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variable / @typed/fx

Fx.filterEffect

Filters elements of an Fx using an effectful predicate function.

Package version
2.0.0-beta.13
Category
Selecting values
Since
1.0.0
Member of
Fx

Follow one execution

Admit each value only after its asynchronous even-number check succeeds. Concurrent producers can overlap callback Effects; these rows assume serial delivery.

Fx timelinefilterEffect(oneTurnCallback)filterEffect
OperatorfilterEffect(oneTurnCallback)
Read this diagram

Follow each lane from left to right. Events stacked vertically share a tick; the green cursor marks the current time across every lane.

  • A value
    The text inside the pill is the emitted value.
  • Work starts
    The raised chevron starts an inner run (^ in the source).
  • The run returns
    The vertical bar ends this lane’s run.
  • A cause is delivered
    The exclamation mark belongs to this lane.
  • Work is interrupted
    The cross marks cancellation of this run.
  • Current time
    The line and diamond move together across all lanes.
  • Happening now
    A highlighted event is at the current tick.
  • Still ahead
    Muted, dashed values have not happened yet.
  • Time continues
    The lane’s arrow is not a return marker. An empty stretch can be quiet work that is still running.

Illustrated ticks start at 0. At 1×, one illustrated tick takes one second; captions specify real durations when timing matters. A cause or interruption belongs to its lane, and other work may continue. Scroll horizontally to inspect the rest of a long timeline.

A predicate Effect belongs to the producer callback that invoked it. Its Cause is sent to the Sink, R2 stays required, and interruption follows that delivery. No lock or queue is added.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

import { Fx } from "@typed/fx";

Access Fx.filterEffect through the imported Fx export. Its declaration below describes the member.

This public exposure is a re-export. Its import path is supported; declaration documentation is shared with the other public exposures below.

Signatures

export declare const filterEffect: {
    <A, E2, R2>(f: (a: A) => Effect.Effect<boolean, E2, R2>): <E, R>(self: Fx<A, E | E2, R>) => Fx<A, E | E2, R | R2>;
    <A, E, R, E2, R2>(self: Fx<A, E | E2, R>, f: (a: A) => Effect.Effect<boolean, E2, R2>): Fx<A, E | E2, R | R2>;
};

Why

filterEffect supports service-backed or failing decisions without flattening a second Fx. Each input runs one predicate Effect; true emits once and false emits nothing. The adapter does not serialize concurrent producer deliveries, so accepted values may arrive out of input order.

Ownership and lifetime

A predicate Effect belongs to the producer callback that invoked it. Its Cause is sent to the Sink, R2 stays required, and interruption follows that delivery. No lock or queue is added.

Examples

import { Effect } from "effect"
import { Fx } from "@typed/fx"

const concurrent = Fx.make<number>((sink) =>
  Effect.all([sink.onSuccess(1), sink.onSuccess(2)], { concurrency: "unbounded", discard: true })
)
const positive = concurrent.pipe(Fx.filterEffect((n) => Effect.succeed(n > 0)))

Other public imports

These import paths expose the same declaration. Each page retains its own public name and signature.

Source