<
const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>,
E,
A1,
E1,
R1,
A2 = unassigned,
E2 = never,
R2 = never
>(
k: K,
f: (
e: ExtractTag<
NoInfer<E>,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
) => Stream<A1, E1, R1>,
orElse?:
| ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
) => Stream<A2, E2, R2>)
| undefined
): <A, R>(
self: Stream<A, E, R>
) => Stream<
A | A1 | Exclude<A2, unassigned>,
| E1
| E2
| (A2 extends unassigned
? ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
: never),
R | R1 | R2
>
<
A,
E,
R,
const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>,
R1,
E1,
A1,
A2 = unassigned,
E2 = never,
R2 = never
>(
self: Stream<A, E, R>,
k: K,
f: (
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
) => Stream<A1, E1, R1>,
orElse?:
| ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
) => Stream<A2, E2, R2>)
| undefined
): Stream<
A | A1 | Exclude<A2, unassigned>,
| E1
| E2
| (A2 extends unassigned
? ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K
>
: never),
R | R1 | R2
>Recovers from failures whose _tag matches the provided value by switching to
the stream returned by f.
When to use
Use when you need to handle a specific error case from a stream whose error
type is a tagged union with a readonly _tag field.
Example (Catching tagged failures)
import { Console, Data, Effect, Stream } from "effect"
class HttpError extends Data.TaggedError("HttpError")<{ message: string }> {}
const stream = Stream.fail(new HttpError({ message: "timeout" }))
const recovered = Stream.catchTag(stream, "HttpError", (error) =>
Stream.make(`Recovered: ${error.message}`)
)
const program = Effect.gen(function*() {
const values = yield* Stream.runCollect(recovered)
yield* Console.log(values)
// Output: [ "Recovered: timeout" ]
})
Effect.runPromise(program)error handling
Source effect/Stream.ts:527379 lines
export const const catchTag: {
<
K extends
| Tags<E>
| Arr.NonEmptyReadonlyArray<Tags<E>>,
E,
A1,
E1,
R1,
A2 = unassigned,
E2 = never,
R2 = never
>(
k: K,
f: (
e: ExtractTag<
NoInfer<E>,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>,
orElse?:
| ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined
): <A, R>(
self: Stream<A, E, R>
) => Stream<
A | A1 | Exclude<A2, unassigned>,
| E1
| E2
| (A2 extends unassigned
? ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
: never),
R | R1 | R2
>
<
A,
E,
R,
K extends
| Tags<E>
| Arr.NonEmptyReadonlyArray<Tags<E>>,
R1,
E1,
A1,
A2 = unassigned,
E2 = never,
R2 = never
>(
self: Stream<A, E, R>,
k: K,
f: (
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>,
orElse?:
| ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined
): Stream<
A | A1 | Exclude<A2, unassigned>,
| E1
| E2
| (A2 extends unassigned
? ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
: never),
R | R1 | R2
>
}
Recovers from failures whose _tag matches the provided value by switching to
the stream returned by f.
When to use
Use when you need to handle a specific error case from a stream whose error
type is a tagged union with a readonly _tag field.
Example (Catching tagged failures)
import { Console, Data, Effect, Stream } from "effect"
class HttpError extends Data.TaggedError("HttpError")<{ message: string }> {}
const stream = Stream.fail(new HttpError({ message: "timeout" }))
const recovered = Stream.catchTag(stream, "HttpError", (error) =>
Stream.make(`Recovered: ${error.message}`)
)
const program = Effect.gen(function*() {
const values = yield* Stream.runCollect(recovered)
yield* Console.log(values)
// Output: [ "Recovered: timeout" ]
})
Effect.runPromise(program)
catchTag: {
<
const function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E> | import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E>>,
function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E,
function (type parameter) A1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1,
function (type parameter) E1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1,
function (type parameter) R1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1,
function (type parameter) A2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2 = unassigned,
function (type parameter) E2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2 = never,
function (type parameter) R2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2 = never
>(
k: const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>k: function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K,
f: (
e: ExtractTag<
NoInfer<E>,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>
e: ExtractTag<
NoInfer<E>,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<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) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E>, function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>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<function (type parameter) A1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1, function (type parameter) E1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1, function (type parameter) R1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1>,
orElse: | ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>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<function (type parameter) A2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2, function (type parameter) E2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2, function (type parameter) R2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2>)
| undefined
): <function (type parameter) A in <A, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A, function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>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, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A, function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R>
) => interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<
function (type parameter) A in <A, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A | function (type parameter) A1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1 | type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) A2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2, unassigned>,
| function (type parameter) E1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1
| function (type parameter) E2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2
| (function (type parameter) A2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2 extends unassigned ? type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K> : never),
function (type parameter) R in <A, R>(self: Stream<A, E, R>): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R | function (type parameter) R1 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1 | function (type parameter) R2 in <const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, E, A1, E1, R1, A2 = unassigned, E2 = never, R2 = never>(k: K, f: (e: ExtractTag<NoInfer<E>, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): <A, R>(self: Stream<A, E, R>) => Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2
>
<
function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A,
function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E,
function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R,
const function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E> | import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E>>,
function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1,
function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1,
function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1,
function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2 = unassigned,
function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2 = never,
function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2 = never
>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A, function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R>,
k: const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>k: function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K,
f: (
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>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<function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1, function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1, function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1>,
orElse: | ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>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<function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2, function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2, function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2>)
| undefined
): interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<
function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A | function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A1 | type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2, unassigned>,
| function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E1
| function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E2
| (function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>A2 extends unassigned ? type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>K> : never),
function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R | function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R1 | function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = unassigned, E2 = never, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A | A1 | Exclude<A2, unassigned>, E1 | E2 | (A2 extends unassigned ? ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K> : never), R | R1 | R2>R2
>
} = import dualdual(
(args: anyargs) => 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: anyargs[0]),
<
function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A,
function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E,
function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R,
const function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K extends type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E> | import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E>>,
function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R1,
function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E1,
function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A1,
function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A2 = never,
function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E2 = type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K>,
function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R2 = never
>(
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A, function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E, function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R>,
k: const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>k: function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K,
f: (
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>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<function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A1, function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E1, function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R1>,
orElse: | ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
type ExcludeTag<E, K extends string> = E extends {
readonly _tag: K;
} ? never : E
Excludes members of a tagged union by their _tag value.
When to use
Use to remove tagged-union members whose _tag matches a specific value in
type-level code.
Details
Non-tagged members of the union are preserved.
Example (Removing a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type WithoutTimeout = Types.ExcludeTag<MyError, "Timeout">
// { readonly _tag: "NotFound"; readonly id: string } | string
ExcludeTag<function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E, function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K extends import ArrArr.type Arr.NonEmptyReadonlyArray = /*unresolved*/ anyNonEmptyReadonlyArray<string> ? function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>K[number] : function (type parameter) K in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>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<function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A2, function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E2, function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R2>)
| undefined
): interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A1 | function (type parameter) A in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A | function (type parameter) A2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>A2, function (type parameter) E1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E1 | function (type parameter) E2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E2, function (type parameter) R1 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R1 | function (type parameter) R in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R | function (type parameter) R2 in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>R2> => {
const const pred: anypred = var Array: ArrayConstructorArray.ArrayConstructor.isArray(arg: any): arg is any[]isArray(k: const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>k)
? ((e: Ee: function (type parameter) E in <A, E, R, const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>, R1, E1, A1, A2 = never, E2 = ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>, R2 = never>(self: Stream<A, E, R>, k: K, f: (e: ExtractTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A1, E1, R1>, orElse?: ((e: ExcludeTag<E, K extends Arr.NonEmptyReadonlyArray<string> ? K[number] : K>) => Stream<A2, E2, R2>) | undefined): Stream<A1 | A | A2, E1 | E2, R1 | R | R2>E): e: Ee is any => import hasPropertyhasProperty(e: Ee, "_tag") && k: K & any[]k.includes(e: Ee._tag))
: import isTaggedisTagged(k: const K extends Tags<E> | Arr.NonEmptyReadonlyArray<Tags<E>>k as string)
return const catchIf: {
<
E,
EB extends E,
A2,
E2,
R2,
A3 = unassigned,
E3 = never,
R3 = never
>(
refinement: Refinement<NoInfer<E>, EB>,
f: (e: EB) => Stream<A2, E2, R2>,
orElse?:
| ((
e: Exclude<E, EB>
) => Stream<A3, E3, R3>)
| undefined
): <A, R>(
self: Stream<A, E, R>
) => Stream<
A | A2 | Exclude<A3, unassigned>,
| E2
| E3
| (A3 extends unassigned
? Exclude<E, EB>
: never),
R | R2 | R3
>
<
E,
A2,
E2,
R2,
A3 = unassigned,
E3 = never,
R3 = never
>(
predicate: Predicate<NoInfer<E>>,
f: (e: NoInfer<E>) => Stream<A2, E2, R2>,
orElse?:
| ((e: NoInfer<E>) => Stream<A3, E3, R3>)
| undefined
): <A, R>(
self: Stream<A, E, R>
) => Stream<
A | A2 | Exclude<A3, unassigned>,
E2 | E3 | (A3 extends unassigned ? E : never),
R | R2 | R3
>
<
A,
E,
R,
EB extends E,
A2,
E2,
R2,
A3 = unassigned,
E3 = never,
R3 = never
>(
self: Stream<A, E, R>,
refinement: Refinement<E, EB>,
f: (e: EB) => Stream<A2, E2, R2>,
orElse?:
| ((
e: Exclude<E, EB>
) => Stream<A3, E3, R3>)
| undefined
): Stream<
A | A2 | Exclude<A3, unassigned>,
| E2
| E3
| (A3 extends unassigned
? Exclude<E, EB>
: never),
R | R2 | R3
>
<
A,
E,
R,
A2,
E2,
R2,
A3 = unassigned,
E3 = never,
R3 = never
>(
self: Stream<A, E, R>,
predicate: Predicate<E>,
f: (e: E) => Stream<A2, E2, R2>,
orElse?:
| ((e: E) => Stream<A3, E3, R3>)
| undefined
): Stream<
A | A2 | Exclude<A3, unassigned>,
E2 | E3 | (A3 extends unassigned ? E : never),
R | R2 | R3
>
}
self: Stream<A, E, R>(parameter) self: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
const pred: anypred, f: (
e: ExtractTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A1, E1, R1>
orElse: | ((
e: ExcludeTag<
E,
K extends Arr.NonEmptyReadonlyArray<string>
? K[number]
: K
>
) => Stream<A2, E2, R2>)
| undefined