<OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(
predicate: Predicate.Predicate<Cause.Cause<OutErr>>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): <OutElem, OutDone, InElem, InErr, InDone, Env>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>
) => Channel<
OutElem | OutElem1,
OutErr | OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env | Env1
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>,
predicate: Predicate.Predicate<Cause.Cause<OutErr>>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): Channel<
OutElem | OutElem1,
OutErr | OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env | Env1
>Catches causes of failure that match a specific filter, allowing conditional error recovery based on the type of failure.
When to use
Use to recover a channel only when its full Cause satisfies a boolean
predicate.
Details
When the predicate matches, the recovery function receives the original cause. When it does not match, the returned channel fails with the original cause.
Source effect/Channel.ts:4086103 lines
export const const catchCauseIf: {
<
OutErr,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
predicate: Predicate.Predicate<
Cause.Cause<OutErr>
>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): <
OutElem,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem | OutElem1,
OutErr | OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env | Env1
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
predicate: Predicate.Predicate<
Cause.Cause<OutErr>
>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): Channel<
OutElem | OutElem1,
OutErr | OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env | Env1
>
}
Catches causes of failure that match a specific filter, allowing
conditional error recovery based on the type of failure.
When to use
Use to recover a channel only when its full Cause satisfies a boolean
predicate.
Details
When the predicate matches, the recovery function receives the original
cause. When it does not match, the returned channel fails with the original
cause.
catchCauseIf: {
<
function (type parameter) OutErr in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr,
function (type parameter) OutElem1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1,
function (type parameter) OutErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr1,
function (type parameter) OutDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone1,
function (type parameter) InElem1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem1,
function (type parameter) InErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr1,
function (type parameter) InDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone1,
function (type parameter) Env1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1
>(
predicate: Predicate.Predicate<Cause.Cause<OutErr>>predicate: import PredicatePredicate.interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<function (type parameter) OutErr in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 CauseCause.type Cause.Cause = /*unresolved*/ anyCause<function (type parameter) OutErr in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>) => 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 <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1, function (type parameter) OutErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr1, function (type parameter) OutDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone1, function (type parameter) InElem1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem1, function (type parameter) InErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr1, function (type parameter) InDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone1, function (type parameter) Env1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1>
): <
function (type parameter) OutElem in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem,
function (type parameter) OutDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone,
function (type parameter) InElem in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem,
function (type parameter) InErr in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr,
function (type parameter) InDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone,
function (type parameter) Env in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem, function (type parameter) OutErr in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr, function (type parameter) OutDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone, function (type parameter) InElem in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem, function (type parameter) InErr in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr, function (type parameter) InDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone, function (type parameter) Env in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem | function (type parameter) OutElem1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1,
function (type parameter) OutErr in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr | function (type parameter) OutErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr1,
function (type parameter) OutDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone | function (type parameter) OutDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutDone1,
function (type parameter) InElem in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem & function (type parameter) InElem1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InElem1,
function (type parameter) InErr in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr & function (type parameter) InErr1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InErr1,
function (type parameter) InDone in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone & function (type parameter) InDone1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone1,
function (type parameter) Env in <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env | function (type parameter) Env1 in <OutErr, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): <OutElem, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1
>
<
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env>,
predicate: Predicate.Predicate<Cause.Cause<OutErr>>predicate: import PredicatePredicate.interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 CauseCause.type Cause.Cause = /*unresolved*/ anyCause<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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>) => 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr | 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env | 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1
>
} = 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>>(arity: 3, body: <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>): ((...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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>) => Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>) (+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(3, <
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env>,
predicate: Predicate.Predicate<Cause.Cause<OutErr>>predicate: import PredicatePredicate.interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<import CauseCause.type Cause.Cause = /*unresolved*/ anyCause<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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>>,
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 CauseCause.type Cause.Cause = /*unresolved*/ anyCause<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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr>) => 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr | 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>InDone1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env | 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1
> =>
const catchCause: {
<
OutErr,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
f: (
d: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): <
OutElem,
OutDone,
InElem,
InErr,
InDone,
Env
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>
) => Channel<
OutElem | OutElem1,
OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
Env | Env1
>
<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env,
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>(
self: Channel<
OutElem,
OutErr,
OutDone,
InElem,
InErr,
InDone,
Env
>,
f: (
d: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
): Channel<
OutElem | OutElem1,
OutErr1,
OutDone | OutDone1,
InElem & InElem1,
InErr & InErr1,
InDone & InDone1,
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; <…;
}
cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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;
}
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutElem1,
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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>OutErr | 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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>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>, predicate: Predicate.Predicate<Cause.Cause<OutErr>>, f: (cause: Cause.Cause<OutErr>) => Channel<OutElem1, OutErr1, OutDone1, InElem1, InErr1, InDone1, Env1>): Channel<OutElem | OutElem1, OutErr | OutErr1, OutDone | OutDone1, InElem & InElem1, InErr & InErr1, InDone & InDone1, Env | Env1>Env1
> => {
return predicate: Predicate.Predicate<Cause.Cause<OutErr>>predicate(cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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;
}
f: (
cause: Cause.Cause<OutErr>
) => Channel<
OutElem1,
OutErr1,
OutDone1,
InElem1,
InErr1,
InDone1,
Env1
>
cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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 failCause: <E>(
cause: Cause.Cause<E>
) => Channel<never, E, never>
Constructs a channel that fails immediately with the specified Cause.
When to use
Use when the channel failure must preserve a full Cause, such as defects,
interruptions, or combined failures.
Example (Failing with causes)
import { Cause, Channel } from "effect"
// Create a channel that fails with a simple cause
const simpleCause = Cause.fail("Simple error")
const failedChannel = Channel.failCause(simpleCause)
// Create a channel with a die cause
const dieCause = Cause.die(new Error("System error"))
const dieFailure = Channel.failCause(dieCause)
// Create a channel with a simple fail cause
const failCause = Cause.fail("Simple error")
const simpleFail = Channel.failCause(failCause)
failCause(cause: Cause.Cause<OutErr>(parameter) cause: {
reasons: ReadonlyArray<Reason<E>>;
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