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fp-ts

ReaderEither overview

Added in v2.0.0

Table of contents

Alt

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>

Added in v2.0.0

altW

Less strict version of alt.

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, B | A>

Added in v2.9.0

Apply

ap

Apply a function to an argument under a type constructor.

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>

Added in v2.0.0

apW

Less strict version of ap.

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, E2 | E1, B>

Added in v2.8.0

Bifunctor

bimap

Map a pair of functions over the two last type arguments of the bifunctor.

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>

Added in v2.0.0

mapLeft

Map a function over the second type argument of a bifunctor.

Signature

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

Added in v2.0.0

Functor

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>

Added in v2.0.0

Monad

chain

Composes computations in sequence, using the return value of one computation to determine the next computation.

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>

Added in v2.0.0

chainW

Less strict version of chain.

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, E2 | E1, B>

Added in v2.6.0

MonadThrow

throwError

Signature

export declare const throwError: <R, E, A>(e: E) => ReaderEither<R, E, A>

Added in v2.7.0

Pointed

of

Signature

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

Added in v2.8.5

combinators

apFirst

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

Derivable from Apply.

Signature

export declare const apFirst: <R, E, B>(
  second: ReaderEither<R, E, B>
) => <A>(first: ReaderEither<R, E, A>) => ReaderEither<R, E, A>

Added in v2.0.0

apSecond

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

Derivable from Apply.

Signature

export declare const apSecond: <R, E, B>(
  second: ReaderEither<R, E, B>
) => <A>(first: ReaderEither<R, E, A>) => ReaderEither<R, E, B>

Added in v2.0.0

asksReaderEither

Effectfully accesses the environment.

Signature

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

Added in v2.11.0

asksReaderEitherW

Less strict version of asksReaderEither.

Signature

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

Added in v2.11.0

chainEitherK

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>

Added in v2.4.0

chainEitherKW

Less strict version of chainEitherK.

Signature

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

Added in v2.6.1

chainFirst

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

Derivable from Chain.

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>

Added in v2.0.0

chainFirstReaderK

Signature

export declare const chainFirstReaderK: <A, R, B>(
  f: (a: A) => R.Reader<R, B>
) => <E = never>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, A>

Added in v2.11.0

chainFirstReaderKW

Less strict version of chainReaderK.

Signature

export declare const chainFirstReaderKW: <A, R1, B>(
  f: (a: A) => R.Reader<R1, B>
) => <R2, E = never>(ma: ReaderEither<R2, E, A>) => ReaderEither<R1 & R2, E, A>

Added in v2.11.0

chainFirstW

Less strict version of chainFirst

Derivable from Chain.

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, E2 | E1, A>

Added in v2.8.0

chainOptionK

Signature

export declare const chainOptionK: <E>(
  onNone: Lazy<E>
) => <A, B>(f: (a: A) => Option<B>) => <R>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, B>

Added in v2.10.0

chainReaderK

Signature

export declare const chainReaderK: <A, R, B>(
  f: (a: A) => R.Reader<R, B>
) => <E = never>(ma: ReaderEither<R, E, A>) => ReaderEither<R, E, B>

Added in v2.11.0

chainReaderKW

Less strict version of chainReaderK.

Signature

export declare const chainReaderKW: <A, R2, B>(
  f: (a: A) => R.Reader<R2, B>
) => <R1, E = never>(ma: ReaderEither<R1, E, A>) => ReaderEither<R1 & R2, E, B>

Added in v2.11.0

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>
}

Added in v2.0.0

filterOrElseW

Less strict version of filterOrElse.

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, E2 | E1, B>
  <A, E2>(predicate: Predicate<A>, onFalse: (a: A) => E2): <R, E1, B extends A>(
    mb: ReaderEither<R, E1, B>
  ) => ReaderEither<R, E2 | E1, B>
  <A, E2>(predicate: Predicate<A>, onFalse: (a: A) => E2): <R, E1>(
    ma: ReaderEither<R, E1, A>
  ) => ReaderEither<R, E2 | E1, A>
}

Added in v2.9.0

flap

Derivable from Functor.

Signature

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

Added in v2.10.0

flatten

Derivable from Chain.

Signature

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

Added in v2.0.0

flattenW

Less strict version of flatten.

Signature

export declare const flattenW: <R1, R2, E1, E2, A>(
  mma: ReaderEither<R1, E1, ReaderEither<R2, E2, A>>
) => ReaderEither<R1 & R2, E1 | E2, A>

Added in v2.11.0

fromEitherK

Signature

export declare const fromEitherK: <E, A extends readonly unknown[], B>(
  f: (...a: A) => E.Either<E, B>
) => <R>(...a: A) => ReaderEither<R, E, B>

Added in v2.4.0

fromOptionK

Signature

export declare const fromOptionK: <E>(
  onNone: Lazy<E>
) => <A, B>(f: (...a: A) => Option<B>) => <R>(...a: A) => ReaderEither<R, E, B>

Added in v2.10.0

fromReaderK

Signature

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

Added in v2.11.0

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>

Added in v2.0.0

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>

Added in v2.0.0

orElseFirst

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>

Added in v2.11.0

orElseFirstW

Signature

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

Added in v2.11.0

orElseW

Less strict version of orElse.

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, B | A>

Added in v2.10.0

orLeft

Signature

export declare const orLeft: <E1, R, E2>(
  onLeft: (e: E1) => R.Reader<R, E2>
) => <A>(fa: ReaderEither<R, E1, A>) => ReaderEither<R, E2, A>

Added in v2.11.0

swap

Signature

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

Added in v2.0.0

constructors

ask

Reads the current context.

Signature

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

Added in v2.0.0

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>

Added in v2.0.0

fromPredicate

Signature

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

Added in v2.0.0

left

Signature

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

Added in v2.0.0

leftReader

Signature

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

Added in v2.0.0

Signature

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

Added in v2.0.0

rightReader

Signature

export declare const rightReader: <R, E = never, A = never>(ma: R.Reader<R, A>) => ReaderEither<R, E, A>

Added in v2.0.0

destructors

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>

Added in v2.0.0

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>

Added in v2.10.0

getOrElse

Signature

export declare const getOrElse: <E, R, A>(
  onLeft: (e: E) => R.Reader<R, A>
) => (ma: ReaderEither<R, E, A>) => R.Reader<R, A>

Added in v2.0.0

getOrElseW

Less strict version of getOrElse.

Signature

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

Added in v2.6.0

match

Signature

export declare const match: <E, B, A>(
  onLeft: (e: E) => B,
  onRight: (a: A) => B
) => <R>(ma: ReaderEither<R, E, A>) => R.Reader<R, B>

Added in v2.10.0

matchE

Signature

export declare const matchE: <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>

Added in v2.10.0

matchEW

Less strict version of matchE.

Signature

export declare const matchEW: <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>

Added in v2.10.0

matchW

Less strict version of match.

Signature

export declare const matchW: <E, B, A, C>(
  onLeft: (e: E) => B,
  onRight: (a: A) => C
) => <R>(ma: R.Reader<R, E.Either<E, A>>) => R.Reader<R, B | C>

Added in v2.10.0

instances

Alt

Signature

export declare const Alt: Alt3<'ReaderEither'>

Added in v2.7.0

Applicative

Signature

export declare const Applicative: Applicative3<'ReaderEither'>

Added in v2.7.0

Apply

Signature

export declare const Apply: Apply3<'ReaderEither'>

Added in v2.10.0

Bifunctor

Signature

export declare const Bifunctor: Bifunctor3<'ReaderEither'>

Added in v2.7.0

Chain

Signature

export declare const Chain: Chain3<'ReaderEither'>

Added in v2.10.0

FromEither

Signature

export declare const FromEither: FromEither3<'ReaderEither'>

Added in v2.10.0

FromReader

Signature

export declare const FromReader: FromReader3<'ReaderEither'>

Added in v2.11.0

Functor

Signature

export declare const Functor: Functor3<'ReaderEither'>

Added in v2.7.0

Monad

Signature

export declare const Monad: Monad3<'ReaderEither'>

Added in v2.7.0

MonadThrow

Signature

export declare const MonadThrow: MonadThrow3<'ReaderEither'>

Added in v2.7.0

Pointed

Signature

export declare const Pointed: Pointed3<'ReaderEither'>

Added in v2.10.0

URI

Signature

export declare const URI: 'ReaderEither'

Added in v2.0.0

URI (type alias)

Signature

export type URI = typeof URI

Added in v2.0.0

getAltReaderValidation

Signature

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

Added in v2.7.0

getApplicativeReaderValidation

Signature

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

Added in v2.7.0

getCompactable

Signature

export declare const getCompactable: <E>(M: Monoid<E>) => Compactable3C<'ReaderEither', E>

Added in v2.10.0

getFilterable

Signature

export declare function getFilterable<E>(M: Monoid<E>): Filterable3C<URI, E>

Added in v2.10.0

getApplyMonoid

Use getApplicativeMonoid instead.

Signature

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

Added in v2.0.0

getApplySemigroup

Use getApplySemigroup instead.

Signature

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

Added in v2.0.0

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>

Added in v2.3.0

getSemigroup

Use getApplySemigroup instead.

Signature

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

Added in v2.0.0

readerEither

Use small, specific instances instead.

Signature

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

Added in v2.0.0

interop

toUnion

Signature

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

Added in v2.10.0

model

ReaderEither (interface)

Signature

export interface ReaderEither<R, E, A> extends Reader<R, Either<E, A>> {}

Added in v2.0.0

natural transformations

fromEither

Signature

export declare const fromEither: NaturalTransformation23<'Either', 'ReaderEither'>

Added in v2.0.0

fromOption

Signature

export declare const fromOption: <E>(onNone: Lazy<E>) => NaturalTransformation13C<'Option', 'ReaderEither', E>

Added in v2.0.0

fromReader

Signature

export declare const fromReader: NaturalTransformation23R<'Reader', 'ReaderEither'>

Added in v2.11.0

utils

ApT

Signature

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

Added in v2.11.0

Do

Signature

export declare const Do: ReaderEither<unknown, never, {}>

Added in v2.9.0

apS

Signature

export declare const apS: <N, 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 }>

Added in v2.8.0

apSW

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, E2 | E1, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

Added in v2.8.0

bind

Signature

export declare const bind: <N, 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 }>

Added in v2.8.0

bindTo

Signature

export declare const bindTo: <N>(
  name: N
) => <R, E, A>(fa: ReaderEither<R, E, A>) => ReaderEither<R, E, { readonly [K in N]: A }>

Added in v2.8.0

bindW

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, E2 | E1, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>

Added in v2.8.0

sequenceArray

Signature

export declare const sequenceArray: <R, E, A>(arr: readonly ReaderEither<R, E, A>[]) => ReaderEither<R, E, readonly A[]>

Added in v2.9.0

traverseArray

Signature

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

Added in v2.9.0

traverseArrayWithIndex

Signature

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

Added in v2.9.0

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[]>

Added in v2.11.0

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>>

Added in v2.11.0