<S, A, B>(
initial: LazyArg<S>,
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>],
options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined
}
): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
<A, E, R, S, B>(
self: Stream<A, E, R>,
initial: LazyArg<S>,
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>],
options?: { readonly onHalt?: ((state: S) => Array<B>) | undefined }
): Stream<B, E, R>Maps over non-empty chunk arrays statefully, emitting zero or more values per chunk.
Details
The mapping function runs once per chunk and the state is threaded across chunks.
Example (Statefully mapping stream chunks)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const output = yield* Stream.make(1, 2, 3, 4, 5, 6).pipe(
Stream.rechunk(2),
Stream.mapAccumArray(() => 0, (sum: number, chunk) => {
const next = chunk.reduce((acc, n) => acc + n, sum)
return [next, [next]]
}),
Stream.runCollect
)
yield* Console.log(output)
})
Effect.runPromise(program)
// Output: [ 3, 10, 21 ]mapping
Source effect/Stream.ts:750141 lines
export const const mapAccumArray: {
<S, A, B>(
initial: LazyArg<S>,
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [
state: S,
values: ReadonlyArray<B>
],
options?: {
readonly onHalt?:
| ((state: S) => ReadonlyArray<B>)
| undefined
}
): <E, R>(
self: Stream<A, E, R>
) => Stream<B, E, R>
<A, E, R, S, B>(
self: Stream<A, E, R>,
initial: LazyArg<S>,
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [
state: S,
values: ReadonlyArray<B>
],
options?: {
readonly onHalt?:
| ((state: S) => Array<B>)
| undefined
}
): Stream<B, E, R>
}
Maps over non-empty chunk arrays statefully, emitting zero or more values per chunk.
Details
The mapping function runs once per chunk and the state is threaded across chunks.
Example (Statefully mapping stream chunks)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const output = yield* Stream.make(1, 2, 3, 4, 5, 6).pipe(
Stream.rechunk(2),
Stream.mapAccumArray(() => 0, (sum: number, chunk) => {
const next = chunk.reduce((acc, n) => acc + n, sum)
return [next, [next]]
}),
Stream.runCollect
)
yield* Console.log(output)
})
Effect.runPromise(program)
// Output: [ 3, 10, 21 ]
mapAccumArray: {
<function (type parameter) S in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
function (type parameter) A in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
function (type parameter) B in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
initial: LazyArg<S>initial: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>]
s: Ss: function (type parameter) S in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
a: Arr.NonEmptyReadonlyArray<A>(parameter) a: {
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>;
}
import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
Sstate: function (type parameter) S in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
readonly B[]values: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) B in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
options: | {
readonly onHalt?:
| ((state: S) => ReadonlyArray<B>)
| undefined
}
| undefined
onHalt?: | ((state: S) => ReadonlyArray<B>)
| undefined
state: Sstate: function (type parameter) S in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
interface ReadonlyArray<T>ReadonlyArray<function (type parameter) B in <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
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 <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
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 <S, A, B>(initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): <E, R>(self: Stream<A, E, R>) => Stream<B, E, R>
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, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, 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, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
initial: LazyArg<S>initial: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>]
s: Ss: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
a: Arr.NonEmptyReadonlyArray<A>(parameter) a: {
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>;
}
import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
Sstate: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
readonly B[]values: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
options: | {
readonly onHalt?:
| ((state: S) => Array<B>)
| undefined
}
| undefined
onHalt?: ((state: S) => Array<B>) | undefinedonHalt?: ((state: Sstate: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
interface Array<T>Array<function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, 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, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => Array<B>) | undefined;
}): Stream<B, E, R>
dual<(...args: Array<any>) => any, <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}) => Stream<B, E, R>>(isDataFirst: (args: IArguments) => boolean, body: <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}) => Stream<B, E, R>): ((...args: Array<any>) => any) & (<A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}) => 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((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, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, 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, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
initial: LazyArg<S>initial: type LazyArg<A> = () => AA zero-argument function that produces a value when invoked.
When to use
Use to type a lazy value provider that should not run until called.
Example (Creating a lazy argument)
import { Function } from "effect"
const constNull: Function.LazyArg<null> = Function.constant(null)
LazyArg<function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>]
s: Ss: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
a: Arr.NonEmptyReadonlyArray<A>(parameter) a: {
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>;
}
import ArrArr.type NonEmptyReadonlyArray<A> = readonly [
A,
...A[]
]
A readonly array guaranteed to have at least one element.
When to use
Use when non-emptiness must be tracked at the type level while preventing mutation.
Many Array module functions accept or return this type.
Example (Typing a non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyReadonlyArray<number> = [1, 2, 3]
const head: number = nonEmpty[0] // guaranteed to exist
NonEmptyReadonlyArray<function (type parameter) A in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
Sstate: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
readonly B[]values: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
options: | {
readonly onHalt?:
| ((state: S) => ReadonlyArray<B>)
| undefined
}
| undefined
onHalt?: | ((state: S) => ReadonlyArray<B>)
| undefined
state: Sstate: function (type parameter) S in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
interface ReadonlyArray<T>ReadonlyArray<function (type parameter) B in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, 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, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) E in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
function (type parameter) R in <A, E, R, S, B>(self: Stream<A, E, R>, initial: LazyArg<S>, f: (s: S, a: Arr.NonEmptyReadonlyArray<A>) => readonly [state: S, values: ReadonlyArray<B>], options?: {
readonly onHalt?: ((state: S) => ReadonlyArray<B>) | undefined;
}): Stream<B, E, R>
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 mapAccum: {
<S, OutElem, B, E = never, R = never>(
initial: LazyArg<S>,
f: (
s: S,
a: Types.NoInfer<OutElem>
) =>
| Effect.Effect<
readonly [
state: S,
values: ReadonlyArray<B>
],
E,
R
>
| readonly [
state: S,
values: ReadonlyArray<B>
],
options?: {
readonly onHalt?:
| ((state: S) => Array<B>)
| undefined
}
): <
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
B,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Env | R
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
S,
B,
E = never,
R = never
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
initial: LazyArg<S>,
f: (
s: S,
a: Types.NoInfer<OutElem>
) =>
| Effect.Effect<
readonly [
state: S,
values: ReadonlyArray<B>
],
E,
R
>
| readonly [
state: S,
values: ReadonlyArray<B>
],
options?: {
readonly onHalt?:
| ((state: S) => Array<B>)
| undefined
}
): Channel<
B,
OutErr | E,
OutDone,
InElem,
InErr,
InDone,
Env | 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; <…;
}
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; <…;
}
initial: LazyArg<S>initial,
(state: Sstate, arr: readonly [A, ...A[]](parameter) arr: {
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 newState: SnewState, const values: readonly B[]values] = f: (
s: S,
a: Arr.NonEmptyReadonlyArray<A>
) => readonly [state: S, values: ReadonlyArray<B>]
state: Sstate, arr: readonly [A, ...A[]](parameter) arr: {
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>;
}
state: Sstate = const newState: SnewState
return [state: Sstate, import ArrArr.const isReadonlyArrayNonEmpty: <A>(
self: ReadonlyArray<A>
) => self is NonEmptyReadonlyArray<A>
Checks whether a ReadonlyArray is non-empty, narrowing the type to
NonEmptyReadonlyArray.
When to use
Use when you need to prove a readonly array has at least one element without
requiring mutable array methods afterward.
Example (Checking for a non-empty readonly array)
import { Array } from "effect"
console.log(Array.isReadonlyArrayNonEmpty([])) // false
console.log(Array.isReadonlyArrayNonEmpty([1, 2, 3])) // true
isReadonlyArrayNonEmpty(const values: readonly B[]values) ? import ArrArr.const of: <A>(a: A) => NonEmptyArray<A>Wraps a single value in a NonEmptyArray.
Example (Creating a single-element array)
import { Array } from "effect"
console.log(Array.of(1)) // [1]
of(const values: readonly [B, ...B[]]const values: {
0: B;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<B>>): Array<B>; (...items: Array<B | ConcatArray<B>>): Array<B> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<B>;
indexOf: (searchElement: B, fromIndex?: number) => number;
lastIndexOf: (searchElement: B, fromIndex?: number) => number;
every: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: B, index: number, array: ReadonlyArray<B>) => void, thisArg?: any) => void;
map: (callbackfn: (value: B, index: number, array: ReadonlyArray<B>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): Array<S>; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): Array<B> };
reduce: { (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B): B; (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B, initialValue: B): B; (callbac…;
reduceRight: { (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B): B; (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B, initialValue: B): B; (callbac…;
find: { (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => value is S, thisArg?: any): S | undefined; (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => unknown, thisArg?: any): B | undefined };
findIndex: (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, B]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<B>;
includes: (searchElement: B, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: B, index: number, array: Array<B>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => B | undefined;
findLast: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): S | undefined; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): B | undefined };
findLastIndex: (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any) => number;
toReversed: () => Array<B>;
toSorted: (compareFn?: ((a: B, b: B) => number) | undefined) => Array<B>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<B>): Array<B>; (start: number, deleteCount?: number): Array<B> };
with: (index: number, value: B) => Array<B>;
}
const emptyArr: never[]emptyArr]
},
options: | {
readonly onHalt?:
| ((state: S) => ReadonlyArray<B>)
| undefined
}
| undefined
onHalt?: | ((state: S) => ReadonlyArray<B>)
| undefined
onHalt?: | ((state: S) => (readonly [B, ...B[]])[])
| undefined
state: Sstate) {
const const arr: readonly B[]arr = options: {
readonly onHalt?:
| ((state: S) => ReadonlyArray<B>)
| undefined
}
onHalt?: | ((state: S) => ReadonlyArray<B>)
| undefined
state: Sstate)
return import ArrArr.const isReadonlyArrayNonEmpty: <A>(
self: ReadonlyArray<A>
) => self is NonEmptyReadonlyArray<A>
Checks whether a ReadonlyArray is non-empty, narrowing the type to
NonEmptyReadonlyArray.
When to use
Use when you need to prove a readonly array has at least one element without
requiring mutable array methods afterward.
Example (Checking for a non-empty readonly array)
import { Array } from "effect"
console.log(Array.isReadonlyArrayNonEmpty([])) // false
console.log(Array.isReadonlyArrayNonEmpty([1, 2, 3])) // true
isReadonlyArrayNonEmpty(const arr: readonly B[]arr) ? import ArrArr.const of: <A>(a: A) => NonEmptyArray<A>Wraps a single value in a NonEmptyArray.
Example (Creating a single-element array)
import { Array } from "effect"
console.log(Array.of(1)) // [1]
of(const arr: readonly [B, ...B[]]const arr: {
0: B;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<B>>): Array<B>; (...items: Array<B | ConcatArray<B>>): Array<B> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<B>;
indexOf: (searchElement: B, fromIndex?: number) => number;
lastIndexOf: (searchElement: B, fromIndex?: number) => number;
every: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: B, index: number, array: ReadonlyArray<B>) => void, thisArg?: any) => void;
map: (callbackfn: (value: B, index: number, array: ReadonlyArray<B>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): Array<S>; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): Array<B> };
reduce: { (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B): B; (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B, initialValue: B): B; (callbac…;
reduceRight: { (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B): B; (callbackfn: (previousValue: B, currentValue: B, currentIndex: number, array: ReadonlyArray<B>) => B, initialValue: B): B; (callbac…;
find: { (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => value is S, thisArg?: any): S | undefined; (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => unknown, thisArg?: any): B | undefined };
findIndex: (predicate: (value: B, index: number, obj: ReadonlyArray<B>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, B]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<B>;
includes: (searchElement: B, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: B, index: number, array: Array<B>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => B | undefined;
findLast: { (predicate: (value: B, index: number, array: ReadonlyArray<B>) => value is S, thisArg?: any): S | undefined; (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any): B | undefined };
findLastIndex: (predicate: (value: B, index: number, array: ReadonlyArray<B>) => unknown, thisArg?: any) => number;
toReversed: () => Array<B>;
toSorted: (compareFn?: ((a: B, b: B) => number) | undefined) => Array<B>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<B>): Array<B>; (start: number, deleteCount?: number): Array<B> };
with: (index: number, value: B) => Array<B>;
}
const emptyArr: never[]emptyArr
}
} :
var undefinedundefined
)))Referenced by 6 symbols