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Fx.sample

Emits the latest source value whenever sampler emits. Source values that arrive between sampler ticks are not forwarded until the next tick.

Completion: Completes when the source completes. Errors: The first failure from either stream fails the result.

Package version
2.0.0-beta.7
Category
Time and rate
Since
1.0.0
Member of
Fx

Follow one execution

Emits the latest source value whenever sampler emits. Source values that arrive between sampler ticks are not forwarded until the next tick. Completion: Completes when the source completes. Errors: The first failure from either stream fails the result.

Fx timelinesample reads the latest source value on each sampler ticksample
Operatorsample(values, sampler)
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.

One latest-value cell and a child sampler fiber belong to each run. Source completion interrupts the sampler; any failure or consumer interruption stops both and releases the retained value.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.sample 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 sample: {
    <S, E2, R2>(sampler: Fx<S, E2, R2>): <A, E, R>(self: Fx<A, E, R>) => Fx<A, E | E2, R | R2>;
    <A, E, R, S, E2, R2>(self: Fx<A, E, R>, sampler: Fx<S, E2, R2>): Fx<A, E | E2, R | R2>;
};

Why

sample separates value production from observation cadence. A sampler tick emits the latest source value once, or nothing before the source’s first value; repeated ticks may repeat a value.

Ownership and lifetime

One latest-value cell and a child sampler fiber belong to each run. Source completion interrupts the sampler; any failure or consumer interruption stops both and releases the retained value.

Examples

import { Fx } from "@typed/fx"
const snapshots = Fx.sample(Fx.fromIterable([10, 20]), Fx.fromIterable(["tick"]))

Other public imports

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

Source