<A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<
A,
Pull.ExcludeDone<E>,
R
>Creates a stream by repeatedly running an effect that yields an iterable of values.
Example (Repeating an iterable effect)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.fromIterableEffectRepeat(Effect.succeed([1, 2])).pipe(
Stream.take(5)
)
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 1, 2, 1 ]export const const fromIterableEffectRepeat: <A, E, R>(
iterable: Effect.Effect<Iterable<A>, E, R>
) => Stream<A, Pull.ExcludeDone<E>, R>
Creates a stream by repeatedly running an effect that yields an iterable of values.
Example (Repeating an iterable effect)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.fromIterableEffectRepeat(Effect.succeed([1, 2])).pipe(
Stream.take(5)
)
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 1, 2, 1 ]
fromIterableEffectRepeat = <function (type parameter) A in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>A, function (type parameter) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>E, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>R>(
iterable: Effect.Effect<Iterable<A>, E, R>(parameter) iterable: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.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<interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>A>, function (type parameter) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>E, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<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>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>A, 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) E in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>E>, function (type parameter) R in <A, E, R>(iterable: Effect.Effect<Iterable<A>, E, R>): Stream<A, Pull.ExcludeDone<E>, R>R> => const flatMap: {
<A, A2, E2, R2>(
f: (a: A) => Stream<A2, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly bufferSize?: number | undefined
}
| undefined
): <E, R>(
self: Stream<A, E, R>
) => Stream<A2, E2 | E, R2 | R>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
f: (a: A) => Stream<A2, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly bufferSize?: number | undefined
}
| undefined
): Stream<A2, E | E2, R | R2>
}
const fromEffectRepeat: <A, E, R>(
effect: Effect.Effect<A, E, R>
) => Stream<A, Pull.ExcludeDone<E>, R>
Creates a stream from an effect producing a value of type A which repeats forever.
Example (Repeating an effect forever)
import { Console, Effect, Random, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.fromEffectRepeat(Random.nextInt).pipe(
Stream.take(5)
)
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 3891571149, 4239494205, 2352981603, 2339111046, 1488052210 ]
fromEffectRepeat(iterable: Effect.Effect<Iterable<A>, E, R>(parameter) iterable: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const fromIterable: <A>(
iterable: Iterable<A>,
options?: {
readonly chunkSize?: number | undefined
}
) => Stream<A>
Creates a new Stream from an iterable collection of values.
Details
chunkSize: Maximum number of values emitted per chunk.
Example (Creating a stream from an iterable)
import { Console, Effect, Stream } from "effect"
const numbers = [1, 2, 3]
const program = Effect.gen(function*() {
const stream = Stream.fromIterable(numbers)
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]
fromIterable)