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TaskEither

Instances​

Combinators​

Constructors​

Conversions​

Do notation​

Error handling​

Filtering​

Instance methods​

Interop​

Legacy​

Lifting​

Mapping​

Model​

Pattern matching​

Sequencing​

Traversing​

Type lambdas​

Utilities​

Instances​

Alt​

Signature​

export declare const Alt: Alt2<URI>

Details​

  • Added in 0.1.0

License​

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

ApplicativePar​

Runs computations in parallel.

Signature​

export declare const ApplicativePar: Applicative2<URI>

Details​

  • Added in 0.1.0

License​

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

ApplicativeSeq​

Runs computations sequentially.

Signature​

export declare const ApplicativeSeq: Applicative2<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: Apply2<URI>

Details​

  • Added in 0.1.0

License​

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

ApplySeq​

Runs computations sequentially.

Signature​

export declare const ApplySeq: Apply2<URI>

Details​

  • Added in 0.1.0

License​

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

Bifunctor​

Signature​

export declare const Bifunctor: Bifunctor2<URI>

Details​

  • Added in 0.1.0

License​

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

Chain​

Signature​

export declare const Chain: chainable.Chain2<URI>

Details​

  • Added in 0.1.0

License​

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

ChainRec​

ChainRec for TaskEither

Signature​

export declare const ChainRec: ChainRec2<URI>

Details​

  • Added in 0.1.0

License​

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

FromEither​

Signature​

export declare const FromEither: FromEither2<URI>

Details​

  • Added in 0.1.0

License​

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

FromIO​

Signature​

export declare const FromIO: FromIO2<URI>

Details​

  • Added in 0.1.0

License​

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

FromTask​

Signature​

export declare const FromTask: FromTask2<URI>

Details​

  • Added in 0.1.0

License​

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

Functor​

Signature​

export declare const Functor: Functor2<URI>

Details​

  • Added in 0.1.0

License​

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

Monad​

Signature​

export declare const Monad: Monad2<URI>

Details​

  • Added in 0.1.0

License​

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

MonadIO​

Signature​

export declare const MonadIO: MonadIO2<URI>

Details​

  • Added in 0.1.0

License​

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

MonadTask​

Signature​

export declare const MonadTask: MonadTask2<URI>

Details​

  • Added in 0.1.0

License​

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

MonadThrow​

Signature​

export declare const MonadThrow: MonadThrow2<URI>

Details​

  • Added in 0.1.0

License​

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

Pointed​

Signature​

export declare const Pointed: Pointed2<URI>

Details​

  • Added in 0.1.0

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: {
  <E1, A, E2, _>(self: TaskEither<E1, A>, f: (a: A) => TaskEither<E2, _>): TaskEither<E1 | E2, A>
  <A, E2, _>(f: (a: A) => TaskEither<E2, _>): <E1>(self: TaskEither<E1, A>) => TaskEither<E2 | E1, A>
}

Details​

  • Added in 0.1.0

License​

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

tapEither​

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 tapEither: {
  <A, E2, _>(f: (a: A) => Either<E2, _>): <E1>(self: TaskEither<E1, A>) => TaskEither<E2 | E1, A>
  <E1, A, E2, _>(self: TaskEither<E1, A>, f: (a: A) => Either<E2, _>): TaskEither<E1 | E2, A>
}

Details​

  • Added in 0.1.0

Example​

import * as E from '@fp-tx/core/Either'
import { pipe } from '@fp-tx/core/function'
import * as TE from '@fp-tx/core/TaskEither'

const checkString = (value: string) =>
  pipe(
    TE.of(value),
    TE.tapEither(() => (value.length > 0 ? E.right('ok') : E.left('error'))),
  )

async function test() {
  assert.deepStrictEqual(await checkString('')(), E.left('error'))
  assert.deepStrictEqual(await checkString('fp-ts')(), E.right('fp-ts'))
}

test()

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<_>): <E>(self: TaskEither<E, A>) => TaskEither<E, A>
  <E, A, _>(self: TaskEither<E, A>, f: (a: A) => IO<_>): TaskEither<E, A>
}

Details​

  • Added in 0.1.0

Example​

import { pipe } from '@fp-tx/core/function'
import * as TE from '@fp-tx/core/TaskEither'
import * as E from '@fp-tx/core/Either'
import * as Console from '@fp-tx/core/Console'

// Will produce `Hello, fp-ts` to the stdout
const effectA = TE.tapIO(TE.of(1), value => Console.log(`Hello, ${value}`))

// No output to the stdout
const effectB = pipe(
  TE.left('error'),
  TE.tapIO(value => Console.log(`Hello, ${value}`)),
)

async function test() {
  assert.deepStrictEqual(await effectA(), E.of(1))
  assert.deepStrictEqual(await effectB(), E.left('error'))
}

test()

License​

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

tapTask​

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 tapTask: {
  <A, _>(f: (a: A) => Task<_>): <E>(self: TaskEither<E, A>) => TaskEither<E, A>
  <E, A, _>(self: TaskEither<E, A>, f: (a: A) => Task<_>): TaskEither<E, A>
}

Details​

  • Added in 0.1.0

Example​

import * as TE from '@fp-tx/core/TaskEither'
import * as T from '@fp-tx/core/Task'
import * as E from '@fp-tx/core/Either'

const effect = TE.tapIO(TE.of(1), value => T.of(value + 1))

async function test() {
  assert.deepStrictEqual(await effect(), E.of(1))
}

test()

License​

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

Constructors​

left​

Signature​

export declare const left: <E = never, A = never>(e: E) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

leftIO​

Signature​

export declare const leftIO: <E = never, A = never>(me: IO<E>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

leftTask​

Signature​

export declare const leftTask: <E = never, A = never>(me: Task<E>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

of​

Signature​

export declare const of: <E = never, A = never>(a: A) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

Signature​

export declare const right: <E = never, A = never>(a: A) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

rightIO​

Signature​

export declare const rightIO: <E = never, A = never>(ma: IO<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

rightTask​

Signature​

export declare const rightTask: <E = never, A = never>(ma: Task<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

Conversions​

fromEither​

Signature​

export declare const fromEither: <E, A>(fa: Either<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

fromIO​

Signature​

export declare const fromIO: <A, E = never>(fa: IO<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

fromIOEither​

Signature​

export declare const fromIOEither: <E, A>(fa: IOEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

fromNullable​

Signature​

export declare const fromNullable: <E>(e: E) => <A>(a: A) => TaskEither<E, NonNullable<A>>

Details​

  • Added in 0.1.0

License​

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

fromOption​

Signature​

export declare const fromOption: <E>(onNone: LazyArg<E>) => <A>(fa: Option<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

fromTask​

Signature​

export declare const fromTask: <A, E = never>(fa: Task<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

fromTaskOption​

Signature​

export declare const fromTaskOption: <E>(onNone: LazyArg<E>) => <A>(fa: TaskOption<A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

toUnion​

Signature​

export declare const toUnion: <E, A>(fa: TaskEither<E, A>) => Task<E | A>

Details​

  • Added in 0.1.0

License​

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

Do notation​

Do​

Signature​

export declare const Do: TaskEither<never, {}>

Details​

  • Added in 0.1.0

License​

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

apS​

Signature​

export declare const apS: <N extends string, A, E, B>(
  name: Exclude<N, keyof A>,
  fb: TaskEither<E, B>,
) => (fa: TaskEither<E, A>) => TaskEither<E, { 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

apSW​

Less strict version of apS.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const apSW: <A, N extends string, E2, B>(
  name: Exclude<N, keyof A>,
  fb: TaskEither<E2, B>,
) => <E1>(fa: TaskEither<E1, A>) => TaskEither<
  E1 | E2,
  {
    readonly [K in keyof A | N]: 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, E, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => TaskEither<E, B>,
) => (ma: TaskEither<E, A>) => TaskEither<E, { 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,
) => <E, A>(fa: TaskEither<E, A>) => TaskEither<E, { readonly [K in N]: A }>

Details​

  • Added in 0.1.0

License​

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

bindW​

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const bindW: <N extends string, A, E2, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => TaskEither<E2, B>,
) => <E1>(fa: TaskEither<E1, A>) => TaskEither<
  E1 | E2,
  {
    readonly [K in keyof A | N]: K extends keyof A ? A[K] : B
  }
>

Details​

  • Added in 0.1.0

License​

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

Error handling​

alt​

Identifies an associative operation on a type constructor. It is similar to Semigroup, except that it applies to types of kind * -> *.

In case of TaskEither returns fa if is a Right or the value returned by that otherwise.

See also orElse.

Signature​

export declare const alt: <E, A>(that: LazyArg<TaskEither<E, A>>) => (fa: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

Example​

import * as E from '@fp-tx/core/Either'
import { pipe } from '@fp-tx/core/function'
import * as TE from '@fp-tx/core/TaskEither'

async function test() {
  assert.deepStrictEqual(
    await pipe(
      TE.right(1),
      TE.alt(() => TE.right(2)),
    )(),
    E.right(1),
  )
  assert.deepStrictEqual(
    await pipe(
      TE.left('a'),
      TE.alt(() => TE.right(2)),
    )(),
    E.right(2),
  )
  assert.deepStrictEqual(
    await pipe(
      TE.left('a'),
      TE.alt(() => TE.left('b')),
    )(),
    E.left('b'),
  )
}

test()

License​

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

altW​

Less strict version of alt.

The W suffix (short for Widening) means that the error and the return types will be merged.

Signature​

export declare const altW: <E2, B>(
  that: LazyArg<TaskEither<E2, B>>,
) => <E1, A>(fa: TaskEither<E1, A>) => TaskEither<E2, A | B>

Details​

  • Added in 0.1.0

License​

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

getAltTaskValidation​

The default Alt instance returns the last error, if you want to get all errors you need to provide a way to concatenate them via a Semigroup.

See getAltValidation.

Signature​

export declare function getAltTaskValidation<E>(S: Semigroup<E>): Alt2C<URI, E>

Details​

  • Added in 0.1.0

License​

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

getApplicativeTaskValidation​

The default ApplicativePar instance returns the first error, if you want to get all errors you need to provide a way to concatenate them via a Semigroup.

Signature​

export declare function getApplicativeTaskValidation<E>(A: Apply1<T.URI>, S: Semigroup<E>): Applicative2C<URI, E>

Details​

  • Added in 0.1.0

Example​

import * as E from '@fp-tx/core/Either'
import { pipe } from '@fp-tx/core/function'
import * as RA from '@fp-tx/core/ReadonlyArray'
import * as S from '@fp-tx/core/Semigroup'
import * as string from '@fp-tx/core/string'
import * as T from '@fp-tx/core/Task'
import * as TE from '@fp-tx/core/TaskEither'

interface User {
  readonly id: string
  readonly name: string
}

const remoteDatabase: ReadonlyArray<User> = [
  { id: 'id1', name: 'John' },
  { id: 'id2', name: 'Mary' },
  { id: 'id3', name: 'Joey' },
]

const fetchUser = (id: string): TE.TaskEither<string, User> =>
  pipe(
    remoteDatabase,
    RA.findFirst(user => user.id === id),
    TE.fromOption(() => `${id} not found`),
  )

async function test() {
  assert.deepStrictEqual(
    await pipe(['id4', 'id5'], RA.traverse(TE.ApplicativePar)(fetchUser))(),
    E.left('id4 not found'), // <= first error
  )

  const Applicative = TE.getApplicativeTaskValidation(T.ApplyPar, pipe(string.Semigroup, S.intercalate(', ')))

  assert.deepStrictEqual(
    await pipe(['id4', 'id5'], RA.traverse(Applicative)(fetchUser))(),
    E.left('id4 not found, id5 not found'), // <= all errors
  )
}

test()

License​

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

getOrElse​

Signature​

export declare const getOrElse: <E, A>(onLeft: (e: E) => Task<A>) => (ma: TaskEither<E, A>) => Task<A>

Details​

  • Added in 0.1.0

License​

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

getOrElseW​

Less strict version of getOrElse.

The W suffix (short for Widening) means that the handler return type will be merged.

Signature​

export declare const getOrElseW: <E, B>(onLeft: (e: E) => Task<B>) => <A>(ma: TaskEither<E, A>) => Task<A | B>

Details​

  • Added in 0.1.0

License​

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

mapBoth​

Returns a TaskEither whose failure and success channels have been mapped by the specified pair of functions, f and g.

Signature​

export declare const mapBoth: {
  <E, G, A, B>(f: (e: E) => G, g: (a: A) => B): (self: TaskEither<E, A>) => TaskEither<G, B>
  <E, A, G, B>(self: TaskEither<E, A>, f: (e: E) => G, g: (a: A) => B): TaskEither<G, B>
}

Details​

  • Added in 0.1.0

Example​

import * as TaskEither from '@fp-tx/core/TaskEither'
import * as Either from '@fp-tx/core/Either'

const f = (s: string) => new Error(s)
const g = (n: number) => n * 2

async function test() {
  assert.deepStrictEqual(await TaskEither.mapBoth(TaskEither.right(1), f, g)(), Either.right(2))
  assert.deepStrictEqual(await TaskEither.mapBoth(TaskEither.left('err'), f, g)(), Either.left(new Error('err')))
}

test()

License​

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

mapError​

Returns a TaskEither with its error channel mapped using the specified function.

Signature​

export declare const mapError: {
  <E, G>(f: (e: E) => G): <A>(self: TaskEither<E, A>) => TaskEither<G, A>
  <E, A, G>(self: TaskEither<E, A>, f: (e: E) => G): TaskEither<G, A>
}

Details​

  • Added in 0.1.0

Example​

import * as TaskEither from '@fp-tx/core/TaskEither'
import * as Either from '@fp-tx/core/Either'

const f = (s: string) => new Error(s)

async function test() {
  assert.deepStrictEqual(await TaskEither.mapError(TaskEither.right(1), f)(), Either.right(1))
  assert.deepStrictEqual(await TaskEither.mapError(TaskEither.left('err'), f)(), Either.left(new Error('err')))
}

test()

License​

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

orElse​

Returns ma if is a Right or the value returned by onLeft otherwise.

See also alt.

Signature​

export declare const orElse: <E1, A, E2>(
  onLeft: (e: E1) => TaskEither<E2, A>,
) => (ma: TaskEither<E1, A>) => TaskEither<E2, A>

Details​

  • Added in 0.1.0

Example​

import * as E from '@fp-tx/core/Either'
import { pipe } from '@fp-tx/core/function'
import * as TE from '@fp-tx/core/TaskEither'

async function test() {
  const errorHandler = TE.orElse((error: string) => TE.right(`recovering from ${error}...`))
  assert.deepStrictEqual(await pipe(TE.right('ok'), errorHandler)(), E.right('ok'))
  assert.deepStrictEqual(await pipe(TE.left('ko'), errorHandler)(), E.right('recovering from ko...'))
}

test()

License​

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

orElseFirstIOK​

Signature​

export declare const orElseFirstIOK: <E, B>(onLeft: (e: E) => IO<B>) => <A>(ma: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

orElseFirstTaskK​

Signature​

export declare const orElseFirstTaskK: <E, B>(
  onLeft: (e: E) => Task<B>,
) => <A>(ma: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

orElseW​

Less strict version of orElse.

The W suffix (short for Widening) means that the return types will be merged.

Signature​

export declare const orElseW: <E1, E2, B>(
  onLeft: (e: E1) => TaskEither<E2, B>,
) => <A>(ma: TaskEither<E1, A>) => TaskEither<E2, A | B>

Details​

  • Added in 0.1.0

License​

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

orLeft​

Signature​

export declare const orLeft: <E1, E2>(onLeft: (e: E1) => Task<E2>) => <A>(fa: TaskEither<E1, A>) => TaskEither<E2, A>

Details​

  • Added in 0.1.0

License​

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

tapError​

Returns an effect that effectfully "peeks" at the failure of this effect.

Signature​

export declare const tapError: {
  <E1, E2, _>(onLeft: (e: E1) => TaskEither<E2, _>): <A>(self: TaskEither<E1, A>) => TaskEither<E1 | E2, A>
  <E1, A, E2, _>(self: TaskEither<E1, A>, onLeft: (e: E1) => TaskEither<E2, _>): TaskEither<E1 | E2, A>
}

Details​

  • Added in 0.1.0

License​

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

Filtering​

filterOrElse​

Signature​

export declare const filterOrElse: {
  <E, A, B extends A>(refinement: Refinement<A, B>, onFalse: (a: A) => E): (ma: TaskEither<E, A>) => TaskEither<E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): <B extends A>(mb: TaskEither<E, B>) => TaskEither<E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): (ma: TaskEither<E, A>) => TaskEither<E, A>
}

Details​

  • Added in 0.1.0

License​

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

filterOrElseW​

Less strict version of filterOrElse.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const filterOrElseW: {
  <A, B extends A, E2>(
    refinement: Refinement<A, B>,
    onFalse: (a: A) => E2,
  ): <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>
  <A, E2>(
    predicate: Predicate<A>,
    onFalse: (a: A) => E2,
  ): <E1, B extends A>(mb: TaskEither<E1, B>) => TaskEither<E1 | E2, B>
  <A, E2>(predicate: Predicate<A>, onFalse: (a: A) => E2): <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, A>
}

Details​

  • Added in 0.1.0

License​

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

getCompactable​

Signature​

export declare const getCompactable: <E>(M: Monoid<E>) => Compactable2C<'TaskEither', E>

Details​

  • Added in 0.1.0

License​

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

getFilterable​

Signature​

export declare function getFilterable<E>(M: Monoid<E>): Filterable2C<URI, E>

Details​

  • Added in 0.1.0

License​

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

Instance methods​

chainRec​

Signature​

export declare const chainRec: ChainRec2<URI>['chainRec']

Details​

  • Added in 0.1.0

License​

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

Interop​

taskify​

Convert a node style callback function to one returning a TaskEither

Note. If the function f admits multiple overloadings, taskify will pick last one. If you want a different behaviour, add an explicit type annotation

// readFile admits multiple overloadings

// const readFile: (a: string) => TaskEither<NodeJS.ErrnoException, Buffer>
const readFile = taskify(fs.readFile)

const readFile2: (filename: string, encoding: string) => TaskEither<NodeJS.ErrnoException, Buffer> = taskify(
  fs.readFile,
)

Signature​

export declare function taskify<L, R>(f: (cb: (e: L | null | undefined, r?: R) => void) => void): () => TaskEither<L, R>



export declare function taskify<A, L, R>(
  f: (a: A, cb: (e: L | null | undefined, r?: R) => void) => void,
): (a: A) => TaskEither<L, R>



export declare function taskify<A, B, L, R>(
  f: (a: A, b: B, cb: (e: L | null | undefined, r?: R) => void) => void,
): (a: A, b: B) => TaskEither<L, R>



export declare function taskify<A, B, C, L, R>(
  f: (a: A, b: B, c: C, cb: (e: L | null | undefined, r?: R) => void) => void,
): (a: A, b: B, c: C) => TaskEither<L, R>



export declare function taskify<A, B, C, D, L, R>(
  f: (a: A, b: B, c: C, d: D, cb: (e: L | null | undefined, r?: R) => void) => void,
): (a: A, b: B, c: C, d: D) => TaskEither<L, R>



export declare function taskify<A, B, C, D, E, L, R>(
  f: (a: A, b: B, c: C, d: D, e: E, cb: (e: L | null | undefined, r?: R) => void) => void,
): (a: A, b: B, c: C, d: D, e: E) => TaskEither<L, R>

Details​

  • Added in 0.1.0

Example​

import { taskify } from '@fp-tx/core/TaskEither'
import * as fs from 'fs'

// const stat: (a: string | Buffer) => TaskEither<NodeJS.ErrnoException, fs.Stats>
const stat = taskify(fs.stat)
assert.strictEqual(stat.length, 0)

License​

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

tryCatch​

Transforms a Promise that may reject to a Promise that never rejects and returns an Either instead.

See also tryCatchK.

Signature​

export declare const tryCatch: <E, A>(f: LazyArg<Promise<A>>, onRejected: (reason: unknown) => E) => TaskEither<E, A>

Details​

  • Added in 0.1.0

Example​

import { left, right } from '@fp-tx/core/Either'
import { tryCatch } from '@fp-tx/core/TaskEither'

tryCatch(() => Promise.resolve(1), String)().then(result => {
  assert.deepStrictEqual(result, right(1))
})
tryCatch(() => Promise.reject('error'), String)().then(result => {
  assert.deepStrictEqual(result, left('error'))
})

License​

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

tryCatchK​

Converts a function returning a Promise to one returning a TaskEither.

Signature​

export declare const tryCatchK: <E, A extends readonly unknown[], B>(
  f: (...a: A) => Promise<B>,
  onRejected: (reason: unknown) => E,
) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

Legacy​

bimap​

Alias of mapBoth.

Signature​

export declare const bimap: <E, G, A, B>(f: (e: E) => G, g: (a: A) => B) => (fa: TaskEither<E, A>) => TaskEither<G, B>

Details​

  • Added in 0.1.0

License​

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

chain​

Alias of flatMap.

Signature​

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

Details​

  • Added in 0.1.0

License​

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

chainEitherK​

Alias of flatMapEither.

Signature​

export declare const chainEitherK: <E, A, B>(f: (a: A) => E.Either<E, B>) => (ma: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainEitherKW​

Alias of flatMapEither.

Signature​

export declare const chainEitherKW: <E2, A, B>(
  f: (a: A) => Either<E2, B>,
) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

chainFirst​

Alias of tap.

Signature​

export declare const chainFirst: <E, A, B>(f: (a: A) => TaskEither<E, B>) => (ma: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstEitherK​

Alias of tapEither.

Signature​

export declare const chainFirstEitherK: <A, E, B>(
  f: (a: A) => E.Either<E, B>,
) => (ma: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstEitherKW​

Alias of tapEither.

Less strict version of chainFirstEitherK.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const chainFirstEitherKW: <A, E2, B>(
  f: (a: A) => E.Either<E2, B>,
) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, 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>) => <E>(first: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstTaskK​

Alias of tapTask.

Signature​

export declare const chainFirstTaskK: <A, B>(f: (a: A) => T.Task<B>) => <E>(first: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstW​

Alias of tap.

Signature​

export declare const chainFirstW: <E2, A, B>(
  f: (a: A) => TaskEither<E2, B>,
) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, A>

Details​

  • Added in 0.1.0

License​

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

chainIOEitherK​

Alias of flatMapIOEither.

Signature​

export declare const chainIOEitherK: <E, A, B>(
  f: (a: A) => IOEither<E, B>,
) => (ma: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainIOEitherKW​

Alias of flatMapIOEither.

Less strict version of chainIOEitherK.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const chainIOEitherKW: <E2, A, B>(
  f: (a: A) => IOEither<E2, B>,
) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>

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>) => <E>(first: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainNullableK​

Use flatMapNullable.

Signature​

export declare const chainNullableK: <E>(
  e: E,
) => <A, B>(f: (a: A) => B | null | undefined) => (ma: TaskEither<E, A>) => TaskEither<E, NonNullable<B>>

Details​

  • Added in 0.1.0

License​

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

chainOptionK​

Use flatMapOption.

Signature​

export declare const chainOptionK: <E>(
  onNone: LazyArg<E>,
) => <A, B>(f: (a: A) => Option<B>) => (ma: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainOptionKW​

Use flatMapOption.

Signature​

export declare const chainOptionKW: <E2>(
  onNone: LazyArg<E2>,
) => <A, B>(f: (a: A) => Option<B>) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

chainTaskK​

Alias of flatMapTask.

Signature​

export declare const chainTaskK: <A, B>(f: (a: A) => T.Task<B>) => <E>(first: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainTaskOptionK​

Use flatMapTaskOption.

Signature​

export declare const chainTaskOptionK: <E>(
  onNone: LazyArg<E>,
) => <A, B>(f: (a: A) => TaskOption<B>) => (ma: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

chainTaskOptionKW​

Use flatMapTaskOption.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const chainTaskOptionKW: <E2>(
  onNone: LazyArg<E2>,
) => <A, B>(f: (a: A) => TaskOption<B>) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E2 | E1, B>

Details​

  • Added in 0.1.0

License​

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

chainW​

Alias of flatMap.

Signature​

export declare const chainW: <E2, A, B>(
  f: (a: A) => TaskEither<E2, B>,
) => <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

fromNullableK​

Use liftNullable.

Signature​

export declare const fromNullableK: <E>(
  e: E,
) => <A extends ReadonlyArray<unknown>, B>(
  f: (...a: A) => B | null | undefined,
) => (...a: A) => TaskEither<E, NonNullable<B>>

Details​

  • Added in 0.1.0

License​

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

fromOptionK​

Use liftOption.

Signature​

export declare const fromOptionK: <E>(
  onNone: LazyArg<E>,
) => <A extends ReadonlyArray<unknown>, B>(f: (...a: A) => Option<B>) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

mapLeft​

Alias of mapError.

Signature​

export declare const mapLeft: <E, G>(f: (e: E) => G) => <A>(fa: TaskEither<E, A>) => TaskEither<G, A>

Details​

  • Added in 0.1.0

License​

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

orElseFirst​

Alias of tapError.

Signature​

export declare const orElseFirst: <E, B>(
  onLeft: (e: E) => TaskEither<E, B>,
) => <A>(ma: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

orElseFirstW​

Alias of tapError.

Signature​

export declare const orElseFirstW: <E1, E2, B>(
  onLeft: (e: E1) => TaskEither<E2, B>,
) => <A>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, A>

Details​

  • Added in 0.1.0

License​

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

Lifting​

fromEitherK​

Signature​

export declare const fromEitherK: <E, A extends ReadonlyArray<unknown>, B>(
  f: (...a: A) => E.Either<E, B>,
) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

fromIOEitherK​

Signature​

export declare const fromIOEitherK: <E, A extends readonly unknown[], B>(
  f: (...a: A) => IOEither<E, B>,
) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

fromIOK​

Signature​

export declare const fromIOK: <A extends ReadonlyArray<unknown>, B>(
  f: (...a: A) => IO<B>,
) => <E = never>(...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

fromPredicate​

Signature​

export declare const fromPredicate: {
  <E, A, B extends A>(refinement: Refinement<A, B>, onFalse: (a: A) => E): (a: A) => TaskEither<E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): <B extends A>(b: B) => TaskEither<E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): (a: A) => TaskEither<E, A>
}

Details​

  • Added in 0.1.0

License​

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

fromTaskK​

Signature​

export declare const fromTaskK: <A extends ReadonlyArray<unknown>, B>(
  f: (...a: A) => T.Task<B>,
) => <E = never>(...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

fromTaskOptionK​

Signature​

export declare const fromTaskOptionK: <E>(
  onNone: LazyArg<E>,
) => <A extends readonly unknown[], B>(f: (...a: A) => TaskOption<B>) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

liftNullable​

Signature​

export declare const liftNullable: <A extends ReadonlyArray<unknown>, B, E>(
  f: (...a: A) => B | null | undefined,
  onNullable: (...a: A) => E,
) => (...a: A) => TaskEither<E, NonNullable<B>>

Details​

  • Added in 0.1.0

License​

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

liftOption​

Signature​

export declare const liftOption: <A extends ReadonlyArray<unknown>, B, E>(
  f: (...a: A) => Option<B>,
  onNone: (...a: A) => E,
) => (...a: A) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

Mapping​

as​

Maps the Right value of this TaskEither to the specified constant value.

Signature​

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

Details​

  • Added in 0.1.0

License​

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

asUnit​

Maps the Right value of this TaskEither to the void constant value.

Signature​

export declare const asUnit: <E, _>(self: TaskEither<E, _>) => TaskEither<E, void>

Details​

  • Added in 0.1.0

License​

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

flap​

Signature​

export declare const flap: <A>(a: A) => <E, B>(fab: TaskEither<E, (a: A) => B>) => TaskEither<E, 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) => <E>(fa: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

Model​

TaskEither​

Signature​

export interface TaskEither<E, A> extends Task<Either<E, A>> {}

Details​

  • Added in 0.1.0

License​

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

Pattern matching​

fold​

Alias of matchE.

Signature​

export declare const fold: <E, A, B>(
  onLeft: (e: E) => T.Task<B>,
  onRight: (a: A) => T.Task<B>,
) => (ma: TaskEither<E, A>) => T.Task<B>

Details​

  • Added in 0.1.0

License​

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

foldW​

Alias of matchEW.

Signature​

export declare const foldW: <E, B, A, C>(
  onLeft: (e: E) => T.Task<B>,
  onRight: (a: A) => T.Task<C>,
) => (ma: TaskEither<E, A>) => T.Task<B | C>

Details​

  • Added in 0.1.0

License​

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

match​

Signature​

export declare const match: <E, B, A>(onLeft: (e: E) => B, onRight: (a: A) => B) => (ma: TaskEither<E, A>) => Task<B>

Details​

  • Added in 0.1.0

License​

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

matchE​

The E suffix (short for Effect) means that the handlers return an effect (Task).

Signature​

export declare const matchE: <E, A, B>(
  onLeft: (e: E) => Task<B>,
  onRight: (a: A) => Task<B>,
) => (ma: TaskEither<E, A>) => Task<B>

Details​

  • Added in 0.1.0

License​

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

matchEW​

Less strict version of matchE.

The W suffix (short for Widening) means that the handler return types will be merged.

Signature​

export declare const matchEW: <E, B, A, C>(
  onLeft: (e: E) => Task<B>,
  onRight: (a: A) => Task<C>,
) => (ma: TaskEither<E, A>) => Task<B | C>

Details​

  • Added in 0.1.0

License​

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

matchW​

Less strict version of match.

The W suffix (short for Widening) means that the handler return types will be merged.

Signature​

export declare const matchW: <E, B, A, C>(
  onLeft: (e: E) => B,
  onRight: (a: A) => C,
) => (ma: TaskEither<E, A>) => Task<B | C>

Details​

  • Added in 0.1.0

License​

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

Sequencing​

flatMap​

Signature​

export declare const flatMap: {
  <A, E2, B>(f: (a: A) => TaskEither<E2, B>): <E1>(ma: TaskEither<E1, A>) => TaskEither<E1 | E2, B>
  <E1, A, E2, B>(ma: TaskEither<E1, A>, f: (a: A) => TaskEither<E2, B>): TaskEither<E1 | E2, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapEither​

Signature​

export declare const flatMapEither: {
  <A, E2, B>(f: (a: A) => E.Either<E2, B>): <E1>(self: TaskEither<E1, A>) => TaskEither<E1 | E2, B>
  <E1, A, E2, B>(self: TaskEither<E1, A>, f: (a: A) => E.Either<E2, B>): TaskEither<E1 | E2, 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>): <E>(self: TaskEither<E, A>) => TaskEither<E, B>
  <E, A, B>(self: TaskEither<E, A>, f: (a: A) => IO<B>): TaskEither<E, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapIOEither​

Signature​

export declare const flatMapIOEither: {
  <A, E2, B>(f: (a: A) => IOEither<E2, B>): <E1>(self: TaskEither<E1, A>) => TaskEither<E1 | E2, B>
  <E1, A, E2, B>(self: TaskEither<E1, A>, f: (a: A) => IOEither<E2, B>): TaskEither<E1 | E2, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapNullable​

Signature​

export declare const flatMapNullable: {
  <A, B, E2>(
    f: (a: A) => B | null | undefined,
    onNullable: (a: A) => E2,
  ): <E1>(self: TaskEither<E1, A>) => TaskEither<E2 | E1, NonNullable<B>>
  <E1, A, B, E2>(
    self: TaskEither<E1, A>,
    f: (a: A) => B | null | undefined,
    onNullable: (a: A) => E2,
  ): TaskEither<E1 | E2, NonNullable<B>>
}

Details​

  • Added in 0.1.0

License​

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

flatMapOption​

Signature​

export declare const flatMapOption: {
  <A, B, E2>(f: (a: A) => Option<B>, onNone: (a: A) => E2): <E1>(self: TaskEither<E1, A>) => TaskEither<E2 | E1, B>
  <E1, A, B, E2>(self: TaskEither<E1, A>, f: (a: A) => Option<B>, onNone: (a: A) => E2): TaskEither<E1 | E2, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapTask​

Signature​

export declare const flatMapTask: {
  <A, B>(f: (a: A) => Task<B>): <E>(self: TaskEither<E, A>) => TaskEither<E, B>
  <E, A, B>(self: TaskEither<E, A>, f: (a: A) => Task<B>): TaskEither<E, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapTaskOption​

Signature​

export declare const flatMapTaskOption: {
  <A, E2, B>(f: (a: A) => TaskOption<B>, onNone: (a: A) => E2): <E1>(self: TaskEither<E1, A>) => TaskEither<E1 | E2, B>
  <E1, A, E2, B>(self: TaskEither<E1, A>, f: (a: A) => TaskOption<B>, onNone: (a: A) => E2): TaskEither<E1 | E2, B>
}

Details​

  • Added in 0.1.0

License​

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

flatten​

Signature​

export declare const flatten: <E, A>(mma: TaskEither<E, TaskEither<E, A>>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

flattenW​

Less strict version of flatten.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const flattenW: <E1, E2, A>(mma: TaskEither<E1, TaskEither<E2, A>>) => TaskEither<E1 | E2, 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, E>(arr: ReadonlyArray<TaskEither<E, A>>) => TaskEither<E, 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, E>(arr: ReadonlyArray<TaskEither<E, A>>) => TaskEither<E, 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, E>(
  f: (a: A) => TaskEither<E, B>,
) => (as: readonly A[]) => TaskEither<E, 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, E>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: ReadonlyArray<A>) => TaskEither<E, 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, E, B>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: readonly A[]) => TaskEither<E, 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, E, B>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: readonly A[]) => TaskEither<E, 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, E, B>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: ReadonlyNonEmptyArray<A>) => TaskEither<E, ReadonlyNonEmptyArray<B>>

Details​

  • Added in 0.1.0

License​

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

traverseReadonlyNonEmptyArrayWithIndexSeq​

Equivalent to ReadonlyArray#traverseWithIndex(ApplicativeSeq).

Signature​

export declare const traverseReadonlyNonEmptyArrayWithIndexSeq: <A, E, B>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: ReadonlyNonEmptyArray<A>) => TaskEither<E, 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, E>(
  f: (a: A) => TaskEither<E, B>,
) => (as: readonly A[]) => TaskEither<E, 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, E>(
  f: (index: number, a: A) => TaskEither<E, B>,
) => (as: ReadonlyArray<A>) => TaskEither<E, 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 = 'TaskEither'

Details​

  • Added in 0.1.0

License​

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

Utilities​

ApT​

Signature​

export declare const ApT: TaskEither<never, readonly []>

Details​

  • Added in 0.1.0

License​

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

ap​

Signature​

export declare const ap: <E, A>(fa: TaskEither<E, A>) => <B>(fab: TaskEither<E, (a: A) => B>) => TaskEither<E, 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: <E, B>(second: TaskEither<E, B>) => <A>(first: TaskEither<E, A>) => TaskEither<E, A>

Details​

  • Added in 0.1.0

License​

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

apFirstW​

Less strict version of apFirst.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const apFirstW: <E2, B>(
  second: TaskEither<E2, B>,
) => <E1, A>(first: TaskEither<E1, A>) => TaskEither<E1 | E2, 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: <E, B>(second: TaskEither<E, B>) => <A>(first: TaskEither<E, A>) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

apSecondW​

Less strict version of apSecond.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const apSecondW: <E2, B>(
  second: TaskEither<E2, B>,
) => <E1, A>(first: TaskEither<E1, A>) => TaskEither<E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

apW​

Less strict version of ap.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const apW: <E2, A>(
  fa: TaskEither<E2, A>,
) => <E1, B>(fab: TaskEither<E1, (a: A) => B>) => TaskEither<E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

bracket​

Make sure that a resource is cleaned up in the event of an exception (). The release action is called regardless of whether the body action throws () or returns.

(*) i.e. returns a Left

Signature​

export declare const bracket: <E, A, B>(
  acquire: TaskEither<E, A>,
  use: (a: A) => TaskEither<E, B>,
  release: (a: A, e: E.Either<E, B>) => TaskEither<E, void>,
) => TaskEither<E, B>

Details​

  • Added in 0.1.0

License​

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

bracketW​

Less strict version of bracket.

The W suffix (short for Widening) means that the error types will be merged.

Signature​

export declare const bracketW: <E1, A, E2, B, E3>(
  acquire: TaskEither<E1, A>,
  use: (a: A) => TaskEither<E2, B>,
  release: (a: A, e: E.Either<E2, B>) => TaskEither<E3, void>,
) => TaskEither<E1 | E2 | E3, B>

Details​

  • Added in 0.1.0

License​

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

do​

Signature​

export declare const do_: <MA extends TaskEitherIterable<any, any>, A>(
  yieldFunction: (unwrap: <E, A>(ma: TaskEither<E, A>) => TaskEitherIterable<E, A>) => Generator<MA, A>,
) => TaskEither<MA extends TaskEitherIterable<infer E, any> ? E : never, A>

getApplyMonoid​

Use getApplicativeMonoid instead.

Signature​

export declare const getApplyMonoid: <E, A>(M: Monoid<A>) => Monoid<TaskEither<E, A>>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

getApplySemigroup​

Use getApplySemigroup instead.

Signature​

export declare const getApplySemigroup: <E, A>(S: Semigroup<A>) => Semigroup<TaskEither<E, 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: <E, A>(S: Semigroup<A>) => Semigroup<TaskEither<E, A>>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

getTaskValidation​

Use getApplicativeTaskValidation and getAltTaskValidation instead.

Signature​

export declare function getTaskValidation<E>(
  SE: Semigroup<E>,
): Monad2C<URI, E> & Bifunctor2<URI> & Alt2C<URI, E> & MonadTask2C<URI, E> & MonadThrow2C<URI, E>

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,
) => <E>(fa: TaskEither<E, A>) => TaskEither<E, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

swap​

Signature​

export declare const swap: <E, A>(ma: TaskEither<E, A>) => TaskEither<A, E>

Details​

  • Added in 0.1.0

License​

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

taskEither​

This instance is deprecated, use small, specific instances instead. For example if a function needs a Functor instance, pass TE.Functor instead of TE.taskEither (where TE is from import TE from 'fp-ts/TaskEither')

Signature​

export declare const taskEither: Monad2<URI> & Bifunctor2<URI> & Alt2<URI> & MonadTask2<URI> & MonadThrow2<URI>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

taskEitherSeq​

This instance is deprecated, use small, specific instances instead. For example if a function needs a Functor instance, pass TE.Functor instead of TE.taskEitherSeq (where TE is from import TE from 'fp-ts/TaskEither')

Signature​

export declare const taskEitherSeq: typeof taskEither

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

throwError​

Signature​

export declare const throwError: MonadThrow2<URI>['throwError']

Details​

  • Added in 0.1.0

License​

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