@typed/fp
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Data Structures and Resources for fp-ts
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---
title: Env.ts
nav_order: 13
parent: Modules
---
## Env overview
`Env` is the core of the higher-level modules like [Ref](./Ref.ts.md) and is a `ReaderT` of
[Resume](./Resume.ts.md); but to be honest, being used so much, I didn't like writing
`ReaderResume<E, A>` and chose to shorten to `Env<E, A>` for the "environmental" quality Reader
provides. Combining Reader and Resume allows for creating APIs capable of utilizing dependency
injection for their configuration and testability while still combining your sync/async workflows.
While designing application APIs it is often better to describe the logic of your system separate
from the implementation details. `Env` or rather `Reader` helps you accomplish this through the
[Dependency Inversion Principle](https://alexnault.dev/dependency-inversion-principle-in-functional-typescript).
This principle is one of the easiest ways to begin improving any codebase.
Added in v0.9.2
---
<h2 class="text-delta">Table of contents</h2>
- [Combinator](#combinator)
- [FromResume](#fromresume)
- [alt](#alt)
- [altAll](#altall)
- [altW](#altw)
- [ap](#ap)
- [apFirst](#apfirst)
- [apFirstW](#apfirstw)
- [apS](#aps)
- [apSW](#apsw)
- [apSecond](#apsecond)
- [apSecondW](#apsecondw)
- [apT](#apt)
- [apTW](#aptw)
- [apW](#apw)
- [askAndProvide](#askandprovide)
- [askAndUse](#askanduse)
- [bind](#bind)
- [bindTo](#bindto)
- [bindW](#bindw)
- [chain](#chain)
- [chainFirst](#chainfirst)
- [chainFirstIOK](#chainfirstiok)
- [chainFirstResumeK](#chainfirstresumek)
- [chainFirstTaskK](#chainfirsttaskk)
- [chainFirstW](#chainfirstw)
- [chainIOK](#chainiok)
- [chainReaderK](#chainreaderk)
- [chainRec](#chainrec)
- [chainResumeK](#chainresumek)
- [chainTaskK](#chaintaskk)
- [chainW](#chainw)
- [combineAll](#combineall)
- [combineStruct](#combinestruct)
- [constant](#constant)
- [flap](#flap)
- [flatten](#flatten)
- [flattenW](#flattenw)
- [map](#map)
- [provideAll](#provideall)
- [provideAllWith](#provideallwith)
- [provideSome](#providesome)
- [provideSomeWith](#providesomewith)
- [race](#race)
- [raceW](#racew)
- [tap](#tap)
- [toResume](#toresume)
- [toResumeK](#toresumek)
- [tupled](#tupled)
- [useAll](#useall)
- [useAllWith](#useallwith)
- [useSome](#usesome)
- [useSomeWith](#usesomewith)
- [zip](#zip)
- [zipW](#zipw)
- [Constructor](#constructor)
- [Do](#do)
- [ask](#ask)
- [asks](#asks)
- [asksE](#askse)
- [asksIOK](#asksiok)
- [asksTaskK](#askstaskk)
- [fromIO](#fromio)
- [fromIOK](#fromiok)
- [fromReader](#fromreader)
- [fromReaderK](#fromreaderk)
- [fromResume](#fromresume)
- [fromResumeK](#fromresumek)
- [fromTask](#fromtask)
- [fromTaskK](#fromtaskk)
- [of](#of)
- [op](#op)
- [Execution](#execution)
- [execWith](#execwith)
- [runWith](#runwith)
- [Instance](#instance)
- [Alt](#alt)
- [Applicative](#applicative)
- [Apply](#apply)
- [Chain](#chain)
- [ChainRec](#chainrec)
- [FromIO](#fromio)
- [FromReader](#fromreader)
- [FromTask](#fromtask)
- [Functor](#functor)
- [Monad](#monad)
- [MonadRec](#monadrec)
- [Pointed](#pointed)
- [Provide](#provide)
- [ProvideAll](#provideall)
- [ProvideSome](#providesome)
- [UseAll](#useall)
- [UseSome](#usesome)
- [Model](#model)
- [Env (interface)](#env-interface)
- [Of (type alias)](#of-type-alias)
- [Type-level](#type-level)
- [RequirementsOf (type alias)](#requirementsof-type-alias)
- [ValueOf (type alias)](#valueof-type-alias)
- [Typeclass Constructor](#typeclass-constructor)
- [getMonoid](#getmonoid)
- [getSemigroup](#getsemigroup)
- [URI](#uri)
- [URI](#uri-1)
- [URI (type alias)](#uri-type-alias)
---
# Combinator
## FromResume
**Signature**
```ts
export declare const FromResume: FRe.FromResume2<'/fp/Env'>
```
Added in v0.9.2
## alt
**Signature**
```ts
export declare const alt: <E, A>(second: FN.Lazy<Env<E, A>>) => (first: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## altAll
**Signature**
```ts
export declare const altAll: <E, A>(startWith: Env<E, A>) => (as: readonly Env<E, A>[]) => Env<E, A>
```
Added in v0.9.2
## altW
**Signature**
```ts
export declare const altW: <E1, A>(
snd: FN.Lazy<Env<E1, A>>,
) => <E2>(fst: Env<E2, A>) => Env<E1 & E2, A>
```
Added in v0.9.2
## ap
**Signature**
```ts
export declare const ap: <R, A>(fa: Env<R, A>) => <B>(fab: Env<R, Arity1<A, B>>) => Env<R, B>
```
Added in v0.9.2
## apFirst
**Signature**
```ts
export declare const apFirst: <E, B>(second: Env<E, B>) => <A>(first: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## apFirstW
**Signature**
```ts
export declare const apFirstW: <E1, B>(
second: Env<E1, B>,
) => <E2, A>(first: Env<E2, A>) => Env<E1 & E2, A>
```
Added in v0.9.2
## apS
**Signature**
```ts
export declare const apS: <N, A, E, B>(
name: Exclude<N, keyof A>,
fb: Env<E, B>,
) => (fa: Env<E, A>) => Env<E, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>
```
Added in v0.9.2
## apSW
**Signature**
```ts
export declare const apSW: <N extends string, A, E1, B>(
name: Exclude<N, keyof A>,
fb: Env<E1, B>,
) => <E2>(
fa: Env<E2, A>,
) => Env<E1 & E2, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>
```
Added in v0.9.2
## apSecond
**Signature**
```ts
export declare const apSecond: <E, B>(second: Env<E, B>) => <A>(first: Env<E, A>) => Env<E, B>
```
Added in v0.9.2
## apSecondW
**Signature**
```ts
export declare const apSecondW: <E1, B>(
second: Env<E1, B>,
) => <E2, A>(first: Env<E2, A>) => Env<E1 & E2, B>
```
Added in v0.9.2
## apT
**Signature**
```ts
export declare const apT: <E, B>(fb: Env<E, B>) => <A>(fas: Env<E, A>) => Env<E, readonly [...A, B]>
```
Added in v0.9.2
## apTW
**Signature**
```ts
export declare const apTW: <E1, B>(
fb: Env<E1, B>,
) => <E2, A extends readonly unknown[]>(fas: Env<E2, A>) => Env<E1 & E2, readonly [...A, B]>
```
Added in v0.9.2
## apW
**Signature**
```ts
export declare const apW: <R1, A>(
fa: Env<R1, A>,
) => <R2, B>(fab: Env<R2, Arity1<A, B>>) => Env<R1 & R2, B>
```
Added in v0.9.2
## askAndProvide
**Signature**
```ts
export declare const askAndProvide: <E, B>(hkt: Env<E, B>) => Env<E, Env<unknown, B>>
```
Added in v0.9.2
## askAndUse
**Signature**
```ts
export declare const askAndUse: <E, B>(hkt: Env<E, B>) => Env<E, Env<unknown, B>>
```
Added in v0.9.2
## bind
**Signature**
```ts
export declare const bind: <N, A, E, B>(
name: Exclude<N, keyof A>,
f: (a: A) => Env<E, B>,
) => (ma: Env<E, A>) => Env<E, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>
```
Added in v0.9.2
## bindTo
**Signature**
```ts
export declare const bindTo: <N>(
name: N,
) => <E, A>(fa: Env<E, A>) => Env<E, { readonly [K in N]: A }>
```
Added in v0.9.2
## bindW
**Signature**
```ts
export declare const bindW: <N extends string, A, E1, B>(
name: Exclude<N, keyof A>,
f: (a: A) => Env<E1, B>,
) => <E2>(
ma: Env<E2, A>,
) => Env<E1 & E2, { readonly [K in N | keyof A]: K extends keyof A ? A[K] : B }>
```
Added in v0.9.2
## chain
**Signature**
```ts
export declare const chain: <A, R, B>(
f: (a: A) => Re.Reader<R, R.Resume<B>>,
) => (ma: Re.Reader<R, R.Resume<A>>) => Re.Reader<R, R.Resume<B>>
```
Added in v0.9.2
## chainFirst
**Signature**
```ts
export declare const chainFirst: <A, E, B>(
f: (a: A) => Env<E, B>,
) => (first: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## chainFirstIOK
**Signature**
```ts
export declare const chainFirstIOK: <A, B>(
f: (a: A) => IO.IO<B>,
) => <E>(first: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## chainFirstResumeK
**Signature**
```ts
export declare const chainFirstResumeK: <A, B>(
f: (value: A) => R.Resume<B>,
) => <E>(hkt: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## chainFirstTaskK
**Signature**
```ts
export declare const chainFirstTaskK: <A, B>(
f: (a: A) => Task.Task<B>,
) => <E>(first: Env<E, A>) => Env<E, A>
```
Added in v0.9.2
## chainFirstW
**Signature**
```ts
export declare const chainFirstW: <A, E1, B>(
f: (a: A) => Env<E1, B>,
) => <E2>(first: Env<E2, A>) => Env<E1 & E2, A>
```
Added in v0.9.2
## chainIOK
**Signature**
```ts
export declare const chainIOK: <A, B>(f: (a: A) => IO.IO<B>) => <E>(first: Env<E, A>) => Env<E, B>
```
Added in v0.9.2
## chainReaderK
**Signature**
```ts
export declare const chainReaderK: <A, R, B>(
f: (a: A) => Re.Reader<R, B>,
) => (ma: Env<R, A>) => Env<R, B>
```
Added in v0.9.2
## chainRec
**Signature**
```ts
export declare function chainRec<F extends (value: any) => Env<any, E.Either<any, any>>>(
f: F,
): (
value: ArgsOf<F>[0],
) => Env<
RequirementsOf<ReturnType<F>>,
[ValueOf<ReturnType<F>>] extends [E.Either<any, infer R>] ? R : never
>
```
Added in v0.9.2
## chainResumeK
**Signature**
```ts
export declare const chainResumeK: <A, B>(
f: (value: A) => R.Resume<B>,
) => <E>(hkt: Env<E, A>) => Env<E, B>
```
Added in v0.9.2
## chainTaskK
**Signature**
```ts
export declare const chainTaskK: <A, B>(
f: (a: A) => Task.Task<B>,
) => <E>(first: Env<E, A>) => Env<E, B>
```
Added in v0.9.2
## chainW
**Signature**
```ts
export declare const chainW: <A, R1, B>(
f: (a: A) => Env<R1, B>,
) => <R2>(ma: Env<R2, A>) => Env<R1 & R2, B>
```
Added in v0.9.2
## combineAll
**Signature**
```ts
export declare const combineAll: <A extends readonly Env<any, any>[]>(
...envs: A
) => Env<
Intersect<{ [K in keyof A]: RequirementsOf<A[K]> }, unknown>,
{ [K in keyof A]: ValueOf<A[K]> }
>
```
Added in v0.9.2
## combineStruct
**Signature**
```ts
export declare const combineStruct: <Props extends Readonly<Record<string, Env<any, any>>>>(
props: Props,
) => Env<unknown, { readonly [K in keyof Props]: ValueOf<Props[K]> }>
```
Added in v0.11.0
## constant
**Signature**
```ts
export declare const constant: <A>(a: A) => <R>(fa: Env<R, unknown>) => Env<R, A>
```
Added in v0.9.2
## flap
**Signature**
```ts
export declare const flap: <A>(a: A) => <E, B>(fab: Env<E, (a: A) => B>) => Env<E, B>
```
Added in v0.9.2
## flatten
**Signature**
```ts
export declare const flatten: <E, A>(env: Env<E, Env<E, A>>) => Env<E, A>
```
Added in v0.9.2
## flattenW
**Signature**
```ts
export declare const flattenW: <E1, E2, A>(env: Env<E1, Env<E2, A>>) => Env<E1 & E2, A>
```
Added in v0.9.2
## map
**Signature**
```ts
export declare const map: <A, B>(f: (a: A) => B) => <R>(fa: Env<R, A>) => Env<R, B>
```
Added in v0.9.2
## provideAll
**Signature**
```ts
export declare const provideAll: <E1>(provided: E1) => <A>(env: Env<E1, A>) => Env<unknown, A>
```
Added in v0.9.2
## provideAllWith
**Signature**
```ts
export declare const provideAllWith: <R, A>(provider: Env<R, A>) => <B>(hkt: Env<A, B>) => Env<R, B>
```
Added in v0.9.2
## provideSome
**Signature**
```ts
export declare const provideSome: <E1>(provided: E1) => <E2, A>(env: Env<E1 & E2, A>) => Env<E2, A>
```
Added in v0.9.2
## provideSomeWith
**Signature**
```ts
export declare const provideSomeWith: <E1, A>(
provider: Env<E1, A>,
) => P.Provider2<'/fp/Env', A, E1>
```
Added in v0.9.2
## race
**Signature**
```ts
export declare const race: <E, A>(a: Env<E, A>) => <B>(b: Env<E, B>) => Env<E, A | B>
```
Added in v0.9.2
## raceW
**Signature**
```ts
export declare const raceW: <E1, A>(a: Env<E1, A>) => <E2, B>(b: Env<E2, B>) => Env<E1 & E2, A | B>
```
Added in v0.9.2
## tap
**Signature**
```ts
export declare const tap: <A>(f: (a: A) => any) => <R>(fa: Env<R, A>) => Env<R, A>
```
Added in v0.9.2
## toResume
**Signature**
```ts
export declare const toResume: <E, B>(hkt: Env<E, B>) => Env<E, R.Resume<B>>
```
Added in v0.9.2
## toResumeK
**Signature**
```ts
export declare const toResumeK: <Args extends readonly any[], E, A>(
envK: (...args: Args) => Env<E, A>,
) => Env<E, (...args: Args) => R.Resume<A>>
```
Added in v0.9.2
## tupled
**Signature**
```ts
export declare const tupled: <E, A>(fa: Env<E, A>) => Env<E, readonly [A]>
```
Added in v0.9.2
## useAll
**Signature**
```ts
export declare const useAll: <E1>(provided: E1) => <A>(env: Env<E1, A>) => Env<unknown, A>
```
Added in v0.9.2
## useAllWith
**Signature**
```ts
export declare const useAllWith: <R, A>(provider: Env<R, A>) => <B>(hkt: Env<A, B>) => Env<R, B>
```
Added in v0.9.2
## useSome
**Signature**
```ts
export declare const useSome: <E1>(provided: E1) => <E2, A>(env: Env<E1 & E2, A>) => Env<E2, A>
```
Added in v0.9.2
## useSomeWith
**Signature**
```ts
export declare const useSomeWith: <E1, A>(
provider: Env<E1, A>,
) => P.Provider2<'/fp/Env', A, E1>
```
Added in v0.9.2
## zip
**Signature**
```ts
export declare const zip: <E, A>(ta: readonly Env<E, A>[]) => Env<E, readonly A[]>
```
Added in v0.9.2
## zipW
**Signature**
```ts
export declare const zipW: <A extends readonly Env<any, any>[]>(
envs: A,
) => Env<
Intersect<{ [K in keyof A]: RequirementsOf<A[K]> }, unknown>,
{ [K in keyof A]: ValueOf<A[K]> }
>
```
Added in v0.9.2
# Constructor
## Do
**Signature**
```ts
export declare const Do: Env<unknown, {}>
```
Added in v0.9.2
## ask
**Signature**
```ts
export declare const ask: <R>() => Env<R, R>
```
Added in v0.9.2
## asks
**Signature**
```ts
export declare const asks: <R, A>(f: (r: R) => A) => Env<R, A>
```
Added in v0.9.2
## asksE
**Signature**
```ts
export declare const asksE: <R, E, A>(f: (r: R) => Env<E, A>) => Env<E & R, A>
```
Added in v0.9.2
## asksIOK
**Signature**
```ts
export declare const asksIOK: <R, A>(f: (r: R) => IO.IO<A>) => Env<R, A>
```
Added in v0.9.2
## asksTaskK
**Signature**
```ts
export declare const asksTaskK: <R, A>(f: (r: R) => Task.Task<A>) => Env<R, A>
```
Added in v0.9.2
## fromIO
**Signature**
```ts
export declare const fromIO: <A>(fa: IO.IO<A>) => Env<unknown, A>
```
Added in v0.9.2
## fromIOK
**Signature**
```ts
export declare const fromIOK: <A, B>(f: (...a: A) => IO.IO<B>) => <E>(...a: A) => Env<E, B>
```
Added in v0.9.2
## fromReader
**Signature**
```ts
export declare const fromReader: <R, A>(ma: Re.Reader<R, A>) => Env<R, A>
```
Added in v0.9.2
## fromReaderK
**Signature**
```ts
export declare const fromReaderK: <A, R, B>(
f: (...a: A) => Re.Reader<R, B>,
) => (...a: A) => Env<R, B>
```
Added in v0.9.2
## fromResume
**Signature**
```ts
export declare const fromResume: <A, E = unknown>(resume: R.Resume<A>) => Env<E, A>
```
Added in v0.9.2
## fromResumeK
**Signature**
```ts
export declare const fromResumeK: <A, B>(
f: (...args: A) => R.Resume<B>,
) => <E>(...args: A) => Env<E, B>
```
Added in v0.9.2
## fromTask
**Signature**
```ts
export declare const fromTask: <A, E = unknown>(fa: Task.Task<A>) => Env<E, A>
```
Added in v0.9.2
## fromTaskK
**Signature**
```ts
export declare const fromTaskK: <A, B>(f: (...a: A) => Task.Task<B>) => <E>(...a: A) => Env<E, B>
```
Added in v0.9.2
## of
**Signature**
```ts
export declare const of: <A>(a: A) => Of<A>
```
Added in v0.9.2
## op
Construct an Env to a lazily-defined Env-based effect that must be provided later. Does not support
functions which require type-parameters as they will resolve to unknown, due to limitations in TS,
if you need this maybe use [asksE](#askse)
**Signature**
```ts
export declare const op: <F extends (...args: readonly any[]) => Env<any, any>>() => <
K extends string | number | symbol,
>(
key: K,
) => {
(...args: ArgsOf<F>): Env<{ readonly [_ in K]: F }, ValueOf<ReturnType<F>>>
readonly key: K
}
```
Added in v0.9.2
# Execution
## execWith
**Signature**
```ts
export declare const execWith: <E>(requirements: E) => (env: Env<E, any>) => Disposable
```
Added in v0.9.2
## runWith
**Signature**
```ts
export declare const runWith: <A>(
f: (value: A) => Disposable,
) => <E>(requirements: E) => (env: Env<E, A>) => Disposable
```
Added in v0.9.2
# Instance
## Alt
**Signature**
```ts
export declare const Alt: Alt_.Alt2<'/fp/Env'>
```
Added in v0.9.2
## Applicative
**Signature**
```ts
export declare const Applicative: FpApplicative.Applicative2<'/fp/Env'>
```
Added in v0.9.2
## Apply
**Signature**
```ts
export declare const Apply: Ap.Apply2<'/fp/Env'>
```
Added in v0.9.2
## Chain
**Signature**
```ts
export declare const Chain: FpChain.Chain2<'/fp/Env'>
```
Added in v0.9.2
## ChainRec
**Signature**
```ts
export declare const ChainRec: ChainRec2<'/fp/Env'>
```
Added in v0.9.2
## FromIO
**Signature**
```ts
export declare const FromIO: FIO.FromIO2<'/fp/Env'>
```
Added in v0.9.2
## FromReader
**Signature**
```ts
export declare const FromReader: FR.FromReader2<'/fp/Env'>
```
Added in v0.9.2
## FromTask
**Signature**
```ts
export declare const FromTask: FT.FromTask2<'/fp/Env'>
```
Added in v0.9.2
## Functor
**Signature**
```ts
export declare const Functor: Functor2<'/fp/Env'>
```
Added in v0.9.2
## Monad
**Signature**
```ts
export declare const Monad: Monad2<'/fp/Env'>
```
Added in v0.9.2
## MonadRec
**Signature**
```ts
export declare const MonadRec: MonadRec2<'/fp/Env'>
```
Added in v0.9.2
## Pointed
**Signature**
```ts
export declare const Pointed: Pointed2<'/fp/Env'>
```
Added in v0.9.2
## Provide
**Signature**
```ts
export declare const Provide: P.Provide2<'/fp/Env'>
```
Added in v0.9.2
## ProvideAll
**Signature**
```ts
export declare const ProvideAll: P.ProvideAll2<'/fp/Env'>
```
Added in v0.9.2
## ProvideSome
**Signature**
```ts
export declare const ProvideSome: P.ProvideSome2<'/fp/Env'>
```
Added in v0.9.2
## UseAll
**Signature**
```ts
export declare const UseAll: P.UseAll2<'/fp/Env'>
```
Added in v0.9.2
## UseSome
**Signature**
```ts
export declare const UseSome: P.UseSome2<'/fp/Env'>
```
Added in v0.9.2
# Model
## Env (interface)
Env is specialization of Reader<R, Resume<A>>
**Signature**
```ts
export interface Env<R, A> extends Re.Reader<R, R.Resume<A>> {}
```
Added in v0.9.2
## Of (type alias)
**Signature**
```ts
export type Of<A> = Env<unknown, A>
```
Added in v0.9.2
# Type-level
## RequirementsOf (type alias)
**Signature**
```ts
export type RequirementsOf<A> = [A] extends [Env<infer R, any>]
? R
: [A] extends [FN.FunctionN<any, Env<infer R, any>>]
? R
: never
```
Added in v0.9.2
## ValueOf (type alias)
**Signature**
```ts
export type ValueOf<A> = A extends Env<any, infer R>
? R
: A extends FN.FunctionN<any, Env<any, infer R>>
? R
: never
```
Added in v0.9.2
# Typeclass Constructor
## getMonoid
**Signature**
```ts
export declare const getMonoid: <A, E>(M: Monoid<A>) => Monoid<Env<E, A>>
```
Added in v0.9.2
## getSemigroup
**Signature**
```ts
export declare const getSemigroup: <A, E>(S: Semigroup<A>) => Semigroup<Env<E, A>>
```
Added in v0.9.2
# URI
## URI
**Signature**
```ts
export declare const URI: '/fp/Env'
```
Added in v0.9.2
## URI (type alias)
**Signature**
```ts
export type URI = typeof URI
```
Added in v0.9.2