<A, XR>(
context: Context.Context<XR>,
options?: { readonly strategy?: QueuingStrategy<A> | undefined }
): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
<A, E, XR, R extends XR>(
self: Stream<A, E, R>,
context: Context.Context<XR>,
options?: { readonly strategy?: QueuingStrategy<A> | undefined }
): ReadableStream<A>Converts the stream to a ReadableStream using the provided services.
When to use
Use when bridging to Web Streams and you already have the Context required
to run the stream outside an Effect.
Details
See https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream.
Example (Converting to a ReadableStream with services)
import { Context, Stream } from "effect"
const stream = Stream.make(1, 2, 3, 4, 5)
const readableStream = Stream.toReadableStreamWith(stream, Context.empty())destructors
Source effect/Stream.ts:1114556 lines
export const const toReadableStreamWith: (<A, XR>(
context: Context.Context<XR>,
options?: {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
) => <E, R extends XR>(
self: Stream<A, E, R>
) => ReadableStream<A>) &
(<A, E, XR, R extends XR>(
self: Stream<A, E, R>,
context: Context.Context<XR>,
options?: {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
) => ReadableStream<A>)
Converts the stream to a ReadableStream using the provided services.
When to use
Use when bridging to Web Streams and you already have the Context required
to run the stream outside an Effect.
Details
See https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream.
Example (Converting to a ReadableStream with services)
import { Context, Stream } from "effect"
const stream = Stream.make(1, 2, 3, 4, 5)
const readableStream = Stream.toReadableStreamWith(stream, Context.empty())
toReadableStreamWith = dual<<A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}) => <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>, <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}) => ReadableStream<A>>(isDataFirst: (args: IArguments) => boolean, body: <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}) => ReadableStream<A>): (<A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}) => <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>) & (<A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}) => ReadableStream<A>) (+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<
<function (type parameter) A in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
function (type parameter) XR in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
options: | {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
| undefined
strategy?: QueuingStrategy<A> | undefinedstrategy?: interface QueuingStrategy<T = any>QueuingStrategy<function (type parameter) A in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
function (type parameter) E in <E, R extends XR>(self: Stream<A, E, R>): ReadableStream<A>E, function (type parameter) R in <E, R extends XR>(self: Stream<A, E, R>): ReadableStream<A>R extends function (type parameter) XR in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
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, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
function (type parameter) E in <E, R extends XR>(self: Stream<A, E, R>): ReadableStream<A>E, function (type parameter) R in <E, R extends XR>(self: Stream<A, E, R>): ReadableStream<A>R>) => interface ReadableStream<R = any>The ReadableStream interface of the Streams API represents a readable stream of byte data.
ReadableStream<function (type parameter) A in <A, XR>(context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): <E, R extends XR>(self: Stream<A, E, R>) => ReadableStream<A>
function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
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, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
options: | {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
| undefined
strategy?: QueuingStrategy<A> | undefinedstrategy?: interface QueuingStrategy<T = any>QueuingStrategy<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
interface ReadableStream<R = any>The ReadableStream interface of the Streams API represents a readable stream of byte data.
ReadableStream<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
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, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
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, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
function (type parameter) R in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 ContextContext.interface Context<in Services>Immutable collection of service implementations used for dependency
injection in Effect programs.
Details
The type parameter tracks the service identifiers available in the context.
At runtime, services are stored by each key's string key.
Example (Creating a context with multiple services)
import { Context } from "effect"
// Create a context with multiple services
const Logger = Context.Service<{ log: (msg: string) => void }>("Logger")
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
const context = Context.make(Logger, {
log: (msg: string) => console.log(msg)
})
.pipe(Context.add(Database, { query: (sql) => `Result: ${sql}` }))
Context<function (type parameter) XR in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
options: | {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
| undefined
strategy?: QueuingStrategy<A> | undefinedstrategy?: interface QueuingStrategy<T = any>QueuingStrategy<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
interface ReadableStream<R = any>The ReadableStream interface of the Streams API represents a readable stream of byte data.
ReadableStream<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
let currentResolve:
| (() => void)
| undefined
var undefinedundefined
let let fiber:
| Fiber.Fiber<void, E>
| undefined
import FiberFiber.interface Fiber<out A, out E = never>A runtime fiber is a lightweight thread that executes Effects. Fibers are
the unit of concurrency in Effect. They provide a way to run multiple
Effects concurrently while maintaining structured concurrency and
cancellation safety.
When to use
Use to observe, join, interrupt, or coordinate work that has already been
forked.
Details
A fiber exposes both safe Effect-based operations, such as
await
,
join
, and
interrupt
, and low-level runtime fields used by
the scheduler and runtime internals.
Gotchas
Prefer the exported functions in this module over calling interruptUnsafe
or pollUnsafe directly. The unsafe methods are immediate runtime hooks and
do not provide the same Effect-based sequencing guarantees.
Example (Awaiting a forked fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Fork an effect to run in a new fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Wait for the fiber to complete and get its result
const result = yield* Fiber.await(fiber)
console.log(result) // Exit.succeed(42)
return result
})
The Fiber namespace contains utility types and functions for working with fibers.
It provides type-level utilities for fiber operations and variance encoding.
When to use
Use to reference type-level helpers associated with Fiber.
Details
The namespace currently exposes type-level support used by the Fiber
interface. Runtime operations are exported as module-level functions.
Example (Working with fiber types)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
// Create a fiber
const fiber = yield* Effect.forkChild(Effect.succeed(42))
// Use namespace types for variance
const typedFiber: Fiber.Fiber<number, never> = fiber
// Access fiber properties
console.log(`Fiber ID: ${fiber.id}`)
// Join the fiber
const result = yield* Fiber.join(fiber)
return result // 42
})
Fiber<void, function (type parameter) E in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
var undefinedundefined
const const latch: Latch.Latchconst latch: {
open: Effect.Effect<boolean>;
openUnsafe: (this: Latch) => boolean;
release: Effect.Effect<boolean>;
await: Effect.Effect<void>;
close: Effect.Effect<boolean>;
closeUnsafe: (this: Latch) => boolean;
whenOpen: <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
isOpen: (this: Latch) => boolean;
}
import LatchLatch.const makeUnsafe: (
open?: boolean | undefined
) => Latch
Creates a Latch synchronously, outside of Effect.
When to use
Use when you need to allocate a Latch synchronously outside an Effect
workflow.
Details
The latch starts closed by default; pass true to create it open.
Example (Creating a latch unsafely)
import { Effect, Latch } from "effect"
const latch = Latch.makeUnsafe(false)
const waiter = Effect.gen(function*() {
yield* Effect.log("Waiting for latch to open...")
yield* latch.await
yield* Effect.log("Latch opened! Continuing...")
})
const opener = Effect.gen(function*() {
yield* Effect.sleep("2 seconds")
yield* Effect.log("Opening latch...")
yield* latch.open
})
const program = Effect.all([waiter, opener])
makeUnsafe(false)
return new var ReadableStream: new <A>(underlyingSource: UnderlyingDefaultSource<A>, strategy?: QueuingStrategy<A> | undefined) => ReadableStream<A> (+2 overloads)ReadableStream<function (type parameter) A in <A, E, XR, R extends XR>(self: Stream<A, E, R>, context: Context.Context<XR>, options?: {
readonly strategy?: QueuingStrategy<A> | undefined;
}): ReadableStream<A>
UnderlyingDefaultSource<A>.start?: ((controller: ReadableStreamDefaultController<A>) => any) | undefinedstart(controller: ReadableStreamDefaultController<A>controller) {
let fiber:
| Fiber.Fiber<void, E>
| undefined
import EffectEffect.const runFork: <A, E>(
effect: Effect<A, E, never>,
options?: RunOptions | undefined
) => Fiber<A, E>
Runs an effect in the background, returning a fiber that can
be observed or interrupted.
When to use
Use when you need to start an effect in the background and receive a fiber.
Example (Running an effect in the background)
import { Console, Effect, Fiber, Schedule } from "effect"
// ┌─── Effect<number, never, never>
// ▼
const program = Effect.repeat(
Console.log("running..."),
Schedule.spaced("200 millis")
)
// ┌─── RuntimeFiber<number, never>
// ▼
const fiber = Effect.runFork(program)
setTimeout(() => {
Effect.runFork(Fiber.interrupt(fiber))
}, 500)
runFork(import EffectEffect.const provideContext: {
<XR>(context: Context.Context<XR>): <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E, Exclude<R, XR>>
<A, E, R, XR>(
self: Effect<A, E, R>,
context: Context.Context<XR>
): Effect<A, E, Exclude<R, XR>>
}
const runForEachArray: {
<A, X, E2, R2>(
f: (
a: Arr.NonEmptyReadonlyArray<A>
) => Effect.Effect<X, E2, R2>
): <E, R>(
self: Stream<A, E, R>
) => Effect.Effect<void, E2 | E, R2 | R>
<A, E, R, X, E2, R2>(
self: Stream<A, E, R>,
f: (
a: Arr.NonEmptyReadonlyArray<A>
) => Effect.Effect<X, E2, R2>
): Effect.Effect<void, 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; <…;
}
chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
const latch: Latch.Latchconst latch: {
open: Effect.Effect<boolean>;
openUnsafe: (this: Latch) => boolean;
release: Effect.Effect<boolean>;
await: Effect.Effect<void>;
close: Effect.Effect<boolean>;
closeUnsafe: (this: Latch) => boolean;
whenOpen: <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
isOpen: (this: Latch) => boolean;
}
Latch.whenOpen<A, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R>Runs the given effect only after the latch allows waiting fibers to
continue.
When to use
Use to gate an effect behind the latch signal.
whenOpen(import EffectEffect.const sync: <A>(
thunk: LazyArg<A>
) => Effect<A>
Creates an Effect that represents a synchronous side-effectful computation.
When to use
Use when you need to wrap a synchronous side-effectful operation that is not
expected to throw.
Details
The provided function is evaluated lazily when the effect runs.
Gotchas
The function must not throw. If it throws, the thrown value is treated as a
defect, not as a typed failure. Use try when throwing is expected.
Example (Capturing synchronous logging in an Effect)
import { Effect } from "effect"
const log = (message: string) =>
Effect.sync(() => {
console.log(message) // side effect
})
// ┌─── Effect<void, never, never>
// ▼
const program = log("Hello, World!")
sync(() => {
const latch: Latch.Latchconst latch: {
open: Effect.Effect<boolean>;
openUnsafe: (this: Latch) => boolean;
release: Effect.Effect<boolean>;
await: Effect.Effect<void>;
close: Effect.Effect<boolean>;
closeUnsafe: (this: Latch) => boolean;
whenOpen: <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
isOpen: (this: Latch) => boolean;
}
Latch.closeUnsafe(this: Latch): booleanCloses the latch synchronously so future waiters suspend again.
When to use
Use when synchronous code must close the latch immediately.
closeUnsafe()
for (let let i: numberi = 0; let i: numberi < chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
length: numberlength; let i: numberi++) {
controller: ReadableStreamDefaultController<A>controller.ReadableStreamDefaultController<A>.enqueue(chunk?: A | undefined): voidThe enqueue() method of the js-nolint enqueue(chunk) - chunk - : The chunk to enqueue.
enqueue(chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let i: numberi])
}
let currentResolve:
| (() => void)
| undefined
let currentResolve:
| (() => void)
| undefined
var undefinedundefined
}))),
context: Context.Context<XR>(parameter) context: {
mapUnsafe: ReadonlyMap<string, any>;
mutable: boolean;
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 fiber:
| Fiber.Fiber<void, E>
| undefined
let fiber: {
id: number;
currentOpCount: number;
getRef: <A>(ref: Context.Reference<A>) => A;
context: Context.Context<never>;
setContext: (context: Context.Context<never>) => void;
currentScheduler: Scheduler;
currentDispatcher: SchedulerDispatcher;
currentSpan: AnySpan | undefined;
currentLogLevel: LogLevel;
minimumLogLevel: LogLevel;
currentStackFrame: StackFrame | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
addObserver: (cb: (exit: Exit<A, E>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit<A, E> | undefined;
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; <…;
}
Fiber<void, E>.addObserver: (cb: (exit: Exit<A, E>) => void) => () => voidaddObserver((exit: Exit.Exit<void, E>exit) => {
if (exit: Exit.Exit<void, E>exit._tag: "Success" | "Failure"_tag === "Failure") {
controller: ReadableStreamDefaultController<A>controller.ReadableStreamDefaultController<A>.error(e?: any): voidThe error() method of the with the associated stream to error.
error(import CauseCause.const squash: <E>(
self: Cause<E>
) => unknown
Collapses a Cause into a single unknown value, picking the "most
important" failure in this order:
When to use
Use to collapse a structured cause to the single value that synchronous and
promise runners would throw.
Details
- First
Fail error (the E value)
- First
Die defect
- A generic
Error("All fibers interrupted without error") for interrupt-only causes
- A generic
Error("Empty cause") for empty
This is the function used by Effect.runPromise and Effect.runSync to
decide what to throw.
Gotchas
This function is lossy. Use
prettyErrors
or iterate cause.reasons
when you need all failures.
Example (Squashing a cause)
import { Cause } from "effect"
console.log(Cause.squash(Cause.fail("error"))) // "error"
console.log(Cause.squash(Cause.die("defect"))) // "defect"
squash(exit: Exit.Failure<void, E>(parameter) exit: {
_tag: "Failure";
cause: Cause.Cause<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;
}
Failure<void, E>.cause: Cause.Cause<E>(property) Failure<void, E>.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;
}
controller: ReadableStreamDefaultController<A>controller.ReadableStreamDefaultController<A>.close(): voidThe close() method of the ReadableStreamDefaultController interface closes the associated stream.
close()
}
})
},
UnderlyingDefaultSource<A>.pull?: ((controller: ReadableStreamDefaultController<A>) => void | PromiseLike<void>) | undefinedpull() {
return new var Promise: PromiseConstructor
new <void>(executor: (resolve: (value: void | PromiseLike<void>) => void, reject: (reason?: any) => void) => void) => Promise<void>
Creates a new Promise.
Promise<void>((resolve: (
value: void | PromiseLike<void>
) => void
let currentResolve:
| (() => void)
| undefined
resolve: (
value: void | PromiseLike<void>
) => void
const latch: Latch.Latchconst latch: {
open: Effect.Effect<boolean>;
openUnsafe: (this: Latch) => boolean;
release: Effect.Effect<boolean>;
await: Effect.Effect<void>;
close: Effect.Effect<boolean>;
closeUnsafe: (this: Latch) => boolean;
whenOpen: <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
isOpen: (this: Latch) => boolean;
}
Latch.openUnsafe(this: Latch): booleanOpens the latch synchronously, releasing all fibers waiting on it.
When to use
Use when synchronous code must open the latch immediately.
openUnsafe()
})
},
UnderlyingDefaultSource<A>.cancel?: UnderlyingSourceCancelCallback | undefinedcancel() {
if (!let fiber:
| Fiber.Fiber<void, E>
| undefined
import EffectEffect.const runPromise: <A, E>(
effect: Effect<A, E>,
options?: RunOptions | undefined
) => Promise<A>
Executes an effect and returns the result as a Promise.
When to use
Use when you need to execute an effect and work with the
result using Promise syntax, typically for compatibility with other
promise-based code.
If the effect succeeds, the promise will resolve with the result. If the
effect fails, the promise will reject with an error.
Example (Running a successful effect as a Promise)
import { Effect } from "effect"
Effect.runPromise(Effect.succeed(1)).then(console.log)
// Output: 1
Example (Running effects as promises)
//Example: Handling a Failing Effect as a Rejected Promise
import { Effect } from "effect"
Effect.runPromise(Effect.fail("my error")).catch(console.error)
// Output:
// (FiberFailure) Error: my error
runPromise(import EffectEffect.const asVoid: <A, E, R>(
self: Effect<A, E, R>
) => Effect<void, E, R>
Maps the success value of an Effect to void, preserving failures.
Example (Discarding success values)
import { Effect } from "effect"
const program = Effect.asVoid(Effect.succeed(42))
Effect.runPromise(program).then(console.log)
// undefined (void)
asVoid(import FiberFiber.const interrupt: <A, E>(
self: Fiber<A, E>
) => Effect<void>
Interrupts a fiber, causing it to stop executing and clean up any
acquired resources.
When to use
Use when you need to cancel a forked fiber and wait for its cleanup to
complete.
Details
The returned Effect completes only after the interrupted fiber has completed.
Gotchas
Interruption is cooperative. A fiber can continue running while it is inside
uninterruptible work or finalizers.
Example (Interrupting a fiber)
import { Effect, Fiber } from "effect"
const program = Effect.gen(function*() {
const fiber = yield* Effect.forkChild(
Effect.delay("1 second")(Effect.succeed(42))
)
yield* Fiber.interrupt(fiber)
console.log("Fiber interrupted")
})
interrupt(let fiber:
| Fiber.Fiber<void, E>
| undefined
let fiber: {
id: number;
currentOpCount: number;
getRef: <A>(ref: Context.Reference<A>) => A;
context: Context.Context<never>;
setContext: (context: Context.Context<never>) => void;
currentScheduler: Scheduler;
currentDispatcher: SchedulerDispatcher;
currentSpan: AnySpan | undefined;
currentLogLevel: LogLevel;
minimumLogLevel: LogLevel;
currentStackFrame: StackFrame | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
addObserver: (cb: (exit: Exit<A, E>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit<A, E> | undefined;
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; <…;
}
options: | {
readonly strategy?:
| QueuingStrategy<A>
| undefined
}
| undefined
strategy?: QueuingStrategy<A> | undefinedstrategy)
}
)Referenced by 2 symbols