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variable / @typed/fx/Fx

flatMap

Maps each source value to an inner Fx and merges every inner concurrently.

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

Follow one execution

Maps each source value to an inner Fx and merges every inner concurrently.

Fx timelineflatMap runs every inner and lets their values interleaveflatMap
OperatorflatMap(load)
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 inner failures are forwarded; their required services are unioned. A FiberSet in the required Scope owns all inner fibers. Source completion waits for the set to empty. Interrupting observation closes the Scope and interrupts every active inner, running each inner Scope’s finalizers.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const flatMap: FlatMapLike;

Why

flatMap is the unconstrained merge policy for independent pushed work. It preserves push-based production instead of collecting an inner Fx before the next source value can be handled.

Concurrency, ordering, and cardinality

Every source value creates exactly one inner Fx with no concurrency limit. Each inner retains its own emission order, but values from different inners interleave according to arrival time. There is no output buffer or global ordering guarantee.

Ownership and lifetime

Source and inner failures are forwarded; their required services are unioned. A FiberSet in the required Scope owns all inner fibers. Source completion waits for the set to empty. Interrupting observation closes the Scope and interrupts every active inner, running each inner Scope’s finalizers.

Examples

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

const rows = Fx.flatMap(Fx.fromIterable([
  { id: "slow", wait: "20 millis" as const },
  { id: "fast", wait: "1 millis" as const }
]), ({ id, wait }) => Fx.at(id, wait))

Effect.runPromise(Effect.scoped(Fx.collectAll(rows))).then(console.log)
// ["fast", "slow"]: inners overlap and results arrive by production time

Other public imports

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

Source