Follow one execution
Each fresh right value permits one left value; the right payload is discarded.
zipLeftTick 0. Left: left-1.
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.
Both sources run concurrently. The first run to complete ends pairing and interrupts the other, while consumer interruption stops both. A failure Cause is delivered to the Sink but does not by itself end pairing; a producer may continue and supply a value afterward.
Import
import { Fx } from "@typed/fx";Access Fx.zipLeft 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 zipLeft: {
<A2, E2, R2>(that: Fx<A2, E2, R2>): <A, E, R>(self: Fx<A, E, R>) => Fx<A, E | E2, R | R2>;
<A, E, R, A2, E2, R2>(self: Fx<A, E, R>, that: Fx<A2, E2, R2>): Fx<A, E | E2, R | R2>;
};Why
zipLeft uses the right source as a one-for-one pacing or validation partner while retaining the
left payload. It emits one left value per completed pair and preserves pair order.
Ownership and lifetime
Both sources run concurrently. The first run to complete ends pairing and interrupts the other, while consumer interruption stops both. A failure Cause is delivered to the Sink but does not by itself end pairing; a producer may continue and supply a value afterward.
Examples
import { Cause, Effect, Ref } from "effect"
import { Fx, Sink } from "@typed/fx"
const program = Effect.gen(function* () {
const deliveries = yield* Ref.make<Array<string>>([])
const left = Fx.make<number, string>((sink) =>
sink.onFailure(Cause.fail("warning")).pipe(Effect.andThen(sink.onSuccess(1)))
)
yield* Fx.zipLeft(left, Fx.succeed("pair")).run(Sink.make(
() => Ref.update(deliveries, (xs) => [...xs, "failure"]),
(value) => Ref.update(deliveries, (xs) => [...xs, `value:${value}`])
))
return yield* Ref.get(deliveries) // ["failure", "value:1"]
})Other public imports
These import paths expose the same declaration. Each page retains its own public name and signature.