<A2, E2, R2, S, E, A, A3, E3, R3>(
that: Stream<A2, E2, R2>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>,
pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>
) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>
): <R>(
self: Stream<A, E, R>
) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>
<R, A2, E2, R2, S, E, A, A3, E3, R3>(
self: Stream<A, E, R>,
that: Stream<A2, E2, R2>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>,
pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>
) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>
): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>Combines two streams chunk-by-chunk with a stateful pull function.
When to use
Use to coordinate pulling chunks from two streams when each emitted chunk depends on both sides and local state.
Details
The combining function receives the current state and pull functions for the left and right streams. It returns the next non-empty chunk together with the next state.
Example (Combining stream chunks with state)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2).pipe(
Stream.combineArray(
Stream.make(10, 20),
() => true,
(useLeft, pullLeft, pullRight) =>
Effect.gen(function*() {
const array = useLeft ? yield* pullLeft : yield* pullRight
return [array, !useLeft] as const
})
)
)
const program = Effect.gen(function*() {
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 10, 20 ]sequencing
Source effect/Stream.ts:736036 lines
export const const combineArray: {
<A2, E2, R2, S, E, A, A3, E3, R3>(
that: Stream<A2, E2, R2>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>
): <R>(
self: Stream<A, E, R>
) => Stream<
A3,
Pull.ExcludeDone<E3>,
R2 | R3 | R
>
<R, A2, E2, R2, S, E, A, A3, E3, R3>(
self: Stream<A, E, R>,
that: Stream<A2, E2, R2>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>
): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>
}
Combines two streams chunk-by-chunk with a stateful pull function.
When to use
Use to coordinate pulling chunks from two streams when each emitted chunk
depends on both sides and local state.
Details
The combining function receives the current state and pull functions for the
left and right streams. It returns the next non-empty chunk together with the
next state.
Example (Combining stream chunks with state)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2).pipe(
Stream.combineArray(
Stream.make(10, 20),
() => true,
(useLeft, pullLeft, pullRight) =>
Effect.gen(function*() {
const array = useLeft ? yield* pullLeft : yield* pullRight
return [array, !useLeft] as const
})
)
)
const program = Effect.gen(function*() {
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 10, 20 ]
combineArray: {
<function (type parameter) A2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A2, function (type parameter) E2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E2, function (type parameter) R2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R2, function (type parameter) S in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>S, function (type parameter) E in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E, function (type parameter) A in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A, function (type parameter) A3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A3, function (type parameter) E3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E3, function (type parameter) R3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R3>(
that: Stream<A2, E2, R2>(parameter) that: {
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) A2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A2, function (type parameter) E2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E2, function (type parameter) R2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R2>,
s: LazyArg<S>s: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>S>,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>
s: Ss: function (type parameter) S in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>
(parameter) pullLeft: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A>, function (type parameter) E in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E, void>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
(parameter) pullRight: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A2>, function (type parameter) E2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E2, void>
) => 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<readonly [import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A3>, function (type parameter) S in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>S], function (type parameter) E3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E3, function (type parameter) R3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R3>
): <function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | 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 <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A, function (type parameter) E in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E, function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R>) => 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) A3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>A3, import PullPull.type ExcludeDone<E> =
E extends Cause.Done<any> ? never : E
Excludes Cause.Done completion signals from an error type union.
When to use
Use to describe the ordinary error type that remains after Cause.Done
completion signals have been handled or filtered out of an error union.
ExcludeDone<function (type parameter) E3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>E3>, function (type parameter) R2 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R2 | function (type parameter) R3 in <A2, E2, R2, S, E, A, A3, E3, R3>(that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): <R>(self: Stream<A, E, R>) => Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R3 | function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A3, Pull.ExcludeDone<E3>, R2 | R3 | R>R>
<function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R, function (type parameter) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2, function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, function (type parameter) A in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A, function (type parameter) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3, function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3, function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3>(
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 <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R>,
that: Stream<A2, E2, R2>(parameter) that: {
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) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2>,
s: LazyArg<S>s: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S>,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>
s: Ss: function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>
(parameter) pullLeft: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A>, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, void>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
(parameter) pullRight: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2>, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, void>
) => 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<readonly [import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3>, function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S], function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3, function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3>
): 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) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3, import PullPull.type ExcludeDone<E> =
E extends Cause.Done<any> ? never : E
Excludes Cause.Done completion signals from an error type union.
When to use
Use to describe the ordinary error type that remains after Cause.Done
completion signals have been handled or filtered out of an error union.
ExcludeDone<function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3>, function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R | function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2 | function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3>
} = dual<(...args: Array<any>) => any, <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>) => Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>>(arity: 4, body: <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>) => Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>): ((...args: Array<any>) => any) & (<R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>) => Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>) (+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(4, <function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R, function (type parameter) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2, function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, function (type parameter) A in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A, function (type parameter) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3, function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3, function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3>(
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 <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R>,
that: Stream<A2, E2, R2>(parameter) that: {
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) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2>,
s: LazyArg<S>s: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S>,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>
s: Ss: function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>
(parameter) pullLeft: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A>, function (type parameter) E in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E, void>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
(parameter) pullRight: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A2>, function (type parameter) E2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E2, void>
) => 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<readonly [import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3>, function (type parameter) S in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>S], function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3, function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3>
): 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) A3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>A3, import PullPull.type ExcludeDone<E> =
E extends Cause.Done<any> ? never : E
Excludes Cause.Done completion signals from an error type union.
When to use
Use to describe the ordinary error type that remains after Cause.Done
completion signals have been handled or filtered out of an error union.
ExcludeDone<function (type parameter) E3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>E3>, function (type parameter) R in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R | function (type parameter) R2 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R2 | function (type parameter) R3 in <R, A2, E2, R2, S, E, A, A3, E3, R3>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>, s: LazyArg<S>, f: (s: S, pullLeft: Pull.Pull<Arr.NonEmptyReadonlyArray<A>, E, void>, pullRight: Pull.Pull<Arr.NonEmptyReadonlyArray<A2>, E2, void>) => Effect.Effect<readonly [Arr.NonEmptyReadonlyArray<A3>, S], E3, R3>): Stream<A3, Pull.ExcludeDone<E3>, R | R2 | R3>R3> =>
const fromChannel: <
Arr extends Arr.NonEmptyReadonlyArray<any>,
E,
R
>(
channel: Channel.Channel<
Arr,
E,
void,
unknown,
unknown,
unknown,
R
>
) => Stream<
Arr extends Arr.NonEmptyReadonlyArray<infer A>
? A
: never,
E,
R
>
Creates a stream from a array-emitting Channel.
Example (Creating a stream from an array-emitting channel)
import { Channel, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const channel = Channel.succeed([1, 2, 3] as const)
const stream = Stream.fromChannel(channel)
const result = yield* Stream.runCollect(stream)
yield* Console.log(result)
})
// Output: [ 1, 2, 3 ]
fromChannel(import ChannelChannel.const combine: {
<
OutElem2,
OutErr2,
OutDone2,
InElem2,
InErr2,
InDone2,
Env2,
S,
OutElem,
OutErr,
OutDone,
A,
E,
R
>(
that: Channel<
OutElem2,
OutErr2,
OutDone2,
InElem2,
InErr2,
InDone2,
Env2
>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<
OutElem,
OutErr,
OutDone
>,
pullRight: Pull.Pull<
OutElem2,
OutErr2,
OutDone2
>
) => Effect.Effect<readonly [A, S], E, R>
): <InElem, InErr, InDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
A,
Pull.ExcludeDone<E>,
Cause.Done.Extract<E>,
InElem & InElem2,
InErr & InErr2,
InDone & InDone2,
Env | Env2 | R
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem2,
OutErr2,
OutDone2,
InElem2,
InErr2,
InDone2,
Env2,
S,
A,
E,
R
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
that: Channel<
OutElem2,
OutErr2,
OutDone2,
InElem2,
InErr2,
InDone2,
Env2
>,
s: LazyArg<S>,
f: (
s: S,
pullLeft: Pull.Pull<
OutElem,
OutErr,
OutDone
>,
pullRight: Pull.Pull<
OutElem2,
OutErr2,
OutDone2
>
) => Effect.Effect<readonly [A, S], E, R>
): Channel<
A,
Pull.ExcludeDone<E>,
Cause.Done.Extract<E>,
InElem & InElem2,
InErr & InErr2,
InDone & InDone2,
Env | Env2 | 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; <…;
}
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; <…;
}
that: Stream<A2, E2, R2>(parameter) that: {
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<A2, E2, R2>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<A2, E2, R2>.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; <…;
}
s: LazyArg<S>s,
f: (
s: S,
pullLeft: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
pullRight: Pull.Pull<
Arr.NonEmptyReadonlyArray<A2>,
E2,
void
>
) => Effect.Effect<
readonly [Arr.NonEmptyReadonlyArray<A3>, S],
E3,
R3
>