Sink Operations
In the previous sections, we learned how to create and use sinks. Now, let’s explore some operations you can perform on sinks to transform or filter their behavior.
Sometimes, you have a sink that works perfectly with one type of input, but you want to use it with a different type. This is where Sink.mapInput comes in handy. While Sink.map modifies the output of a function, Sink.mapInput modifies the input. It allows you to adapt your sink to work with a different input.
Imagine you have a Sink.sum that calculates the sum of incoming numeric values. However, your stream contains strings, not numbers. You can use mapInput to convert your strings into numbers and make Sink.sum compatible with your stream:
1import { import StreamStream, import SinkSink, import EffectEffect } from "effect"2
3const const numericSum: Sink.Sink<number, number, never, never, never>numericSum = import SinkSink.const sum: Sink.Sink<number, number, never, never, never>A sink that sums incoming numeric values.
sum4
5const const stringSum: Sink.Sink<number, string, never, never, never>stringSum = const numericSum: Sink.Sink<number, number, never, never, never>numericSum.(method) Pipeable.pipe<Sink.Sink<number, number, never, never, never>, Sink.Sink<number, string, never, never, never>>(this: Sink.Sink<...>, ab: (_: Sink.Sink<number, number, never, never, never>) => Sink.Sink<...>): Sink.Sink<...> (+21 overloads)pipe(6 import SinkSink.const mapInput: <string, number>(f: (input: string) => number) => <A, L, E, R>(self: Sink.Sink<A, number, L, E, R>) => Sink.Sink<A, string, L, E, R> (+1 overload)Transforms this sink's input elements.
mapInput(((parameter) s: strings: string) => var Number: NumberConstructorAn object that represents a number of any kind. All JavaScript numbers are 64-bit floating-point numbers.
Number.(method) NumberConstructor.parseFloat(string: string): numberConverts a string to a floating-point number.
parseFloat((parameter) s: strings))7)8
9import EffectEffect.const runPromise: <number, never>(effect: Effect.Effect<number, never, never>, options?: {
readonly signal?: AbortSignal;
} | undefined) => Promise<number>Runs an `Effect` workflow, returning a `Promise` which resolves with the
result of the workflow or rejects with an error.
runPromise(10 import StreamStream.const make: <[string, string, string, string, string]>(as_0: string, as_1: string, as_2: string, as_3: string, as_4: string) => Stream.Stream<string, never, never>Creates a stream from an sequence of values.
make("1", "2", "3", "4", "5").(method) Pipeable.pipe<Stream.Stream<string, never, never>, Effect.Effect<number, never, never>>(this: Stream.Stream<...>, ab: (_: Stream.Stream<string, never, never>) => Effect.Effect<number, never, never>): Effect.Effect<...> (+21 overloads)pipe(import StreamStream.const run: <number, string, never, never>(sink: Sink.Sink<number, string, unknown, never, never>) => <E, R>(self: Stream.Stream<string, E, R>) => Effect.Effect<number, E, Exclude<R, Scope>> (+1 overload)Runs the sink on the stream to produce either the sink's result or an error.
run(const stringSum: Sink.Sink<number, string, never, never, never>stringSum))11).(method) Promise<number>.then<void, never>(onfulfilled?: ((value: number) => void | PromiseLike<void>) | null | undefined, onrejected?: ((reason: any) => PromiseLike<never>) | null | undefined): Promise<...>Attaches callbacks for the resolution and/or rejection of the Promise.
then(namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.
_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.
Example using the global `console`:
```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```
Example using the `Console` class:
```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).
```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```
See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log)12/*13Output:141515*/If you need to change both the input and output of a sink, you can use Sink.dimap. It’s an extended version of mapInput that lets you transform both types. This can be useful when you need to perform a complete conversion between your input and output types:
1import { import StreamStream, import SinkSink, import EffectEffect } from "effect"2
3// Convert its input to integers, do the computation and then4// convert them back to a string5const const sumSink: Sink.Sink<string, string, never, never, never>sumSink = import SinkSink.const sum: Sink.Sink<number, number, never, never, never>A sink that sums incoming numeric values.
sum.(method) Pipeable.pipe<Sink.Sink<number, number, never, never, never>, Sink.Sink<string, string, never, never, never>>(this: Sink.Sink<...>, ab: (_: Sink.Sink<number, number, never, never, never>) => Sink.Sink<...>): Sink.Sink<...> (+21 overloads)pipe(6 import SinkSink.const dimap: <string, number, number, string>(options: {
readonly onInput: (input: string) => number;
readonly onDone: (a: number) => string;
}) => <L, E, R>(self: Sink.Sink<number, number, L, E, R>) => Sink.Sink<...> (+1 overload)Transforms both inputs and result of this sink using the provided
functions.
dimap({7 (property) onInput: (input: string) => numberonInput: ((parameter) s: strings: string) => var Number: NumberConstructorAn object that represents a number of any kind. All JavaScript numbers are 64-bit floating-point numbers.
Number.(method) NumberConstructor.parseFloat(string: string): numberConverts a string to a floating-point number.
parseFloat((parameter) s: strings),8 (property) onDone: (a: number) => stringonDone: ((parameter) n: numbern) => var String: StringConstructor
(value?: any) => stringAllows manipulation and formatting of text strings and determination and location of substrings within strings.
String((parameter) n: numbern)9 })10)11
12import EffectEffect.const runPromise: <string, never>(effect: Effect.Effect<string, never, never>, options?: {
readonly signal?: AbortSignal;
} | undefined) => Promise<string>Runs an `Effect` workflow, returning a `Promise` which resolves with the
result of the workflow or rejects with an error.
runPromise(13 import StreamStream.const make: <[string, string, string, string, string]>(as_0: string, as_1: string, as_2: string, as_3: string, as_4: string) => Stream.Stream<string, never, never>Creates a stream from an sequence of values.
make("1", "2", "3", "4", "5").(method) Pipeable.pipe<Stream.Stream<string, never, never>, Effect.Effect<string, never, never>>(this: Stream.Stream<...>, ab: (_: Stream.Stream<string, never, never>) => Effect.Effect<string, never, never>): Effect.Effect<...> (+21 overloads)pipe(import StreamStream.const run: <string, string, never, never>(sink: Sink.Sink<string, string, unknown, never, never>) => <E, R>(self: Stream.Stream<string, E, R>) => Effect.Effect<string, E, Exclude<R, Scope>> (+1 overload)Runs the sink on the stream to produce either the sink's result or an error.
run(const sumSink: Sink.Sink<string, string, never, never, never>sumSink))14).(method) Promise<string>.then<void, never>(onfulfilled?: ((value: string) => void | PromiseLike<void>) | null | undefined, onrejected?: ((reason: any) => PromiseLike<never>) | null | undefined): Promise<...>Attaches callbacks for the resolution and/or rejection of the Promise.
then(namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.
_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.
Example using the global `console`:
```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```
Example using the `Console` class:
```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).
```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```
See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log)15/*16Output:1715 <-- as string18*/Sinks offer a way to filter incoming elements using Sink.filterInput. This allows you to collect or process only the elements that meet a specific condition. In the following example, we collect elements in chunks of three and filter out the negative numbers:
1import { import StreamStream, import SinkSink, import EffectEffect } from "effect"2
3const const values: number[]values = [1, -2, 0, 1, 3, -3, 4, 2, 0, 1, -3, 1, 1, 6]4const const stream: Stream.Stream<Chunk<number>, never, never>stream = import StreamStream.const fromIterable: <number>(iterable: Iterable<number>) => Stream.Stream<number, never, never>Creates a new `Stream` from an iterable collection of values.
fromIterable(const values: number[]values).(method) Pipeable.pipe<Stream.Stream<number, never, never>, Stream.Stream<Chunk<number>, never, never>>(this: Stream.Stream<...>, ab: (_: Stream.Stream<number, never, never>) => Stream.Stream<Chunk<number>, never, never>): Stream.Stream<...> (+21 overloads)pipe(5 import StreamStream.const transduce: <Chunk<number>, number, never, never>(sink: Sink.Sink<Chunk<number>, number, number, never, never>) => <E, R>(self: Stream.Stream<number, E, R>) => Stream.Stream<...> (+1 overload)Applies the transducer to the stream and emits its outputs.
transduce(6 import SinkSink.const collectAllN: <number>(n: number) => Sink.Sink<Chunk<number>, number, number, never, never>A sink that collects first `n` elements into a chunk.
collectAllN<number>(3).(method) Pipeable.pipe<Sink.Sink<Chunk<number>, number, number, never, never>, Sink.Sink<Chunk<number>, number, number, never, never>>(this: Sink.Sink<...>, ab: (_: Sink.Sink<Chunk<number>, number, number, never, never>) => Sink.Sink<...>): Sink.Sink<...> (+21 overloads)pipe(import SinkSink.const filterInput: <number, number>(f: Predicate<number>) => <A, L, E, R>(self: Sink.Sink<A, number, L, E, R>) => Sink.Sink<A, number, L, E, R> (+1 overload)Filters the sink's input with the given predicate.
filterInput(((parameter) n: numbern) => (parameter) n: numbern > 0))7 )8)9
10import EffectEffect.const runPromise: <Chunk<Chunk<number>>, never>(effect: Effect.Effect<Chunk<Chunk<number>>, never, never>, options?: {
readonly signal?: AbortSignal;
} | undefined) => Promise<...>Runs an `Effect` workflow, returning a `Promise` which resolves with the
result of the workflow or rejects with an error.
runPromise(import StreamStream.const runCollect: <Chunk<number>, never, never>(self: Stream.Stream<Chunk<number>, never, never>) => Effect.Effect<Chunk<Chunk<number>>, never, never>Runs the stream and collects all of its elements to a chunk.
runCollect(const stream: Stream.Stream<Chunk<number>, never, never>stream)).(method) Promise<Chunk<Chunk<number>>>.then<void, never>(onfulfilled?: ((value: Chunk<Chunk<number>>) => void | PromiseLike<void>) | null | undefined, onrejected?: ((reason: any) => PromiseLike<never>) | null | undefined): Promise<...>Attaches callbacks for the resolution and/or rejection of the Promise.
then(namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.
_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.
Example using the global `console`:
```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```
Example using the `Console` class:
```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).
```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```
See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log)11/*12Output:13{14 _id: "Chunk",15 values: [16 {17 _id: "Chunk",18 values: [ 1, 1, 3 ]19 }, {20 _id: "Chunk",21 values: [ 4, 2, 1 ]22 }, {23 _id: "Chunk",24 values: [ 1, 1, 6 ]25 }, {26 _id: "Chunk",27 values: []28 }29 ]30}31*/