<A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(
self: Stream<A, E, R>
) => Stream<A, E2 | E, R2 | R>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
that: Stream<A2, E2, R2>
): Stream<A, E | E2, R | R2>Runs the provided stream in the background while this stream runs, interrupting it when this stream completes and failing if the background stream fails or defects.
Example (Draining a stream in the background)
import { Console, Effect, Stream } from "effect"
const foreground = Stream.make(1, 2)
const background = Stream.fromEffect(Console.log("background task"))
const program = Effect.gen(function*() {
const values = yield* foreground.pipe(
Stream.drainFork(background),
Stream.runCollect
)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: background task
// Output: [ 1, 2 ]export const const drainFork: {
<A2, E2, R2>(that: Stream<A2, E2, R2>): <
A,
E,
R
>(
self: Stream<A, E, R>
) => Stream<A, E2 | E, R2 | R>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
that: Stream<A2, E2, R2>
): Stream<A, E | E2, R | R2>
}
Runs the provided stream in the background while this stream runs, interrupting it
when this stream completes and failing if the background stream fails or defects.
Example (Draining a stream in the background)
import { Console, Effect, Stream } from "effect"
const foreground = Stream.make(1, 2)
const background = Stream.fromEffect(Console.log("background task"))
const program = Effect.gen(function*() {
const values = yield* foreground.pipe(
Stream.drainFork(background),
Stream.runCollect
)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: background task
// Output: [ 1, 2 ]
drainFork: {
<function (type parameter) A2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>A2, function (type parameter) E2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>E2, function (type parameter) R2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>R2>(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>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>A2, function (type parameter) E2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>E2, function (type parameter) R2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>R2>): <function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | 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>): Stream<A, E2 | E, R2 | R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | 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<A, E, R>): Stream<A, E2 | E, R2 | R>A, function (type parameter) E2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>E2 | function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R2 in <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>R2 | function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>R>
<function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R, function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, 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, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>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 <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, 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) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R2>
} = dual<(...args: Array<any>) => any, <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>) => Stream<A, E | E2, R | R2>>(arity: 2, body: <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>) => Stream<A, E | E2, R | R2>): ((...args: Array<any>) => any) & (<A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>) => Stream<A, E | E2, R | R2>) (+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(
2,
<function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R, function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, 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, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>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 <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, 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) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E | function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>E2, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R | function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>R2> =>
const mergeEffect: {
<A2, E2, R2>(
effect: Effect.Effect<A2, E2, R2>
): <A, E, R>(
self: Stream<A, E, R>
) => Stream<A, E2 | E, R2 | R>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
effect: Effect.Effect<A2, E2, R2>
): Stream<A, E | E2, R | 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; <…;
}
const runDrain: <A, E, R>(
self: Stream<A, E, R>
) => Effect.Effect<void, E, R>
Runs the stream for its effects, discarding emitted elements.
Example (Draining a stream run)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.make(1, 2, 3).pipe(
Stream.mapEffect((n) => Console.log(`Processing: ${n}`))
)
yield* Stream.runDrain(stream)
})
Effect.runPromise(program)
// Processing: 1
// Processing: 2
// Processing: 3
runDrain(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; <…;
}