<A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>Runs the stream and returns the last element as an Option.
When to use
Use to consume a finite stream when only the final emitted element matters.
Details
Option.some contains the last emitted element. Option.none means the
stream completed without emitting.
Gotchas
The returned effect waits for the stream to complete before it can produce a value.
export const const runLast: <A, E, R>(
self: Stream<A, E, R>
) => Effect.Effect<Option.Option<A>, E, R>
Runs the stream and returns the last element as an Option.
When to use
Use to consume a finite stream when only the final emitted element matters.
Details
Option.some contains the last emitted element. Option.none means the
stream completed without emitting.
Gotchas
The returned effect waits for the stream to complete before it can produce a
value.
runLast = <function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, 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 <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>R>): import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<import OptionOption.type Option.Option = /*unresolved*/ anyOption<function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>A>, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Effect.Effect<Option.Option<A>, E, R>R> =>
import EffectEffect.map(import ChannelChannel.runLast(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 OptionOption.map(import ArrArr.lastNonEmpty))