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Task

Instances​

Combinators​

Constructors​

Conversions​

Do notation​

Instance methods​

Legacy​

Lifting​

Mapping​

Model​

Sequencing​

Traversing​

Type lambdas​

Utilities​

Instances​

ApplicativePar​

Runs computations in parallel.

Signature​

export declare const ApplicativePar: Applicative1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

ApplicativeSeq​

Runs computations sequentially.

Signature​

export declare const ApplicativeSeq: Applicative1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

ApplyPar​

Runs computations in parallel.

Signature​

export declare const ApplyPar: Apply1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

ApplySeq​

Runs computations sequentially.

Signature​

export declare const ApplySeq: Apply1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Chain​

Signature​

export declare const Chain: chainable.Chain1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

ChainRec​

ChainRec for Task

Signature​

export declare const ChainRec: ChainRec1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2022-present Jacob Alford

FromIO​

Signature​

export declare const FromIO: FromIO1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

FromTask​

Signature​

export declare const FromTask: FromTask1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Functor​

Signature​

export declare const Functor: Functor1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Monad​

Signature​

export declare const Monad: Monad1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

MonadIO​

Signature​

export declare const MonadIO: MonadIO1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

MonadTask​

Signature​

export declare const MonadTask: MonadTask1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Pointed​

Signature​

export declare const Pointed: Pointed1<URI>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

getRaceMonoid​

Monoid returning the first completed task.

Note: uses Promise.race internally.

Signature​

export declare function getRaceMonoid<A = never>(): Monoid<Task<A>>

Details​

  • Added in 0.1.0

Example​

import * as T from '@fp-tx/core/Task'

async function test() {
  const S = T.getRaceMonoid<string>()
  const fa = T.delay(20)(T.of('a'))
  const fb = T.delay(10)(T.of('b'))
  assert.deepStrictEqual(await S.concat(fa, fb)(), 'b')
}

test()

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Combinators​

tap​

Composes computations in sequence, using the return value of one computation to determine the next computation and keeping only the result of the first.

Signature​

export declare const tap: {
  <A, _>(self: Task<A>, f: (a: A) => Task<_>): Task<A>
  <A, _>(f: (a: A) => Task<_>): (self: Task<A>) => Task<A>
}

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

tapIO​

Composes computations in sequence, using the return value of one computation to determine the next computation and keeping only the result of the first.

Signature​

export declare const tapIO: {
  <A, _>(f: (a: A) => IO<_>): (self: Task<A>) => Task<A>
  <A, _>(self: Task<A>, f: (a: A) => IO<_>): Task<A>
}

Details​

  • Added in 0.1.0

Example​

import { pipe } from '@fp-tx/core/function'
import * as T from '@fp-tx/core/Task'
import * as Console from '@fp-tx/core/Console'

// Will produce `Hello, fp-ts` to the stdout
const effect = pipe(
  T.of('fp-ts'),
  T.tapIO(value => Console.log(`Hello, ${value}`)),
)

async function test() {
  assert.deepStrictEqual(await effect(), 'fp-ts')
}

test()

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Constructors​

of​

Signature​

export declare const of: <A>(a: A) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Conversions​

fromIO​

Signature​

export declare const fromIO: <A>(fa: IO<A>) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Do notation​

Do​

Signature​

export declare const Do: Task<{}>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

apS​

Signature​

export declare const apS: <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  fb: Task<B>,
) => (fa: Task<A>) => Task<{ readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

bind​

Signature​

export declare const bind: <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => Task<B>,
) => (ma: Task<A>) => Task<{ readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

bindTo​

Signature​

export declare const bindTo: <N extends string>(name: N) => <A>(fa: Task<A>) => Task<{ readonly [K in N]: A }>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Instance methods​

chainRec​

Signature​

export declare const chainRec: ChainRec1<URI>['chainRec']

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2022-present Jacob Alford

Legacy​

chain​

Alias of flatMap.

Signature​

export declare const chain: <A, B>(f: (a: A) => Task<B>) => (ma: Task<A>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

chainFirst​

Alias of tap.

Signature​

export declare const chainFirst: <A, B>(f: (a: A) => Task<B>) => (first: Task<A>) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

chainFirstIOK​

Alias of tapIO.

Signature​

export declare const chainFirstIOK: <A, B>(f: (a: A) => IO<B>) => (first: Task<A>) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

chainIOK​

Alias of flatMapIO.

Signature​

export declare const chainIOK: <A, B>(f: (a: A) => IO<B>) => (first: Task<A>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Lifting​

fromIOK​

Signature​

export declare const fromIOK: <A extends ReadonlyArray<unknown>, B>(f: (...a: A) => IO<B>) => (...a: A) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Mapping​

as​

Maps the value to the specified constant value.

Signature​

export declare const as: {
  <A>(a: A): <_>(self: Task<_>) => Task<A>
  <_, A>(self: Task<_>, a: A): Task<A>
}

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

asUnit​

Maps the value to the void constant value.

Signature​

export declare const asUnit: <_>(self: Task<_>) => Task<void>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

flap​

Signature​

export declare const flap: <A>(a: A) => <B>(fab: Task<(a: A) => B>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

map​

map can be used to turn functions (a: A) => B into functions (fa: F<A>) => F<B> whose argument and return types use the type constructor F to represent some computational context.

Signature​

export declare const map: <A, B>(f: (a: A) => B) => (fa: Task<A>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Model​

Task​

Signature​

export interface Task<A> {
  (): Promise<A>
}

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Sequencing​

flatMap​

Signature​

export declare const flatMap: {
  <A, B>(f: (a: A) => Task<B>): (ma: Task<A>) => Task<B>
  <A, B>(ma: Task<A>, f: (a: A) => Task<B>): Task<B>
}

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

flatMapIO​

Signature​

export declare const flatMapIO: {
  <A, B>(f: (a: A) => IO<B>): (self: Task<A>) => Task<B>
  <A, B>(self: Task<A>, f: (a: A) => IO<B>): Task<B>
}

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

flatten​

Signature​

export declare const flatten: <A>(mma: Task<Task<A>>) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Traversing​

sequenceArray​

Equivalent to ReadonlyArray#sequence(Applicative).

Signature​

export declare const sequenceArray: <A>(arr: ReadonlyArray<Task<A>>) => Task<ReadonlyArray<A>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

sequenceSeqArray​

Equivalent to ReadonlyArray#sequence(ApplicativeSeq).

Signature​

export declare const sequenceSeqArray: <A>(arr: ReadonlyArray<Task<A>>) => Task<ReadonlyArray<A>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseArray​

Equivalent to ReadonlyArray#traverse(Applicative).

Signature​

export declare const traverseArray: <A, B>(f: (a: A) => Task<B>) => (as: readonly A[]) => Task<readonly B[]>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseArrayWithIndex​

Equivalent to ReadonlyArray#traverseWithIndex(Applicative).

Signature​

export declare const traverseArrayWithIndex: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: ReadonlyArray<A>) => Task<ReadonlyArray<B>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseReadonlyArrayWithIndex​

Equivalent to ReadonlyArray#traverseWithIndex(ApplicativePar).

Signature​

export declare const traverseReadonlyArrayWithIndex: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: readonly A[]) => Task<readonly B[]>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseReadonlyArrayWithIndexSeq​

Equivalent to ReadonlyArray#traverseWithIndex(ApplicativeSeq).

Signature​

export declare const traverseReadonlyArrayWithIndexSeq: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: readonly A[]) => Task<readonly B[]>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseReadonlyNonEmptyArrayWithIndex​

Equivalent to ReadonlyNonEmptyArray#traverseWithIndex(ApplicativePar).

Signature​

export declare const traverseReadonlyNonEmptyArrayWithIndex: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: ReadonlyNonEmptyArray<A>) => Task<ReadonlyNonEmptyArray<B>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseReadonlyNonEmptyArrayWithIndexSeq​

Equivalent to ReadonlyNonEmptyArray#traverseWithIndex(ApplicativeSeq).

Signature​

export declare const traverseReadonlyNonEmptyArrayWithIndexSeq: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: ReadonlyNonEmptyArray<A>) => Task<ReadonlyNonEmptyArray<B>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseSeqArray​

Equivalent to ReadonlyArray#traverse(ApplicativeSeq).

Signature​

export declare const traverseSeqArray: <A, B>(f: (a: A) => Task<B>) => (as: readonly A[]) => Task<readonly B[]>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

traverseSeqArrayWithIndex​

Equivalent to ReadonlyArray#traverseWithIndex(ApplicativeSeq).

Signature​

export declare const traverseSeqArrayWithIndex: <A, B>(
  f: (index: number, a: A) => Task<B>,
) => (as: ReadonlyArray<A>) => Task<ReadonlyArray<B>>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Type lambdas​

URI​

Signature​

export type URI = typeof URI

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

URI​

Signature​

export declare const URI = 'Task'

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

Utilities​

ApT​

Signature​

export declare const ApT: Task<readonly []>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

ap​

Signature​

export declare const ap: <A>(fa: Task<A>) => <B>(fab: Task<(a: A) => B>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

apFirst​

Combine two effectful actions, keeping only the result of the first.

Signature​

export declare const apFirst: <B>(second: Task<B>) => <A>(first: Task<A>) => Task<A>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

apSecond​

Combine two effectful actions, keeping only the result of the second.

Signature​

export declare const apSecond: <B>(second: Task<B>) => <A>(first: Task<A>) => Task<B>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

delay​

Creates a task that will complete after a time delay

Signature​

export declare function delay(millis: number): <A>(ma: Task<A>) => Task<A>

Details​

  • Added in 0.1.0

Example​

import { sequenceT } from '@fp-tx/core/Apply'
import * as T from '@fp-tx/core/Task'
import { takeRight } from '@fp-tx/core/Array'

async function test() {
  const log: Array<string> = []
  const append = (message: string): T.Task<void> =>
    T.fromIO(() => {
      log.push(message)
    })
  const fa = append('a')
  const fb = T.delay(20)(append('b'))
  const fc = T.delay(10)(append('c'))
  const fd = append('d')
  await sequenceT(T.ApplyPar)(fa, fb, fc, fd)()
  assert.deepStrictEqual(takeRight(2)(log), ['c', 'b'])
}

test()

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

do​

Signature​

export declare const do_: <MA extends TaskIterable<any>, A>(
  yieldFunction: (unwrap: <A>(ma: Task<A>) => TaskIterable<A>) => Generator<MA, A>,
) => Task<A>

fromTask​

Signature​

export declare const fromTask: <A>(fa: Task<A>) => Task<A>

Details​

  • Added in 0.1.0
  • Deprecated

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

getMonoid​

Use getApplicativeMonoid instead.

Lift a monoid into 'Task', the inner values are concatenated using the provided Monoid.

Signature​

export declare const getMonoid: <A>(M: Monoid<A>) => Monoid<Task<A>>

Details​

  • Added in 0.1.0
  • Deprecated

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

getSemigroup​

Use getApplySemigroup instead.

Signature​

export declare const getSemigroup: <A>(S: Semigroup<A>) => Semigroup<Task<A>>

Details​

  • Added in 0.1.0
  • Deprecated

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

let​

Signature​

export declare const let_: <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B,
) => (fa: Task<A>) => Task<{ readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

never​

A Task that never completes.

Signature​

export declare const never: Task<never>

Details​

  • Added in 0.1.0

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

task​

This instance is deprecated, use small, specific instances instead. For example if a function needs a Functor instance, pass T.Functor instead of T.task (where T is from import T from 'fp-ts/Task')

Signature​

export declare const task: Monad1<URI> & MonadTask1<URI>

Details​

  • Added in 0.1.0
  • Deprecated

License​

  • MIT – Copyright (c) 2017-present Giulio Canti

taskSeq​

This instance is deprecated, use small, specific instances instead. For example if a function needs a Functor instance, pass T.Functor instead of T.taskSeq (where T is from import T from 'fp-ts/Task')

Signature​

export declare const taskSeq: Monad1<URI> & MonadTask1<URI>

Details​

  • Added in 0.1.0
  • Deprecated

License​

  • MIT – Copyright (c) 2017-present Giulio Canti