<S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <
E,
R
>(
self: Stream<A, E, R>
) => Stream<S, E | E2, R | R2>
<A, E, R, S, E2, R2>(
self: Stream<A, E, R>,
initial: S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>
): Stream<S, E | E2, R | R2>Accumulates state effectfully and emits the initial state plus each accumulated state.
Example (Effectfully scanning stream state)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const states = yield* Stream.make(1, 2, 3).pipe(
Stream.scanEffect(0, (sum, n) => Effect.succeed(sum + n)),
Stream.runCollect
)
yield* Console.log(states)
// Output: [ 0, 1, 3, 6 ]
})Accumulation
Source effect/Stream.ts:779321 lines
export const const scanEffect: {
<S, A, E2, R2>(
initial: S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>
): <E, R>(
self: Stream<A, E, R>
) => Stream<S, E | E2, R | R2>
<A, E, R, S, E2, R2>(
self: Stream<A, E, R>,
initial: S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>
): Stream<S, E | E2, R | R2>
}
Accumulates state effectfully and emits the initial state plus each accumulated state.
Example (Effectfully scanning stream state)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const states = yield* Stream.make(1, 2, 3).pipe(
Stream.scanEffect(0, (sum, n) => Effect.succeed(sum + n)),
Stream.runCollect
)
yield* Console.log(states)
// Output: [ 0, 1, 3, 6 ]
})
scanEffect: {
<function (type parameter) S in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>S, function (type parameter) A in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>A, function (type parameter) E2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>R2>(
initial: Sinitial: function (type parameter) S in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>f: (s: Ss: function (type parameter) S in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>S, a: Aa: function (type parameter) A in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>A) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) S in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>S, function (type parameter) E2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>R2>
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>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 <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>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) S in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>S, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>E | function (type parameter) E2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>E2, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<S, E | E2, R | R2>R | function (type parameter) R2 in <S, A, E2, R2>(initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): <E, R>(self: Stream<A, E, R>) => Stream<S, E | E2, R | R2>R2>
<function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R, function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R>,
initial: Sinitial: function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>f: (s: Ss: function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, a: Aa: function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2>
): 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) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2>
} = import dualdual(3, <function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R, function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R>,
initial: Sinitial: function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S,
f: (s: S, a: A) => Effect.Effect<S, E2, R2>f: (s: Ss: function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, a: Aa: function (type parameter) A in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>A) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<function (type parameter) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2>
): 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) S in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>S, function (type parameter) E in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, S, E2, R2>(self: Stream<A, E, R>, initial: S, f: (s: S, a: A) => Effect.Effect<S, E2, R2>): Stream<S, E | E2, R | R2>R2> =>
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Stream<out A, out E = never, out R = never>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<out A, out E = never, out R = never>.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; <…;
}
import ChannelChannel.flattenArray,
import ChannelChannel.scanEffect(initial: Sinitial, f: (s: S, a: A) => Effect.Effect<S, E2, R2>f),
import ChannelChannel.map(import ArrArr.of),
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
))