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aivi.option ​

Utilities for working with Option A — a value that may or may not be present. All functions are pure and can be freely composed with pipes.

aivi
use aivi.option (
    isSome
    isNone
    getOrElse
    orElse
    flatMap
    flatten
    toList
    toResult
    map
    filter
    zip
    fromBool
)

isSome ​

Returns True if the option holds a value.

Type: opt:(Option A) -> Bool

aivi
use aivi.option (isSome)

type Option Int -> Bool
func hasValue = opt =>
    isSome opt

isNone ​

Returns True if the option is empty.

Type: opt:(Option A) -> Bool

aivi
use aivi.option (isNone)

type Option Text -> Bool
func isMissing = opt =>
    isNone opt

getOrElse ​

Extracts the value from Some, or returns the fallback if None.

Type: fallback:A -> opt:(Option A) -> A

aivi
use aivi.option (getOrElse)

type Option Text -> Text
func displayName = opt =>
    getOrElse "Anonymous" opt

orElse ​

Returns the option unchanged if it is Some, otherwise returns the fallback option.

Type: fallback:(Option A) -> opt:(Option A) -> Option A

aivi
use aivi.option (orElse)

type Option Text -> (Option Text) -> (Option Text)
func firstAvailable = primary secondary => primary
  |> orElse secondary

flatMap ​

Chains an Option-returning function over a Some value. Returns None when the input is None or when the function returns None.

Type: next:(A -> Option B) -> opt:(Option A) -> Option B

aivi
use aivi.option (flatMap)

type Int -> (Option Int)
func parsePositive = n => n > 0
 T|> Some n
 F|> None

type Option Int -> (Option Int)
func parseAndFilter = opt => opt
  |> flatMap parsePositive

flatten ​

Removes one layer of nesting from an Option (Option A).

Type: opt:(Option (Option A)) -> Option A

aivi
use aivi.option (flatten)

type Option (Option Int) -> (Option Int)
func unwrapNested = opt =>
    flatten opt

toList ​

Converts Some value to a one-element list, or None to an empty list.

Type: opt:(Option A) -> List A

aivi
use aivi.option (toList)

type Option Int -> (List Int)
func optionItems = opt =>
    toList opt

toResult ​

Converts an Option to a Result. Some value becomes Ok value; None becomes Err error.

Type: error:E -> opt:(Option A) -> Result E A

aivi
use aivi.option (toResult)

type Option Text -> (Result Text Text)
func requireName = opt =>
    toResult "Name is required" opt

map ​

Transforms the value inside Some using a function, leaving None untouched.

Type: transform:(A -> B) -> opt:(Option A) -> Option B

aivi
use aivi.option (map)

type Int -> Int
func double = n =>
    n * 2

type Option Int -> (Option Int)
func doubleOpt = opt => opt
  |> map double

filter ​

Keeps the Some value only if it satisfies the predicate; otherwise returns None.

Type: predicate:(A -> Bool) -> opt:(Option A) -> Option A

aivi
use aivi.option (filter)

type Int -> Bool
func isPositive = n =>
    n > 0

type Option Int -> (Option Int)
func keepPositive = opt => opt
  |> filter isPositive

zip ​

Pairs two options together. Produces Some (a, b) only when both inputs are Some.

Type: left:(Option A) -> right:(Option B) -> Option (A, B)

aivi
use aivi.option (zip)

type Option Int -> (Option Text) -> (Option (Int, Text))
func pairIfBoth = count label =>
    zip count label

fromBool ​

Wraps item in Some when b is True, or returns None when b is False.

Type: item:A -> b:Bool -> Option A

aivi
use aivi.option (fromBool)

type Bool -> Text -> (Option Text)
func whenEnabled = enabled label =>
    fromBool label enabled

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