<A, K>(f: (a: NoInfer<A>) => K): <E, R>(
self: Stream<A, E, R>
) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>
<A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<
readonly [K, Arr.NonEmptyArray<A>],
E,
R
>Groups consecutive elements that have equal keys into non-empty arrays.
When to use
Use when you already have a stream ordered by the grouping key and want to emit each consecutive run as a non-empty array while keeping later non-adjacent runs separate.
Details
The key is computed with f; adjacent elements whose keys are equal by
Equal.equals are emitted as one [key, group]. Later non-adjacent runs
with the same key are emitted separately.
Source effect/Stream.ts:845553 lines
export const const groupAdjacentBy: {
<A, K>(f: (a: NoInfer<A>) => K): <E, R>(
self: Stream<A, E, R>
) => Stream<
readonly [K, Arr.NonEmptyArray<A>],
E,
R
>
<A, E, R, K>(
self: Stream<A, E, R>,
f: (a: NoInfer<A>) => K
): Stream<
readonly [K, Arr.NonEmptyArray<A>],
E,
R
>
}
Groups consecutive elements that have equal keys into non-empty arrays.
When to use
Use when you already have a stream ordered by the grouping key and want to
emit each consecutive run as a non-empty array while keeping later
non-adjacent runs separate.
Details
The key is computed with f; adjacent elements whose keys are equal by
Equal.equals are emitted as one [key, group]. Later non-adjacent runs
with the same key are emitted separately.
groupAdjacentBy: {
<function (type parameter) A in <A, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) K in <A, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K>(
f: (a: NoInfer<A>) => Kf: (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, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>) => function (type parameter) K in <A, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K
): <function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], 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, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], 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<readonly [function (type parameter) K in <A, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K, import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, K>(f: (a: NoInfer<A>) => K): <E, R>(self: Stream<A, E, R>) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>], function (type parameter) E in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <E, R>(self: Stream<A, E, R>): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R>
<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R, function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K>(
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, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R>,
f: (a: NoInfer<A>) => Kf: (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, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>) => function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K
): 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<readonly [function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K, import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>], function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R>
} = dual<(...args: Array<any>) => any, <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>>(arity: 2, body: <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K) => Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>): ((...args: Array<any>) => any) & (<A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K) => Stream<readonly [K, Arr.NonEmptyArray<A>], 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, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R, function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K>(
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, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A, function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R>,
f: (a: NoInfer<A>) => Kf: (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, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>) => function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K
): 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<readonly [function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K, import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>], function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E, function (type parameter) R in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>R> =>
const transformPull: <
A,
E,
R,
B,
E2,
R2,
EX,
RX
>(
self: Stream<A, E, R>,
f: (
pull: Pull.Pull<
Arr.NonEmptyReadonlyArray<A>,
E,
void
>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<
Arr.NonEmptyReadonlyArray<B>,
E2,
void,
R2
>,
EX,
RX
>
) => Stream<
B,
EX | Pull.ExcludeDone<E2>,
R | R2 | RX
>
Derives a stream by transforming its pull effect.
Example (Transforming a pull effect)
import { Console, Effect, Stream } from "effect"
const stream = Stream.make(1, 2, 3)
const transformed = Stream.transformPull(stream, (pull) => Effect.succeed(pull))
const program = Effect.gen(function*() {
const values = yield* Stream.runCollect(transformed)
yield* Console.log(values)
})
Effect.runPromise(program)
// Output: [ 1, 2, 3 ]
transformPull(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; <…;
}
pull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
never
>
(parameter) pull: {
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;
}
_scope: Scope.Scope(parameter) _scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const sync: <A>(
thunk: LazyArg<A>
) => Effect<A>
Creates an Effect that represents a synchronous side-effectful computation.
When to use
Use when you need to wrap a synchronous side-effectful operation that is not
expected to throw.
Details
The provided function is evaluated lazily when the effect runs.
Gotchas
The function must not throw. If it throws, the thrown value is treated as a
defect, not as a typed failure. Use try when throwing is expected.
Example (Capturing synchronous logging in an Effect)
import { Effect } from "effect"
const log = (message: string) =>
Effect.sync(() => {
console.log(message) // side effect
})
// ┌─── Effect<void, never, never>
// ▼
const program = log("Hello, World!")
sync(() => {
let let currentKey: KcurrentKey: function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K = var undefinedundefined as any
let let group:
| Arr.NonEmptyArray<A>
| undefined
import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A> | undefined
let let toEmit: (readonly [K, [A, ...A[]]])[]toEmit = import ArrArr.const empty: <readonly [K, [A, ...A[]]]>() => (readonly [K, [A, ...A[]]])[]Creates an empty array.
When to use
Use to create a typed empty array without allocating placeholder elements.
Example (Creating an empty array)
import { Array } from "effect"
const result = Array.empty<number>()
console.log(result) // []
empty<readonly [function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K, import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>]>()
const const loop: Pull.Pull<
Arr.NonEmptyReadonlyArray<
readonly [K, Arr.NonEmptyArray<A>]
>,
E
>
const loop: {
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 PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<
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<readonly [function (type parameter) K in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>K, import ArrArr.type NonEmptyArray<A> = [A, ...A[]]A mutable array guaranteed to have at least one element.
When to use
Use when mutation is acceptable and non-emptiness must be tracked at the type
level.
Details
This is the mutable counterpart of
NonEmptyReadonlyArray
. Most Array
module functions return NonEmptyArray when the result is guaranteed
non-empty.
Example (Typing a mutable non-empty array)
import type { Array } from "effect"
const nonEmpty: Array.NonEmptyArray<number> = [1, 2, 3]
nonEmpty.push(4)
NonEmptyArray<function (type parameter) A in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>A>]>,
function (type parameter) E in <A, E, R, K>(self: Stream<A, E, R>, f: (a: NoInfer<A>) => K): Stream<readonly [K, Arr.NonEmptyArray<A>], E, R>E
> = pull: Pull.Pull<
readonly [A, ...A[]],
E,
void,
never
>
(parameter) pull: {
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<Pull.Pull<readonly [A, ...A[]], E, void, never>, Effect.Effect<readonly [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]], Cause.Done<void> | E, never>>(this: Pull.Pull<readonly [A, ...A[]], E, void, never>, ab: (_: Pull.Pull<readonly [A, ...A[]], E, void, never>) => Effect.Effect<readonly [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]], Cause.Done<void> | E, never>): Effect.Effect<readonly [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]], Cause.Done<void> | E, never> (+21 overloads)pipe(
import EffectEffect.const flatMap: {
<A, B, E1, R1>(
f: (a: A) => Effect<B, E1, R1>
): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E1 | E, R1 | R>
<A, E, R, B, E1, R1>(
self: Effect<A, E, R>,
f: (a: A) => Effect<B, E1, R1>
): Effect<B, E | E1, R | R1>
}
chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let i: numberi = 0; let i: numberi < chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
length: numberlength; let i: numberi++) {
const const item: Aitem = chunk: readonly [A, ...A[]](parameter) chunk: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
slice: (start?: number, end?: number) => Array<A>;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): this is readonly S[]; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: ReadonlyArray<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: ReadonlyArray<A>) => A, initialValue: A): A; (callbac…;
find: { (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
entries: () => ArrayIterator<[number, A]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<A>;
includes: (searchElement: A, fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: A, index: number, array: Array<A>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => A | undefined;
findLast: { (predicate: (value: A, index: number, array: ReadonlyArray<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: ReadonlyArray<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let i: numberi]
const const key: Kkey = f: (a: NoInfer<A>) => Kf(const item: Aitem)
if (let group:
| Arr.NonEmptyArray<A>
| undefined
var undefinedundefined) {
let currentKey: KcurrentKey = const key: Kkey
let group:
| Arr.NonEmptyArray<A>
| undefined
const item: Aitem]
continue
} else if (import EqualEqual.function equals<K, K>(self: K, that: K): boolean (+1 overload)Checks whether two values are deeply structurally equal.
When to use
Use when you need Effect's default structural equality check.
Details
Returns a boolean and never throws. Primitives are compared by value, and
NaN equals NaN. Objects implementing Equal delegate to their
[Equal.symbol] method; if only one operand implements Equal, the result
is false.
Dates compare by ISO string, RegExps compare by string representation,
arrays compare element-by-element, Maps and Sets compare entries
order-independently, and plain objects compare enumerable keys recursively.
Functions without an Equal implementation compare by reference. Circular
references are handled when both structures are circular at the same depth.
Hash values are checked first as a fast-path rejection. The function also
supports dual data-last usage: call it with one argument to get a curried
predicate.
Gotchas
- Results are cached per object pair in a WeakMap. Objects must not be
mutated after their first comparison.
- Map and Set comparisons are O(n²) in size.
Example (Comparing values)
import { Equal } from "effect"
// Primitives
console.log(Equal.equals(1, 1)) // true
console.log(Equal.equals(NaN, NaN)) // true
console.log(Equal.equals("a", "b")) // false
// Objects and arrays
console.log(Equal.equals({ a: 1, b: 2 }, { a: 1, b: 2 })) // true
console.log(Equal.equals([1, [2, 3]], [1, [2, 3]])) // true
// Dates
console.log(Equal.equals(new Date("2024-01-01"), new Date("2024-01-01"))) // true
// Maps (order-independent)
const m1 = new Map([["a", 1], ["b", 2]])
const m2 = new Map([["b", 2], ["a", 1]])
console.log(Equal.equals(m1, m2)) // true
// Curried form
const is5 = Equal.equals(5)
console.log(is5(5)) // true
console.log(is5(3)) // false
equals(const key: Kkey, let currentKey: KcurrentKey)) {
let group:
| Arr.NonEmptyArray<A>
| undefined
let group: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => A | undefined;
push: (...items: Array<A>) => number;
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
reverse: () => Array<A>;
shift: () => A | undefined;
slice: (start?: number, end?: number) => Array<A>;
sort: (compareFn?: ((a: A, b: A) => number) | undefined) => [A, ...A[]];
splice: { (start: number, deleteCount?: number): Array<A>; (start: number, deleteCount: number, ...items: Array<A>): Array<A> };
unshift: (...items: Array<A>) => number;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): this is S[]; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: Array<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: Array<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
find: { (predicate: (value: A, index: number, obj: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any) => number;
fill: (value: A, start?: number, end?: number) => [A, ...A[]];
copyWithin: (target: number, start: number, end?: number) => [A, ...A[]];
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: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: Array<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>;
}
Array<A>.push(...items: A[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const item: Aitem)
continue
}
let toEmit: (readonly [K, [A, ...A[]]])[]toEmit.Array<readonly [K, [A, ...A[]]]>.push(...items: (readonly [K, [A, ...A[]]])[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push([let currentKey: KcurrentKey, let group:
| Arr.NonEmptyArray<A>
| undefined
let group: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => A | undefined;
push: (...items: Array<A>) => number;
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
reverse: () => Array<A>;
shift: () => A | undefined;
slice: (start?: number, end?: number) => Array<A>;
sort: (compareFn?: ((a: A, b: A) => number) | undefined) => [A, ...A[]];
splice: { (start: number, deleteCount?: number): Array<A>; (start: number, deleteCount: number, ...items: Array<A>): Array<A> };
unshift: (...items: Array<A>) => number;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): this is S[]; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: Array<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: Array<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
find: { (predicate: (value: A, index: number, obj: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any) => number;
fill: (value: A, start?: number, end?: number) => [A, ...A[]];
copyWithin: (target: number, start: number, end?: number) => [A, ...A[]];
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: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any) => number;
toReversed: () => Array<A>;
toSorted: (compareFn?: ((a: A, b: A) => number) | undefined) => Array<A>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<A>): Array<A>; (start: number, deleteCount?: number): Array<A> };
with: (index: number, value: A) => Array<A>;
}
let currentKey: KcurrentKey = const key: Kkey
let group:
| Arr.NonEmptyArray<A>
| undefined
const item: Aitem]
}
if (import ArrArr.const isArrayNonEmpty: <A>(
self: Array<A>
) => self is NonEmptyArray<A>
Checks whether a mutable Array is non-empty, narrowing the type to
NonEmptyArray.
When to use
Use when you need the narrowed value to remain a mutable Array after proving
it has at least one element.
Example (Checking for a non-empty array)
import { Array } from "effect"
console.log(Array.isArrayNonEmpty([])) // false
console.log(Array.isArrayNonEmpty([1, 2, 3])) // true
isArrayNonEmpty(let toEmit: (readonly [K, [A, ...A[]]])[]toEmit)) {
const const out: [
readonly [K, [A, ...A[]]],
...(readonly [K, [A, ...A[]]])[]
]
const out: {
0: readonly [K, [A, ...A[]]];
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => readonly [K, [A, ...A[]]] | undefined;
push: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
concat: { (...items: Array<ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]>; (...items: Array<readonly [K, [A, ...A[]]] | ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]> };
join: (separator?: string) => string;
reverse: () => Array<readonly [K, [A, ...A[]]]>;
shift: () => readonly [K, [A, ...A[]]] | undefined;
slice: (start?: number, end?: number) => Array<readonly [K, [A, ...A[]]]>;
sort: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
splice: { (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]> };
unshift: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
indexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
lastIndexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
every: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): this is S[]; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A…;
some: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => void, thisArg?: any) => void;
map: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): Array<S>; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, .…;
reduce: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
reduceRight: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
find: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, …;
findIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
fill: (value: readonly [K, [A, ...A[]]], start?: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
copyWithin: (target: number, start: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
entries: () => ArrayIterator<[number, readonly [K, [A, ...A[]]]]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<readonly [K, [A, ...A[]]]>;
includes: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => readonly [K, [A, ...A[]]] | undefined;
findLast: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, …;
findLastIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
toReversed: () => Array<readonly [K, [A, ...A[]]]>;
toSorted: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => Array<readonly [K, [A, ...A[]]]>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]> };
with: (index: number, value: readonly [K, [A, ...A[]]]) => Array<readonly [K, [A, ...A[]]]>;
}
let toEmit: [
readonly [K, [A, ...A[]]],
...(readonly [K, [A, ...A[]]])[]
]
let toEmit: {
0: readonly [K, [A, ...A[]]];
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => readonly [K, [A, ...A[]]] | undefined;
push: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
concat: { (...items: Array<ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]>; (...items: Array<readonly [K, [A, ...A[]]] | ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]> };
join: (separator?: string) => string;
reverse: () => Array<readonly [K, [A, ...A[]]]>;
shift: () => readonly [K, [A, ...A[]]] | undefined;
slice: (start?: number, end?: number) => Array<readonly [K, [A, ...A[]]]>;
sort: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
splice: { (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]> };
unshift: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
indexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
lastIndexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
every: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): this is S[]; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A…;
some: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => void, thisArg?: any) => void;
map: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): Array<S>; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, .…;
reduce: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
reduceRight: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
find: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, …;
findIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
fill: (value: readonly [K, [A, ...A[]]], start?: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
copyWithin: (target: number, start: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
entries: () => ArrayIterator<[number, readonly [K, [A, ...A[]]]]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<readonly [K, [A, ...A[]]]>;
includes: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => readonly [K, [A, ...A[]]] | undefined;
findLast: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, …;
findLastIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
toReversed: () => Array<readonly [K, [A, ...A[]]]>;
toSorted: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => Array<readonly [K, [A, ...A[]]]>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]> };
with: (index: number, value: readonly [K, [A, ...A[]]]) => Array<readonly [K, [A, ...A[]]]>;
}
let toEmit: (readonly [K, [A, ...A[]]])[]toEmit = []
return import EffectEffect.const succeed: <A>(value: A) => Effect<A>Creates an Effect that always succeeds with a given value.
When to use
Use when an effect should complete successfully with a specific value without any errors
or external dependencies.
Example (Creating a successful effect)
import { Effect } from "effect"
// Creating an effect that represents a successful scenario
//
// ┌─── Effect<number, never, never>
// ▼
const success = Effect.succeed(42)
succeed(const out: [
readonly [K, [A, ...A[]]],
...(readonly [K, [A, ...A[]]])[]
]
const out: {
0: readonly [K, [A, ...A[]]];
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => readonly [K, [A, ...A[]]] | undefined;
push: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
concat: { (...items: Array<ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]>; (...items: Array<readonly [K, [A, ...A[]]] | ConcatArray<readonly [K, [A, ...A[]]]>>): Array<readonly [K, [A, ...A[]]]> };
join: (separator?: string) => string;
reverse: () => Array<readonly [K, [A, ...A[]]]>;
shift: () => readonly [K, [A, ...A[]]] | undefined;
slice: (start?: number, end?: number) => Array<readonly [K, [A, ...A[]]]>;
sort: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
splice: { (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]> };
unshift: (...items: Array<readonly [K, [A, ...A[]]]>) => number;
indexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
lastIndexOf: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => number;
every: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): this is S[]; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A…;
some: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => void, thisArg?: any) => void;
map: (callbackfn: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): Array<S>; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, .…;
reduce: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
reduceRight: { (callbackfn: (previousValue: readonly [K, [A, ...A[]]], currentValue: readonly [K, [A, ...A[]]], currentIndex: number, array: Array<readonly [K, [A, ...A[]]]>) => readonly [K, [A, ...A[]]]): readonly [K, [A, ...A[]]]; (callbackfn: (previ…;
find: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, …;
findIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, obj: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
fill: (value: readonly [K, [A, ...A[]]], start?: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
copyWithin: (target: number, start: number, end?: number) => [readonly [K, [A, ...A[]]], ...(readonly [K, [A, ...A[]]])[]];
entries: () => ArrayIterator<[number, readonly [K, [A, ...A[]]]]>;
keys: () => ArrayIterator<number>;
values: () => ArrayIterator<readonly [K, [A, ...A[]]]>;
includes: (searchElement: readonly [K, [A, ...A[]]], fromIndex?: number) => boolean;
flatMap: (callback: (this: This, value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => U | ReadonlyArray<U>, thisArg?: This | undefined) => Array<U>;
flat: (this: A, depth?: D | undefined) => Array<FlatArray<A, D>>;
at: (index: number) => readonly [K, [A, ...A[]]] | undefined;
findLast: { (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => value is S, thisArg?: any): S | undefined; (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, …;
findLastIndex: (predicate: (value: readonly [K, [A, ...A[]]], index: number, array: Array<readonly [K, [A, ...A[]]]>) => unknown, thisArg?: any) => number;
toReversed: () => Array<readonly [K, [A, ...A[]]]>;
toSorted: (compareFn?: ((a: readonly [K, [A, ...A[]]], b: readonly [K, [A, ...A[]]]) => number) | undefined) => Array<readonly [K, [A, ...A[]]]>;
toSpliced: { (start: number, deleteCount: number, ...items: Array<readonly [K, [A, ...A[]]]>): Array<readonly [K, [A, ...A[]]]>; (start: number, deleteCount?: number): Array<readonly [K, [A, ...A[]]]> };
with: (index: number, value: readonly [K, [A, ...A[]]]) => Array<readonly [K, [A, ...A[]]]>;
}
const loop: Pull.Pull<
Arr.NonEmptyReadonlyArray<
readonly [K, Arr.NonEmptyArray<A>]
>,
E
>
const loop: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
let done: booleandone = false
return import PullPull.const catchDone: {
<E, A2, E2, R2>(
f: (
leftover: Cause.Done.Extract<E>
) => Effect<A2, E2, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A | A2, ExcludeDone<E> | E2, R | R2>
<A, R, E, A2, E2, R2>(
self: Effect<A, E, R>,
f: (
leftover: Cause.Done.Extract<E>
) => Effect<A2, E2, R2>
): Effect<A | A2, ExcludeDone<E> | E2, R | R2>
}
import EffectEffect.const suspend: <A, E, R>(
effect: LazyArg<Effect<A, E, R>>
) => Effect<A, E, R>
Creates an Effect lazily, delaying construction until it is needed.
When to use
Use when you need to defer the evaluation of an effect until it is required.
Details
suspend takes a thunk that represents an effect and delays creating it
until the suspended effect is evaluated. This is useful for optimizing
expensive computations, managing circular dependencies such as recursive
functions, and helping TypeScript unify return types when branches construct
different effects. Any side effects or scoped captures inside the thunk are
re-executed on each invocation.
Example (Lazily evaluating side effects)
import { Effect } from "effect"
let i = 0
const bad = Effect.succeed(i++)
const good = Effect.suspend(() => Effect.succeed(i++))
console.log(Effect.runSync(bad)) // Output: 0
console.log(Effect.runSync(bad)) // Output: 0
console.log(Effect.runSync(good)) // Output: 1
console.log(Effect.runSync(good)) // Output: 2
Example (Suspending recursive Fibonacci evaluation)
import { Effect } from "effect"
const blowsUp = (n: number): Effect.Effect<number> =>
n < 2
? Effect.succeed(1)
: Effect.zipWith(blowsUp(n - 1), blowsUp(n - 2), (a, b) => a + b)
// console.log(Effect.runSync(blowsUp(32)))
// crash: JavaScript heap out of memory
const allGood = (n: number): Effect.Effect<number> =>
n < 2
? Effect.succeed(1)
: Effect.zipWith(
Effect.suspend(() => allGood(n - 1)),
Effect.suspend(() => allGood(n - 2)),
(a, b) => a + b
)
console.log(Effect.runSync(allGood(32)))
// Output: 3524578
Example (Helping TypeScript infer recursive effect types)
import { Effect } from "effect"
// Without suspend, TypeScript may struggle with type inference.
// Inferred type:
// (a: number, b: number) =>
// Effect<never, Error, never> | Effect<number, never, never>
const withoutSuspend = (a: number, b: number) =>
b === 0
? Effect.fail(new Error("Cannot divide by zero"))
: Effect.succeed(a / b)
// Using suspend to unify return types.
// Inferred type:
// (a: number, b: number) => Effect<number, Error, never>
const withSuspend = (a: number, b: number) =>
Effect.suspend(() =>
b === 0
? Effect.fail(new Error("Cannot divide by zero"))
: Effect.succeed(a / b)
)
suspend(() => let done: booleandone ? import CauseCause.const done: <A = void>(
value?: A
) => Effect.Effect<never, Done<A>>
Creates an Effect that fails with a Done error. Shorthand for
Effect.fail(Cause.Done(value)).
When to use
Use when you model stream or queue completion through the error channel.
Example (Failing with Done)
import { Cause, Effect } from "effect"
const program = Cause.done("finished")
Effect.runPromiseExit(program).then((exit) => {
console.log(exit._tag) // "Failure"
})
done() : const loop: Pull.Pull<
Arr.NonEmptyReadonlyArray<
readonly [K, Arr.NonEmptyArray<A>]
>,
E
>
const loop: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
let done: booleandone = true
const const out: [A, ...A[]] | undefinedout = let group:
| Arr.NonEmptyArray<A>
| undefined
let group:
| Arr.NonEmptyArray<A>
| undefined
var undefinedundefined
return const out: [A, ...A[]] | undefinedout && import ArrArr.const isArrayNonEmpty: <A>(
self: Array<A>
) => self is NonEmptyArray<A>
Checks whether a mutable Array is non-empty, narrowing the type to
NonEmptyArray.
When to use
Use when you need the narrowed value to remain a mutable Array after proving
it has at least one element.
Example (Checking for a non-empty array)
import { Array } from "effect"
console.log(Array.isArrayNonEmpty([])) // false
console.log(Array.isArrayNonEmpty([1, 2, 3])) // true
isArrayNonEmpty(const out: [A, ...A[]]const out: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => A | undefined;
push: (...items: Array<A>) => number;
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
reverse: () => Array<A>;
shift: () => A | undefined;
slice: (start?: number, end?: number) => Array<A>;
sort: (compareFn?: ((a: A, b: A) => number) | undefined) => [A, ...A[]];
splice: { (start: number, deleteCount?: number): Array<A>; (start: number, deleteCount: number, ...items: Array<A>): Array<A> };
unshift: (...items: Array<A>) => number;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): this is S[]; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: Array<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: Array<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
find: { (predicate: (value: A, index: number, obj: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any) => number;
fill: (value: A, start?: number, end?: number) => [A, ...A[]];
copyWithin: (target: number, start: number, end?: number) => [A, ...A[]];
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: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: Array<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 EffectEffect.const succeed: <A>(value: A) => Effect<A>Creates an Effect that always succeeds with a given value.
When to use
Use when an effect should complete successfully with a specific value without any errors
or external dependencies.
Example (Creating a successful effect)
import { Effect } from "effect"
// Creating an effect that represents a successful scenario
//
// ┌─── Effect<number, never, never>
// ▼
const success = Effect.succeed(42)
succeed(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([let currentKey: KcurrentKey, const out: [A, ...A[]]const out: {
0: A;
length: number;
toString: () => string;
toLocaleString: { (): string; (locales: string | string[], options?: Intl.NumberFormatOptions & Intl.DateTimeFormatOptions): string };
pop: () => A | undefined;
push: (...items: Array<A>) => number;
concat: { (...items: Array<ConcatArray<A>>): Array<A>; (...items: Array<A | ConcatArray<A>>): Array<A> };
join: (separator?: string) => string;
reverse: () => Array<A>;
shift: () => A | undefined;
slice: (start?: number, end?: number) => Array<A>;
sort: (compareFn?: ((a: A, b: A) => number) | undefined) => [A, ...A[]];
splice: { (start: number, deleteCount?: number): Array<A>; (start: number, deleteCount: number, ...items: Array<A>): Array<A> };
unshift: (...items: Array<A>) => number;
indexOf: (searchElement: A, fromIndex?: number) => number;
lastIndexOf: (searchElement: A, fromIndex?: number) => number;
every: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): this is S[]; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): boolean };
some: (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any) => boolean;
forEach: (callbackfn: (value: A, index: number, array: Array<A>) => void, thisArg?: any) => void;
map: (callbackfn: (value: A, index: number, array: Array<A>) => U, thisArg?: any) => Array<U>;
filter: { (predicate: (value: A, index: number, array: Array<A>) => value is S, thisArg?: any): Array<S>; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): Array<A> };
reduce: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
reduceRight: { (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A): A; (callbackfn: (previousValue: A, currentValue: A, currentIndex: number, array: Array<A>) => A, initialValue: A): A; (callbackfn: (previousVa…;
find: { (predicate: (value: A, index: number, obj: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any): A | undefined };
findIndex: (predicate: (value: A, index: number, obj: Array<A>) => unknown, thisArg?: any) => number;
fill: (value: A, start?: number, end?: number) => [A, ...A[]];
copyWithin: (target: number, start: number, end?: number) => [A, ...A[]];
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: Array<A>) => value is S, thisArg?: any): S | undefined; (predicate: (value: A, index: number, array: Array<A>) => unknown, thisArg?: any): A | undefined };
findLastIndex: (predicate: (value: A, index: number, array: Array<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 CauseCause.const done: <A = void>(
value?: A
) => Effect.Effect<never, Done<A>>
Creates an Effect that fails with a Done error. Shorthand for
Effect.fail(Cause.Done(value)).
When to use
Use when you model stream or queue completion through the error channel.
Example (Failing with Done)
import { Cause, Effect } from "effect"
const program = Cause.done("finished")
Effect.runPromiseExit(program).then((exit) => {
console.log(exit._tag) // "Failure"
})
done()
})
})))