<A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<
A,
E,
R
>Flattens a stream of non-empty arrays into a stream of elements.
Example (Flattening a stream of non-empty arrays into a stream of elements)
import { Array, Console, Effect, Stream } from "effect"
const stream = Stream.make(Array.make(1, 2), Array.make(3))
const program = Effect.gen(function* () {
const result = yield* Stream.runCollect(Stream.flattenArray(stream))
yield* Console.log(result)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]export const const flattenArray: <A, E, R>(
self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>
) => Stream<A, E, R>
Flattens a stream of non-empty arrays into a stream of elements.
Example (Flattening a stream of non-empty arrays into a stream of elements)
import { Array, Console, Effect, Stream } from "effect"
const stream = Stream.make(Array.make(1, 2), Array.make(3))
const program = Effect.gen(function* () {
const result = yield* Stream.runCollect(Stream.flattenArray(stream))
yield* Console.log(result)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]
flattenArray = <function (type parameter) A in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>R>(self: Stream<
Arr.NonEmptyReadonlyArray<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<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 <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>A>, function (type parameter) E in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, 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) A in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<Arr.NonEmptyReadonlyArray<A>, E, R>): Stream<A, E, R>R> =>
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 flattenArray: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
ReadonlyArray<OutElem>,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
Flattens a channel that outputs arrays into a channel that outputs individual elements.
Example (Flattening arrays of channel output)
import { Channel, Data } from "effect"
class FlattenError extends Data.TaggedError("FlattenError")<{
readonly message: string
}> {}
// Create a channel that outputs arrays
const arrayChannel = Channel.fromIterable([
[1, 2, 3],
[4, 5],
[6, 7, 8, 9]
])
// Flatten the arrays into individual elements
const flattenedChannel = Channel.flattenArray(arrayChannel)
// Outputs: 1, 2, 3, 4, 5, 6, 7, 8, 9
flattenArray(self: Stream<
Arr.NonEmptyReadonlyArray<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<readonly [A, ...A[]], E, R>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<readonly [A, ...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; <…;
}