<R2, E, E2, A, A2>(
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>
<R, R2, E, E2, A, A2>(
self: Stream<A, E, R>,
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
): Stream<A2, E | E2, R | R2>Pipes values through the provided channel while preserving this stream's failures alongside any channel failures.
Details
Upstream failures are not passed to the channel, so the resulting stream can fail with either the original stream error or the channel error.
Example (Piping through a channel with failures)
import { Array, Channel, Effect, Stream } from "effect"
type NumberChunk = readonly [number, ...Array<number>]
const stringifyChunks = Channel.identity<NumberChunk, "StreamError", unknown>().pipe(
Channel.map((chunk) => Array.map(chunk, String))
)
Effect.runPromise(Effect.gen(function*() {
const result = yield* Stream.make(1, 2, 3).pipe(
Stream.rechunk(2),
Stream.pipeThroughChannelOrFail(stringifyChunks),
Stream.runCollect
)
yield* Effect.sync(() => console.log(result))
}))
// [ "1", "2", "3" ]Pipe
Source effect/Stream.ts:909712 lines
export const const pipeThroughChannelOrFail: {
<R2, E, E2, A, A2>(
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
): <R>(
self: Stream<A, E, R>
) => Stream<A2, E | E2, R2 | R>
<R, R2, E, E2, A, A2>(
self: Stream<A, E, R>,
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
): Stream<A2, E | E2, R | R2>
}
Pipes values through the provided channel while preserving this stream's
failures alongside any channel failures.
Details
Upstream failures are not passed to the channel, so the resulting stream can
fail with either the original stream error or the channel error.
Example (Piping through a channel with failures)
import { Array, Channel, Effect, Stream } from "effect"
type NumberChunk = readonly [number, ...Array<number>]
const stringifyChunks = Channel.identity<NumberChunk, "StreamError", unknown>().pipe(
Channel.map((chunk) => Array.map(chunk, String))
)
Effect.runPromise(Effect.gen(function*() {
const result = yield* Stream.make(1, 2, 3).pipe(
Stream.rechunk(2),
Stream.pipeThroughChannelOrFail(stringifyChunks),
Stream.runCollect
)
yield* Effect.sync(() => console.log(result))
}))
// [ "1", "2", "3" ]
pipeThroughChannelOrFail: {
<function (type parameter) R2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>R2, function (type parameter) E in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E, function (type parameter) E2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E2, function (type parameter) A in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A, function (type parameter) A2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A2>(
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
(parameter) 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 ChannelChannel.interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<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) A2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A2>, function (type parameter) E2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E2, unknown, 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 <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A>, function (type parameter) E in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E, unknown, function (type parameter) R2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>R2>
): <function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A2, E | E2, 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 <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A, function (type parameter) E in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E, function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A2, E | E2, 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) A2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>A2, function (type parameter) E in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E | function (type parameter) E2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>E2, function (type parameter) R2 in <R2, E, E2, A, A2>(channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): <R>(self: Stream<A, E, R>) => Stream<A2, E | E2, R2 | R>R2 | function (type parameter) R in <R>(self: Stream<A, E, R>): Stream<A2, E | E2, R2 | R>R>
<function (type parameter) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R, function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R2, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, function (type parameter) A in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A, function (type parameter) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2>(
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 <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, function (type parameter) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R>,
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
(parameter) 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 ChannelChannel.interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<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) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2>, function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, unknown, 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 <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A>, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, unknown, function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, 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) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E | function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, function (type parameter) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R | function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R2>
} = dual<(...args: Array<any>) => any, <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>) => Stream<A2, E | E2, R | R2>>(arity: 2, body: <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>) => Stream<A2, E | E2, R | R2>): ((...args: Array<any>) => any) & (<R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>) => Stream<A2, 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) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R, function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R2, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, function (type parameter) A in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A, function (type parameter) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2>(
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 <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, function (type parameter) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R>,
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
(parameter) 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 ChannelChannel.interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<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) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2>, function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, unknown, 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 <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A>, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E, unknown, function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, 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) A2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>A2, function (type parameter) E in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E | function (type parameter) E2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>E2, function (type parameter) R in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R | function (type parameter) R2 in <R, R2, E, E2, A, A2>(self: Stream<A, E, R>, channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A2>, E2, unknown, Arr.NonEmptyReadonlyArray<A>, E, unknown, R2>): Stream<A2, E | E2, R | R2>R2> => 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 pipeToOrFail: {
<
OutElem2,
OutErr2,
OutDone2,
OutElem,
OutDone,
Env2
>(
that: Channel<
OutElem2,
OutErr2,
OutDone2,
OutElem,
never,
OutDone,
Env2
>
): <OutErr, InElem, InErr, InDone, Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem2,
OutErr | OutErr2,
OutDone2,
InElem,
InErr,
InDone,
Env2 | Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem2,
OutErr2,
OutDone2,
Env2
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
that: Channel<
OutElem2,
OutErr2,
OutDone2,
OutElem,
never,
OutDone,
Env2
>
): Channel<
OutElem2,
OutErr | OutErr2,
OutDone2,
InElem,
InErr,
InDone,
Env2 | Env
>
}
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<A, E, R>.channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>(property) Stream<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; <…;
}
channel: Channel.Channel<
Arr.NonEmptyReadonlyArray<A2>,
E2,
unknown,
Arr.NonEmptyReadonlyArray<A>,
E,
unknown,
R2
>
(parameter) 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; <…;
}