PTraversal

A Traversal is an optic that allows to see into a structure with 0 to N foci.

Traversal is a generalisation of kotlin.collections.map and can be seen as a representation of modify. all methods are written in terms of modify

Parameters

the source of a PTraversal

the modified source of a PTraversal

the target of a PTraversal

the modified target of a PTraversal

Inheritors

POptional

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> 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> 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> 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> 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> 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> 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 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: 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> 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.

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

abstract 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

index

@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> 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

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

Modify polymorphically the focus of a PTraversal 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: PTraversal<in A, out B, out C, in D>): PTraversal<S, T, C, D>

set

open fun set(source: S, focus: B): T

Set polymorphically the focus of a PTraversal with a value focus.

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>