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ReaderEither

Instances​

Combinators​

Constructors​

Conversions​

Do notation​

Error handling​

Filtering​

Instance methods​

Legacy​

Lifting​

Mapping​

Model​

Pattern matching​

Sequencing​

Traversing​

Type lambdas​

Utilities​

Instances​

Alt​

Signature​

export declare const Alt: Alt3<URI>

Details​

  • Added in 0.1.0

License​

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

Applicative​

Signature​

export declare const Applicative: Applicative3<URI>

Details​

  • Added in 0.1.0

License​

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

Apply​

Signature​

export declare const Apply: Apply3<URI>

Details​

  • Added in 0.1.0

License​

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

Bifunctor​

Signature​

export declare const Bifunctor: Bifunctor3<URI>

Details​

  • Added in 0.1.0

License​

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

Chain​

Signature​

export declare const Chain: chainable.Chain3<URI>

Details​

  • Added in 0.1.0

License​

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

ChainRec​

ChainRec for ReaderEither

Signature​

export declare const ChainRec: ChainRec3<URI>

Details​

  • Added in 0.1.0

License​

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

FromEither​

Signature​

export declare const FromEither: FromEither3<URI>

Details​

  • Added in 0.1.0

License​

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

FromReader​

Signature​

export declare const FromReader: FromReader3<URI>

Details​

  • Added in 0.1.0

License​

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

Functor​

Signature​

export declare const Functor: Functor3<URI>

Details​

  • Added in 0.1.0

License​

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

Monad​

Signature​

export declare const Monad: Monad3<URI>

Details​

  • Added in 0.1.0

License​

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

MonadThrow​

Signature​

export declare const MonadThrow: MonadThrow3<URI>

Details​

  • Added in 0.1.0

License​

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

Pointed​

Signature​

export declare const Pointed: Pointed3<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: {
  <R1, E1, A, R2, E2, _>(
    self: ReaderEither<R1, E1, A>,
    f: (a: A) => ReaderEither<R2, E2, _>,
  ): ReaderEither<R1 & R2, E1 | E2, A>
  <A, R2, E2, _>(
    f: (a: A) => ReaderEither<R2, E2, _>,
  ): <R1, E1>(self: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, 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, _>): <R1, E1>(self: ReaderEither<R1, E1, A>) => ReaderEither<R1, E1 | E2, A>
  <R1, E1, A, E2, _>(self: ReaderEither<R1, E1, A>, f: (a: A) => Either<E2, _>): ReaderEither<R1, 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 RE from '@fp-tx/core/ReaderEither'

const checkString = (value: string) =>
  pipe(
    RE.ask<number>(),
    RE.tapEither(minLength => (value.length > minLength ? E.right('ok') : E.left('error'))),
  )

assert.deepStrictEqual(checkString('')(1), E.left('error'))
assert.deepStrictEqual(checkString('fp-ts')(2), E.right(2))

License​

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

tapReader​

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 tapReader: {
  <R2, A, E, _>(f: (a: A) => Reader<R2, _>): <R1>(self: ReaderEither<R1, E, A>) => ReaderEither<R1 & R2, E, A>
  <R1, R2, E, A, _>(self: ReaderEither<R1, E, A>, f: (a: A) => Reader<R2, _>): ReaderEither<R1 & R2, E, A>
}

Details​

  • Added in 0.1.0

License​

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

Constructors​

ask​

Reads the current context.

Signature​

export declare const ask: <R, E = never>() => ReaderEither<R, E, R>

Details​

  • Added in 0.1.0

License​

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

asks​

Projects a value from the global context in a ReaderEither.

Signature​

export declare const asks: <R, A, E = never>(f: (r: R) => A) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

asksReaderEither​

Effectfully accesses the environment.

Signature​

export declare const asksReaderEither: <R, E, A>(f: (r: R) => ReaderEither<R, E, A>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

asksReaderEitherW​

Less strict version of asksReaderEither.

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

Signature​

export declare const asksReaderEitherW: <R1, R2, E, A>(
  f: (r1: R1) => ReaderEither<R2, E, A>,
) => ReaderEither<R1 & R2, E, A>

Details​

  • Added in 0.1.0

License​

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

left​

Signature​

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

Details​

  • Added in 0.1.0

License​

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

leftReader​

Signature​

export declare const leftReader: <R, E = never, A = never>(me: Reader<R, E>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

of​

Signature​

export declare const of: <R = unknown, E = never, A = never>(a: A) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

Signature​

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

Details​

  • Added in 0.1.0

License​

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

rightReader​

Signature​

export declare const rightReader: <R, E = never, A = never>(ma: Reader<R, A>) => ReaderEither<R, 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, R = unknown>(fa: Either<E, A>) => ReaderEither<R, E, 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, R = unknown>(fa: Option<A>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

fromReader​

Signature​

export declare const fromReader: <R, A, E = never>(fa: Reader<R, A>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

toUnion​

Signature​

export declare const toUnion: <R, E, A>(fa: ReaderEither<R, E, A>) => Reader<R, E | A>

Details​

  • Added in 0.1.0

License​

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

Do notation​

Do​

Signature​

export declare const Do: ReaderEither<unknown, 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, R, E, B>(
  name: Exclude<N, keyof A>,
  fb: ReaderEither<R, E, B>,
) => (fa: ReaderEither<R, E, A>) => ReaderEither<R, 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 environment types and the error types will be merged.

Signature​

export declare const apSW: <A, N extends string, R2, E2, B>(
  name: Exclude<N, keyof A>,
  fb: ReaderEither<R2, E2, B>,
) => <R1, E1>(
  fa: ReaderEither<R1, E1, A>,
) => ReaderEither<
  R1 & R2,
  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, R, E, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => ReaderEither<R, E, B>,
) => (ma: ReaderEither<R, E, A>) => ReaderEither<R, 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,
) => <R, E, A>(fa: ReaderEither<R, E, A>) => ReaderEither<R, 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 environment types and the error types will be merged.

Signature​

export declare const bindW: <N extends string, A, R2, E2, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => ReaderEither<R2, E2, B>,
) => <R1, E1>(
  fa: ReaderEither<R1, E1, A>,
) => ReaderEither<
  R1 & R2,
  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 * -> *.

Signature​

export declare const alt: <R, E, A>(
  that: () => ReaderEither<R, E, A>,
) => (fa: ReaderEither<R, E, A>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

altW​

Less strict version of alt.

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

Signature​

export declare const altW: <R2, E2, B>(
  that: () => ReaderEither<R2, E2, B>,
) => <R1, E1, A>(fa: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, E2, A | B>

Details​

  • Added in 0.1.0

License​

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

getAltReaderValidation​

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 getAltReaderValidation<E>(S: Semigroup<E>): Alt3C<URI, E>

Details​

  • Added in 0.1.0

License​

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

getApplicativeReaderValidation​

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

See getApplicativeValidation.

Signature​

export declare function getApplicativeReaderValidation<E>(S: Semigroup<E>): Applicative3C<URI, E>

Details​

  • Added in 0.1.0

License​

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

getOrElse​

Signature​

export declare const getOrElse: <E, R, A>(onLeft: (e: E) => Reader<R, A>) => (ma: ReaderEither<R, E, A>) => Reader<R, 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: <R2, E, B>(
  onLeft: (e: E) => Reader<R2, B>,
) => <R1, A>(ma: ReaderEither<R1, E, A>) => Reader<R1 & R2, A | B>

Details​

  • Added in 0.1.0

License​

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

mapBoth​

Returns a ReaderEither 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): <R>(self: ReaderEither<R, E, A>) => ReaderEither<R, G, B>
  <R, E, A, G, B>(self: ReaderEither<R, E, A>, f: (e: E) => G, g: (a: A) => B): ReaderEither<R, G, B>
}

Details​

  • Added in 0.1.0

Example​

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

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

assert.deepStrictEqual(ReaderEither.mapBoth(ReaderEither.right(1), f, g)({}), Either.right(2))
assert.deepStrictEqual(ReaderEither.mapBoth(ReaderEither.left('err'), f, g)({}), Either.left(new Error('err')))

License​

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

mapError​

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

Signature​

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

Details​

  • Added in 0.1.0

Example​

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

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

assert.deepStrictEqual(ReaderEither.mapError(ReaderEither.right(1), f)({}), Either.right(1))
assert.deepStrictEqual(ReaderEither.mapError(ReaderEither.left('err'), f)({}), Either.left(new Error('err')))

License​

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

orElse​

Signature​

export declare const orElse: <E1, R, E2, A>(
  onLeft: (e: E1) => ReaderEither<R, E2, A>,
) => (ma: ReaderEither<R, E1, A>) => ReaderEither<R, E2, 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 environment types and the return types will be merged.

Signature​

export declare const orElseW: <E1, R1, E2, B>(
  onLeft: (e: E1) => ReaderEither<R1, E2, B>,
) => <R2, A>(ma: ReaderEither<R2, E1, A>) => ReaderEither<R1 & R2, E2, A | B>

Details​

  • Added in 0.1.0

License​

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

orLeft​

Signature​

export declare const orLeft: <E1, R, E2>(
  onLeft: (e: E1) => Reader<R, E2>,
) => <A>(fa: ReaderEither<R, E1, A>) => ReaderEither<R, 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, R2, E2, _>(
    onLeft: (e: E1) => ReaderEither<R2, E2, _>,
  ): <R1, A>(self: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, E1 | E2, A>
  <R1, E1, A, R2, E2, _>(
    self: ReaderEither<R1, E1, A>,
    onLeft: (e: E1) => ReaderEither<R2, E2, _>,
  ): ReaderEither<R1 & R2, 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,
  ): <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, B>
  <E, A>(
    predicate: Predicate<A>,
    onFalse: (a: A) => E,
  ): <R, B extends A>(mb: ReaderEither<R, E, B>) => ReaderEither<R, E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, 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,
  ): <R, E1>(ma: ReaderEither<R, E1, A>) => ReaderEither<R, E1 | E2, B>
  <A, E2>(
    predicate: Predicate<A>,
    onFalse: (a: A) => E2,
  ): <R, E1, B extends A>(mb: ReaderEither<R, E1, B>) => ReaderEither<R, E1 | E2, B>
  <A, E2>(
    predicate: Predicate<A>,
    onFalse: (a: A) => E2,
  ): <R, E1>(ma: ReaderEither<R, E1, A>) => ReaderEither<R, 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>) => Compactable3C<'ReaderEither', 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>): Filterable3C<URI, E>

Details​

  • Added in 0.1.0

License​

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

Instance methods​

chainRec​

Signature​

export declare const chainRec: ChainRec3<URI>['chainRec']

Details​

  • Added in 0.1.0

License​

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

Legacy​

bimap​

Alias of mapBoth.

Signature​

export declare const bimap: <E, G, A, B>(
  f: (e: E) => G,
  g: (a: A) => B,
) => <R>(fa: ReaderEither<R, E, A>) => ReaderEither<R, 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: <R, E, A, B>(
  f: (a: A) => ReaderEither<R, E, B>,
) => (ma: ReaderEither<R, E, A>) => ReaderEither<R, 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>,
) => <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, 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>,
) => <R, E1>(ma: ReaderEither<R, E1, A>) => ReaderEither<R, 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: <R, E, A, B>(
  f: (a: A) => ReaderEither<R, E, B>,
) => (ma: ReaderEither<R, E, A>) => ReaderEither<R, 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>,
) => <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, 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 environment types will be merged.

Signature​

export declare const chainFirstEitherKW: <A, E2, B>(
  f: (a: A) => Either<E2, B>,
) => <R, E1>(ma: ReaderEither<R, E1, A>) => ReaderEither<R, E1 | E2, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstReaderK​

Alias of tapReader.

Signature​

export declare const chainFirstReaderK: <A, R, B>(
  f: (a: A) => Reader<R, B>,
) => <E>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, A>

Details​

  • Added in 0.1.0

License​

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

chainFirstReaderKW​

Alias of tapReader.

Less strict version of chainReaderK.

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

Signature​

export declare const chainFirstReaderKW: <A, R1, B>(
  f: (a: A) => Reader<R1, B>,
) => <R2, E>(ma: ReaderEither<R2, E, A>) => ReaderEither<R1 & R2, 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: <R2, E2, A, B>(
  f: (a: A) => ReaderEither<R2, E2, B>,
) => <R1, E1>(ma: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, E1 | E2, A>

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>) => <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, 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>) => <R, E1>(ma: ReaderEither<R, E1, A>) => ReaderEither<R, E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

chainReaderK​

Alias of flatMapReader.

Signature​

export declare const chainReaderK: <A, R, B>(
  f: (a: A) => Reader<R, B>,
) => <E>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, B>

Details​

  • Added in 0.1.0

License​

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

chainReaderKW​

Alias of flatMapReader.

Less strict version of chainReaderK.

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

Signature​

export declare const chainReaderKW: <A, R2, B>(
  f: (a: A) => Reader<R2, B>,
) => <R1, E>(ma: ReaderEither<R1, E, A>) => ReaderEither<R1 & R2, E, B>

Details​

  • Added in 0.1.0

License​

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

chainW​

Alias of flatMap.

Signature​

export declare const chainW: <R2, E2, A, B>(
  f: (a: A) => ReaderEither<R2, E2, B>,
) => <R1, E1>(ma: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, E1 | E2, 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>) => <R = unknown>(...a: A) => ReaderEither<R, 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) => <R, A>(fa: ReaderEither<R, E, A>) => ReaderEither<R, 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, R, B>(
  onLeft: (e: E) => ReaderEither<R, E, B>,
) => <A>(ma: ReaderEither<R, E, A>) => ReaderEither<R, 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, R2, E2, B>(
  onLeft: (e: E1) => ReaderEither<R2, E2, B>,
) => <R1, A>(ma: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, 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>,
) => <R = unknown>(...a: A) => ReaderEither<R, 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): <R = unknown>(a: A) => ReaderEither<R, E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): <R = unknown, B extends A = A>(b: B) => ReaderEither<R, E, B>
  <E, A>(predicate: Predicate<A>, onFalse: (a: A) => E): <R = unknown>(a: A) => ReaderEither<R, E, A>
}

Details​

  • Added in 0.1.0

License​

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

fromReaderK​

Signature​

export declare const fromReaderK: <A extends ReadonlyArray<unknown>, R, B>(
  f: (...a: A) => Reader<R, B>,
) => <E = never>(...a: A) => ReaderEither<R, 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,
) => <R>(...a: A) => ReaderEither<R, 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,
) => <R>(...a: A) => ReaderEither<R, E, B>

Details​

  • Added in 0.1.0

License​

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

Mapping​

as​

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

Signature​

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

Details​

  • Added in 0.1.0

License​

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

asUnit​

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

Signature​

export declare const asUnit: <R, E, _>(self: ReaderEither<R, E, _>) => ReaderEither<R, 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) => <R, E, B>(fab: ReaderEither<R, E, (a: A) => B>) => ReaderEither<R, 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) => <R, E>(fa: ReaderEither<R, E, A>) => ReaderEither<R, E, B>

Details​

  • Added in 0.1.0

License​

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

Model​

ReaderEither​

Signature​

export interface ReaderEither<R, E, A> extends Reader<R, 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: <R, E, A, B>(
  onLeft: (e: E) => R.Reader<R, B>,
  onRight: (a: A) => R.Reader<R, B>,
) => (ma: ReaderEither<R, E, A>) => R.Reader<R, 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, R2, B, A, R3, C>(
  onLeft: (e: E) => R.Reader<R2, B>,
  onRight: (a: A) => R.Reader<R3, C>,
) => <R1>(ma: ReaderEither<R1, E, A>) => R.Reader<R1 & R2 & R3, 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,
) => <R>(ma: ReaderEither<R, E, A>) => Reader<R, 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 (Reader).

Signature​

export declare const matchE: <R, E, A, B>(
  onLeft: (e: E) => Reader<R, B>,
  onRight: (a: A) => Reader<R, B>,
) => (ma: ReaderEither<R, E, A>) => Reader<R, 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, R2, B, A, R3, C>(
  onLeft: (e: E) => Reader<R2, B>,
  onRight: (a: A) => Reader<R3, C>,
) => <R1>(ma: ReaderEither<R1, E, A>) => Reader<R1 & R2 & R3, 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,
) => <R>(ma: Reader<R, Either<E, A>>) => Reader<R, B | C>

Details​

  • Added in 0.1.0

License​

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

Sequencing​

flatMap​

Signature​

export declare const flatMap: {
  <A, R2, E2, B>(
    f: (a: A) => ReaderEither<R2, E2, B>,
  ): <R1, E1>(ma: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, E1 | E2, B>
  <R1, E1, A, R2, E2, B>(
    ma: ReaderEither<R1, E1, A>,
    f: (a: A) => ReaderEither<R2, E2, B>,
  ): ReaderEither<R1 & R2, 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>): <R, E1>(self: ReaderEither<R, E1, A>) => ReaderEither<R, E1 | E2, B>
  <R, E1, A, E2, B>(self: ReaderEither<R, E1, A>, f: (a: A) => E.Either<E2, B>): ReaderEither<R, 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,
  ): <R, E1>(self: ReaderEither<R, E1, A>) => ReaderEither<R, E2 | E1, NonNullable<B>>
  <R, E1, A, B, E2>(
    self: ReaderEither<R, E1, A>,
    f: (a: A) => B | null | undefined,
    onNullable: (a: A) => E2,
  ): ReaderEither<R, 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,
  ): <R, E1>(self: ReaderEither<R, E1, A>) => ReaderEither<R, E2 | E1, B>
  <R, E1, A, B, E2>(
    self: ReaderEither<R, E1, A>,
    f: (a: A) => Option<B>,
    onNone: (a: A) => E2,
  ): ReaderEither<R, E1 | E2, B>
}

Details​

  • Added in 0.1.0

License​

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

flatMapReader​

Signature​

export declare const flatMapReader: {
  <A, R2, B>(f: (a: A) => Reader<R2, B>): <R1, E>(self: ReaderEither<R1, E, A>) => ReaderEither<R1 & R2, E, B>
  <R1, E, A, R2, B>(self: ReaderEither<R1, E, A>, f: (a: A) => Reader<R2, B>): ReaderEither<R1 & R2, E, B>
}

Details​

  • Added in 0.1.0

License​

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

flatten​

Signature​

export declare const flatten: <R, E, A>(mma: ReaderEither<R, E, ReaderEither<R, E, A>>) => ReaderEither<R, 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 environment types and the error types will be merged.

Signature​

export declare const flattenW: <R1, R2, E1, E2, A>(
  mma: ReaderEither<R1, E1, ReaderEither<R2, E2, A>>,
) => ReaderEither<R1 & R2, 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: <R, E, A>(
  arr: ReadonlyArray<ReaderEither<R, E, A>>,
) => ReaderEither<R, 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: <R, E, A, B>(
  f: (a: A) => ReaderEither<R, E, B>,
) => (as: readonly A[]) => ReaderEither<R, 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: <R, E, A, B>(
  f: (index: number, a: A) => ReaderEither<R, E, B>,
) => (as: ReadonlyArray<A>) => ReaderEither<R, E, ReadonlyArray<B>>

Details​

  • Added in 0.1.0

License​

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

traverseReadonlyArrayWithIndex​

Equivalent to ReadonlyArray#traverseWithIndex(Applicative).

Signature​

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

Details​

  • Added in 0.1.0

License​

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

traverseReadonlyNonEmptyArrayWithIndex​

Equivalent to ReadonlyNonEmptyArray#traverseWithIndex(Applicative).

Signature​

export declare const traverseReadonlyNonEmptyArrayWithIndex: <A, R, E, B>(
  f: (index: number, a: A) => ReaderEither<R, E, B>,
) => (as: ReadonlyNonEmptyArray<A>) => ReaderEither<R, E, ReadonlyNonEmptyArray<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 = 'ReaderEither'

Details​

  • Added in 0.1.0

License​

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

Utilities​

ApT​

Signature​

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

Details​

  • Added in 0.1.0

License​

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

ap​

Signature​

export declare const ap: <R, E, A>(
  fa: ReaderEither<R, E, A>,
) => <B>(fab: ReaderEither<R, E, (a: A) => B>) => ReaderEither<R, 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: <R, E, B>(
  second: ReaderEither<R, E, B>,
) => <A>(first: ReaderEither<R, E, A>) => ReaderEither<R, 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 environment types and the error types will be merged.

Signature​

export declare const apFirstW: <R2, E2, B>(
  second: ReaderEither<R2, E2, B>,
) => <R1, E1, A>(first: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, 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: <R, E, B>(
  second: ReaderEither<R, E, B>,
) => <A>(first: ReaderEither<R, E, A>) => ReaderEither<R, 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 environment types and the error types will be merged.

Signature​

export declare const apSecondW: <R2, E2, B>(
  second: ReaderEither<R2, E2, B>,
) => <R1, E1, A>(first: ReaderEither<R1, E1, A>) => ReaderEither<R1 & R2, 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 environment types and the error types will be merged.

Signature​

export declare const apW: <R2, E2, A>(
  fa: ReaderEither<R2, E2, A>,
) => <R1, E1, B>(fab: ReaderEither<R1, E1, (a: A) => B>) => ReaderEither<R1 & R2, E1 | E2, B>

Details​

  • Added in 0.1.0

License​

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

do​

Signature​

export declare const do_: <MA extends ReaderEitherIterable<any, any, any>, A>(
  yieldFunction: (unwrap: <R, E, A>(ma: ReaderEither<R, E, A>) => ReaderEitherIterable<R, E, A>) => Generator<MA, A>,
) => ReaderEither<
  _.UnionToIntersection<MA extends ReaderEitherIterable<infer R, any, any> ? R : never>,
  MA extends ReaderEitherIterable<any, infer E, any> ? E : never,
  A
>

getApplyMonoid​

Use getApplicativeMonoid instead.

Signature​

export declare const getApplyMonoid: <R, E, A>(M: Monoid<A>) => Monoid<ReaderEither<R, 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: <R, E, A>(S: Semigroup<A>) => Semigroup<ReaderEither<R, E, A>>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

getReaderValidation​

Use getApplicativeReaderValidation and getAltReaderValidation instead.

Signature​

export declare function getReaderValidation<E>(
  SE: Semigroup<E>,
): Monad3C<URI, E> & Bifunctor3<URI> & Alt3C<URI, E> & MonadThrow3C<URI, E>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

getSemigroup​

Use getApplySemigroup instead.

Signature​

export declare const getSemigroup: <R, E, A>(S: Semigroup<A>) => Semigroup<ReaderEither<R, E, 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,
) => <R, E>(
  fa: ReaderEither<R, E, A>,
) => ReaderEither<R, E, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

local​

Changes the value of the local context during the execution of the action ma (similar to Contravariant's contramap).

Signature​

export declare const local: <R2, R1>(f: (r2: R2) => R1) => <E, A>(ma: ReaderEither<R1, E, A>) => ReaderEither<R2, E, A>

Details​

  • Added in 0.1.0

License​

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

readerEither​

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

Signature​

export declare const readerEither: Monad3<URI> & Bifunctor3<URI> & Alt3<URI> & MonadThrow3<URI>

Details​

  • Added in 0.1.0
  • Deprecated

License​

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

swap​

Signature​

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

Details​

  • Added in 0.1.0

License​

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

throwError​

Signature​

export declare const throwError: MonadThrow3<URI>['throwError']

Details​

  • Added in 0.1.0

License​

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