<B>(values: Iterable<B>): <A, E, R>(
self: Stream<A, E, R>
) => Stream<B | A, E, R>
<A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<
A | B,
E,
R
>Prepends the values from the provided iterable before the stream's elements.
Example (Prepending values)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const values = yield* Stream.make(3, 4).pipe(
Stream.prepend([1, 2]),
Stream.runCollect
)
yield* Console.log(values)
// Output: [ 1, 2, 3, 4 ]
})
Effect.runPromise(program)export const const prepend: {
<B>(values: Iterable<B>): <A, E, R>(
self: Stream<A, E, R>
) => Stream<B | A, E, R>
<A, E, R, B>(
self: Stream<A, E, R>,
values: Iterable<B>
): Stream<A | B, E, R>
}
Prepends the values from the provided iterable before the stream's elements.
Example (Prepending values)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const values = yield* Stream.make(3, 4).pipe(
Stream.prepend([1, 2]),
Stream.runCollect
)
yield* Console.log(values)
// Output: [ 1, 2, 3, 4 ]
})
Effect.runPromise(program)
prepend: {
<function (type parameter) B in <B>(values: Iterable<B>): <A, E, R>(self: Stream<A, E, R>) => Stream<B | A, E, R>B>(values: Iterable<B>values: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) B in <B>(values: Iterable<B>): <A, E, R>(self: Stream<A, E, R>) => Stream<B | A, E, R>B>): <function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<B | 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>): Stream<B | A, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<B | 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) B in <B>(values: Iterable<B>): <A, E, R>(self: Stream<A, E, R>) => Stream<B | A, E, R>B | function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<B | A, E, R>R>
<function (type parameter) A in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R, function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B>(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, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R>, values: Iterable<B>values: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B>): 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, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A | function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R>
} = dual<(...args: Array<any>) => any, <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>) => Stream<A | B, E, R>>(arity: 2, body: <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>) => Stream<A | B, E, R>): ((...args: Array<any>) => any) & (<A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>) => Stream<A | B, E, R>) (+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, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R, function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B>(
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, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R>,
values: Iterable<B>values: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B>
): 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, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>A | function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>B, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, values: Iterable<B>): Stream<A | B, E, R>R> => const concat: {
<A2, E2, R2>(that: Stream<A2, E2, R2>): <
A,
E,
R
>(
self: Stream<A, E, R>
) => Stream<A | A2, E | E2, R | R2>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
that: Stream<A2, E2, R2>
): Stream<A | A2, E | E2, R | R2>
}
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(values: Iterable<B>values), 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; <…;
}