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fp-ts

function overview

Added in v2.0.0

Table of contents

instances

getBooleanAlgebra

Signature

export declare const getBooleanAlgebra: <B>(B: BooleanAlgebra<B>) => <A = never>() => BooleanAlgebra<(a: A) => B>

Added in v2.10.0

getMonoid

Unary functions form a monoid as long as you can provide a monoid for the codomain.

Signature

export declare const getMonoid: <M>(M: Monoid<M>) => <A = never>() => Monoid<(a: A) => M>

Example

import { Predicate } from 'fp-ts/Predicate'
import { getMonoid } from 'fp-ts/function'
import * as B from 'fp-ts/boolean'

const f: Predicate<number> = (n) => n <= 2
const g: Predicate<number> = (n) => n >= 0

const M1 = getMonoid(B.MonoidAll)<number>()

assert.deepStrictEqual(M1.concat(f, g)(1), true)
assert.deepStrictEqual(M1.concat(f, g)(3), false)

const M2 = getMonoid(B.MonoidAny)<number>()

assert.deepStrictEqual(M2.concat(f, g)(1), true)
assert.deepStrictEqual(M2.concat(f, g)(3), true)

Added in v2.10.0

getRing

Signature

export declare const getRing: <A, B>(R: Ring<B>) => Ring<(a: A) => B>

Added in v2.10.0

getSemigroup

Unary functions form a semigroup as long as you can provide a semigroup for the codomain.

Signature

export declare const getSemigroup: <S>(S: Semigroup<S>) => <A = never>() => Semigroup<(a: A) => S>

Example

import { Predicate, getSemigroup } from 'fp-ts/function'
import * as B from 'fp-ts/boolean'

const f: Predicate<number> = (n) => n <= 2
const g: Predicate<number> = (n) => n >= 0

const S1 = getSemigroup(B.SemigroupAll)<number>()

assert.deepStrictEqual(S1.concat(f, g)(1), true)
assert.deepStrictEqual(S1.concat(f, g)(3), false)

const S2 = getSemigroup(B.SemigroupAny)<number>()

assert.deepStrictEqual(S2.concat(f, g)(1), true)
assert.deepStrictEqual(S2.concat(f, g)(3), true)

Added in v2.10.0

getSemiring

Signature

export declare const getSemiring: <A, B>(S: Semiring<B>) => Semiring<(a: A) => B>

Added in v2.10.0

getEndomorphismMonoid

Use Endomorphism module instead.

Signature

export declare const getEndomorphismMonoid: <A = never>() => Monoid<Endomorphism<A>>

Added in v2.10.0

utils

FunctionN (interface)

Signature

export interface FunctionN<A extends ReadonlyArray<unknown>, B> {
  (...args: A): B
}

Example

import { FunctionN } from 'fp-ts/function'

export const sum: FunctionN<[number, number], number> = (a, b) => a + b

Added in v2.0.0

Lazy (interface)

A thunk

Signature

export interface Lazy<A> {
  (): A
}

Added in v2.0.0

SK

Signature

export declare const SK: <A, B>(_: A, b: B) => B

Added in v2.11.0

absurd

Signature

export declare function absurd<A>(_: never): A

Added in v2.0.0

apply

Signature

export declare const apply: <A>(a: A) => <B>(f: (a: A) => B) => B

Added in v2.11.0

constFalse

A thunk that returns always false.

Signature

export declare const constFalse: Lazy<boolean>

Added in v2.0.0

constNull

A thunk that returns always null.

Signature

export declare const constNull: Lazy<null>

Added in v2.0.0

constTrue

A thunk that returns always true.

Signature

export declare const constTrue: Lazy<boolean>

Added in v2.0.0

constUndefined

A thunk that returns always undefined.

Signature

export declare const constUndefined: Lazy<undefined>

Added in v2.0.0

constVoid

A thunk that returns always void.

Signature

export declare const constVoid: Lazy<void>

Added in v2.0.0

constant

Signature

export declare function constant<A>(a: A): Lazy<A>

Added in v2.0.0

decrement

Signature

export declare function decrement(n: number): number

Added in v2.0.0

flip

Flips the order of the arguments of a function of two arguments.

Signature

export declare function flip<A, B, C>(f: (a: A, b: B) => C): (b: B, a: A) => C

Added in v2.0.0

flow

Performs left-to-right function composition. The first argument may have any arity, the remaining arguments must be unary.

See also pipe.

Signature

export declare function flow<A extends ReadonlyArray<unknown>, B>(ab: (...a: A) => B): (...a: A) => B
export declare function flow<A extends ReadonlyArray<unknown>, B, C>(
  ab: (...a: A) => B,
  bc: (b: B) => C
): (...a: A) => C
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D
): (...a: A) => D
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E
): (...a: A) => E
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E, F>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F
): (...a: A) => F
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E, F, G>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G
): (...a: A) => G
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E, F, G, H>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H
): (...a: A) => H
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E, F, G, H, I>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I
): (...a: A) => I
export declare function flow<A extends ReadonlyArray<unknown>, B, C, D, E, F, G, H, I, J>(
  ab: (...a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J
): (...a: A) => J

Example

import { flow } from 'fp-ts/function'

const len = (s: string): number => s.length
const double = (n: number): number => n * 2

const f = flow(len, double)

assert.strictEqual(f('aaa'), 6)

Added in v2.0.0

hole

Type hole simulation

Signature

export declare const hole: <T>() => T

Added in v2.7.0

identity

Signature

export declare function identity<A>(a: A): A

Added in v2.0.0

increment

Signature

export declare function increment(n: number): number

Added in v2.0.0

pipe

Pipes the value of an expression into a pipeline of functions.

See also flow.

Signature

export declare function pipe<A>(a: A): A
export declare function pipe<A, B>(a: A, ab: (a: A) => B): B
export declare function pipe<A, B, C>(a: A, ab: (a: A) => B, bc: (b: B) => C): C
export declare function pipe<A, B, C, D>(a: A, ab: (a: A) => B, bc: (b: B) => C, cd: (c: C) => D): D
export declare function pipe<A, B, C, D, E>(a: A, ab: (a: A) => B, bc: (b: B) => C, cd: (c: C) => D, de: (d: D) => E): E
export declare function pipe<A, B, C, D, E, F>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F
): F
export declare function pipe<A, B, C, D, E, F, G>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G
): G
export declare function pipe<A, B, C, D, E, F, G, H>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H
): H
export declare function pipe<A, B, C, D, E, F, G, H, I>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I
): I
export declare function pipe<A, B, C, D, E, F, G, H, I, J>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J
): J
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K
): K
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L
): L
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M
): M
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N
): N
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O
): O
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O,
  op: (o: O) => P
): P
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O,
  op: (o: O) => P,
  pq: (p: P) => Q
): Q
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O,
  op: (o: O) => P,
  pq: (p: P) => Q,
  qr: (q: Q) => R
): R
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O,
  op: (o: O) => P,
  pq: (p: P) => Q,
  qr: (q: Q) => R,
  rs: (r: R) => S
): S
export declare function pipe<A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T>(
  a: A,
  ab: (a: A) => B,
  bc: (b: B) => C,
  cd: (c: C) => D,
  de: (d: D) => E,
  ef: (e: E) => F,
  fg: (f: F) => G,
  gh: (g: G) => H,
  hi: (h: H) => I,
  ij: (i: I) => J,
  jk: (j: J) => K,
  kl: (k: K) => L,
  lm: (l: L) => M,
  mn: (m: M) => N,
  no: (n: N) => O,
  op: (o: O) => P,
  pq: (p: P) => Q,
  qr: (q: Q) => R,
  rs: (r: R) => S,
  st: (s: S) => T
): T

Example

import { pipe } from 'fp-ts/function'

const len = (s: string): number => s.length
const double = (n: number): number => n * 2

// without pipe
assert.strictEqual(double(len('aaa')), 6)

// with pipe
assert.strictEqual(pipe('aaa', len, double), 6)

Added in v2.6.3

tuple

Signature

export declare function tuple<T extends ReadonlyArray<any>>(...t: T): T

Added in v2.0.0

tupled

Creates a tupled version of this function: instead of n arguments, it accepts a single tuple argument.

Signature

export declare function tupled<A extends ReadonlyArray<unknown>, B>(f: (...a: A) => B): (a: A) => B

Example

import { tupled } from 'fp-ts/function'

const add = tupled((x: number, y: number): number => x + y)

assert.strictEqual(add([1, 2]), 3)

Added in v2.4.0

unsafeCoerce

Signature

export declare const unsafeCoerce: <A, B>(a: A) => B

Added in v2.0.0

untupled

Inverse function of tupled

Signature

export declare function untupled<A extends ReadonlyArray<unknown>, B>(f: (a: A) => B): (...a: A) => B

Added in v2.4.0

Endomorphism (interface)

Use Endomorphism module instead.

Signature

export interface Endomorphism<A> {
  (a: A): A
}

Added in v2.0.0

Predicate (interface)

Use Predicate module instead.

Signature

export interface Predicate<A> {
  (a: A): boolean
}

Added in v2.0.0

Refinement (interface)

Use Refinement module instead.

Signature

export interface Refinement<A, B extends A> {
  (a: A): a is B
}

Added in v2.0.0

not

Use Predicate module instead.

Signature

export declare function not<A>(predicate: Predicate<A>): Predicate<A>

Added in v2.0.0