Overview

Adapted from https://github.com/purescript/purescript-arrays


Table of contents


URI (type alias)

Signature

export type URI = typeof URI

Added in v2.0.0

URI (constant)

Signature

export const URI: "Array" = ...

Added in v2.0.0

array (constant)

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

empty (constant)

An empty array

Signature

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

Added in v2.0.0

chop (function)

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 function 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 (function)

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 function 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

comprehension (function)

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 (function)

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

Signature

export function 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 (function)

Signature

export function copy<A>(as: Array<A>): Array<A> { ... }

Added in v2.0.0

deleteAt (function)

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

Signature

export function 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 (function)

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 function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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

elem (function)

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 function 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

findFirst (function)

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 (function)

Find the first element returned by an option based selector function

Signature

export function 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 (function)

Find the first index for which a predicate holds

Signature

export function 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 (function)

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 (function)

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

Signature

export function 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 (function)

Find the last element returned by an option based selector function

Signature

export function 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 (function)

Removes one level of nesting

Signature

export function 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 (function)

Break an array into its first element and remaining elements

Signature

export function 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

foldRight (function)

Break an array into its initial elements and the last element

Signature

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

Added in v2.0.0

getEq (function)

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 function 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 (function)

Returns a Monoid for Array<A>

Signature

export function 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 (function)

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 function 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 (function)

Signature

export function getShow<A>(S: Show<A>): Show<Array<A>> { ... }

Added in v2.0.0

head (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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 function 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 (function)

Test whether an array is empty

Signature

export function isEmpty<A>(as: Array<A>): boolean { ... }

Example

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

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

Added in v2.0.0

isNonEmpty (function)

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

Signature

export function isNonEmpty<A>(as: Array<A>): as is NonEmptyArray<A> { ... }

Added in v2.0.0

isOutOfBound (function)

Test whether an array contains a particular index

Signature

export function isOutOfBound<A>(i: number, as: Array<A>): boolean { ... }

Added in v2.0.0

last (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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

modifyAt (function)

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 function 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 (function)

Signature

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

Added in v2.0.0

range (function)

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

Signature

export function 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

replicate (function)

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

Signature

export function 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 (function)

Reverse an array, creating a new array

Signature

export function 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 (function)

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

Signature

export function 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 (function)

Rotate an array to the right by n steps

Signature

export function 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 (function)

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 function scanLeft<A, B>(b: B, f: (b: B, a: A) => B): (as: Array<A>) => Array<B> { ... }

Added in v2.0.0

scanRight (function)

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

Signature

export function 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

snoc (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

Signature

export function unsafeDeleteAt<A>(i: number, as: Array<A>): Array<A> { ... }

Added in v2.0.0

unsafeInsertAt (function)

Signature

export function unsafeInsertAt<A>(i: number, a: A, as: Array<A>): Array<A> { ... }

Added in v2.0.0

unsafeUpdateAt (function)

Signature

export function unsafeUpdateAt<A>(i: number, a: A, as: Array<A>): Array<A> { ... }

Added in v2.0.0

unzip (function)

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

Signature

export function 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 (function)

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

Signature

export function 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 (function)

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 function 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 (function)

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 function 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

alt (export)

Signature

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

Added in v2.0.0

ap (export)

Signature

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

Added in v2.0.0

apFirst (export)

Signature

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

Added in v2.0.0

apSecond (export)

Signature

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

Added in v2.0.0

chain (export)

Signature

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

Added in v2.0.0

chainFirst (export)

Signature

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

Added in v2.0.0

compact (export)

Signature

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

Added in v2.0.0

duplicate (export)

Signature

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

Added in v2.0.0

extend (export)

Signature

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

Added in v2.0.0

filter (export)

Signature

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

Added in v2.0.0

filterMap (export)

Signature

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

Added in v2.0.0

filterMapWithIndex (export)

Signature

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

Added in v2.0.0

filterWithIndex (export)

Signature

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

Added in v2.0.0

foldMap (export)

Signature

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

Added in v2.0.0

foldMapWithIndex (export)

Signature

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

Added in v2.0.0

map (export)

Signature

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

Added in v2.0.0

mapWithIndex (export)

Signature

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

Added in v2.0.0

partition (export)

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 (export)

Signature

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

Added in v2.0.0

partitionMapWithIndex (export)

Signature

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

Added in v2.0.0

partitionWithIndex (export)

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

reduce (export)

Signature

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

Added in v2.0.0

reduceRight (export)

Signature

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

Added in v2.0.0

reduceRightWithIndex (export)

Signature

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

Added in v2.0.0

reduceWithIndex (export)

Signature

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

Added in v2.0.0

separate (export)

Signature

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

Added in v2.0.0