<A, Pass, Fail>(
filter: Filter.Filter<NoInfer<A>, Pass, Fail>,
options?: { readonly capacity?: number | "unbounded" | undefined }
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<
[
passes: Queue.Dequeue<Pass, E | Cause.Done>,
fails: Queue.Dequeue<Fail, E | Cause.Done>
],
never,
R | Scope.Scope
>
<A, E, R, Pass, Fail>(
self: Stream<A, E, R>,
filter: Filter.Filter<NoInfer<A>, Pass, Fail>,
options?: { readonly capacity?: number | "unbounded" | undefined }
): Effect.Effect<
[
passes: Queue.Dequeue<Pass, E | Cause.Done>,
fails: Queue.Dequeue<Fail, E | Cause.Done>
],
never,
R | Scope.Scope
>Partitions a stream using a Filter and exposes passing and failing values
as scoped queues.
Details
The queues are backed by a fiber in the current scope and should be consumed
while that scope remains open. Each queue fails with the stream error or
Cause.Done when the source ends.
Example (Partitioning a stream into queues)
import { Console, Effect, Result, Stream } from "effect"
const program = Effect.gen(function*() {
const [passes, fails] = yield* Stream.make(1, 2, 3, 4).pipe(
Stream.partitionQueue((n) => n % 2 === 0 ? Result.succeed(n) : Result.fail(n))
)
const passValues = yield* Stream.fromQueue(passes).pipe(Stream.runCollect)
const failValues = yield* Stream.fromQueue(fails).pipe(Stream.runCollect)
yield* Console.log(passValues)
// Output: [ 2, 4 ]
yield* Console.log(failValues)
// Output: [ 1, 3 ]
})
Effect.runPromise(Effect.scoped(program))export const const partitionQueue: {
<A, Pass, Fail>(
filter: Filter.Filter<NoInfer<A>, Pass, Fail>,
options?: {
readonly capacity?:
| number
| "unbounded"
| undefined
}
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<
[
passes: Queue.Dequeue<Pass, E | Cause.Done>,
fails: Queue.Dequeue<Fail, E | Cause.Done>
],
never,
R | Scope.Scope
>
<A, E, R, Pass, Fail>(
self: Stream<A, E, R>,
filter: Filter.Filter<NoInfer<A>, Pass, Fail>,
options?: {
readonly capacity?:
| number
| "unbounded"
| undefined
}
): Effect.Effect<
[
passes: Queue.Dequeue<Pass, E | Cause.Done>,
fails: Queue.Dequeue<Fail, E | Cause.Done>
],
never,
R | Scope.Scope
>
}
Partitions a stream using a Filter and exposes passing and failing values
as scoped queues.
Details
The queues are backed by a fiber in the current scope and should be consumed
while that scope remains open. Each queue fails with the stream error or
Cause.Done when the source ends.
Example (Partitioning a stream into queues)
import { Console, Effect, Result, Stream } from "effect"
const program = Effect.gen(function*() {
const [passes, fails] = yield* Stream.make(1, 2, 3, 4).pipe(
Stream.partitionQueue((n) => n % 2 === 0 ? Result.succeed(n) : Result.fail(n))
)
const passValues = yield* Stream.fromQueue(passes).pipe(Stream.runCollect)
const failValues = yield* Stream.fromQueue(fails).pipe(Stream.runCollect)
yield* Console.log(passValues)
// Output: [ 2, 4 ]
yield* Console.log(failValues)
// Output: [ 1, 3 ]
})
Effect.runPromise(Effect.scoped(program))
partitionQueue: {
<function (type parameter) A in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
filter: Filter.Filter<NoInfer<A>, Pass, Fail>filter: import FilterFilter.interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
options: | {
readonly capacity?:
| number
| "unbounded"
| undefined
}
| undefined
capacity?: number | "unbounded" | undefinedcapacity?: number | "unbounded" | undefined
}): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>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, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>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<
[
Queue.Dequeue<Pass, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
passes: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Pass in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>E | import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>,
Queue.Dequeue<Fail, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
fails: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Fail in <A, Pass, Fail>(filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>E | import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>
],
never,
function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>R | import ScopeScope.Scope
>
<function (type parameter) A in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
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, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
filter: Filter.Filter<NoInfer<A>, Pass, Fail>filter: import FilterFilter.interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
options: | {
readonly capacity?:
| number
| "unbounded"
| undefined
}
| undefined
capacity?: number | "unbounded" | undefinedcapacity?: number | "unbounded" | undefined
}
): 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<
[
Queue.Dequeue<Pass, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
passes: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>,
Queue.Dequeue<Fail, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
fails: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>
],
never,
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.Effect<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import ScopeScope.Scope
>
} = dual<(...args: Array<any>) => any, <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined) => Effect.Effect<[passes: Queue.Dequeue<Pass, Cause.Done<void> | E>, fails: Queue.Dequeue<Fail, Cause.Done<void> | E>], never, Scope.Scope | R>>(isDataFirst: (args: IArguments) => boolean, body: <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined) => Effect.Effect<[passes: Queue.Dequeue<Pass, Cause.Done<void> | E>, fails: Queue.Dequeue<Fail, Cause.Done<void> | E>], never, Scope.Scope | R>): ((...args: Array<any>) => any) & (<A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined) => Effect.Effect<[passes: Queue.Dequeue<Pass, Cause.Done<void> | E>, fails: Queue.Dequeue<Fail, Cause.Done<void> | E>], never, Scope.Scope | R>) (+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(
(args: IArgumentsargs) => const isStream: (
u: unknown
) => u is Stream<unknown, unknown, unknown>
Checks whether a value is a Stream.
Example (Checking whether a value is a Stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.make(1, 2, 3)
const notStream = { data: [1, 2, 3] }
yield* Console.log(Stream.isStream(stream))
// true
yield* Console.log(Stream.isStream(notStream))
// false
})
Effect.runPromise(program)
isStream(args: IArgumentsargs[0]),
import EffectEffect.const fnUntraced: <Effect.Effect<any, never, Scope.Scope | R>, [passes: Queue.Dequeue<Pass, Cause.Done<void> | E>, fails: Queue.Dequeue<Fail, Cause.Done<void> | E>], [self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined]>(body: (this: unassigned, self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined) => Generator<...>) => <A, E, R, Pass, Fail>(self: Stream<...>, filter: Filter.Filter<...>, options?: {
readonly capacity?: number | "unbounded" | undefined;
} | undefined) => Effect.Effect<...> (+41 overloads)
function (type parameter) A in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
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, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
filter: Filter.Filter<NoInfer<A>, Pass, Fail>filter: import FilterFilter.interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
options: | {
readonly capacity?:
| number
| "unbounded"
| undefined
}
| undefined
capacity?: number | "unbounded" | undefinedcapacity?: number | "unbounded" | undefined
}
): import EffectEffect.fn.type fn.Return<A, E = never, R = never> = Generator<Effect.Effect<any, E, R>, A, any>Generator return type accepted by
fn
and
fnUntraced
.
When to use
Use when you need to annotate the return type of a generator body while
keeping the produced function's Effect return type inferred.
Example (Annotating an Effect function)
import { Effect } from "effect"
const f = Effect.fnUntraced(function*(
value: string
): Effect.fn.Return<number> {
return yield* Effect.succeed(value.length)
})
// ┌─── Effect.Effect<number>
// ▼
const program = f("hello")
Example (Annotating a parametric Effect function)
import { Effect } from "effect"
const f = Effect.fnUntraced(function*<A>(
value: A
): Effect.fn.Return<A> {
return yield* Effect.succeed(value)
})
// ┌─── Effect.Effect<string>
// ▼
const program = f("hello")
Return<
[
Queue.Dequeue<Pass, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
passes: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>,
Queue.Dequeue<Fail, Cause.Done<void> | E>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
fails: import QueueQueue.interface Dequeue<out A, out E = never>A Dequeue is a queue that can be taken from.
Details
This interface represents the read-only part of a Queue, allowing you to take
elements from the queue but not offer elements to it.
Example (Taking through dequeue handles)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<string, never>(10)
// A Dequeue can only take elements
const dequeue: Queue.Dequeue<string> = queue
// Pre-populate the queue
yield* Queue.offerAll(queue, ["a", "b", "c"])
// Take elements using dequeue interface
const item = yield* Queue.take(dequeue)
console.log(item) // "a"
})
Companion namespace containing type-level metadata for the Dequeue
read-only queue interface.
Dequeue<function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>
],
never,
function (type parameter) R in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import ScopeScope.Scope
> {
const const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const scope: Effect<Scope, never, Scope>const scope: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
Returns the current scope for resource management.
Example (Accessing the current scope)
import { Console, Effect } from "effect"
const program = Effect.gen(function*() {
const currentScope = yield* Effect.scope
yield* Console.log("Got scope for resource management")
// Use the scope to manually manage resources if needed
const resource = yield* Effect.acquireRelease(
Console.log("Acquiring resource").pipe(Effect.as("resource")),
() => Console.log("Releasing resource")
)
return resource
})
Effect.runPromise(Effect.scoped(program)).then(console.log)
// Output:
// Got scope for resource management
// Acquiring resource
// resource
// Releasing resource
scope
const const pull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
R
>
const pull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import ChannelChannel.const toPullScoped: <
OutElem,
OutErr,
OutDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone, Env>,
never,
Env
>
Converts a channel to a Pull within an existing scope.
Example (Converting channels to scoped pulls)
import { Channel, Data, Effect, Scope } from "effect"
class ScopedPullError extends Data.TaggedError("ScopedPullError")<{
readonly reason: string
}> {}
// Create a channel
const numbersChannel = Channel.fromIterable([1, 2, 3])
// Convert to Pull with explicit scope
const scopedPullEffect = Effect.gen(function*() {
const scope = yield* Scope.make()
const pull = yield* Channel.toPullScoped(numbersChannel, scope)
return pull
})
toPullScoped(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; <…;
}
const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
const capacity: number | undefinedcapacity = options: | {
readonly capacity?:
| number
| "unbounded"
| undefined
}
| undefined
capacity?: number | "unbounded" | undefinedcapacity === "unbounded" ? var undefinedundefined : options: | {
readonly capacity?:
| number
| "unbounded"
| undefined
}
| undefined
capacity?: number | undefinedcapacity ?? const DefaultChunkSize: numberThe default chunk size used by Stream constructors and combinators.
Example (Reading the default chunk size)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Console.log(Stream.DefaultChunkSize)
})
Effect.runPromise(program)
// Output: 4096
DefaultChunkSize
const const passes: Queue.Queue<
Pass,
Cause.Done<void> | E
>
const passes: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.const make: <A, E = never>(
options?:
| {
readonly capacity?: number | undefined
readonly strategy?:
| "suspend"
| "dropping"
| "sliding"
| undefined
}
| undefined
) => Effect<Queue<A, E>>
Creates a Queue with optional capacity and overflow strategy.
Details
By default the queue is unbounded and uses the "suspend" strategy. Provide
capacity for a bounded queue and choose "suspend", "dropping", or
"sliding" to control what happens when the queue is full. The returned
queue can be offered to, taken from, failed, ended, interrupted, or shut down.
Example (Creating queues)
import { Cause, Effect, Queue } from "effect"
Effect.gen(function*() {
const queue = yield* Queue.make<number, string | Cause.Done>()
// add messages to the queue
yield* Queue.offer(queue, 1)
yield* Queue.offer(queue, 2)
yield* Queue.offerAll(queue, [3, 4, 5])
// take messages from the queue
const messages = yield* Queue.takeAll(queue)
console.log(messages) // [1, 2, 3, 4, 5]
// signal that the queue is done
yield* Queue.end(queue)
const done = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(done)) // true
// signal that another queue has failed
const failedQueue = yield* Queue.make<number, string>()
const failed = yield* Queue.fail(failedQueue, "boom")
console.log(failed) // true
})
make<function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>({ capacity?: number | undefinedcapacity })
const const fails: Queue.Queue<
Fail,
Cause.Done<void> | E
>
const fails: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.const make: <A, E = never>(
options?:
| {
readonly capacity?: number | undefined
readonly strategy?:
| "suspend"
| "dropping"
| "sliding"
| undefined
}
| undefined
) => Effect<Queue<A, E>>
Creates a Queue with optional capacity and overflow strategy.
Details
By default the queue is unbounded and uses the "suspend" strategy. Provide
capacity for a bounded queue and choose "suspend", "dropping", or
"sliding" to control what happens when the queue is full. The returned
queue can be offered to, taken from, failed, ended, interrupted, or shut down.
Example (Creating queues)
import { Cause, Effect, Queue } from "effect"
Effect.gen(function*() {
const queue = yield* Queue.make<number, string | Cause.Done>()
// add messages to the queue
yield* Queue.offer(queue, 1)
yield* Queue.offer(queue, 2)
yield* Queue.offerAll(queue, [3, 4, 5])
// take messages from the queue
const messages = yield* Queue.takeAll(queue)
console.log(messages) // [1, 2, 3, 4, 5]
// signal that the queue is done
yield* Queue.end(queue)
const done = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(done)) // true
// signal that another queue has failed
const failedQueue = yield* Queue.make<number, string>()
const failed = yield* Queue.fail(failedQueue, "boom")
console.log(failed) // true
})
make<function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
function (type parameter) E in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>({ capacity?: number | undefinedcapacity })
yield* import EffectEffect.const gen: {
<Eff extends Effect<any, any, any>, AEff>(
f: () => Generator<Eff, AEff, never>
): Effect<
AEff,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer E, infer _R>
]
? E
: never,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer _E, infer R>
]
? R
: never
>
<Self, Eff extends Effect<any, any, any>, AEff>(
options: { readonly self: Self },
f: (this: Self) => Generator<Eff, AEff, never>
): Effect<
AEff,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer E, infer _R>
]
? E
: never,
[Eff] extends [never]
? never
: [Eff] extends [
Effect<infer _A, infer _E, infer R>
]
? R
: never
>
}
const chunk: readonly [A, ...A[]]const chunk: {
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>;
}
const pull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
R
>
const pull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
const excluded: Fail[]excluded: interface Array<T>Array<function (type parameter) Fail in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
const satisfying: Pass[]satisfying: interface Array<T>Array<function (type parameter) Pass in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
let i: numberi = 0; let i: numberi < const chunk: readonly [A, ...A[]]const chunk: {
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; let i: numberi++) {
const const result: Result.Result<Pass, Fail>result = filter: Filter.Filter<NoInfer<A>, Pass, Fail>filter(const chunk: readonly [A, ...A[]]const chunk: {
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] as type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, E, R, Pass, Fail>(self: Stream<A, E, R>, filter: Filter.Filter<NoInfer<A>, Pass, Fail>, options?: {
readonly capacity?: number | "unbounded" | undefined;
}): Effect.fn.Return<[passes: Queue.Dequeue<Pass, E | Cause.Done>, fails: Queue.Dequeue<Fail, E | Cause.Done>], never, R | Scope.Scope>
import ResultResult.const isFailure: <A, E>(
self: Result<A, E>
) => self is Failure<A, E>
Checks whether a Result is a Failure.
When to use
Use to narrow a known Result to the Failure variant.
Details
- Acts as a TypeScript type guard, narrowing to
Failure<A, E>
- After narrowing, you can access
.failure to read the error value
Example (Narrowing to failure)
import { Result } from "effect"
const result = Result.fail("oops")
if (Result.isFailure(result)) {
console.log(result.failure)
// Output: "oops"
}
isFailure(const result: Result.Result<Pass, Fail>result)) {
const excluded: Fail[]excluded.Array<Fail>.push(...items: Fail[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const result: Result.Failure<Pass, Fail>const result: {
_tag: "Failure";
_op: "Failure";
failure: E;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
Failure<Pass, Fail>.failure: Failfailure)
} else {
const satisfying: Pass[]satisfying.Array<Pass>.push(...items: Pass[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const result: Result.Success<Pass, Fail>const result: {
_tag: "Success";
_op: "Success";
success: A;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
Success<Pass, Fail>.success: Passsuccess)
}
}
let let passFiber:
| Fiber.Fiber<any>
| undefined
import FiberFiber.interface Fiber<out A, out E = never>A runtime fiber is a lightweight thread that executes Effects. Fibers are
the unit of concurrency in Effect. They provide a way to run multiple
Effects concurrently while maintaining structured concurrency and
cancellation safety.
When to use
Use to observe, join, interrupt, or coordinate work that has already been
forked.
Details
A fiber exposes both safe Effect-based operations, such as
await
,
join
, and
interrupt
, and low-level runtime fields used by
the scheduler and runtime internals.
Gotchas
Prefer the exported functions in this module over calling interruptUnsafe
or pollUnsafe directly. The unsafe methods are immediate runtime hooks and
do not provide the same Effect-based sequencing guarantees.
Example (Awaiting a forked fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Fork an effect to run in a new fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Wait for the fiber to complete and get its result
const result = yield* Fiber.await(fiber)
console.log(result) // Exit.succeed(42)
return result
})
The Fiber namespace contains utility types and functions for working with fibers.
It provides type-level utilities for fiber operations and variance encoding.
When to use
Use to reference type-level helpers associated with Fiber.
Details
The namespace currently exposes type-level support used by the Fiber
interface. Runtime operations are exported as module-level functions.
Example (Working with fiber types)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Create a fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Use namespace types for variance
const typedFiber: Fiber.Fiber<number, never> = fiber
// Access fiber properties
console.log(`Fiber ID: ${fiber.id}`)
// Join the fiber
const result = yield* Fiber.join(fiber)
return result // 42
})
Fiber<any> | undefined = var undefinedundefined
if (const satisfying: Pass[]satisfying.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length > 0) {
const const leftover: Pass[]leftover = import QueueQueue.const offerAllUnsafe: <A, E>(
self: Enqueue<A, E>,
messages: Iterable<A>
) => Array<A>
Adds multiple messages to the queue synchronously. Returns the remaining messages that
were not added.
When to use
Use when queue internals or a performance boundary need a synchronous batch
offer and can handle any messages that do not fit.
Gotchas
This is an unsafe operation that directly modifies the queue without Effect wrapping.
Example (Offering multiple values synchronously)
import { Cause, Effect, Queue } from "effect"
// Create a bounded queue and use unsafe API
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(3)
// Try to add 5 messages to capacity-3 queue using unsafe API
const remaining = Queue.offerAllUnsafe(queue, [1, 2, 3, 4, 5])
console.log(remaining) // [4, 5] - couldn't fit the last 2
// Check what's in the queue
const size = Queue.sizeUnsafe(queue)
console.log(size) // 3
})
offerAllUnsafe(const passes: Queue.Queue<
Pass,
Cause.Done<void> | E
>
const passes: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const satisfying: Pass[]satisfying)
if (const leftover: Pass[]leftover.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length > 0) {
let passFiber:
| Fiber.Fiber<any>
| undefined
import EffectEffect.const forkChild: <
Arg extends
| Effect<any, any, any>
| {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
| undefined = {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
>(
effectOrOptions?: Arg,
options?:
| {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
| undefined
) => [Arg] extends [
Effect<infer _A, infer _E, infer _R>
]
? Effect<Fiber<_A, _E>, never, _R>
: <A, E, R>(
self: Effect<A, E, R>
) => Effect<Fiber<A, E>, never, R>
Returns an effect that forks this effect into its own separate fiber,
returning the fiber immediately, without waiting for it to begin executing
the effect.
Details
You can use the forkChild method whenever you want to execute an effect in a
new fiber, concurrently and without "blocking" the fiber executing other
effects. Using fibers can be tricky, so instead of using this method
directly, consider other higher-level methods, such as raceWith,
zipPar, and so forth.
The fiber returned by this method has methods to interrupt the fiber and to
wait for it to finish executing the effect. See Fiber for more
information.
Whenever you use this method to launch a new fiber, the new fiber is
attached to the parent fiber's scope. This means when the parent fiber
terminates, the child fiber will be terminated as well, ensuring that no
fibers leak. This behavior is called "auto supervision", and if this
behavior is not desired, you may use the forkDetach or forkIn methods.
Example (Forking a child fiber)
import { Effect, Fiber } from "effect"
const longRunningTask = Effect.gen(function*() {
yield* Effect.sleep("2 seconds")
yield* Effect.log("Task completed")
return "result"
})
const program = Effect.gen(function*() {
const fiber = yield* longRunningTask.pipe(Effect.forkChild)
// or fork a fiber that starts immediately:
yield* longRunningTask.pipe(Effect.forkChild({ startImmediately: true }))
yield* Effect.log("Task forked, continuing...")
const result = yield* Fiber.join(fiber)
return result
})
forkChild(import QueueQueue.const offerAll: <A, E>(
self: Enqueue<A, E>,
messages: Iterable<A>
) => Effect<Array<A>>
Adds multiple messages to the queue. Returns the remaining messages that
were not added.
When to use
Use when producers can submit a batch at once and need to know which messages
did not fit under the queue's capacity strategy.
Details
For bounded queues, this operation may suspend if the queue doesn't have
enough capacity. The operation returns an array of messages that couldn't
be added (empty array means all messages were successfully added).
Example (Offering multiple values)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.dropping<number>(3)
// Try to add more messages than capacity without suspending
const remaining1 = yield* Queue.offerAll(queue, [1, 2, 3, 4, 5])
console.log(remaining1) // [4, 5] - couldn't fit the last 2
})
offerAll(const passes: Queue.Queue<
Pass,
Cause.Done<void> | E
>
const passes: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const leftover: Pass[]leftover))
}
}
if (const excluded: Fail[]excluded.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length > 0) {
const const leftover: Fail[]leftover = import QueueQueue.const offerAllUnsafe: <A, E>(
self: Enqueue<A, E>,
messages: Iterable<A>
) => Array<A>
Adds multiple messages to the queue synchronously. Returns the remaining messages that
were not added.
When to use
Use when queue internals or a performance boundary need a synchronous batch
offer and can handle any messages that do not fit.
Gotchas
This is an unsafe operation that directly modifies the queue without Effect wrapping.
Example (Offering multiple values synchronously)
import { Cause, Effect, Queue } from "effect"
// Create a bounded queue and use unsafe API
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number>(3)
// Try to add 5 messages to capacity-3 queue using unsafe API
const remaining = Queue.offerAllUnsafe(queue, [1, 2, 3, 4, 5])
console.log(remaining) // [4, 5] - couldn't fit the last 2
// Check what's in the queue
const size = Queue.sizeUnsafe(queue)
console.log(size) // 3
})
offerAllUnsafe(const fails: Queue.Queue<
Fail,
Cause.Done<void> | E
>
const fails: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const excluded: Fail[]excluded)
if (const leftover: Fail[]leftover.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length > 0) {
yield* import QueueQueue.const offerAll: <A, E>(
self: Enqueue<A, E>,
messages: Iterable<A>
) => Effect<Array<A>>
Adds multiple messages to the queue. Returns the remaining messages that
were not added.
When to use
Use when producers can submit a batch at once and need to know which messages
did not fit under the queue's capacity strategy.
Details
For bounded queues, this operation may suspend if the queue doesn't have
enough capacity. The operation returns an array of messages that couldn't
be added (empty array means all messages were successfully added).
Example (Offering multiple values)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.dropping<number>(3)
// Try to add more messages than capacity without suspending
const remaining1 = yield* Queue.offerAll(queue, [1, 2, 3, 4, 5])
console.log(remaining1) // [4, 5] - couldn't fit the last 2
})
offerAll(const fails: Queue.Queue<
Fail,
Cause.Done<void> | E
>
const fails: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const leftover: Fail[]leftover)
}
}
if (let passFiber:
| Fiber.Fiber<any>
| undefined
import FiberFiber.const join: <A, E>(
self: Fiber<A, E>
) => Effect<A, E>
Joins a fiber, blocking until it completes. If the fiber succeeds,
returns its value. If it fails, the error is propagated.
When to use
Use when you need a forked fiber's failure to fail the current Effect because
that fiber is part of the current workflow.
Gotchas
Joining a failed fiber propagates the fiber's Cause. Use
await
when
you need to inspect the Exit instead of failing.
Example (Joining a fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
const fiber = yield* Effect.forkChild(Effect.succeed(42))
const result = yield* Fiber.join(fiber)
console.log(result) // 42
})
join(let passFiber:
| Fiber.Fiber<any>
| undefined
let passFiber: {
id: number;
currentOpCount: number;
getRef: <A>(ref: Context.Reference<A>) => A;
context: Context.Context<never>;
setContext: (context: Context.Context<never>) => void;
currentScheduler: Scheduler;
currentDispatcher: SchedulerDispatcher;
currentSpan: AnySpan | undefined;
currentLogLevel: LogLevel;
minimumLogLevel: LogLevel;
currentStackFrame: StackFrame | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
addObserver: (cb: (exit: Exit<A, E>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit<A, E> | undefined;
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; <…;
}
Pipeable.pipe<Effect.Effect<never, Cause.Done<void> | E, R>, Effect.Effect<never, Cause.Done<void> | E, R>, Effect.Effect<Fiber.Fiber<never, Cause.Done<void> | E>, never, R>>(this: Effect.Effect<...>, ab: (_: Effect.Effect<never, Cause.Done<void> | E, R>) => Effect.Effect<never, Cause.Done<void> | E, R>, bc: (_: Effect.Effect<never, Cause.Done<void> | E, R>) => Effect.Effect<Fiber.Fiber<never, Cause.Done<void> | E>, never, R>): Effect.Effect<...> (+21 overloads)pipe(
import EffectEffect.const onError: {
<E, X, R2>(
cleanup: (
cause: Cause.Cause<E>
) => Effect<X, never, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A, E, R2 | R>
<A, E, R, X, R2>(
self: Effect<A, E, R>,
cleanup: (
cause: Cause.Cause<E>
) => Effect<X, never, R2>
): Effect<A, E, R2 | R>
}
cause: Cause.Cause<Cause.Done<void> | E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.const failCauseUnsafe: <A, E>(
self: Enqueue<A, E>,
cause: Cause<E>
) => boolean
Fails the queue with a cause synchronously. If the queue is already done, false is
returned.
When to use
Use when queue completion must be driven from synchronous internals while
preserving the full failure Cause.
Gotchas
This is an unsafe operation that directly modifies the queue without Effect wrapping.
Example (Failing queues with a cause synchronously)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, string>(10)
// Create a cause and fail the queue synchronously
const cause = Cause.fail("Processing error")
const failed = Queue.failCauseUnsafe(queue, cause)
console.log(failed) // true
// The queue is now done with the specified failure cause
console.log(queue.state._tag) // "Done"
})
failCauseUnsafe(const passes: Queue.Queue<
Pass,
Cause.Done<void> | E
>
const passes: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
cause: Cause.Cause<Cause.Done<void> | E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.const failCauseUnsafe: <A, E>(
self: Enqueue<A, E>,
cause: Cause<E>
) => boolean
Fails the queue with a cause synchronously. If the queue is already done, false is
returned.
When to use
Use when queue completion must be driven from synchronous internals while
preserving the full failure Cause.
Gotchas
This is an unsafe operation that directly modifies the queue without Effect wrapping.
Example (Failing queues with a cause synchronously)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, string>(10)
// Create a cause and fail the queue synchronously
const cause = Cause.fail("Processing error")
const failed = Queue.failCauseUnsafe(queue, cause)
console.log(failed) // true
// The queue is now done with the specified failure cause
console.log(queue.state._tag) // "Done"
})
failCauseUnsafe(const fails: Queue.Queue<
Fail,
Cause.Done<void> | E
>
const fails: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
cause: Cause.Cause<Cause.Done<void> | E>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const void: Effect.Effect<void, never, never>(alias) const void: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
Returns an effect that succeeds with void.
void
}),
import EffectEffect.const forkIn: {
(
scope: Scope,
options?: {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
): <A, E, R>(
self: Effect<A, E, R>
) => Effect<Fiber<A, E>, never, R>
<A, E, R>(
self: Effect<A, E, R>,
scope: Scope,
options?: {
readonly startImmediately?:
| boolean
| undefined
readonly uninterruptible?:
| boolean
| "inherit"
| undefined
}
): Effect<Fiber<A, E>, never, R>
}
const scope: Scope.Scopeconst scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
const passes: Queue.Queue<
Pass,
Cause.Done<void> | E
>
const passes: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
const fails: Queue.Queue<
Fail,
Cause.Done<void> | E
>
const fails: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}