fp-ts

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function overview

Added in v2.0.0

Table of contents

utils

Endomorphism (interface)

Signature

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

Added in v2.0.0

FunctionN (interface)

Signature

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

Example

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

Predicate (interface)

Signature

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

Added in v2.0.0

Refinement (interface)

Signature

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

Added in v2.0.0

absurd

Signature

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

Added in v2.0.0

constFalse

A thunk that returns always false

Signature

export declare const constFalse: () => boolean

Added in v2.0.0

constNull

A thunk that returns always null

Signature

export declare const constNull: () => null

Added in v2.0.0

constTrue

A thunk that returns always true

Signature

export declare const constTrue: () => boolean

Added in v2.0.0

constUndefined

A thunk that returns always undefined

Signature

export declare const constUndefined: () => undefined

Added in v2.0.0

constVoid

A thunk that returns always void

Signature

export declare const constVoid: () => 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/lib/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

not

Signature

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

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

Example

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