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variable / @typed/fx/Fx

sync

Lazily evaluates a synchronous function once for each Fx run.

Package version
2.0.0-beta.7
Category
Value sources
Since
2.0.0

Follow one execution

The thunk is evaluated anew for each run; this run reads 7.

Fx timelinesync(readNow)sync
Operatorsync(readNow)
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.

Construction performs no work. Each run evaluates evaluate exactly once in the run’s fiber, emits its result, and completes after the Sink handles it. A thrown exception is an Effect defect; use Fx.fromEffect(Effect.try(...)) when failure is expected and belongs in the typed error channel.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const sync: <A>(evaluate: () => A) => Fx<A>;

Why

sync is the direct constructor for one value that must be computed at run time, such as a fresh DOM node or a snapshot read from an imperative API. Unlike succeed, it does not evaluate the function while the Fx is being assembled.

Ownership and lifetime

Construction performs no work. Each run evaluates evaluate exactly once in the run’s fiber, emits its result, and completes after the Sink handles it. A thrown exception is an Effect defect; use Fx.fromEffect(Effect.try(...)) when failure is expected and belongs in the typed error channel.

Examples

import { Fx } from "@typed/fx"

const element = Fx.sync(() => document.createElement("div"))

Other public imports

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

Source