforming contained values

Transform the Some:

filter calls the provided predicate function on the contained value T if the Option is Some<T>, and returns Some<T> if the function returns true; otherwise, returns None
flat removes one level of nesting from an Option<Option<T>>
map transforms Option<T> to Option<U> by applying the provided function to the contained value of Some and leaving None values unchanged

Transform Option<T> to a value of a possibly different type U:

mapOr applies the provided function to the contained value of Some, or returns the provided default value if the Option is None
mapOrElse applies the provided function to the contained value of Some, or returns the result of evaluating the provided fallback function if the Option is None

Combine the Some of two Option values:

zip returns Some<[T, | U]> if option is Some<T> and the provided Option value is Some<U>; otherwise, returns None

Logical operators

Treat the Option as a boolean value, where Some acts like true and None acts like false.

The and, or, and xor take another Option, and produce an Option as output. Only the and can produce an Option<U> value having a different inner type U than Option<T>.

name	option	input	output
`and`	`None`	-	`None`
`and`	`Some<T>`	`None`	`None`
`and`	`Some<T>`	`Some<U>`	`Some<U>`
`or`	`None`	`None`	`None`
`or`	`None`	`Some<U>`	`Some<U>`
`or`	`Some<T>`	-	`Some<T>`
`xor`	`None`	`None`	`None`
`xor`	`None`	`Some<U>`	`Some<U>`
`xor`	`Some<T>`	`None`	`Some<T>`
`xor`	`Some<T>`	`Some<U>`	`None`

The andThen and orElse take a function as input, and only evaluate the function when they need to produce a new value. Only the andThen can produce an Option<U> value having a different inner type U than Option<T>.

name	option	function input	function result	output
`andThen`	`None`	-	-	`None`
`andThen`	`Some<T>`	`T`	`None`	`None`
`andThen`	`Some<T>`	`T`	`Some<U>`	`Some<U>`
`orElse`	`None`	-	`None`	`None`
`orElse`	`None`	-	`Some<U>`	`Some<U>`
`orElse`	`Some<T>`	-	-	`Some<T>`

Enums

OptionType

The option type.

Variables

v None	No value.
v Some	`Some` constructor.

Functions

f and	Returns `None` if the `option` is `None`, otherwise returns `optb`.
f andThen	Returns `None` if the `option` is `None`, otherwise calls `fn` with the wrapped value and returns the result.
f expect	Returns the contained `Some` value.
f filter	Returns `None` if the `option` is `None`, otherwise calls predicate with the wrapped value and returns: `Some` if predicate returns `true`. `None` if predicate returns `false`.
f flat	Converts from `Option<Option<T>>` to `Option<T>`.
f isNone	Returns `true` if the `option` is a `None`.
f isSome	Returns `true` if the `option` is a `Some`.
f map	Maps an `Option<T>` to `Option<U>` by applying a function to a contained value(if `Some`) or returns `None`(if `None`).
f mapOr	Returns the provided default value (if `None`), or applies a function to the contained value (if `Some`).
f mapOrElse	Computes a default function result (if `None`), or applies a different function to the contained value (if `Some`).
f match	Pattern matching for `option`. Match on `matcher.Some` if `Some`, otherwise match on `matcher.None`.
f or	Returns the `option` if it contains a value, otherwise returns `obtb`.
f orElse	Returns the `option` if it `Some`, otherwise calls `fn` and returns the result.
f unwrap	Returns the contained `Some` value.
f unwrapOr	Returns the contained `Some` value, otherwise `defaultValue`.
f unwrapOrElse	Returns the contained `Some` value, otherwise computes it from a closure.
f xor	Returns `Some` if exactly one of `option`, `optb` is `Some`, otherwise returns `None`.
f zip	Zips `option` with another `Option`.

Interfaces

I Matcher	`Option` matcher.
I None	The `None` API.
I Some	The `Some` API.

Type Aliases

Option

Representation of Some or None.