<A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<
[A2, Stream<A, E, never>],
E2 | E,
Scope.Scope | R2 | R
>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
sink: Sink.Sink<A2, A, A, E2, R2>
): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>Runs a sink to peel off enough elements to produce a value and returns that value with the remaining stream in a scope.
Details
The returned stream is only valid within the scope.
Example (Peeling a stream with a sink)
import { Console, Effect, Sink, Stream } from "effect"
const stream = Stream.fromArrays([1, 2, 3], [4, 5, 6])
const sink = Sink.take<number>(3)
const program = Effect.scoped(
Effect.gen(function*() {
const [peeled, rest] = yield* Stream.peel(stream, sink)
const remaining = yield* Stream.runCollect(rest)
yield* Console.log([peeled, remaining])
})
)
Effect.runPromise(program)
// Output: [ [1, 2, 3], [4, 5, 6] ]export const const peel: {
<A2, A, E2, R2>(
sink: Sink.Sink<A2, A, A, E2, R2>
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<
[A2, Stream<A, E, never>],
E2 | E,
Scope.Scope | R2 | R
>
<A, E, R, A2, E2, R2>(
self: Stream<A, E, R>,
sink: Sink.Sink<A2, A, A, E2, R2>
): Effect.Effect<
[A2, Stream<A, E, never>],
E | E2,
Scope.Scope | R | R2
>
}
Runs a sink to peel off enough elements to produce a value and returns that
value with the remaining stream in a scope.
Details
The returned stream is only valid within the scope.
Example (Peeling a stream with a sink)
import { Console, Effect, Sink, Stream } from "effect"
const stream = Stream.fromArrays([1, 2, 3], [4, 5, 6])
const sink = Sink.take<number>(3)
const program = Effect.scoped(
Effect.gen(function*() {
const [peeled, rest] = yield* Stream.peel(stream, sink)
const remaining = yield* Stream.runCollect(rest)
yield* Console.log([peeled, remaining])
})
)
Effect.runPromise(program)
// Output: [ [1, 2, 3], [4, 5, 6] ]
peel: {
<function (type parameter) A2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A2, function (type parameter) A in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A, function (type parameter) E2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E2, function (type parameter) R2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>R2>(
sink: Sink.Sink<A2, A, A, E2, R2>(parameter) sink: {
transform: (upstream: Pull.Pull<NonEmptyReadonlyArray<In>, never, void>, scope: Scope.Scope) => Effect.Effect<End<A, L>, E, 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; <…;
}
import SinkSink.interface Sink<out A, in In = unknown, out L = never, out E = never, out R = never>A Sink<A, In, L, E, R> is used to consume elements produced by a Stream.
You can think of a sink as a function that will consume a variable amount of
In elements (could be 0, 1, or many), might fail with an error of type E,
and will eventually yield a value of type A together with a remainder of
type L (i.e. any leftovers).
Example (Running a sink with a stream)
import { Effect, Sink, Stream } from "effect"
// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42)
// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3)
const program = Stream.run(stream, sink)
Effect.runPromise(program).then(console.log)
// Output: 42
Namespace containing types and interfaces for Sink variance and type relationships.
Sink<function (type parameter) A2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A2, function (type parameter) A in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A, function (type parameter) A in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A, function (type parameter) E2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E2, function (type parameter) R2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>R2>
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | 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 <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>R>) => 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 <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A2, 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 <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E, never>], function (type parameter) E2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E2 | function (type parameter) E in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>E, import ScopeScope.Scope | function (type parameter) R2 in <A2, A, E2, R2>(sink: Sink.Sink<A2, A, A, E2, R2>): <E, R>(self: Stream<A, E, R>) => Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>R2 | function (type parameter) R in <E, R>(self: Stream<A, E, R>): Effect.Effect<[A2, Stream<A, E, never>], E2 | E, Scope.Scope | R2 | R>R>
<function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R, function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | 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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R>,
sink: Sink.Sink<A2, A, A, E2, R2>(parameter) sink: {
transform: (upstream: Pull.Pull<NonEmptyReadonlyArray<In>, never, void>, scope: Scope.Scope) => Effect.Effect<End<A, L>, E, 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; <…;
}
import SinkSink.interface Sink<out A, in In = unknown, out L = never, out E = never, out R = never>A Sink<A, In, L, E, R> is used to consume elements produced by a Stream.
You can think of a sink as a function that will consume a variable amount of
In elements (could be 0, 1, or many), might fail with an error of type E,
and will eventually yield a value of type A together with a remainder of
type L (i.e. any leftovers).
Example (Running a sink with a stream)
import { Effect, Sink, Stream } from "effect"
// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42)
// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3)
const program = Stream.run(stream, sink)
Effect.runPromise(program).then(console.log)
// Output: 42
Namespace containing types and interfaces for Sink variance and type relationships.
Sink<function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R2>
): 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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, 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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, never>], function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E | function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, import ScopeScope.Scope | function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R | function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R2>
} = dual<(...args: Array<any>) => any, <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>) => Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>>(arity: 2, body: <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>) => Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>): ((...args: Array<any>) => any) & (<A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>) => Effect.Effect<[A2, Stream<A, E, never>], E | E2, Scope.Scope | 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,
import EffectEffect.const fnUntraced: <Effect.Effect<any, E | E2, Scope.Scope | R | R2>, [A2, Stream<A, E, never>], [self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>]>(body: (this: unassigned, self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>) => Generator<Effect.Effect<any, E | E2, Scope.Scope | R | R2>, [A2, Stream<A, E, never>], never>) => <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<...>) => Effect.Effect<...> (+41 overloads)fnUntraced(function*<function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R, function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | 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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R>,
sink: Sink.Sink<A2, A, A, E2, R2>(parameter) sink: {
transform: (upstream: Pull.Pull<NonEmptyReadonlyArray<In>, never, void>, scope: Scope.Scope) => Effect.Effect<End<A, L>, E, 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; <…;
}
import SinkSink.interface Sink<out A, in In = unknown, out L = never, out E = never, out R = never>A Sink<A, In, L, E, R> is used to consume elements produced by a Stream.
You can think of a sink as a function that will consume a variable amount of
In elements (could be 0, 1, or many), might fail with an error of type E,
and will eventually yield a value of type A together with a remainder of
type L (i.e. any leftovers).
Example (Running a sink with a stream)
import { Effect, Sink, Stream } from "effect"
// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42)
// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3)
const program = Stream.run(stream, sink)
Effect.runPromise(program).then(console.log)
// Output: 42
Namespace containing types and interfaces for Sink variance and type relationships.
Sink<function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) A in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R2>
): import EffectEffect.fn.type fn.Return<A, E = never, R = never> = Generator<Effect.Effect<any, E, R>, A, any>Generator return type accepted by
fn
and
fnUntraced
.
When to use
Use when you need to annotate the return type of a generator body while
keeping the produced function's Effect return type inferred.
Example (Annotating an Effect function)
import { Effect } from "effect"
const f = Effect.fnUntraced(function*(
value: string
): Effect.fn.Return<number> {
return yield* Effect.succeed(value.length)
})
// ┌─── Effect.Effect<number>
// ▼
const program = f("hello")
Example (Annotating a parametric Effect function)
import { Effect } from "effect"
const f = Effect.fnUntraced(function*<A>(
value: A
): Effect.fn.Return<A> {
return yield* Effect.succeed(value)
})
// ┌─── Effect.Effect<string>
// ▼
const program = f("hello")
Return<[function (type parameter) A2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A2, 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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E, never>], function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E | function (type parameter) E2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E2, import ScopeScope.Scope | function (type parameter) R in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R | function (type parameter) R2 in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>R2> {
let let cause:
| Cause.Cause<E | Cause.Done<void>>
| undefined
import CauseCause.interface Cause<out E>A structured representation of how an Effect failed.
When to use
Use to preserve the full structured failure information for an effect instead
of collapsing it to a single error value.
Details
Access the individual failure entries through the reasons array, then
narrow each entry with
isFailReason
,
isDieReason
, or
- Use
hasFails
/
hasDies
/
hasInterrupts
to test
for the presence of specific reason kinds without iterating.
- Use
findError
/
findDefect
to extract the first value
of a given kind.
- Use
combine
to merge two causes.
Cause implements Equal — two causes with the same reasons (by value)
compare as equal.
Example (Creating and inspecting a cause)
import { Cause } from "effect"
const cause = Cause.fail("Something went wrong")
console.log(cause.reasons.length) // 1
console.log(Cause.isFailReason(cause.reasons[0])) // true
Companion namespace for the Cause interface.
Cause<function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E | import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done<void>> | undefined = var undefinedundefined
const const originalPull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
never
>
const originalPull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import ChannelChannel.const toPull: <
OutElem,
OutErr,
OutDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
unknown,
unknown,
unknown,
Env
>
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone>,
never,
Env | Scope.Scope
>
Converts a channel to a scoped Pull for low-level consumption.
Details
The effect requires a Scope. The returned pull should be consumed only
while that scope remains open. Pulls are serialized so only one pull is
evaluated at a time.
Example (Converting channels to pulls)
import { Channel, Data, Effect } from "effect"
class PullError extends Data.TaggedError("PullError")<{
readonly step: string
}> {}
// Create a channel
const numbersChannel = Channel.fromIterable([1, 2, 3])
// Convert to Pull within a scope
const pullEffect = Effect.scoped(
Channel.toPull(numbersChannel)
)
// Use the Pull to manually consume elements
toPull(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; <…;
}
const pull: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E
>
const pull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<
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 <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A>,
function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E
> = import EffectEffect.const catchCause: {
<E, A2, E2, R2>(
f: (
cause: Cause.Cause<E>
) => Effect<A2, E2, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A2 | A, E2, R2 | R>
<A, E, R, A2, E2, R2>(
self: Effect<A, E, R>,
f: (
cause: Cause.Cause<E>
) => Effect<A2, E2, R2>
): Effect<A | A2, E2, R | R2>
}
const originalPull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
never
>
const originalPull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
cause_: Cause.Cause<Cause.Done<void> | E>(parameter) cause_: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
let cause:
| Cause.Cause<E | Cause.Done<void>>
| undefined
cause_: Cause.Cause<Cause.Done<void> | E>(parameter) cause_: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const failCause: <E>(
cause: Cause.Cause<E>
) => Effect<never, E>
Creates an Effect that represents a failure with a specific Cause.
When to use
Use when you already have a full Cause and need to preserve defects,
interruptions, annotations, or combined failures in the effect's failure
channel.
Details
This function allows you to create effects that fail with complex error
structures, including multiple errors, defects, interruptions, and more.
Example (Failing with a full Cause)
import { Cause, Effect } from "effect"
const program = Effect.failCause(
Cause.fail("Network error")
)
Effect.runPromiseExit(program).then(console.log)
// Output: { _id: 'Exit', _tag: 'Failure', cause: ... }
failCause(cause_: Cause.Cause<Cause.Done<void> | E>(parameter) cause_: {
reasons: ReadonlyArray<Reason<E>>;
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; <…;
toString: () => string;
toJSON: () => unknown;
}
let stream: Stream<A, E, never>let stream: {
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 fromPull: <A, E, R, EX, RX>(
pull: Effect.Effect<
Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
R
>,
EX,
RX
>
) => Stream<A, Pull.ExcludeDone<E> | EX, R | RX>
Creates a stream from a pull effect, such as one produced by Stream.toPull.
Details
A pull effect yields chunks on demand and completes when the upstream stream ends.
See Stream.toPull for a matching producer.
Example (Creating a stream from a pull effect)
import { Console, Effect, Stream } from "effect"
const program = Effect.scoped(
Effect.gen(function*() {
const source = Stream.make(1, 2, 3)
const pull = yield* Stream.toPull(source)
const stream = Stream.fromPull(Effect.succeed(pull))
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
)
Effect.runPromise(program)
// Output: [1, 2, 3]
fromPull(import EffectEffect.const succeed: <A>(value: A) => Effect<A>Creates an Effect that always succeeds with a given value.
When to use
Use when an effect should complete successfully with a specific value without any errors
or external dependencies.
Example (Creating a successful effect)
import { Effect } from "effect"
// Creating an effect that represents a successful scenario
//
// ┌─── Effect<number, never, never>
// ▼
const success = Effect.succeed(42)
succeed(const pull: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E
>
const pull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
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>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>A, function (type parameter) E in <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, sink: Sink.Sink<A2, A, A, E2, R2>): Effect.fn.Return<[A2, Stream<A, E, never>], E | E2, Scope.Scope | R | R2>E>
const const leftover: A2leftover = yield* const run: {
<A2, A, L, E2, R2>(
sink: Sink.Sink<A2, A, L, E2, R2>
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<A2, E2 | E, R | R2>
<A, E, R, L, A2, E2, R2>(
self: Stream<A, E, R>,
sink: Sink.Sink<A2, A, L, E2, R2>
): Effect.Effect<A2, E | E2, R | R2>
}
let stream: Stream<A, E, never>let stream: {
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; <…;
}
sink: Sink.Sink<A2, A, A, E2, R2>(parameter) sink: {
transform: (upstream: Pull.Pull<NonEmptyReadonlyArray<In>, never, void>, scope: Scope.Scope) => Effect.Effect<End<A, L>, E, 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; <…;
}
let cause:
| Cause.Cause<E | Cause.Done<void>>
| undefined
const leftover: A2leftover, const empty: Stream<never>const empty: {
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; <…;
}
Creates an empty stream.
Example (Creating an empty stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const values = yield* Stream.empty.pipe(Stream.runCollect)
yield* Console.log(values)
})
Effect.runPromise(program)
// []
empty]
let stream: Stream<A, E, never>let stream: {
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 fromPull: <A, E, R, EX, RX>(
pull: Effect.Effect<
Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
R
>,
EX,
RX
>
) => Stream<A, Pull.ExcludeDone<E> | EX, R | RX>
Creates a stream from a pull effect, such as one produced by Stream.toPull.
Details
A pull effect yields chunks on demand and completes when the upstream stream ends.
See Stream.toPull for a matching producer.
Example (Creating a stream from a pull effect)
import { Console, Effect, Stream } from "effect"
const program = Effect.scoped(
Effect.gen(function*() {
const source = Stream.make(1, 2, 3)
const pull = yield* Stream.toPull(source)
const stream = Stream.fromPull(Effect.succeed(pull))
const values = yield* Stream.runCollect(stream)
yield* Console.log(values)
})
)
Effect.runPromise(program)
// Output: [1, 2, 3]
fromPull(import EffectEffect.const succeed: <A>(value: A) => Effect<A>Creates an Effect that always succeeds with a given value.
When to use
Use when an effect should complete successfully with a specific value without any errors
or external dependencies.
Example (Creating a successful effect)
import { Effect } from "effect"
// Creating an effect that represents a successful scenario
//
// ┌─── Effect<number, never, never>
// ▼
const success = Effect.succeed(42)
succeed(const originalPull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
never
>
const originalPull: {
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; <…;
toString: () => string;
toJSON: () => unknown;
}
const leftover: A2leftover, let stream: Stream<A, E, never>let stream: {
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; <…;
}