Array overview

Added in v2.0.0


Table of contents


URI (type alias)

Signature

export type URI = typeof URI

Added in v2.0.0

URI

Signature

export const URI: "Array" = ...

Added in v2.0.0

alt

Signature

<A>(that: () => A[]) => (fa: A[]) => A[]

Added in v2.0.0

ap

Signature

<A>(fa: A[]) => <B>(fab: ((a: A) => B)[]) => B[]

Added in v2.0.0

apFirst

Signature

<B>(fb: B[]) => <A>(fa: A[]) => A[]

Added in v2.0.0

apSecond

Signature

<B>(fb: B[]) => <A>(fa: A[]) => B[]

Added in v2.0.0

array

Signature

export const array: Monad1<URI> &
  Foldable1<URI> &
  Unfoldable1<URI> &
  TraversableWithIndex1<URI, number> &
  Alternative1<URI> &
  Extend1<URI> &
  Compactable1<URI> &
  FilterableWithIndex1<URI, number> &
  Witherable1<URI> &
  FunctorWithIndex1<URI, number> &
  FoldableWithIndex1<URI, number> = ...

Added in v2.0.0

chain

Signature

<A, B>(f: (a: A) => B[]) => (ma: A[]) => B[]

Added in v2.0.0

chainFirst

Signature

<A, B>(f: (a: A) => B[]) => (ma: A[]) => A[]

Added in v2.0.0

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 const chop: <A, B>(f: (as: NonEmptyArray<A>) => [B, Array<A>]) => (as: Array<A>) => Array<B> = ...

Example

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

const group = <A>(S: Eq<A>): ((as: Array<A>) => Array<Array<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 v2.0.0

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 const chunksOf: (n: number) => <A>(as: Array<A>) => Array<Array<A>> = ...

Example

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

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

Added in v2.0.0

compact

Signature

<A>(fa: Option<A>[]) => A[]

Added in v2.0.0

comprehension

Array comprehension

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

Signature

export function comprehension<A, B, C, D, R>(
  input: [Array<A>, Array<B>, Array<C>, Array<D>],
  f: (a: A, b: B, c: C, d: D) => R,
  g?: (a: A, b: B, c: C, d: D) => boolean
): Array<R>
export function comprehension<A, B, C, R>(
  input: [Array<A>, Array<B>, Array<C>],
  f: (a: A, b: B, c: C) => R,
  g?: (a: A, b: B, c: C) => boolean
): Array<R>
export function comprehension<A, R>(input: [Array<A>], f: (a: A) => R, g?: (a: A) => boolean): Array<R>
export function comprehension<A, B, R>(
  input: [Array<A>, Array<B>],
  f: (a: A, b: B) => R,
  g?: (a: A, b: B) => boolean
): Array<R>
export function comprehension<A, R>(input: [Array<A>], f: (a: A) => boolean, g?: (a: A) => R): Array<R> { ... }

Example

import { comprehension } from 'fp-ts/lib/Array'
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 v2.0.0

cons

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

Signature

export const cons: <A>(head: A, tail: Array<A>) => NonEmptyArray<A> = ...

Example

import { cons } from 'fp-ts/lib/Array'

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

Added in v2.0.0

copy

Signature

export const copy: <A>(as: Array<A>) => Array<A> = ...

Added in v2.0.0

deleteAt

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

Signature

export const deleteAt: (i: number) => <A>(as: Array<A>) => Option<Array<A>> = ...

Example

import { deleteAt } from 'fp-ts/lib/Array'
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 v2.0.0

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 const difference: <A>(E: Eq<A>) => (xs: Array<A>, ys: Array<A>) => Array<A> = ...

Example

import { difference } from 'fp-ts/lib/Array'
import { eqNumber } from 'fp-ts/lib/Eq'

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

Added in v2.0.0

dropLeft

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

Signature

export const dropLeft: (n: number) => <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

dropLeftWhile

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

Signature

export const dropLeftWhile: <A>(predicate: Predicate<A>) => (as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

dropRight

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

Signature

export const dropRight: (n: number) => <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

duplicate

Signature

<A>(ma: A[]) => A[][]

Added in v2.0.0

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 Array<A>.

Signature

export const elem: <A>(E: Eq<A>) => (a: A, as: Array<A>) => boolean = ...

Example

import { elem } from 'fp-ts/lib/Array'
import { eqNumber } from 'fp-ts/lib/Eq'

assert.strictEqual(elem(eqNumber)(1, [1, 2, 3]), true)
assert.strictEqual(elem(eqNumber)(4, [1, 2, 3]), false)

Added in v2.0.0

empty

An empty array

Signature

export const empty: Array<never> = ...

Added in v2.0.0

extend

Signature

<A, B>(f: (fa: A[]) => B) => (ma: A[]) => B[]

Added in v2.0.0

filter

Signature

{ <A, B>(refinement: Refinement<A, B>): (fa: A[]) => B[]; <A>(predicate: Predicate<A>): (fa: A[]) => A[]; }

Added in v2.0.0

filterMap

Signature

<A, B>(f: (a: A) => Option<B>) => (fa: A[]) => B[]

Added in v2.0.0

filterMapWithIndex

Signature

<A, B>(f: (i: number, a: A) => Option<B>) => (fa: A[]) => B[]

Added in v2.0.0

filterWithIndex

Signature

{ <A, B>(refinementWithIndex: RefinementWithIndex<number, A, B>): (fa: A[]) => B[]; <A>(predicateWithIndex: PredicateWithIndex<number, A>): (fa: A[]) => A[]; }

Added in v2.0.0

findFirst

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

Signature

export function findFirst<A, B extends A>(refinement: Refinement<A, B>): (as: Array<A>) => Option<B>
export function findFirst<A>(predicate: Predicate<A>): (as: Array<A>) => Option<A> { ... }

Example

import { findFirst } from 'fp-ts/lib/Array'
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 v2.0.0

findFirstMap

Find the first element returned by an option based selector function

Signature

export const findFirstMap: <A, B>(f: (a: A) => Option<B>) => (as: Array<A>) => Option<B> = ...

Example

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

interface Person {
  name: string
  age?: number
}

const persons: Array<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 v2.0.0

findIndex

Find the first index for which a predicate holds

Signature

export const findIndex: <A>(predicate: Predicate<A>) => (as: Array<A>) => Option<number> = ...

Example

import { findIndex } from 'fp-ts/lib/Array'
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 v2.0.0

findLast

Find the last element which satisfies a predicate function

Signature

export function findLast<A, B extends A>(refinement: Refinement<A, B>): (as: Array<A>) => Option<B>
export function findLast<A>(predicate: Predicate<A>): (as: Array<A>) => Option<A> { ... }

Example

import { findLast } from 'fp-ts/lib/Array'
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 v2.0.0

findLastIndex

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

Signature

export const findLastIndex: <A>(predicate: Predicate<A>) => (as: Array<A>) => Option<number> = ...

Example

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

interface X {
  a: number
  b: number
}
const xs: Array<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 v2.0.0

findLastMap

Find the last element returned by an option based selector function

Signature

export const findLastMap: <A, B>(f: (a: A) => Option<B>) => (as: Array<A>) => Option<B> = ...

Example

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

interface Person {
  name: string
  age?: number
}

const persons: Array<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 v2.0.0

flatten

Removes one level of nesting

Signature

export const flatten: <A>(mma: Array<Array<A>>) => Array<A> = ...

Example

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

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

Added in v2.0.0

foldLeft

Break an array into its first element and remaining elements

Signature

export const foldLeft: <A, B>(
  onNil: () => B,
  onCons: (head: A, tail: Array<A>) => B
) => (as: Array<A>) => B = ...

Example

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

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

Added in v2.0.0

foldMap

Signature

;<M>(M: Monoid<M>) => <A>(f: (a: A) => M) => (fa: A[]) => M

Added in v2.0.0

foldMapWithIndex

Signature

;<M>(M: Monoid<M>) => <A>(f: (i: number, a: A) => M) => (fa: A[]) => M

Added in v2.0.0

foldRight

Break an array into its initial elements and the last element

Signature

export const foldRight: <A, B>(
  onNil: () => B,
  onCons: (init: Array<A>, last: A) => B
) => (as: Array<A>) => B = ...

Added in v2.0.0

getEq

Derives an Eq over the Array 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 const getEq: <A>(E: Eq<A>) => Eq<Array<A>> = ...

Example

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

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

Added in v2.0.0

getMonoid

Returns a Monoid for Array<A>

Signature

export const getMonoid: <A = never>() => Monoid<Array<A>> = ...

Example

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

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

Added in v2.0.0

getOrd

Derives an Ord over the Array 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 const getOrd: <A>(O: Ord<A>) => Ord<Array<A>> = ...

Example

import { getOrd } from 'fp-ts/lib/Array'
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 v2.0.0

getShow

Signature

export const getShow: <A>(S: Show<A>) => Show<Array<A>> = ...

Added in v2.0.0

head

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

Signature

export const head: <A>(as: Array<A>) => Option<A> = ...

Example

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

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

Added in v2.0.0

init

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

Signature

export const init: <A>(as: Array<A>) => Option<Array<A>> = ...

Example

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

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

Added in v2.0.0

insertAt

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

Signature

export const insertAt: <A>(i: number, a: A) => (as: Array<A>) => Option<Array<A>> = ...

Example

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

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

Added in v2.0.0

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 const intersection: <A>(E: Eq<A>) => (xs: Array<A>, ys: Array<A>) => Array<A> = ...

Example

import { intersection } from 'fp-ts/lib/Array'
import { eqNumber } from 'fp-ts/lib/Eq'

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

Added in v2.0.0

isEmpty

Test whether an array is empty

Signature

export const isEmpty: <A>(as: Array<A>) => boolean = ...

Example

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

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

Added in v2.0.0

isNonEmpty

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

Signature

export const isNonEmpty: <A>(as: Array<A>) => as is NonEmptyArray<A> = ...

Added in v2.0.0

isOutOfBound

Test whether an array contains a particular index

Signature

export const isOutOfBound: <A>(i: number, as: Array<A>) => boolean = ...

Added in v2.0.0

last

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

Signature

export const last: <A>(as: Array<A>) => Option<A> = ...

Example

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

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

Added in v2.0.0

lefts

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

Signature

export const lefts: <E, A>(as: Array<Either<E, A>>) => Array<E> = ...

Example

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

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

Added in v2.0.0

lookup

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

Signature

export const lookup: <A>(i: number, as: Array<A>) => Option<A> = ...

Example

import { lookup } from 'fp-ts/lib/Array'
import { some, none } from 'fp-ts/lib/Option'

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

Added in v2.0.0

makeBy

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

Signature

export const makeBy: <A>(n: number, f: (i: number) => A) => Array<A> = ...

Example

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

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

Added in v2.0.0

map

Signature

<A, B>(f: (a: A) => B) => (fa: A[]) => B[]

Added in v2.0.0

mapWithIndex

Signature

<A, B>(f: (i: number, a: A) => B) => (fa: A[]) => B[]

Added in v2.0.0

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 const modifyAt: <A>(i: number, f: (a: A) => A) => (as: Array<A>) => Option<Array<A>> = ...

Example

import { modifyAt } from 'fp-ts/lib/Array'
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 v2.0.0

of

Signature

export const of: <A>(a: A) => Array<A> = ...

Added in v2.0.0

partition

Signature

{ <A, B>(refinement: Refinement<A, B>): (fa: A[]) => Separated<A[], B[]>; <A>(predicate: Predicate<A>): (fa: A[]) => Separated<A[], A[]>; }

Added in v2.0.0

partitionMap

Signature

<A, B, C>(f: (a: A) => Either<B, C>) => (fa: A[]) => Separated<B[], C[]>

Added in v2.0.0

partitionMapWithIndex

Signature

<A, B, C>(f: (i: number, a: A) => Either<B, C>) => (fa: A[]) => Separated<B[], C[]>

Added in v2.0.0

partitionWithIndex

Signature

{ <A, B>(refinementWithIndex: RefinementWithIndex<number, A, B>): (fa: A[]) => Separated<A[], B[]>; <A>(predicateWithIndex: PredicateWithIndex<number, A>): (fa: A[]) => Separated<A[], A[]>; }

Added in v2.0.0

range

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

Signature

export const range: (start: number, end: number) => Array<number> = ...

Example

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

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

Added in v2.0.0

reduce

Signature

;<A, B>(b: B, f: (b: B, a: A) => B) => (fa: A[]) => B

Added in v2.0.0

reduceRight

Signature

;<A, B>(b: B, f: (a: A, b: B) => B) => (fa: A[]) => B

Added in v2.0.0

reduceRightWithIndex

Signature

;<A, B>(b: B, f: (i: number, a: A, b: B) => B) => (fa: A[]) => B

Added in v2.0.0

reduceWithIndex

Signature

;<A, B>(b: B, f: (i: number, b: B, a: A) => B) => (fa: A[]) => B

Added in v2.0.0

replicate

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

Signature

export const replicate: <A>(n: number, a: A) => Array<A> = ...

Example

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

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

Added in v2.0.0

reverse

Reverse an array, creating a new array

Signature

export const reverse: <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

rights

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

Signature

export const rights: <E, A>(as: Array<Either<E, A>>) => Array<A> = ...

Example

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

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

Added in v2.0.0

rotate

Rotate an array to the right by n steps

Signature

export const rotate: (n: number) => <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

scanLeft

Same as reduce but it carries over the intermediate steps

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

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

Signature

export const scanLeft: <A, B>(b: B, f: (b: B, a: A) => B) => (as: Array<A>) => Array<B> = ...

Added in v2.0.0

scanRight

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

Signature

export const scanRight: <A, B>(b: B, f: (a: A, b: B) => B) => (as: Array<A>) => Array<B> = ...

Example

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

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

Added in v2.0.0

separate

Signature

<A, B>(fa: Either<A, B>[]) => Separated<A[], B[]>

Added in v2.0.0

snoc

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

Signature

export const snoc: <A>(init: Array<A>, end: A) => NonEmptyArray<A> = ...

Example

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

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

Added in v2.0.0

sort

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

Signature

export const sort: <A>(O: Ord<A>) => (as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

sortBy

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

Signature

export const sortBy: <A>(ords: Array<Ord<A>>) => (as: Array<A>) => Array<A> = ...

Example

import { sortBy } from 'fp-ts/lib/Array'
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 v2.0.0

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 function spanLeft<A, B extends A>(
  refinement: Refinement<A, B>
): (as: Array<A>) => { init: Array<B>; rest: Array<A> }
export function spanLeft<A>(predicate: Predicate<A>): (as: Array<A>) => { init: Array<A>; rest: Array<A> } { ... }

Example

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

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

Added in v2.0.0

splitAt

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

Signature

export const splitAt: (n: number) => <A>(as: Array<A>) => [Array<A>, Array<A>] = ...

Example

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

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

Added in v2.0.0

tail

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

Signature

export const tail: <A>(as: Array<A>) => Option<Array<A>> = ...

Example

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

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

Added in v2.0.0

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 const takeLeft: (n: number) => <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

takeLeftWhile

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

Signature

export function takeLeftWhile<A, B extends A>(refinement: Refinement<A, B>): (as: Array<A>) => Array<B>
export function takeLeftWhile<A>(predicate: Predicate<A>): (as: Array<A>) => Array<A> { ... }

Example

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

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

Added in v2.0.0

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 const takeRight: (n: number) => <A>(as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

union

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

Signature

export const union: <A>(E: Eq<A>) => (xs: Array<A>, ys: Array<A>) => Array<A> = ...

Example

import { union } from 'fp-ts/lib/Array'
import { eqNumber } from 'fp-ts/lib/Eq'

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

Added in v2.0.0

uniq

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

Signature

export const uniq: <A>(E: Eq<A>) => (as: Array<A>) => Array<A> = ...

Example

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

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

Added in v2.0.0

unsafeDeleteAt

Signature

export const unsafeDeleteAt: <A>(i: number, as: Array<A>) => Array<A> = ...

Added in v2.0.0

unsafeInsertAt

Signature

export const unsafeInsertAt: <A>(i: number, a: A, as: Array<A>) => Array<A> = ...

Added in v2.0.0

unsafeUpdateAt

Signature

export const unsafeUpdateAt: <A>(i: number, a: A, as: Array<A>) => Array<A> = ...

Added in v2.0.0

unzip

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

Signature

export const unzip: <A, B>(as: Array<[A, B]>) => [Array<A>, Array<B>] = ...

Example

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

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

Added in v2.0.0

updateAt

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

Signature

export const updateAt: <A>(i: number, a: A) => (as: Array<A>) => Option<Array<A>> = ...

Example

import { updateAt } from 'fp-ts/lib/Array'
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 v2.0.0

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 const zip: <A, B>(fa: Array<A>, fb: Array<B>) => Array<[A, B]> = ...

Example

import { zip } from 'fp-ts/lib/Array'

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

Added in v2.0.0

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 const zipWith: <A, B, C>(fa: Array<A>, fb: Array<B>, f: (a: A, b: B) => C) => Array<C> = ...

Example

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

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

Added in v2.0.0