<OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): <OutElem, OutErr, InElem, InErr, InDone, Env>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>
) => Channel<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env1 | Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>,
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): Channel<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env1 | Env
>Runs a fallback channel if this channel completes without emitting any output elements.
Details
If the source emits at least one element, the source is used unchanged. If the source completes before emitting an element, the fallback function receives the source done value and returns the replacement channel.
sequencing
Source effect/Channel.ts:273494 lines
export const const orElseIfEmpty: {
<
OutDone,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): <
OutElem,
OutErr,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env1 | Env
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): Channel<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env1 | Env
>
}
Runs a fallback channel if this channel completes without emitting any
output elements.
Details
If the source emits at least one element, the source is used unchanged. If
the source completes before emitting an element, the fallback function
receives the source done value and returns the replacement channel.
orElseIfEmpty: {
<function (type parameter) OutDone in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone, function (type parameter) OutElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1, function (type parameter) OutErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1, function (type parameter) OutDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1, function (type parameter) InElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1, function (type parameter) InErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1, function (type parameter) InDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1, function (type parameter) Env1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1>(
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
leftover: Types.NoInfer<OutDone>leftover: import TypesTypes.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) OutDone in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone>) => interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1, function (type parameter) OutErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1, function (type parameter) OutDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1, function (type parameter) InElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1, function (type parameter) InErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1, function (type parameter) InDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1, function (type parameter) Env1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1>
): <function (type parameter) OutElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem, function (type parameter) OutErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr, function (type parameter) InElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem, function (type parameter) InErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr, function (type parameter) InDone in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone, function (type parameter) Env in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
(parameter) self: {
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 Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem, function (type parameter) OutErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr, function (type parameter) OutDone in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone, function (type parameter) InElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem, function (type parameter) InErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr, function (type parameter) InDone in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone, function (type parameter) Env in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env>
) => interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<
function (type parameter) OutElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem | function (type parameter) OutElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1,
function (type parameter) OutErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1 | function (type parameter) OutErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr,
function (type parameter) OutDone in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone | function (type parameter) OutDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1,
function (type parameter) InElem in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem & function (type parameter) InElem1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1,
function (type parameter) InErr in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr & function (type parameter) InErr1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1,
function (type parameter) InDone in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone & function (type parameter) InDone1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1,
function (type parameter) Env1 in <OutDone, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1 | function (type parameter) Env in <OutElem, OutErr, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env
>
<
function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem,
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr,
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone,
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem,
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr,
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone,
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env,
function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1,
function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1,
function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1,
function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1,
function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1,
function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1,
function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
(parameter) self: {
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 Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone, function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem, function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr, function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone, function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env>,
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
leftover: Types.NoInfer<OutDone>leftover: import TypesTypes.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) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone>) => interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1, function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1, function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1, function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1, function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1, function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1, function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1>
): interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<
function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem | function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1,
function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1 | function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr,
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone | function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1,
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem & function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1,
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr & function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1,
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone & function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1,
function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1 | function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env
>
} = dual<(...args: Array<any>) => any, <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>>(arity: 2, body: <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>): ((...args: Array<any>) => any) & (<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(2, <
function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem,
function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr,
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone,
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem,
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr,
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone,
function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env,
function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1,
function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1,
function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1,
function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1,
function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1,
function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1,
function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
(parameter) self: {
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 Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem, function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone, function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem, function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr, function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone, function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env>,
f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
leftover: Types.NoInfer<OutDone>leftover: import TypesTypes.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) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone>) => interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1, function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1, function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1, function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1, function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1, function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1, function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1>
): interface Channel<out OutElem, out OutErr = never, out OutDone = void, in InElem = unknown, in InErr = unknown, in InDone = unknown, out Env = never>A Channel is a nexus of I/O operations, which supports both reading and
writing. A channel may read values of type InElem and write values of type
OutElem. When the channel finishes, it yields a value of type OutDone. A
channel may fail with a value of type OutErr.
Details
Channels are the foundation of Streams: both streams and sinks are built on
channels. Most users shouldn't have to use channels directly, as streams and
sinks are much more convenient and cover all common use cases. However, when
adding new stream and sink operators, or doing something highly specialized,
it may be useful to use channels directly.
Channels compose in a variety of ways:
- Piping: One channel can be piped to another channel, assuming the
input type of the second is the same as the output type of the first.
- Sequencing: The terminal value of one channel can be used to create
another channel, and both the first channel and the function that makes
the second channel can be composed into a channel.
- Concatenating: The output of one channel can be used to create other
channels, which are all concatenated together. The first channel and the
function that makes the other channels can be composed into a channel.
Example (Typing channels)
import type { Channel } from "effect"
// A channel that outputs numbers and requires no environment
type NumberChannel = Channel.Channel<number>
// A channel that outputs strings, can fail with Error, completes with boolean
type StringChannel = Channel.Channel<string, Error, boolean>
// A channel with all type parameters specified
type FullChannel = Channel.Channel<
string, // OutElem - output elements
Error, // OutErr - output errors
number, // OutDone - completion value
number, // InElem - input elements
string, // InErr - input errors
boolean, // InDone - input completion
{ db: string } // Env - required environment
>
Channel<
function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem | function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1,
function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1 | function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr,
function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone | function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1,
function (type parameter) InElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem & function (type parameter) InElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InElem1,
function (type parameter) InErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr & function (type parameter) InErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InErr1,
function (type parameter) InDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone & function (type parameter) InDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>InDone1,
function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1 | function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env
> =>
const fromTransform: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
EX,
EnvX,
Env
>(
transform: (
upstream: Pull.Pull<InElem, InErr, InDone>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone, EnvX>,
EX,
Env
>
) => Channel<
OutElem,
Pull.ExcludeDone<OutErr> | EX,
OutDone,
InElem,
InErr,
InDone,
Env | EnvX
>
Creates a Channel from a transformation function that operates on upstream pulls.
Example (Creating channels from transforms)
import { Channel, Effect } from "effect"
const channel = Channel.fromTransform((upstream, scope) =>
Effect.succeed(upstream)
)
fromTransform((upstream: Pull.Pull<
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
never
>
(parameter) upstream: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const sync: <A>(
thunk: LazyArg<A>
) => Effect<A>
Creates an Effect that represents a synchronous side-effectful computation.
When to use
Use when you need to wrap a synchronous side-effectful operation that is not
expected to throw.
Details
The provided function is evaluated lazily when the effect runs.
Gotchas
The function must not throw. If it throws, the thrown value is treated as a
defect, not as a typed failure. Use try when throwing is expected.
Example (Capturing synchronous logging in an Effect)
import { Effect } from "effect"
const log = (message: string) =>
Effect.sync(() => {
console.log(message) // side effect
})
// ┌─── Effect<void, never, never>
// ▼
const program = log("Hello, World!")
sync(() => {
let let currentPull:
| Pull.Pull<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
Env1 | Env
>
| undefined
import PullPull.interface Pull<out A, out E = never, out Done = void, out R = never>An effectful pull step that either produces a value, fails with E, or
signals completion with Cause.Done<Done>.
When to use
Use to model one low-level pull step when a consumer repeatedly evaluates an
effect that may emit a value, fail normally, or signal normal completion
through Cause.Done.
Details
Pull represents completion in the error channel so low-level stream
consumers can distinguish ordinary failures from end-of-input and carry a
leftover value when needed.
Pull<function (type parameter) OutElem in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem | function (type parameter) OutElem1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutElem1, function (type parameter) OutErr1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr1 | function (type parameter) OutErr in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutErr, function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone | function (type parameter) OutDone1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone1, function (type parameter) Env1 in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env1 | function (type parameter) Env in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>Env> | undefined
const const forkedScope: Scope.Closeableconst forkedScope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import ScopeScope.const forkUnsafe: (
scope: Scope,
finalizerStrategy?: "sequential" | "parallel"
) => Closeable
Creates a closeable child scope synchronously and registers it with a parent scope.
When to use
Use when a child scope must be created synchronously and the caller controls
both parent and child scope lifetimes.
Details
Closing the parent closes the child with the same exit value, and closing the
child detaches it from the parent. The optional finalizer strategy configures
the child scope and defaults to "sequential" when omitted.
Example (Creating a child scope synchronously)
import { Console, Effect, Exit, Scope } from "effect"
const program = Effect.gen(function*() {
const parentScope = Scope.makeUnsafe("sequential")
const childScope = Scope.forkUnsafe(parentScope, "parallel")
// Add finalizers to both scopes
yield* Scope.addFinalizer(parentScope, Console.log("Parent cleanup"))
yield* Scope.addFinalizer(childScope, Console.log("Child cleanup"))
// Close child first, then parent
yield* Scope.close(childScope, Exit.void)
yield* Scope.close(parentScope, Exit.void)
})
forkUnsafe(scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
const makePull: Effect.Effect<
OutElem | OutElem1,
| OutErr1
| Cause.Done<OutDone1>
| Exclude<OutErr, Cause.Done<any>>,
Env | Env1
>
const makePull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const flatMap: {
<A, B, E1, R1>(
f: (a: A) => Effect<B, E1, R1>
): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E1 | E, R1 | R>
<A, E, R, B, E1, R1>(
self: Effect<A, E, R>,
f: (a: A) => Effect<B, E1, R1>
): Effect<B, E | E1, R | R1>
}
const toTransform: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
channel: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => (
upstream: Pull.Pull<InElem, InErr, InDone>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone>,
never,
Env
>
Converts a Channel back to its underlying transformation function.
Example (Extracting channel transforms)
import { Channel } from "effect"
const channel = Channel.succeed(42)
const transform = Channel.toTransform(channel)
// transform can now be used directly
toTransform(self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
(parameter) self: {
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; <…;
}
upstream: Pull.Pull<
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
never
>
(parameter) upstream: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const forkedScope: Scope.Closeableconst forkedScope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
pull: Pull.Pull<
OutElem,
OutErr,
OutDone,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const next: Effect.Effect<
OutElem | OutElem1,
| OutErr1
| Cause.Done<OutDone1>
| Exclude<OutErr, Cause.Done<any>>,
Env1
>
const next: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
pull: Pull.Pull<
OutElem,
OutErr,
OutDone,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Pipeable.pipe<Pull.Pull<OutElem, OutErr, OutDone, never>, Effect.Effect<OutElem, any, never>, Effect.Effect<OutElem | OutElem1, any, Env1>>(this: Pull.Pull<OutElem, OutErr, OutDone, never>, ab: (_: Pull.Pull<OutElem, OutErr, OutDone, never>) => Effect.Effect<OutElem, any, never>, bc: (_: Effect.Effect<OutElem, any, never>) => Effect.Effect<OutElem | OutElem1, any, Env1>): Effect.Effect<...> (+21 overloads)pipe(
import EffectEffect.const tap: {
<A, B, E2, R2>(
f: (a: NoInfer<A>) => Effect<B, E2, R2>
): <E, R>(
self: Effect<A, E, R>
) => Effect<A, E | E2, R | R2>
<B, E2, R2>(f: Effect<B, E2, R2>): <A, E, R>(
self: Effect<A, E, R>
) => Effect<A, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: (a: NoInfer<A>) => Effect<B, E2, R2>
): Effect<A, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: Effect<B, E2, R2>
): Effect<A, E | E2, R | R2>
}
let currentPull:
| Pull.Pull<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
Env1 | Env
>
| undefined
pull: Pull.Pull<
OutElem,
OutErr,
OutDone,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const void: Effect.Effect<void, never, never>(alias) const void: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Returns an effect that succeeds with void.
void
}),
import PullPull.const catchDone: {
<E, A2, E2, R2>(
f: (
leftover: Cause.Done.Extract<E>
) => Effect<A2, E2, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A | A2, ExcludeDone<E> | E2, R | R2>
<A, R, E, A2, E2, R2>(
self: Effect<A, E, R>,
f: (
leftover: Cause.Done.Extract<E>
) => Effect<A2, E2, R2>
): Effect<A | A2, ExcludeDone<E> | E2, R | R2>
}
leftover: Cause.Done.Extract<E>leftover) =>
import ScopeScope.const close: <A, E>(
self: Scope,
exit: Exit<A, E>
) => Effect<void>
Closes a scope and runs its registered finalizers.
When to use
Use to close a scope manually with a specific exit value.
Details
Finalizers run in the scope's configured order and receive the supplied
Exit.
Example (Running scope finalizers)
import { Console, Effect, Exit, Scope } from "effect"
const resourceManagement = Effect.gen(function*() {
const scope = yield* Scope.make("sequential")
// Add multiple finalizers
yield* Scope.addFinalizer(scope, Console.log("Close database connection"))
yield* Scope.addFinalizer(scope, Console.log("Close file handle"))
yield* Scope.addFinalizer(scope, Console.log("Release memory"))
// Do some work...
yield* Console.log("Performing operations...")
// Close scope - finalizers run in reverse order of registration
yield* Scope.close(scope, Exit.succeed("Success!"))
// Output: "Release memory", "Close file handle", "Close database connection"
})
close(const forkedScope: Scope.Closeableconst forkedScope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import ExitExit.const succeed: <A>(a: A) => Exit<A>Creates a successful Exit containing the given value.
When to use
Use when you need an Exit that contains a known success value.
Details
Returns a Success<A> with the provided value. Does not perform any
computation.
Example (Creating a successful Exit)
import { Exit } from "effect"
const exit = Exit.succeed(42)
console.log(Exit.isSuccess(exit)) // true
succeed(leftover: Cause.Done.Extract<E>leftover)).Pipeable.pipe<Effect.Effect<void, never, never>, Effect.Effect<Pull.Pull<OutElem1, OutErr1, OutDone1, never>, never, Env1>, Effect.Effect<OutElem1, any, Env1>>(this: Effect.Effect<...>, ab: (_: Effect.Effect<void, never, never>) => Effect.Effect<Pull.Pull<OutElem1, OutErr1, OutDone1, never>, never, Env1>, bc: (_: Effect.Effect<Pull.Pull<OutElem1, OutErr1, OutDone1, never>, never, Env1>) => Effect.Effect<...>): Effect.Effect<...> (+21 overloads)pipe(
import EffectEffect.const andThen: {
<A, B, E2, R2>(
f: (a: A) => Effect<B, E2, R2>
): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E | E2, R | R2>
<B, E2, R2>(f: Effect<B, E2, R2>): <A, E, R>(
self: Effect<A, E, R>
) => Effect<B, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: (a: A) => Effect<B, E2, R2>
): Effect<B, E | E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: Effect<B, E2, R2>
): Effect<B, E | E2, R | R2>
}
const toTransform: <
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>(
channel: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => (
upstream: Pull.Pull<InElem, InErr, InDone>,
scope: Scope.Scope
) => Effect.Effect<
Pull.Pull<OutElem, OutErr, OutDone>,
never,
Env
>
Converts a Channel back to its underlying transformation function.
Example (Extracting channel transforms)
import { Channel } from "effect"
const channel = Channel.succeed(42)
const transform = Channel.toTransform(channel)
// transform can now be used directly
toTransform(f: (
leftover: Types.NoInfer<OutDone>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
leftover: Cause.Done.Extract<E>leftover as function (type parameter) OutDone in <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (leftover: Types.NoInfer<OutDone>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr1 | OutErr, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env1 | Env>OutDone))(upstream: Pull.Pull<
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
never
>
(parameter) upstream: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
scope: Scope.Scope(parameter) scope: {
strategy: "sequential" | "parallel";
state: State.Open | State.Closed | State.Empty;
}
import EffectEffect.const flatMap: {
<A, B, E1, R1>(
f: (a: A) => Effect<B, E1, R1>
): <E, R>(
self: Effect<A, E, R>
) => Effect<B, E1 | E, R1 | R>
<A, E, R, B, E1, R1>(
self: Effect<A, E, R>,
f: (a: A) => Effect<B, E1, R1>
): Effect<B, E | E1, R | R1>
}
pull: Pull.Pull<
OutElem1,
OutErr1,
OutDone1,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
let currentPull:
| Pull.Pull<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
Env1 | Env
>
| undefined
pull: Pull.Pull<
OutElem1,
OutErr1,
OutDone1,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
pull: Pull.Pull<
OutElem1,
OutErr1,
OutDone1,
never
>
(parameter) pull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
let currentPull:
| Pull.Pull<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
Env1 | Env
>
| undefined
const next: Effect.Effect<
OutElem | OutElem1,
| OutErr1
| Cause.Done<OutDone1>
| Exclude<OutErr, Cause.Done<any>>,
Env1
>
const next: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
const next: Effect.Effect<
OutElem | OutElem1,
| OutErr1
| Cause.Done<OutDone1>
| Exclude<OutErr, Cause.Done<any>>,
Env1
>
const next: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.const suspend: <A, E, R>(
effect: LazyArg<Effect<A, E, R>>
) => Effect<A, E, R>
Creates an Effect lazily, delaying construction until it is needed.
When to use
Use when you need to defer the evaluation of an effect until it is required.
Details
suspend takes a thunk that represents an effect and delays creating it
until the suspended effect is evaluated. This is useful for optimizing
expensive computations, managing circular dependencies such as recursive
functions, and helping TypeScript unify return types when branches construct
different effects. Any side effects or scoped captures inside the thunk are
re-executed on each invocation.
Example (Lazily evaluating side effects)
import { Effect } from "effect"
let i = 0
const bad = Effect.succeed(i++)
const good = Effect.suspend(() => Effect.succeed(i++))
console.log(Effect.runSync(bad)) // Output: 0
console.log(Effect.runSync(bad)) // Output: 0
console.log(Effect.runSync(good)) // Output: 1
console.log(Effect.runSync(good)) // Output: 2
Example (Suspending recursive Fibonacci evaluation)
import { Effect } from "effect"
const blowsUp = (n: number): Effect.Effect<number> =>
n < 2
? Effect.succeed(1)
: Effect.zipWith(blowsUp(n - 1), blowsUp(n - 2), (a, b) => a + b)
// console.log(Effect.runSync(blowsUp(32)))
// crash: JavaScript heap out of memory
const allGood = (n: number): Effect.Effect<number> =>
n < 2
? Effect.succeed(1)
: Effect.zipWith(
Effect.suspend(() => allGood(n - 1)),
Effect.suspend(() => allGood(n - 2)),
(a, b) => a + b
)
console.log(Effect.runSync(allGood(32)))
// Output: 3524578
Example (Helping TypeScript infer recursive effect types)
import { Effect } from "effect"
// Without suspend, TypeScript may struggle with type inference.
// Inferred type:
// (a: number, b: number) =>
// Effect<never, Error, never> | Effect<number, never, never>
const withoutSuspend = (a: number, b: number) =>
b === 0
? Effect.fail(new Error("Cannot divide by zero"))
: Effect.succeed(a / b)
// Using suspend to unify return types.
// Inferred type:
// (a: number, b: number) => Effect<number, Error, never>
const withSuspend = (a: number, b: number) =>
Effect.suspend(() =>
b === 0
? Effect.fail(new Error("Cannot divide by zero"))
: Effect.succeed(a / b)
)
suspend(() => let currentPull:
| Pull.Pull<
OutElem | OutElem1,
OutErr1 | OutErr,
OutDone | OutDone1,
Env1 | Env
>
| undefined
const makePull: Effect.Effect<
OutElem | OutElem1,
| OutErr1
| Cause.Done<OutDone1>
| Exclude<OutErr, Cause.Done<any>>,
Env | Env1
>
const makePull: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Referenced by 1 symbols