POptional

interface POptional<S, T, A, B> : PTraversal<S, T, A, B>

Optional is an optic that allows to focus into a structure and querying or copy'ing an optional focus.

import arrow.core.None
import arrow.core.Option
import arrow.core.Some
import arrow.optics.Optional

data class User(val username: String, val email: Option<String>) {
    companion object {
      // can be out generated by @optics
      val email: Optional<User, String> = Optional(User::email) { user, email ->
        user.copy(email = Some(email))
      }
  }
}

fun main() {
  val original = User("arrow-user", None)
  val set = User.email.set(original, "arRoW-UsEr@arrow-Kt.IO")
  val modified = User.email.modify(set, String::lowercase)
  println("original: $original, set: $set, modified: $modified")
}

A (polymorphic) POptional is useful when setting or modifying a value for a type with a optional polymorphic focus i.e. POptional, Either, Int, String>

A POptional can be seen as a weaker Lens and Prism and combines their weakest functions:

set: (S, B) -> T meaning we can focus into an S and set a value B for a target A and obtain a modified source T
getOrModify: (S) -> Either<T, A> meaning it returns the focus of a POptional OR the original value

Parameters

the source of a POptional

the modified source of a POptional

the focus of a POptional

the modified focus of a POptional

Inheritors

PLens

PPrism

Types

Companion

object Companion

Properties

every

@get:JvmName(name = "everyRight")

val <T, Error, A> Traversal<T, Either<Error, A>>.every: Traversal<T, A>

@get:JvmName(name = "everyNonEmptyList")

val <T, A> Traversal<T, NonEmptyList<A>>.every: Traversal<T, A>

@get:JvmName(name = "everySome")

val <T, A> Traversal<T, Option<A>>.every: Traversal<T, A>

@get:JvmName(name = "everyChar")

val <T> Traversal<T, String>.every: Traversal<T, Char>

val <T, A> Traversal<T, List<A>>.every: Traversal<T, A>

@get:JvmName(name = "everyValue")

val <T, K, V> Traversal<T, Map<K, V>>.every: Traversal<T, V>

@get:JvmName(name = "everySequence")

val <T, A> Traversal<T, Sequence<A>>.every: Traversal<T, A>

left

val <A, L, R> Optional<A, Either<L, R>>.left: Optional<A, L>

DSL to compose a Optional with focus Either with a Prism with a focus of Either.Left<L>

val <A, L, R> Traversal<A, Either<L, R>>.left: Traversal<A, L>

DSL to compose a Traversal with focus Either with a Prism with a focus of Either.Left<L>

notNull

val <T, S> Optional<T, S?>.notNull: Optional<T, S>

DSL to compose an Optional with focus on a nullable type with notNull.

val <T, S> Traversal<T, S?>.notNull: Traversal<T, S>

DSL to compose a Traversal with focus on a nullable type with notNull.

right

val <A, L, R> Optional<A, Either<L, R>>.right: Optional<A, R>

DSL to compose a Optional with focus Either with a Prism with a focus of Either.Right<R>

val <A, L, R> Traversal<A, Either<L, R>>.right: Traversal<A, R>

DSL to compose a Traversal with focus Either with a Prism with a focus of Either.Right<R>

some

val <T, S> Optional<T, Option<S>>.some: Optional<T, S>

DSL to compose a Prism with focus arrow.core.Some with a Optional with a focus of Option<S>

val <T, S> Traversal<T, Option<S>>.some: Traversal<T, S>

DSL to compose a Prism with focus arrow.core.Some with a Traversal with a focus of Option<S>

Functions

all

open fun all(source: S, predicate: (focus: A) -> Boolean): Boolean

Check if all targets satisfy the predicate

and

infix fun <T, A, B> PTraversal<T, T, A, B>.and(other: PTraversal<T, T, A, B>): PTraversal<T, T, A, B>

Traversal that aggregates the elements of two other traversals.

any

open fun any(source: S, predicate: (focus: A) -> Boolean): Boolean

Returns true if at least one focus matches the given predicate.

fun <T, K, V> Optional<T, Map<K, V>>.at(key: K): Optional<T, Option<V>>

@JvmName(name = "atSet")

fun <T, A> Optional<T, Set<A>>.at(value: A): Optional<T, Boolean>

fun <T, K, V> Traversal<T, Map<K, V>>.at(key: K): Traversal<T, Option<V>>

@JvmName(name = "atSet")

fun <T, A> Traversal<T, Set<A>>.at(value: A): Traversal<T, Boolean>

fun <T, S, I, A> Optional<T, S>.at(at: At<S, I, A>, i: I): Optional<T, A>

DSL to compose At with an Optional for a structure S to focus in on A at given index I.

fun <T, S, I, A> Traversal<T, S>.at(at: At<S, I, A>, i: I): Traversal<T, A>

DSL to compose At with a Traversal for a structure S to focus in on A at given index I.

choice

open infix fun <S1, T1> choice(other: POptional<S1, T1, A, B>): POptional<Either<S, S1>, Either<T, T1>, A, B>

Join two POptional with the same focus B

open fun <U, V> choice(other: PTraversal<U, V, A, B>): PTraversal<Either<S, U>, Either<T, V>, A, B>

Join two PTraversal with the same target

compose

open infix fun <C, D> compose(other: POptional<in A, out B, out C, in D>): POptional<S, T, C, D>

Compose a POptional with a POptional

open infix fun <C, D> compose(other: PTraversal<in A, out B, out C, in D>): PTraversal<S, T, C, D>

Compose a PTraversal with a PTraversal

composeLazy

open infix fun <C, D> composeLazy(other: () -> PTraversal<in A, out B, out C, in D>): PTraversal<S, T, C, D>

every

fun <T, S, A> Traversal<T, S>.every(tr: Traversal<S, A>): Traversal<T, A>

DSL to compose Traversal with a Traversal for a structure S to see all its foci A

exists

open fun exists(source: S, predicate: (focus: A) -> Boolean): Boolean

Check whether at least one element satisfies the predicate.

filter

fun <S, A> Optional<S, A>.filter(predicate: (A) -> Boolean): Optional<S, A>

Focuses on the value only if the predicate is true.

fun <S, A> Traversal<S, A>.filter(predicate: (A) -> Boolean): Traversal<S, A>

Focuses on those values for which the predicate is true.

filterIndex

@JvmName(name = "filterNonEmptyList")

fun <T, A> Traversal<T, NonEmptyList<A>>.filterIndex(predicate: Predicate<Int>): Traversal<T, A>

@JvmName(name = "filterChars")

fun <T> Traversal<T, String>.filterIndex(predicate: Predicate<Int>): Traversal<T, Char>

fun <T, A> Traversal<T, List<A>>.filterIndex(predicate: Predicate<Int>): Traversal<T, A>

@JvmName(name = "filterValues")

fun <T, K, A> Traversal<T, Map<K, A>>.filterIndex(predicate: Predicate<K>): Traversal<T, A>

@JvmName(name = "filterSequence")

fun <T, A> Traversal<T, Sequence<A>>.filterIndex(predicate: Predicate<Int>): Traversal<T, A>

fun <T, S, I, A> Traversal<T, S>.filterIndex(filter: FilterIndex<S, I, A>, predicate: Predicate<I>): Traversal<T, A>

DSL to compose FilterIndex with an Traversal for a structure S to focus in on A at given index I

findOrNull

open fun findOrNull(source: S, predicate: (focus: A) -> Boolean): A?

Find the first element matching the predicate, if one exists.

first

open fun <C> first(): POptional<Pair<S, C>, Pair<T, C>, Pair<A, C>, Pair<B, C>>

Create a product of the POptional and a type C

firstOrNull

open fun firstOrNull(source: S): A?

Get the first target or null

fold

open fun fold(initial: A, combine: (A, A) -> A, source: S): A

Fold using the given initial value and combine function.

foldMap

open override fun <R> foldMap(initial: R, combine: (R, R) -> R, source: S, map: (focus: A) -> R): R

Map each target to a type R and use a Monoid to fold the results

getAll

open fun getAll(source: S): List<A>

Get all targets of the Traversal

getOrModify

abstract fun getOrModify(source: S): Either<T, A>

Get the focus of a POptional or return the original value while allowing the type to change if it does not match

getOrNull

open fun getOrNull(source: S): A?

Get the focus of an Optional or null if the is not there

index

@JvmName(name = "indexNonEmptyList")

fun <T, A> Optional<T, NonEmptyList<A>>.index(index: Int): Optional<T, A>

@JvmName(name = "indexString")

fun <T> Optional<T, String>.index(index: Int): Optional<T, Char>

fun <T, A> Optional<T, List<A>>.index(index: Int): Optional<T, A>

@JvmName(name = "indexValues")

fun <T, K, A> Optional<T, Map<K, A>>.index(key: K): Optional<T, A>

@JvmName(name = "indexSequence")

fun <T, A> Optional<T, Sequence<A>>.index(index: Int): Optional<T, A>

@JvmName(name = "indexNonEmptyList")

fun <T, A> Traversal<T, NonEmptyList<A>>.index(index: Int): Traversal<T, A>

@JvmName(name = "indexString")

fun <T> Traversal<T, String>.index(index: Int): Traversal<T, Char>

fun <T, A> Traversal<T, List<A>>.index(index: Int): Traversal<T, A>

@JvmName(name = "indexValues")

fun <T, K, A> Traversal<T, Map<K, A>>.index(key: K): Traversal<T, A>

@JvmName(name = "indexSequence")

fun <T, A> Traversal<T, Sequence<A>>.index(index: Int): Traversal<T, A>

fun <T, S, I, A> Optional<T, S>.index(idx: Index<S, I, A>, i: I): Optional<T, A>

DSL to compose Index with an Optional for a structure S to focus in on A at given index I

fun <T, S, I, A> Traversal<T, S>.index(idx: Index<S, I, A>, i: I): Traversal<T, A>

DSL to compose Index with a Traversal for a structure S to focus in on A at given index I

isEmpty

open fun isEmpty(source: S): Boolean

Check if there is no target

isNotEmpty

open fun isNotEmpty(source: S): Boolean

Check if there is at least one target

lastOrNull

open fun lastOrNull(source: S): A?

Get the last target or null

lift

open fun lift(map: (focus: A) -> B): (source: S) -> T

Lift a function map: (A) -> B to the context of S: (S) -> T`

modify

open override fun modify(source: S, map: (focus: A) -> B): T

Modify the focus of a POptional with a function map

modifyNullable

open fun modifyNullable(source: S, map: (focus: A) -> B): T?

Modify the focus of a POptional with a function map

onceOrMore

fun <S, A> Traversal<S, A>.onceOrMore(traversal: Traversal<A, A>): Traversal<S, A>

plus

open operator fun <C, D> plus(other: POptional<in A, out B, out C, in D>): POptional<S, T, C, D>

open operator fun <C, D> plus(other: PTraversal<in A, out B, out C, in D>): PTraversal<S, T, C, D>

second

open fun <C> second(): POptional<Pair<C, S>, Pair<C, T>, Pair<C, A>, Pair<C, B>>

Create a product of a type C and the POptional

set

abstract override fun set(source: S, focus: B): T

Get the modified source of a POptional

setNullable

open fun setNullable(source: S, b: B): T?

Set the focus of a POptional with a value.

size

open fun size(source: S): Int

Calculate the number of targets

times

operator fun <T, A, B> PTraversal<T, T, A, B>.times(other: PTraversal<T, T, A, B>): PTraversal<T, T, A, B>

Traversal that aggregates the elements of two other traversals.

zeroOrMore

fun <S, A> Traversal<S, A>.zeroOrMore(traversal: Traversal<A, A>): Traversal<S, A>