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Effect Documentation

Introduction

Introduction to Sinks

In the world of streams, a Sink<A, In, L, E, R> plays a crucial role. It’s like a specialized function designed to consume elements generated by a Stream. Here’s a breakdown of what a Sink does:

  • It can consume a varying number of In elements, which might be zero, one, or more.
  • It has the potential to encounter errors of type E.
  • Ultimately, it produces a value of type A.
  • Additionally, it can return a remainder of type L, which represents any leftover elements.

To use a Sink for processing a stream, you simply pass it to the Stream.run function:

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import { 
import Stream
Stream, 
import Sink
Sink, 
import Effect
Effect } from "effect"
2


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// Define a stream with numbers 1, 2, and 3
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const 
const stream: Stream.Stream<number, never, never>
stream = 
import Stream
Stream.
const make: <[number, number, number]>(as_0: number, as_1: number, as_2: number) => Stream.Stream<number, never, never>
Creates a stream from an sequence of values.
make(1, 2, 3)
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// Create a sink that sums numbers
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const 
const sink: Sink.Sink<number, number, never, never, never>
sink = 
import Sink
Sink.
const sum: Sink.Sink<number, number, never, never, never>
A sink that sums incoming numeric values.
sum
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// Run the stream through the sink to obtain the result
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const 
const sum: Effect.Effect<number, never, never>
sum = 
import Stream
Stream.
const run: <number, never, never, number, never, never>(self: Stream.Stream<number, never, never>, sink: Sink.Sink<number, number, unknown, never, never>) => Effect.Effect<number, never, never> (+1 overload)
Runs the sink on the stream to produce either the sink's result or an error.
run(
const stream: Stream.Stream<number, never, never>
stream, 
const sink: Sink.Sink<number, number, never, never, never>
sink)
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import Effect
Effect.
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(
const sum: Effect.Effect<number, never, never>
sum).
(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: Console
The `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[]): void
Prints 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)
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/*
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Output:
15
6
16
*/