<A, B>(f: (a: A, i: number) => B): <E, R>(
self: Stream<A, E, R>
) => Stream<B, E, R>
<A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<
B,
E,
R
>Transforms the elements of this stream using the supplied function.
Example (Mapping stream values)
import { Console, Effect, Stream } from "effect"
const stream = Stream.fromArray([1, 2, 3]).pipe(Stream.map((n, i) => n + i))
const program = Stream.runCollect(stream).pipe(
Effect.tap((values) => Console.log(values))
)
Effect.runPromise(program)
// [ 1, 3, 5 ]mapping
Source effect/Stream.ts:187811 lines
export const const map: {
<A, B>(f: (a: A, i: number) => B): <E, R>(
self: Stream<A, E, R>
) => Stream<B, E, R>
<A, E, R, B>(
self: Stream<A, E, R>,
f: (a: A, i: number) => B
): Stream<B, E, R>
}
Transforms the elements of this stream using the supplied function.
Example (Mapping stream values)
import { Console, Effect, Stream } from "effect"
const stream = Stream.fromArray([1, 2, 3]).pipe(Stream.map((n, i) => n + i))
const program = Stream.runCollect(stream).pipe(
Effect.tap((values) => Console.log(values))
)
Effect.runPromise(program)
// [ 1, 3, 5 ]
map: {
<function (type parameter) A in <A, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>A, function (type parameter) B in <A, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>B>(f: (a: A, i: number) => Bf: (a: Aa: function (type parameter) A in <A, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>A, i: numberi: number) => function (type parameter) B in <A, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>B): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<B, E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<B, E, 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, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<B, E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<B, E, 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) B in <A, B>(f: (a: A, i: number) => B): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>B, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<B, E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<B, E, R>R>
<function (type parameter) A in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R, function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B>(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, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R>, f: (a: A, i: number) => Bf: (a: Aa: function (type parameter) A in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, i: numberi: number) => function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B): 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) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R>
} = dual<(...args: Array<any>) => any, <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B) => Stream<B, E, R>>(arity: 2, body: <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B) => Stream<B, E, R>): ((...args: Array<any>) => any) & (<A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B) => Stream<B, E, R>) (+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, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R, function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B>(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, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R>, f: (a: A, i: number) => Bf: (a: Aa: function (type parameter) A in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>A, i: numberi: number) => function (type parameter) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B): 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) B in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>B, function (type parameter) E in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>E, function (type parameter) R in <A, E, R, B>(self: Stream<A, E, R>, f: (a: A, i: number) => B): Stream<B, E, R>R> =>
const suspend: <A, E, R>(
stream: LazyArg<Stream<A, E, R>>
) => Stream<A, E, R>
Creates a lazily constructed stream.
Details
The stream factory is evaluated each time the stream is run.
Example (Creating a lazily constructed stream)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const values = yield* Stream.suspend(() => Stream.make(1, 2, 3)).pipe(Stream.runCollect)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]
suspend(() => {
let let i: numberi = 0
return const fromChannel: <
Arr extends Arr.NonEmptyReadonlyArray<any>,
E,
R
>(
channel: Channel.Channel<
Arr,
E,
void,
unknown,
unknown,
unknown,
R
>
) => Stream<
Arr extends Arr.NonEmptyReadonlyArray<infer A>
? A
: never,
E,
R
>
Creates a stream from a array-emitting Channel.
Example (Creating a stream from an array-emitting channel)
import { Channel, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const channel = Channel.succeed([1, 2, 3] as const)
const stream = Stream.fromChannel(channel)
const result = yield* Stream.runCollect(stream)
yield* Console.log(result)
})
// Output: [ 1, 2, 3 ]
fromChannel(import ChannelChannel.const map: {
<OutElem, OutElem2>(
f: (o: OutElem, i: number) => OutElem2
): <
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem2,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem2
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
f: (o: OutElem, i: number) => OutElem2
): Channel<
OutElem2,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
}
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; <…;
}
import ArrArr.const map: <readonly [A, ...A[]], B>(f: (a: A, i: number) => B) => (self: readonly [A, ...A[]]) => [B, ...B[]] (+1 overload)map((o: Ao) => f: (a: A, i: number) => Bf(o: Ao, let i: numberi++))
))
}))Referenced by 14 symbols
Stream.bindStream.bindToStream.crossWithStream.decodeTextStream.encodeTextStream.mapBothStream.mergeResultStream.resultStream.zipLatestWithStream.zipWithIndexDynamicConfig.layer (hyperlink-ts)Hyperlink.mapSubscribable (hyperlink-ts)MultiNode.mergeNodeStreamsByNode (hyperlink-ts)NodeMultipart.stream (platform-node)