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variable / @typed/fx

Fx.exhaustMap

Maps each element of an Fx to a new Fx, ignoring new elements until the current inner Fx completes.

Package version
2.0.0-beta.13
Category
Concurrent work
Since
1.0.0
Member of
Fx

Follow one execution

Maps each element of an Fx to a new Fx, ignoring new elements until the current inner Fx completes.

Fx timelineexhaustMap ignores arrivals until the active inner completesexhaustMap
OperatorexhaustMap(submit)
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.

Source and admitted-inner failures are forwarded and their services remain typed. A FiberHandle in the required Scope owns the active inner. Source completion waits for that inner; interruption closes the handle and the inner’s child Scope, running its finalizers.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.exhaustMap 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 exhaustMap: FlatMapLike;

Why

exhaustMap is an admission policy for work that must never overlap and does not need a backlog, such as ignoring repeated submit events while one submit is running.

Admission, ordering, and cardinality

The first source value observed while idle admits one inner Fx. For values arriving while it runs, f is still evaluated to construct an inner, but that inner is not run and no value is queued. Every admitted inner may emit any number of values in its own order.

Ownership and lifetime

Source and admitted-inner failures are forwarded and their services remain typed. A FiberHandle in the required Scope owns the active inner. Source completion waits for that inner; interruption closes the handle and the inner’s child Scope, running its finalizers.

Examples

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

const submits = Fx.mergeAll(
  Fx.at("first", "0 millis"),
  Fx.at("ignored while busy", "5 millis"),
  Fx.at("later", "30 millis")
)
const accepted = Fx.exhaustMap(submits, (command) => Fx.at(command, "20 millis"))

Effect.runPromise(Effect.scoped(Fx.collectAll(accepted))).then(console.log)
// ["first", "later"]

Other public imports

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

Source