<A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<void, E2 | E, R2 | R>
<A, E, R, X, E2, R2>(
self: Stream<A, E, R>,
f: (a: A) => Effect.Effect<X, E2, R2>
): Effect.Effect<void, E | E2, R | R2>Runs the provided effectful callback for each element of the stream.
Example (Running an effect for each value)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const program = Effect.gen(function*() {
yield* Stream.runForEach(stream, (n) => Console.log(`Processing: ${n}`))
})
Effect.runPromise(program)
// Processing: 1
// Processing: 2
// Processing: 3export const const runForEach: {
<A, X, E2, R2>(
f: (a: A) => Effect.Effect<X, E2, R2>
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<void, E2 | E, R2 | R>
<A, E, R, X, E2, R2>(
self: Stream<A, E, R>,
f: (a: A) => Effect.Effect<X, E2, R2>
): Effect.Effect<void, E | E2, R | R2>
}
Runs the provided effectful callback for each element of the stream.
Example (Running an effect for each value)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const program = Effect.gen(function*() {
yield* Stream.runForEach(stream, (n) => Console.log(`Processing: ${n}`))
})
Effect.runPromise(program)
// Processing: 1
// Processing: 2
// Processing: 3
runForEach: {
<function (type parameter) A in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>A, function (type parameter) X in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>X, function (type parameter) E2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>E2, function (type parameter) R2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>R2>(
f: (a: A) => Effect.Effect<X, E2, R2>f: (a: Aa: function (type parameter) A in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>A) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>X, function (type parameter) E2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>E2, function (type parameter) R2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>R2>
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>R>(self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>R>) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<void, function (type parameter) E2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>E2 | function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>E, function (type parameter) R2 in <A, X, E2, R2>(f: (a: A) => Effect.Effect<X, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<void, E2 | E, R2 | R>R2 | function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<void, E2 | E, R2 | R>R>
<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R, function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R>,
f: (a: A) => Effect.Effect<X, E2, R2>f: (a: Aa: function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2>
): import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<void, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2>
} = dual<(...args: Array<any>) => any, <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>) => Effect.Effect<void, E | E2, R | R2>>(arity: 2, body: <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>) => Effect.Effect<void, E | E2, R | R2>): ((...args: Array<any>) => any) & (<A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>) => Effect.Effect<void, E | E2, R | R2>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(2, <function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R, function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R>,
f: (a: A) => Effect.Effect<X, E2, R2>f: (a: Aa: function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>A) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>X, function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2>
): import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<void, function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: A) => Effect.Effect<X, E2, R2>): Effect.Effect<void, E | E2, R | R2>R2> =>
import ChannelChannel.const runForEach: {
<OutElem, EX, RX>(
f: (o: OutElem) => Effect.Effect<void, EX, RX>
): <OutErr, OutDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
) => Effect.Effect<
OutDone,
OutErr | EX,
Env | RX
>
<OutElem, OutErr, OutDone, Env, EX, RX>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>,
f: (o: OutElem) => Effect.Effect<void, EX, RX>
): Effect.Effect<OutDone, OutErr | EX, Env | RX>
}
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Stream<A, E, R>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<A, E, R>.channel: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
arr: readonly [A, ...A[]](parameter) arr: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let i: numberi = 0
return import EffectEffect.const whileLoop: <A, E, R>(options: {
readonly while: LazyArg<boolean>
readonly body: LazyArg<Effect<A, E, R>>
readonly step: (a: A) => void
}) => Effect<void, E, R>
Executes a body effect repeatedly while a condition holds true.
Example (Repeating an effectful loop)
import { Effect } from "effect"
let counter = 0
const program = Effect.whileLoop({
while: () => counter < 5,
body: () => Effect.sync(() => ++counter),
step: (n) => console.log(`Current count: ${n}`)
})
Effect.runPromise(program)
// Output:
// Current count: 1
// Current count: 2
// Current count: 3
// Current count: 4
// Current count: 5
whileLoop({
while: LazyArg<boolean>while: () => let i: numberi < arr: readonly [A, ...A[]](parameter) arr: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
length: numberlength,
body: LazyArg<Effect.Effect<X, E2, R2>>body: () => f: (a: A) => Effect.Effect<X, E2, R2>f(arr: readonly [A, ...A[]](parameter) arr: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let i: numberi++]),
step: LazyArg<void>step: const constVoid: LazyArg<void>Returns no meaningful value when called.
When to use
Use when you need a thunk that is called only for its effect and has no
meaningful return value.
Example (Returning void from a thunk)
import { Function } from "effect"
import * as assert from "node:assert"
assert.deepStrictEqual(Function.constVoid(), undefined)
constVoid
})
}))