# instances

## getBooleanAlgebra

Signature

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

## 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)
``````

## getRing

Signature

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

## 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)
``````

## getSemiring

Signature

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

# lagacy

## Lazy (interface)

Use `LazyArg` instead.

Signature

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

# 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
``````

## LazyArg (interface)

A lazy argument.

Signature

``````export interface LazyArg<A> {
(): A
}
``````

## SK

Signature

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

## absurd

Signature

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

## apply

Signature

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

## constFalse

A thunk that returns always `false`.

Signature

``````export declare const constFalse: LazyArg<boolean>
``````

## constNull

A thunk that returns always `null`.

Signature

``````export declare const constNull: LazyArg<null>
``````

## constTrue

A thunk that returns always `true`.

Signature

``````export declare const constTrue: LazyArg<boolean>
``````

## constUndefined

A thunk that returns always `undefined`.

Signature

``````export declare const constUndefined: LazyArg<undefined>
``````

## constVoid

A thunk that returns always `void`.

Signature

``````export declare const constVoid: LazyArg<void>
``````

## constant

Signature

``````export declare function constant<A>(a: A): LazyArg<A>
``````

## decrement

Signature

``````export declare function decrement(n: number): number
``````

## flip

Flips the arguments of a curried function.

Signature

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

Example

``````import { flip } from 'fp-ts/function'

const f = (a: number) => (b: string) => a - b.length

assert.strictEqual(flip(f)('aaa')(2), -1)
``````

## 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)
``````

## hole

Type hole simulation

Signature

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

## identity

Signature

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

## increment

Signature

``````export declare function increment(n: number): number
``````

## 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)
``````

## tuple

Signature

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

## 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)

``````

## unsafeCoerce

Signature

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

## untupled

Inverse function of `tupled`

Signature

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

# zone of death

## Endomorphism (interface)

Use `Endomorphism` module instead.

Signature

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

## Predicate (interface)

Use `Predicate` module instead.

Signature

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

## Refinement (interface)

Use `Refinement` module instead.

Signature

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

## getEndomorphismMonoid

Use `Endomorphism` module instead.

Signature

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

Use `Predicate` module instead.
``````export declare function not<A>(predicate: Predicate<A>): Predicate<A>