ReadonlyArray overview

Added in v2.5.0


Table of contents


Alt

alt

Identifies an associative operation on a type constructor. It is similar to Semigroup, except that it applies to types of kind * -> *.

Signature

export declare const alt: <A>(that: Lazy<readonly A[]>) => (fa: readonly A[]) => readonly A[]

Added in v2.5.0

Alternative

zero

Signature

export declare const zero: <A>() => readonly A[]

Added in v2.7.0

Applicative

of

Signature

export declare const of: <A>(a: A) => readonly A[]

Added in v2.5.0

Apply

ap

Apply a function to an argument under a type constructor.

Signature

export declare const ap: <A>(fa: readonly A[]) => <B>(fab: readonly ((a: A) => B)[]) => readonly B[]

Added in v2.5.0

apFirst

Combine two effectful actions, keeping only the result of the first.

Signature

export declare const apFirst: <B>(fb: readonly B[]) => <A>(fa: readonly A[]) => readonly A[]

Added in v2.5.0

apSecond

Combine two effectful actions, keeping only the result of the second.

Signature

export declare const apSecond: <B>(fb: readonly B[]) => <A>(fa: readonly A[]) => readonly B[]

Added in v2.5.0

Compactable

compact

Signature

export declare const compact: <A>(fa: readonly Option<A>[]) => readonly A[]

Added in v2.5.0

separate

Signature

export declare const separate: <A, B>(fa: readonly Either<A, B>[]) => Separated<readonly A[], readonly B[]>

Added in v2.5.0

Extend

duplicate

Signature

export declare const duplicate: <A>(wa: readonly A[]) => readonly (readonly A[])[]

Added in v2.5.0

extend

Signature

export declare const extend: <A, B>(f: (fa: readonly A[]) => B) => (wa: readonly A[]) => readonly B[]

Added in v2.5.0

Filterable

filter

Signature

export declare const filter: {
  <A, B extends A>(refinement: Refinement<A, B>): (fa: readonly A[]) => readonly B[]
  <A>(predicate: Predicate<A>): (fa: readonly A[]) => readonly A[]
}

Added in v2.5.0

filterMap

Signature

export declare const filterMap: <A, B>(f: (a: A) => Option<B>) => (fa: readonly A[]) => readonly B[]

Added in v2.5.0

partition

Signature

export declare const partition: {
  <A, B extends A>(refinement: Refinement<A, B>): (fa: readonly A[]) => Separated<readonly A[], readonly B[]>
  <A>(predicate: Predicate<A>): (fa: readonly A[]) => Separated<readonly A[], readonly A[]>
}

Added in v2.5.0

partitionMap

Signature

export declare const partitionMap: <A, B, C>(
  f: (a: A) => Either<B, C>
) => (fa: readonly A[]) => Separated<readonly B[], readonly C[]>

Added in v2.5.0

FilterableWithIndex

filterMapWithIndex

Signature

export declare const filterMapWithIndex: <A, B>(f: (i: number, a: A) => Option<B>) => (fa: readonly A[]) => readonly B[]

Added in v2.5.0

filterWithIndex

Signature

export declare const filterWithIndex: {
  <A, B extends A>(refinementWithIndex: RefinementWithIndex<number, A, B>): (fa: readonly A[]) => readonly B[]
  <A>(predicateWithIndex: PredicateWithIndex<number, A>): (fa: readonly A[]) => readonly A[]
}

Added in v2.5.0

partitionMapWithIndex

Signature

export declare const partitionMapWithIndex: <A, B, C>(
  f: (i: number, a: A) => Either<B, C>
) => (fa: readonly A[]) => Separated<readonly B[], readonly C[]>

Added in v2.5.0

partitionWithIndex

Signature

export declare const partitionWithIndex: {
  <A, B extends A>(refinementWithIndex: RefinementWithIndex<number, A, B>): (
    fa: readonly A[]
  ) => Separated<readonly A[], readonly B[]>
  <A>(predicateWithIndex: PredicateWithIndex<number, A>): (fa: readonly A[]) => Separated<readonly A[], readonly A[]>
}

Added in v2.5.0

Foldable

foldMap

Signature

export declare const foldMap: <M>(M: Monoid<M>) => <A>(f: (a: A) => M) => (fa: readonly A[]) => M

Added in v2.5.0

reduce

Signature

export declare const reduce: <A, B>(b: B, f: (b: B, a: A) => B) => (fa: readonly A[]) => B

Added in v2.5.0

reduceRight

Signature

export declare const reduceRight: <A, B>(b: B, f: (a: A, b: B) => B) => (fa: readonly A[]) => B

Added in v2.5.0

FoldableWithIndex

foldMapWithIndex

Signature

export declare const foldMapWithIndex: <M>(M: Monoid<M>) => <A>(f: (i: number, a: A) => M) => (fa: readonly A[]) => M

Added in v2.5.0

reduceRightWithIndex

Signature

export declare const reduceRightWithIndex: <A, B>(b: B, f: (i: number, a: A, b: B) => B) => (fa: readonly A[]) => B

Added in v2.5.0

reduceWithIndex

Signature

export declare const reduceWithIndex: <A, B>(b: B, f: (i: number, b: B, a: A) => B) => (fa: readonly A[]) => B

Added in v2.5.0

Functor

map

map can be used to turn functions (a: A) => B into functions (fa: F<A>) => F<B> whose argument and return types use the type constructor F to represent some computational context.

Signature

export declare const map: <A, B>(f: (a: A) => B) => (fa: readonly A[]) => readonly B[]

Added in v2.5.0

FunctorWithIndex

mapWithIndex

Signature

export declare const mapWithIndex: <A, B>(f: (i: number, a: A) => B) => (fa: readonly A[]) => readonly B[]

Added in v2.5.0

Monad

chain

Composes computations in sequence, using the return value of one computation to determine the next computation.

Signature

export declare const chain: <A, B>(f: (a: A) => readonly B[]) => (ma: readonly A[]) => readonly B[]

Added in v2.5.0

chainFirst

Composes computations in sequence, using the return value of one computation to determine the next computation and keeping only the result of the first.

Signature

export declare const chainFirst: <A, B>(f: (a: A) => readonly B[]) => (ma: readonly A[]) => readonly A[]

Added in v2.5.0

flatten

Removes one level of nesting

Signature

export declare function flatten<A>(mma: ReadonlyArray<ReadonlyArray<A>>): ReadonlyArray<A>

Example

import { flatten } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(flatten([[1], [2], [3]]), [1, 2, 3])

Added in v2.5.0

Traversable

sequence

Signature

export declare const sequence: Sequence1<'ReadonlyArray'>

Added in v2.6.3

traverse

Signature

export declare const traverse: PipeableTraverse1<'ReadonlyArray'>

Added in v2.6.3

TraversableWithIndex

traverseWithIndex

Signature

export declare const traverseWithIndex: PipeableTraverseWithIndex1<'ReadonlyArray', number>

Added in v2.6.3

Unfoldable

unfold

Signature

export declare const unfold: <A, B>(b: B, f: (b: B) => Option<readonly [A, B]>) => readonly A[]

Added in v2.6.6

Whitherable

wilt

Signature

export declare const wilt: PipeableWilt1<'ReadonlyArray'>

Added in v2.6.5

wither

Signature

export declare const wither: PipeableWither1<'ReadonlyArray'>

Added in v2.6.5

combinators

chop

A useful recursion pattern for processing an array to produce a new array, often used for “chopping” up the input array. Typically chop is called with some function that will consume an initial prefix of the array and produce a value and the rest of the array.

Signature

export declare const chop: <A, B>(
  f: (as: ReadonlyNonEmptyArray<A>) => readonly [B, readonly A[]]
) => (as: readonly A[]) => readonly B[]

Example

import { Eq, eqNumber } from 'fp-ts/lib/Eq'
import { chop, spanLeft } from 'fp-ts/lib/ReadonlyArray'

const group = <A>(S: Eq<A>): ((as: ReadonlyArray<A>) => ReadonlyArray<ReadonlyArray<A>>) => {
  return chop((as) => {
    const { init, rest } = spanLeft((a: A) => S.equals(a, as[0]))(as)
    return [init, rest]
  })
}
assert.deepStrictEqual(group(eqNumber)([1, 1, 2, 3, 3, 4]), [[1, 1], [2], [3, 3], [4]])

Added in v2.5.0

difference

Creates an array of array values not included in the other given array using a Eq for equality comparisons. The order and references of result values are determined by the first array.

Signature

export declare function difference<A>(
  E: Eq<A>
): {
  (xs: ReadonlyArray<A>): (ys: ReadonlyArray<A>) => ReadonlyArray<A>
  (xs: ReadonlyArray<A>, ys: ReadonlyArray<A>): ReadonlyArray<A>
}

Example

import { difference } from 'fp-ts/lib/ReadonlyArray'
import { eqNumber } from 'fp-ts/lib/Eq'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2], difference(eqNumber)([2, 3])), [1])

Added in v2.5.0

dropLeft

Drop a number of elements from the start of an array, creating a new array

Signature

export declare function dropLeft(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { dropLeft } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(dropLeft(2)([1, 2, 3]), [3])

Added in v2.5.0

dropLeftWhile

Remove the longest initial subarray for which all element satisfy the specified predicate, creating a new array

Signature

export declare function dropLeftWhile<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { dropLeftWhile } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(dropLeftWhile((n: number) => n % 2 === 1)([1, 3, 2, 4, 5]), [2, 4, 5])

Added in v2.5.0

dropRight

Drop a number of elements from the end of an array, creating a new array

Signature

export declare function dropRight(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { dropRight } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(dropRight(2)([1, 2, 3, 4, 5]), [1, 2, 3])

Added in v2.5.0

intersection

Creates an array of unique values that are included in all given arrays using a Eq for equality comparisons. The order and references of result values are determined by the first array.

Signature

export declare function intersection<A>(
  E: Eq<A>
): {
  (xs: ReadonlyArray<A>): (ys: ReadonlyArray<A>) => ReadonlyArray<A>
  (xs: ReadonlyArray<A>, ys: ReadonlyArray<A>): ReadonlyArray<A>
}

Example

import { intersection } from 'fp-ts/lib/ReadonlyArray'
import { eqNumber } from 'fp-ts/lib/Eq'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2], intersection(eqNumber)([2, 3])), [2])

Added in v2.5.0

reverse

Reverse an array, creating a new array

Signature

export declare function reverse<A>(as: ReadonlyArray<A>): ReadonlyArray<A>

Example

import { reverse } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(reverse([1, 2, 3]), [3, 2, 1])

Added in v2.5.0

rights

Extracts from an array of Either all the Right elements. All the Right elements are extracted in order

Signature

export declare function rights<E, A>(as: ReadonlyArray<Either<E, A>>): ReadonlyArray<A>

Example

import { rights } from 'fp-ts/lib/ReadonlyArray'
import { right, left } from 'fp-ts/lib/Either'

assert.deepStrictEqual(rights([right(1), left('foo'), right(2)]), [1, 2])

Added in v2.5.0

rotate

Rotate an array to the right by n steps

Signature

export declare function rotate(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { rotate } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(rotate(2)([1, 2, 3, 4, 5]), [4, 5, 1, 2, 3])

Added in v2.5.0

scanLeft

Same as reduce but it carries over the intermediate steps

import { scanLeft } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(scanLeft(10, (b, a: number) => b - a)([1, 2, 3]), [10, 9, 7, 4])

Signature

export declare function scanLeft<A, B>(b: B, f: (b: B, a: A) => B): (as: ReadonlyArray<A>) => ReadonlyArray<B>

Added in v2.5.0

scanRight

Fold an array from the right, keeping all intermediate results instead of only the final result

Signature

export declare function scanRight<A, B>(b: B, f: (a: A, b: B) => B): (as: ReadonlyArray<A>) => ReadonlyArray<B>

Example

import { scanRight } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(scanRight(10, (a: number, b) => b - a)([1, 2, 3]), [4, 5, 7, 10])

Added in v2.5.0

sort

Sort the elements of an array in increasing order, creating a new array

Signature

export declare function sort<A>(O: Ord<A>): (as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { sort } from 'fp-ts/lib/ReadonlyArray'
import { ordNumber } from 'fp-ts/lib/Ord'

assert.deepStrictEqual(sort(ordNumber)([3, 2, 1]), [1, 2, 3])

Added in v2.5.0

sortBy

Sort the elements of an array in increasing order, where elements are compared using first ords[0], then ords[1], etc…

Signature

export declare function sortBy<A>(ords: ReadonlyArray<Ord<A>>): (as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { sortBy } from 'fp-ts/lib/ReadonlyArray'
import { ord, ordString, ordNumber } from 'fp-ts/lib/Ord'

interface Person {
  name: string
  age: number
}
const byName = ord.contramap(ordString, (p: Person) => p.name)
const byAge = ord.contramap(ordNumber, (p: Person) => p.age)

const sortByNameByAge = sortBy([byName, byAge])

const persons = [
  { name: 'a', age: 1 },
  { name: 'b', age: 3 },
  { name: 'c', age: 2 },
  { name: 'b', age: 2 },
]
assert.deepStrictEqual(sortByNameByAge(persons), [
  { name: 'a', age: 1 },
  { name: 'b', age: 2 },
  { name: 'b', age: 3 },
  { name: 'c', age: 2 },
])

Added in v2.5.0

takeLeft

Keep only a number of elements from the start of an array, creating a new array. n must be a natural number

Signature

export declare function takeLeft(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { takeLeft } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(takeLeft(2)([1, 2, 3]), [1, 2])

Added in v2.5.0

takeLeftWhile

Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new array

Signature

export declare function takeLeftWhile<A, B extends A>(
  refinement: Refinement<A, B>
): (as: ReadonlyArray<A>) => ReadonlyArray<B>
export declare function takeLeftWhile<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { takeLeftWhile } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(takeLeftWhile((n: number) => n % 2 === 0)([2, 4, 3, 6]), [2, 4])

Added in v2.5.0

union

Creates an array of unique values, in order, from all given arrays using a Eq for equality comparisons

Signature

export declare function union<A>(
  E: Eq<A>
): {
  (xs: ReadonlyArray<A>): (ys: ReadonlyArray<A>) => ReadonlyArray<A>
  (xs: ReadonlyArray<A>, ys: ReadonlyArray<A>): ReadonlyArray<A>
}

Example

import { union } from 'fp-ts/lib/ReadonlyArray'
import { eqNumber } from 'fp-ts/lib/Eq'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2], union(eqNumber)([2, 3])), [1, 2, 3])

Added in v2.5.0

uniq

Remove duplicates from an array, keeping the first occurrence of an element.

Signature

export declare function uniq<A>(E: Eq<A>): (as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { uniq } from 'fp-ts/lib/ReadonlyArray'
import { eqNumber } from 'fp-ts/lib/Eq'

assert.deepStrictEqual(uniq(eqNumber)([1, 2, 1]), [1, 2])

Added in v2.5.0

zip

Takes two arrays and returns an array of corresponding pairs. If one input array is short, excess elements of the longer array are discarded

Signature

export declare function zip<B>(bs: ReadonlyArray<B>): <A>(as: ReadonlyArray<A>) => ReadonlyArray<readonly [A, B]>
export declare function zip<A, B>(as: ReadonlyArray<A>, bs: ReadonlyArray<B>): ReadonlyArray<readonly [A, B]>

Example

import { zip } from 'fp-ts/lib/ReadonlyArray'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2, 3], zip(['a', 'b', 'c', 'd'])), [
  [1, 'a'],
  [2, 'b'],
  [3, 'c'],
])

Added in v2.5.0

zipWith

Apply a function to pairs of elements at the same index in two arrays, collecting the results in a new array. If one input array is short, excess elements of the longer array are discarded.

Signature

export declare function zipWith<A, B, C>(
  fa: ReadonlyArray<A>,
  fb: ReadonlyArray<B>,
  f: (a: A, b: B) => C
): ReadonlyArray<C>

Example

import { zipWith } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(
  zipWith([1, 2, 3], ['a', 'b', 'c', 'd'], (n, s) => s + n),
  ['a1', 'b2', 'c3']
)

Added in v2.5.0

constructors

cons

Attaches an element to the front of an array, creating a new non empty array

Signature

export declare function cons<A>(head: A): (tail: ReadonlyArray<A>) => ReadonlyNonEmptyArray<A>
export declare function cons<A>(head: A, tail: ReadonlyArray<A>): ReadonlyNonEmptyArray<A>

Example

import { cons } from 'fp-ts/lib/ReadonlyArray'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2, 3], cons(0)), [0, 1, 2, 3])

Added in v2.5.0

fromArray

Signature

export declare function fromArray<A>(as: Array<A>): ReadonlyArray<A>

Added in v2.5.0

makeBy

Return a list of length n with element i initialized with f(i)

Signature

export declare function makeBy<A>(n: number, f: (i: number) => A): ReadonlyArray<A>

Example

import { makeBy } from 'fp-ts/lib/ReadonlyArray'

const double = (n: number): number => n * 2
assert.deepStrictEqual(makeBy(5, double), [0, 2, 4, 6, 8])

Added in v2.5.0

range

Create an array containing a range of integers, including both endpoints

Signature

export declare function range(start: number, end: number): ReadonlyArray<number>

Example

import { range } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(range(1, 5), [1, 2, 3, 4, 5])

Added in v2.5.0

replicate

Create an array containing a value repeated the specified number of times

Signature

export declare function replicate<A>(n: number, a: A): ReadonlyArray<A>

Example

import { replicate } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(replicate(3, 'a'), ['a', 'a', 'a'])

Added in v2.5.0

snoc

Append an element to the end of an array, creating a new non empty array

Signature

export declare function snoc<A>(init: ReadonlyArray<A>, end: A): ReadonlyNonEmptyArray<A>

Example

import { snoc } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(snoc([1, 2, 3], 4), [1, 2, 3, 4])

Added in v2.5.0

destructors

foldLeft

Break an array into its first element and remaining elements

Signature

export declare function foldLeft<A, B>(
  onNil: Lazy<B>,
  onCons: (head: A, tail: ReadonlyArray<A>) => B
): (as: ReadonlyArray<A>) => B

Example

import { foldLeft } from 'fp-ts/lib/ReadonlyArray'

const len: <A>(as: ReadonlyArray<A>) => number = foldLeft(
  () => 0,
  (_, tail) => 1 + len(tail)
)
assert.strictEqual(len([1, 2, 3]), 3)

Added in v2.5.0

foldRight

Break an array into its initial elements and the last element

Signature

export declare function foldRight<A, B>(
  onNil: Lazy<B>,
  onCons: (init: ReadonlyArray<A>, last: A) => B
): (as: ReadonlyArray<A>) => B

Added in v2.5.0

toArray

Signature

export declare function toArray<A>(ras: ReadonlyArray<A>): Array<A>

Added in v2.5.0

guards

isNonEmpty

Test whether an array is non empty narrowing down the type to NonEmptyReadonlyArray<A>

Signature

export declare function isNonEmpty<A>(as: ReadonlyArray<A>): as is ReadonlyNonEmptyArray<A>

Added in v2.5.0

instances

URI

Signature

export declare const URI: 'ReadonlyArray'

Added in v2.5.0

URI (type alias)

Signature

export type URI = typeof URI

Added in v2.5.0

altArray

Signature

export declare const altArray: Alt1<'ReadonlyArray'>

Added in v2.7.0

alternativeArray

Signature

export declare const alternativeArray: Alternative1<'ReadonlyArray'>

Added in v2.7.0

applicativeArray

Signature

export declare const applicativeArray: Applicative1<'ReadonlyArray'>

Added in v2.7.0

compactableArray

Signature

export declare const compactableArray: Compactable1<'ReadonlyArray'>

Added in v2.7.0

extendArray

Signature

export declare const extendArray: Extend1<'ReadonlyArray'>

Added in v2.7.0

filterableArray

Signature

export declare const filterableArray: Filterable1<'ReadonlyArray'>

Added in v2.7.0

filterableWithIndexArray

Signature

export declare const filterableWithIndexArray: FilterableWithIndex1<'ReadonlyArray', number>

Added in v2.7.0

foldableArray

Signature

export declare const foldableArray: Foldable1<'ReadonlyArray'>

Added in v2.7.0

foldableWithIndexArray

Signature

export declare const foldableWithIndexArray: FoldableWithIndex1<'ReadonlyArray', number>

Added in v2.7.0

functorArray

Signature

export declare const functorArray: Functor1<'ReadonlyArray'>

Added in v2.7.0

functorWithIndexArray

Signature

export declare const functorWithIndexArray: FunctorWithIndex1<'ReadonlyArray', number>

Added in v2.7.0

getEq

Derives an Eq over the ReadonlyArray of a given element type from the Eq of that type. The derived Eq defines two arrays as equal if all elements of both arrays are compared equal pairwise with the given E. In case of arrays of different lengths, the result is non equality.

Signature

export declare function getEq<A>(E: Eq<A>): Eq<ReadonlyArray<A>>

Example

import { eqString } from 'fp-ts/lib/Eq'
import { getEq } from 'fp-ts/lib/ReadonlyArray'

const E = getEq(eqString)
assert.strictEqual(E.equals(['a', 'b'], ['a', 'b']), true)
assert.strictEqual(E.equals(['a'], []), false)

Added in v2.5.0

getMonoid

Returns a Monoid for ReadonlyArray<A>

Signature

export declare function getMonoid<A = never>(): Monoid<ReadonlyArray<A>>

Example

import { getMonoid } from 'fp-ts/lib/ReadonlyArray'

const M = getMonoid<number>()
assert.deepStrictEqual(M.concat([1, 2], [3, 4]), [1, 2, 3, 4])

Added in v2.5.0

getOrd

Derives an Ord over the ReadonlyArray of a given element type from the Ord of that type. The ordering between two such arrays is equal to: the first non equal comparison of each arrays elements taken pairwise in increasing order, in case of equality over all the pairwise elements; the longest array is considered the greatest, if both arrays have the same length, the result is equality.

Signature

export declare function getOrd<A>(O: Ord<A>): Ord<ReadonlyArray<A>>

Example

import { getOrd } from 'fp-ts/lib/ReadonlyArray'
import { ordString } from 'fp-ts/lib/Ord'

const O = getOrd(ordString)
assert.strictEqual(O.compare(['b'], ['a']), 1)
assert.strictEqual(O.compare(['a'], ['a']), 0)
assert.strictEqual(O.compare(['a'], ['b']), -1)

Added in v2.5.0

getShow

Signature

export declare function getShow<A>(S: Show<A>): Show<ReadonlyArray<A>>

Added in v2.5.0

monadArray

Signature

export declare const monadArray: Monad1<'ReadonlyArray'>

Added in v2.7.0

readonlyArray

Signature

export declare const readonlyArray: FunctorWithIndex1<'ReadonlyArray', number> &
  Monad1<'ReadonlyArray'> &
  Unfoldable1<'ReadonlyArray'> &
  Alternative1<'ReadonlyArray'> &
  Extend1<'ReadonlyArray'> &
  FilterableWithIndex1<'ReadonlyArray', number> &
  FoldableWithIndex1<'ReadonlyArray', number> &
  TraversableWithIndex1<'ReadonlyArray', number> &
  Witherable1<'ReadonlyArray'>

Added in v2.5.0

traversableArray

Signature

export declare const traversableArray: Traversable1<'ReadonlyArray'>

Added in v2.7.0

traversableWithIndexArray

Signature

export declare const traversableWithIndexArray: TraversableWithIndex1<'ReadonlyArray', number>

Added in v2.7.0

unfoldableArray

Signature

export declare const unfoldableArray: Unfoldable1<'ReadonlyArray'>

Added in v2.7.0

witherableArray

Signature

export declare const witherableArray: Witherable1<'ReadonlyArray'>

Added in v2.7.0

unsafe

unsafeDeleteAt

Signature

export declare function unsafeDeleteAt<A>(i: number, as: ReadonlyArray<A>): ReadonlyArray<A>

Added in v2.5.0

unsafeInsertAt

Signature

export declare function unsafeInsertAt<A>(i: number, a: A, as: ReadonlyArray<A>): ReadonlyArray<A>

Added in v2.5.0

unsafeUpdateAt

Signature

export declare function unsafeUpdateAt<A>(i: number, a: A, as: ReadonlyArray<A>): ReadonlyArray<A>

Added in v2.5.0

utils

Spanned (interface)

Signature

export interface Spanned<I, R> {
  readonly init: ReadonlyArray<I>
  readonly rest: ReadonlyArray<R>
}

Added in v2.5.0

chainWithIndex

Signature

export declare const chainWithIndex: <A, B>(f: (i: number, a: A) => readonly B[]) => (ma: readonly A[]) => readonly B[]

Added in v2.7.0

chunksOf

Splits an array into length-n pieces. The last piece will be shorter if n does not evenly divide the length of the array. Note that chunksOf(n)([]) is [], not [[]]. This is intentional, and is consistent with a recursive definition of chunksOf; it satisfies the property that

chunksOf(n)(xs).concat(chunksOf(n)(ys)) == chunksOf(n)(xs.concat(ys)))

whenever n evenly divides the length of xs.

Signature

export declare function chunksOf(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<ReadonlyArray<A>>

Example

import { chunksOf } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(chunksOf(2)([1, 2, 3, 4, 5]), [[1, 2], [3, 4], [5]])

Added in v2.5.0

comprehension

Array comprehension

[ f(x, y, ...) | x ← xs, y ← ys, ..., g(x, y, ...) ]

Signature

export declare function comprehension<A, B, C, D, R>(
  input: readonly [ReadonlyArray<A>, ReadonlyArray<B>, ReadonlyArray<C>, ReadonlyArray<D>],
  f: (a: A, b: B, c: C, d: D) => R,
  g?: (a: A, b: B, c: C, d: D) => boolean
): ReadonlyArray<R>
export declare function comprehension<A, B, C, R>(
  input: readonly [ReadonlyArray<A>, ReadonlyArray<B>, ReadonlyArray<C>],
  f: (a: A, b: B, c: C) => R,
  g?: (a: A, b: B, c: C) => boolean
): ReadonlyArray<R>
export declare function comprehension<A, R>(
  input: readonly [ReadonlyArray<A>],
  f: (a: A) => R,
  g?: (a: A) => boolean
): ReadonlyArray<R>
export declare function comprehension<A, B, R>(
  input: readonly [ReadonlyArray<A>, ReadonlyArray<B>],
  f: (a: A, b: B) => R,
  g?: (a: A, b: B) => boolean
): ReadonlyArray<R>
export declare function comprehension<A, R>(
  input: readonly [ReadonlyArray<A>],
  f: (a: A) => boolean,
  g?: (a: A) => R
): ReadonlyArray<R>

Example

import { comprehension } from 'fp-ts/lib/ReadonlyArray'
import { tuple } from 'fp-ts/lib/function'

assert.deepStrictEqual(
  comprehension(
    [
      [1, 2, 3],
      ['a', 'b'],
    ],
    tuple,
    (a, b) => (a + b.length) % 2 === 0
  ),
  [
    [1, 'a'],
    [1, 'b'],
    [3, 'a'],
    [3, 'b'],
  ]
)

Added in v2.5.0

deleteAt

Delete the element at the specified index, creating a new array, or returning None if the index is out of bounds

Signature

export declare function deleteAt(i: number): <A>(as: ReadonlyArray<A>) => Option<ReadonlyArray<A>>

Example

import { deleteAt } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(deleteAt(0)([1, 2, 3]), some([2, 3]))
assert.deepStrictEqual(deleteAt(1)([]), none)

Added in v2.5.0

elem

Test if a value is a member of an array. Takes a Eq<A> as a single argument which returns the function to use to search for a value of type A in an array of type ReadonlyArray<A>.

Signature

export declare function elem<A>(
  E: Eq<A>
): {
  (a: A): (as: ReadonlyArray<A>) => boolean
  (a: A, as: ReadonlyArray<A>): boolean
}

Example

import { elem } from 'fp-ts/lib/ReadonlyArray'
import { eqNumber } from 'fp-ts/lib/Eq'
import { pipe } from 'fp-ts/lib/function'

assert.strictEqual(pipe([1, 2, 3], elem(eqNumber)(2)), true)
assert.strictEqual(pipe([1, 2, 3], elem(eqNumber)(0)), false)

Added in v2.5.0

empty

An empty array

Signature

export declare const empty: readonly never[]

Added in v2.5.0

findFirst

Find the first element which satisfies a predicate (or a refinement) function

Signature

export declare function findFirst<A, B extends A>(refinement: Refinement<A, B>): (as: ReadonlyArray<A>) => Option<B>
export declare function findFirst<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => Option<A>

Example

import { findFirst } from 'fp-ts/lib/ReadonlyArray'
import { some } from 'fp-ts/lib/Option'

assert.deepStrictEqual(
  findFirst((x: { a: number; b: number }) => x.a === 1)([
    { a: 1, b: 1 },
    { a: 1, b: 2 },
  ]),
  some({ a: 1, b: 1 })
)

Added in v2.5.0

findFirstMap

Find the first element returned by an option based selector function

Signature

export declare function findFirstMap<A, B>(f: (a: A) => Option<B>): (as: ReadonlyArray<A>) => Option<B>

Example

import { findFirstMap } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

interface Person {
  name: string
  age?: number
}

const persons: ReadonlyArray<Person> = [{ name: 'John' }, { name: 'Mary', age: 45 }, { name: 'Joey', age: 28 }]

// returns the name of the first person that has an age
assert.deepStrictEqual(findFirstMap((p: Person) => (p.age === undefined ? none : some(p.name)))(persons), some('Mary'))

Added in v2.5.0

findIndex

Find the first index for which a predicate holds

Signature

export declare function findIndex<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => Option<number>

Example

import { findIndex } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(findIndex((n: number) => n === 2)([1, 2, 3]), some(1))
assert.deepStrictEqual(findIndex((n: number) => n === 2)([]), none)

Added in v2.5.0

findLast

Find the last element which satisfies a predicate function

Signature

export declare function findLast<A, B extends A>(refinement: Refinement<A, B>): (as: ReadonlyArray<A>) => Option<B>
export declare function findLast<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => Option<A>

Example

import { findLast } from 'fp-ts/lib/ReadonlyArray'
import { some } from 'fp-ts/lib/Option'

assert.deepStrictEqual(
  findLast((x: { a: number; b: number }) => x.a === 1)([
    { a: 1, b: 1 },
    { a: 1, b: 2 },
  ]),
  some({ a: 1, b: 2 })
)

Added in v2.5.0

findLastIndex

Returns the index of the last element of the list which matches the predicate

Signature

export declare function findLastIndex<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => Option<number>

Example

import { findLastIndex } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

interface X {
  a: number
  b: number
}
const xs: ReadonlyArray<X> = [
  { a: 1, b: 0 },
  { a: 1, b: 1 },
]
assert.deepStrictEqual(findLastIndex((x: { a: number }) => x.a === 1)(xs), some(1))
assert.deepStrictEqual(findLastIndex((x: { a: number }) => x.a === 4)(xs), none)

Added in v2.5.0

findLastMap

Find the last element returned by an option based selector function

Signature

export declare function findLastMap<A, B>(f: (a: A) => Option<B>): (as: ReadonlyArray<A>) => Option<B>

Example

import { findLastMap } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

interface Person {
  name: string
  age?: number
}

const persons: ReadonlyArray<Person> = [{ name: 'John' }, { name: 'Mary', age: 45 }, { name: 'Joey', age: 28 }]

// returns the name of the last person that has an age
assert.deepStrictEqual(findLastMap((p: Person) => (p.age === undefined ? none : some(p.name)))(persons), some('Joey'))

Added in v2.5.0

Get the first element in an array, or None if the array is empty

Signature

export declare function head<A>(as: ReadonlyArray<A>): Option<A>

Example

import { head } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(head([1, 2, 3]), some(1))
assert.deepStrictEqual(head([]), none)

Added in v2.5.0

init

Get all but the last element of an array, creating a new array, or None if the array is empty

Signature

export declare function init<A>(as: ReadonlyArray<A>): Option<ReadonlyArray<A>>

Example

import { init } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(init([1, 2, 3]), some([1, 2]))
assert.deepStrictEqual(init([]), none)

Added in v2.5.0

insertAt

Insert an element at the specified index, creating a new array, or returning None if the index is out of bounds

Signature

export declare function insertAt<A>(i: number, a: A): (as: ReadonlyArray<A>) => Option<ReadonlyArray<A>>

Example

import { insertAt } from 'fp-ts/lib/ReadonlyArray'
import { some } from 'fp-ts/lib/Option'

assert.deepStrictEqual(insertAt(2, 5)([1, 2, 3, 4]), some([1, 2, 5, 3, 4]))

Added in v2.5.0

isEmpty

Test whether an array is empty

Signature

export declare function isEmpty<A>(as: ReadonlyArray<A>): boolean

Example

import { isEmpty } from 'fp-ts/lib/ReadonlyArray'

assert.strictEqual(isEmpty([]), true)

Added in v2.5.0

isOutOfBound

Test whether an array contains a particular index

Signature

export declare function isOutOfBound<A>(i: number, as: ReadonlyArray<A>): boolean

Added in v2.5.0

last

Get the last element in an array, or None if the array is empty

Signature

export declare function last<A>(as: ReadonlyArray<A>): Option<A>

Example

import { last } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(last([1, 2, 3]), some(3))
assert.deepStrictEqual(last([]), none)

Added in v2.5.0

lefts

Extracts from an array of Either all the Left elements. All the Left elements are extracted in order

Signature

export declare function lefts<E, A>(as: ReadonlyArray<Either<E, A>>): ReadonlyArray<E>

Example

import { lefts } from 'fp-ts/lib/ReadonlyArray'
import { left, right } from 'fp-ts/lib/Either'

assert.deepStrictEqual(lefts([right(1), left('foo'), right(2)]), ['foo'])

Added in v2.5.0

lookup

This function provides a safe way to read a value at a particular index from an array

Signature

export declare function lookup(i: number): <A>(as: ReadonlyArray<A>) => Option<A>
export declare function lookup<A>(i: number, as: ReadonlyArray<A>): Option<A>

Example

import { lookup } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'
import { pipe } from 'fp-ts/lib/function'

assert.deepStrictEqual(pipe([1, 2, 3], lookup(1)), some(2))
assert.deepStrictEqual(pipe([1, 2, 3], lookup(3)), none)

Added in v2.5.0

modifyAt

Apply a function to the element at the specified index, creating a new array, or returning None if the index is out of bounds

Signature

export declare function modifyAt<A>(i: number, f: (a: A) => A): (as: ReadonlyArray<A>) => Option<ReadonlyArray<A>>

Example

import { modifyAt } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

const double = (x: number): number => x * 2
assert.deepStrictEqual(modifyAt(1, double)([1, 2, 3]), some([1, 4, 3]))
assert.deepStrictEqual(modifyAt(1, double)([]), none)

Added in v2.5.0

spanLeft

Split an array into two parts:

  1. the longest initial subarray for which all elements satisfy the specified predicate
  2. the remaining elements

Signature

export declare function spanLeft<A, B extends A>(refinement: Refinement<A, B>): (as: ReadonlyArray<A>) => Spanned<B, A>
export declare function spanLeft<A>(predicate: Predicate<A>): (as: ReadonlyArray<A>) => Spanned<A, A>

Example

import { spanLeft } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(spanLeft((n: number) => n % 2 === 1)([1, 3, 2, 4, 5]), { init: [1, 3], rest: [2, 4, 5] })

Added in v2.5.0

splitAt

Splits an array into two pieces, the first piece has n elements.

Signature

export declare function splitAt(n: number): <A>(as: ReadonlyArray<A>) => readonly [ReadonlyArray<A>, ReadonlyArray<A>]

Example

import { splitAt } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(splitAt(2)([1, 2, 3, 4, 5]), [
  [1, 2],
  [3, 4, 5],
])

Added in v2.5.0

tail

Get all but the first element of an array, creating a new array, or None if the array is empty

Signature

export declare function tail<A>(as: ReadonlyArray<A>): Option<ReadonlyArray<A>>

Example

import { tail } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(tail([1, 2, 3]), some([2, 3]))
assert.deepStrictEqual(tail([]), none)

Added in v2.5.0

takeRight

Keep only a number of elements from the end of an array, creating a new array. n must be a natural number

Signature

export declare function takeRight(n: number): <A>(as: ReadonlyArray<A>) => ReadonlyArray<A>

Example

import { takeRight } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(takeRight(2)([1, 2, 3, 4, 5]), [4, 5])

Added in v2.5.0

unzip

The function is reverse of zip. Takes an array of pairs and return two corresponding arrays

Signature

export declare function unzip<A, B>(as: ReadonlyArray<readonly [A, B]>): readonly [ReadonlyArray<A>, ReadonlyArray<B>]

Example

import { unzip } from 'fp-ts/lib/ReadonlyArray'

assert.deepStrictEqual(
  unzip([
    [1, 'a'],
    [2, 'b'],
    [3, 'c'],
  ]),
  [
    [1, 2, 3],
    ['a', 'b', 'c'],
  ]
)

Added in v2.5.0

updateAt

Change the element at the specified index, creating a new array, or returning None if the index is out of bounds

Signature

export declare function updateAt<A>(i: number, a: A): (as: ReadonlyArray<A>) => Option<ReadonlyArray<A>>

Example

import { updateAt } from 'fp-ts/lib/ReadonlyArray'
import { some, none } from 'fp-ts/lib/Option'

assert.deepStrictEqual(updateAt(1, 1)([1, 2, 3]), some([1, 1, 3]))
assert.deepStrictEqual(updateAt(1, 1)([]), none)

Added in v2.5.0