<A, A2, E2, R2>(
f: (a: A, i: number) => Effect.Effect<A2, E2, R2>,
options?:
| {
readonly concurrency?: number | "unbounded" | undefined
readonly unordered?: boolean | 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, i: number) => Effect.Effect<A2, E2, R2>,
options?:
| {
readonly concurrency?: number | "unbounded" | undefined
readonly unordered?: boolean | undefined
}
| undefined
): Stream<A2, E | E2, R | R2>Maps over elements of the stream with the specified effectful function.
When to use
Use when each stream element transformation needs an Effect, service dependency, failure channel, or configured concurrency.
Example (Effectfully mapping stream values)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const mappedStream = stream.pipe(
Stream.mapEffect((n) =>
Effect.gen(function*() {
yield* Console.log(`Processing: ${n}`)
return n * 2
})
)
)
const program = Effect.gen(function*() {
const result = yield* Stream.runCollect(mappedStream)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output:
// Processing: 1
// Processing: 2
// Processing: 3
// [2, 4, 6]mapping
Source effect/Stream.ts:202030 lines
export const const mapEffect: {
<A, A2, E2, R2>(
f: (
a: A,
i: number
) => Effect.Effect<A2, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | 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,
i: number
) => Effect.Effect<A2, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
| undefined
): Stream<A2, E | E2, R | R2>
}
Maps over elements of the stream with the specified effectful function.
When to use
Use when each stream element transformation needs an Effect, service
dependency, failure channel, or configured concurrency.
Example (Effectfully mapping stream values)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const mappedStream = stream.pipe(
Stream.mapEffect((n) =>
Effect.gen(function*() {
yield* Console.log(`Processing: ${n}`)
return n * 2
})
)
)
const program = Effect.gen(function*() {
const result = yield* Stream.runCollect(mappedStream)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output:
// Processing: 1
// Processing: 2
// Processing: 3
// [2, 4, 6]
mapEffect: {
<function (type parameter) A in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) A2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) E2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) R2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
f: (
a: A,
i: number
) => Effect.Effect<A2, E2, R2>
a: Aa: function (type parameter) A in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
i: numberi: number) => 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<function (type parameter) A2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) E2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) R2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | undefined
readonly unordered?: boolean | undefinedunordered?: boolean | undefined
} | undefined
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A2, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A2, 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, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A2, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A2, 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) A2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) E2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A2, E2 | E, R2 | R>E, function (type parameter) R2 in <A, A2, E2, R2>(f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A2, E2 | E, R2 | R>R>
<function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, 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; <…;
}
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>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
f: (
a: A,
i: number
) => Effect.Effect<A2, E2, R2>
a: Aa: function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
i: numberi: number) => 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<function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | undefined
readonly unordered?: boolean | undefinedunordered?: boolean | undefined
} | undefined
): 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>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
dual<(...args: Array<any>) => any, <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined) => Stream<A2, E | E2, R | R2>>(isDataFirst: (args: IArguments) => boolean, body: <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined) => Stream<A2, E | E2, R | R2>): ((...args: Array<any>) => any) & (<A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined) => 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((args: IArgumentsargs) => const isStream: (
u: unknown
) => u is Stream<unknown, unknown, unknown>
Checks whether a value is a Stream.
Example (Checking whether a value is a Stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const stream = Stream.make(1, 2, 3)
const notStream = { data: [1, 2, 3] }
yield* Console.log(Stream.isStream(stream))
// true
yield* Console.log(Stream.isStream(notStream))
// false
})
Effect.runPromise(program)
isStream(args: IArgumentsargs[0]), <function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, 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; <…;
}
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>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
f: (
a: A,
i: number
) => Effect.Effect<A2, E2, R2>
a: Aa: function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
i: numberi: number) => 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<function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | undefined
readonly unordered?: boolean | undefinedunordered?: boolean | undefined
} | undefined
): 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>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, f: (a: A, i: number) => Effect.Effect<A2, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
readonly unordered?: boolean | undefined;
} | undefined): Stream<A2, 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; <…;
}
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; <…;
}
Pipeable.pipe<Channel.Channel<readonly [A, ...A[]], E, void, unknown, unknown, unknown, R>, Channel.Channel<A, E, void, unknown, unknown, unknown, R>, Channel.Channel<A2, E | E2, void, unknown, unknown, unknown, R | R2>, Channel.Channel<[A2, ...A2[]], E | E2, void, unknown, unknown, unknown, R | R2>, Stream<A2, E | E2, R | R2>>(this: Channel.Channel<...>, ab: (_: Channel.Channel<readonly [A, ...A[]], E, void, unknown, unknown, unknown, R>) => Channel.Channel<A, E, void, unknown, unknown, unknown, R>, bc: (_: Channel.Channel<A, E, void, unknown, unknown, unknown, R>) => Channel.Channel<...>, cd: (_: Channel.Channel<...>) => Channel.Channel<...>, de: (_: Channel.Channel<...>) => Stream<...>): Stream<...> (+21 overloads)pipe(
import ChannelChannel.const flattenArray: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
ReadonlyArray<OutElem>,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
Flattens a channel that outputs arrays into a channel that outputs individual elements.
Example (Flattening arrays of channel output)
import { Channel, Data } from "effect"
class FlattenError extends Data.TaggedError("FlattenError")<{
readonly message: string
}> {}
// Create a channel that outputs arrays
const arrayChannel = Channel.fromIterable([
[1, 2, 3],
[4, 5],
[6, 7, 8, 9]
])
// Flatten the arrays into individual elements
const flattenedChannel = Channel.flattenArray(arrayChannel)
// Outputs: 1, 2, 3, 4, 5, 6, 7, 8, 9
flattenArray,
import ChannelChannel.const mapEffect: {
<OutElem, OutElem1, OutErr1, Env1>(
f: (
d: OutElem,
i: number
) => Effect.Effect<OutElem1, OutErr1, Env1>,
options?: {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
): <
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem1,
OutErr1 | OutErr,
OutDone,
InElem,
InErr,
InDone,
Env1 | Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
f: (
d: OutElem,
i: number
) => Effect.Effect<OutElem1, OutErr1, Env1>,
options?: {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
): Channel<
OutElem1,
OutErr | OutErr1,
OutDone,
InElem,
InErr,
InDone,
Env | Env1
>
}
f: (
a: A,
i: number
) => Effect.Effect<A2, E2, R2>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
readonly unordered?: boolean | undefined
}
| undefined
import ChannelChannel.const map: {
<OutElem, OutElem2>(
f: (o: OutElem, i: number) => OutElem2
): <
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem2,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem2
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
f: (o: OutElem, i: number) => OutElem2
): Channel<
OutElem2,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
}
import ArrArr.const of: <A>(a: A) => NonEmptyArray<A>Wraps a single value in a NonEmptyArray.
Example (Creating a single-element array)
import { Array } from "effect"
console.log(Array.of(1)) // [1]
of),
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
))Referenced by 5 symbols