<A, X, E2, R2>(
f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>,
options?:
| { readonly concurrency?: number | "unbounded" | undefined }
| undefined
): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
<A, E, R, X, E2, R2>(
self: Stream<A, E, R>,
f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>,
options?:
| { readonly concurrency?: number | "unbounded" | undefined }
| undefined
): Stream<A, E | E2, R | R2>Runs the provided effect for each element while preserving the elements.
Example (Tapping stream values)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const result = yield* Stream.fromArray([1, 2, 3]).pipe(
Stream.tap((n) => Console.log(`before mapping: ${n}`)),
Stream.map((n) => n * 2),
Stream.tap((n) => Console.log(`after mapping: ${n}`)),
Stream.runCollect
)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output:
// before mapping: 1
// after mapping: 2
// before mapping: 2
// after mapping: 4
// before mapping: 3
// after mapping: 6
// [ 2, 4, 6 ]export const const tap: {
<A, X, E2, R2>(
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined
): <E, R>(
self: Stream<A, E, R>
) => Stream<A, E2 | E, R2 | R>
<A, E, R, X, E2, R2>(
self: Stream<A, E, R>,
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>,
options?:
| {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined
): Stream<A, E | E2, R | R2>
}
Runs the provided effect for each element while preserving the elements.
Example (Tapping stream values)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const result = yield* Stream.fromArray([1, 2, 3]).pipe(
Stream.tap((n) => Console.log(`before mapping: ${n}`)),
Stream.map((n) => n * 2),
Stream.tap((n) => Console.log(`after mapping: ${n}`)),
Stream.runCollect
)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output:
// before mapping: 1
// after mapping: 2
// before mapping: 2
// after mapping: 4
// before mapping: 3
// after mapping: 6
// [ 2, 4, 6 ]
tap: {
<function (type parameter) A in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) X in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) E2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) R2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>
a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | 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) X in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) E2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) R2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | undefined
} | undefined
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A, 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, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A, 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) A in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) E2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>E, function (type parameter) R2 in <A, X, E2, R2>(f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): <E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<A, E2 | E, R2 | R>R>
<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, 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, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>
a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | 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) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | 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) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
dual<(...args: Array<any>) => any, <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined) => Stream<A, E | E2, R | R2>>(isDataFirst: (args: IArguments) => boolean, body: <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined) => Stream<A, E | E2, R | R2>): ((...args: Array<any>) => any) & (<A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined) => Stream<A, 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, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, 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, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>
a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | 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) X in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined
concurrency?: number | "unbounded" | undefinedconcurrency?: number | "unbounded" | 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) A in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) E2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
function (type parameter) R2 in <A, E, R, X, E2, R2>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => Effect.Effect<X, E2, R2>, options?: {
readonly concurrency?: number | "unbounded" | undefined;
} | undefined): Stream<A, E | E2, R | R2>
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>
}
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; <…;
}
a: Aa) => import EffectEffect.const as: {
<B>(value: B): <A, E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
value: B
): Effect<B, E, R>
}
f: (
a: NoInfer<A>
) => Effect.Effect<X, E2, R2>
a: Aa), a: Aa),
options: | {
readonly concurrency?:
| number
| "unbounded"
| undefined
}
| undefined