<EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(
self: Stream<A, E, R>
) => Stream<A, E | EX, R | RX>
<A, E, R, EX = never, RX = never>(
self: Stream<A, E, R>,
test: Effect.Effect<boolean, EX, RX>
): Stream<A, E | EX, R | RX>Returns the specified stream if the given condition is satisfied, otherwise returns an empty stream.
Example (Conditionally keeping a stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const result = yield* Stream.runCollect(
Stream.when(Stream.make(1, 2, 3), Effect.succeed(false))
)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output: []export const const when: {
<EX = never, RX = never>(
test: Effect.Effect<boolean, EX, RX>
): <A, E, R>(
self: Stream<A, E, R>
) => Stream<A, E | EX, R | RX>
<A, E, R, EX = never, RX = never>(
self: Stream<A, E, R>,
test: Effect.Effect<boolean, EX, RX>
): Stream<A, E | EX, R | RX>
}
Returns the specified stream if the given condition is satisfied, otherwise
returns an empty stream.
Example (Conditionally keeping a stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const result = yield* Stream.runCollect(
Stream.when(Stream.make(1, 2, 3), Effect.succeed(false))
)
yield* Console.log(result)
})
Effect.runPromise(program)
// Output: []
when: {
<function (type parameter) EX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>EX = never, function (type parameter) RX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>RX = never>(
test: Effect.Effect<boolean, EX, RX>(parameter) test: {
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.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<boolean, function (type parameter) EX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>EX, function (type parameter) RX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>RX>
): <function (type parameter) A in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>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, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>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, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>E | function (type parameter) EX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>EX, function (type parameter) R in <A, E, R>(self: Stream<A, E, R>): Stream<A, E | EX, R | RX>R | function (type parameter) RX in <EX = never, RX = never>(test: Effect.Effect<boolean, EX, RX>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E | EX, R | RX>RX>
<function (type parameter) A in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R, function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX = never, function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX = never>(
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, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R>,
test: Effect.Effect<boolean, EX, RX>(parameter) test: {
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.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<boolean, function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX, function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX>
): 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, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E | function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R | function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX>
} = dual<(...args: Array<any>) => any, <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>) => Stream<A, E | EX, R | RX>>(arity: 2, body: <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>) => Stream<A, E | EX, R | RX>): ((...args: Array<any>) => any) & (<A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>) => Stream<A, E | EX, R | RX>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(2, <function (type parameter) A in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R, function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX = never, function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX = never>(
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, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R>,
test: Effect.Effect<boolean, EX, RX>(parameter) test: {
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.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<boolean, function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX, function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX>
): 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, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>A, function (type parameter) E in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>E | function (type parameter) EX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>EX, function (type parameter) R in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>R | function (type parameter) RX in <A, E, R, EX = never, RX = never>(self: Stream<A, E, R>, test: Effect.Effect<boolean, EX, RX>): Stream<A, E | EX, R | RX>RX> =>
test: Effect.Effect<boolean, EX, RX>(parameter) test: {
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;
}
Pipeable.pipe<Effect.Effect<boolean, EX, RX>, Effect.Effect<Stream<A, E, R>, EX, RX>, Stream<A, E | EX, R | Exclude<RX, Scope.Scope>>>(this: Effect.Effect<...>, ab: (_: Effect.Effect<boolean, EX, RX>) => Effect.Effect<Stream<A, E, R>, EX, RX>, bc: (_: Effect.Effect<Stream<A, E, R>, EX, RX>) => Stream<A, E | EX, R | Exclude<RX, Scope.Scope>>): Stream<...> (+21 overloads)pipe(
import EffectEffect.const map: {
<A, B>(f: (a: A) => B): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E, R>
<A, E, R, B>(
self: Effect<A, E, R>,
f: (a: A) => B
): Effect<B, E, R>
}
pass: booleanpass) => pass: booleanpass ? 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; <…;
}
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),
const unwrap: <A, E2, R2, E, R>(
effect: Effect.Effect<Stream<A, E2, R2>, E, R>
) => Stream<
A,
E | E2,
R2 | Exclude<R, Scope.Scope>
>
Creates a stream produced from an Effect.
Example (Unwrapping a stream effect)
import { Console, Effect, Stream } from "effect"
const effect = Effect.succeed(Stream.make(1, 2, 3))
const stream = Stream.unwrap(effect)
const program = Effect.gen(function*() {
const chunk = yield* Stream.runCollect(stream)
yield* Console.log(chunk)
})
// [1, 2, 3]
unwrap
))