Search documentation

Search by topic, API name, or import path.

GitHub ↗

variable / @typed/fx

Fx.skipWhileEffect

Skips elements from an Fx while an effectful predicate returns true. Emits from the first element for which the predicate effect succeeds with false (including that element) and all following elements.

Package version
2.0.0-beta.13
Category
Selecting values
Since
1.0.0
Member of
Fx

Follow one execution

Each predicate Effect takes one turn in this serialized source. Its failure is forwarded rather than treated as false. The predicate still runs after the gate opens.

Fx timelineskipWhileEffect(oneTurnCheck)skipWhileEffect
OperatorskipWhileEffect(oneTurnCheck)
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.

The gate belongs to one run, while predicate invocation inherits the producer’s ordering and concurrency. Predicate failure is delivered even after the gate opened; services remain required and interruption cancels whichever callback Effects the producer attached to the run.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.skipWhileEffect 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 skipWhileEffect: {
    <A, E2, R2>(predicate: (a: A) => Effect.Effect<boolean, E2, R2>): <E, R>(fx: Fx<A, E, R>) => Fx<A, E | E2, R | R2>;
    <A, E, R, E2, R2>(fx: Fx<A, E, R>, predicate: (a: A) => Effect.Effect<boolean, E2, R2>): Fx<A, E | E2, R | R2>;
};

Why

skipWhileEffect performs Effectful prefix decisions. The gate opens at the first false result, but the implementation eagerly constructs and runs predicate(a) before reading that gate, so the predicate still runs for every later input even though those values are always forwarded.

Ownership and lifetime

The gate belongs to one run, while predicate invocation inherits the producer’s ordering and concurrency. Predicate failure is delivered even after the gate opened; services remain required and interruption cancels whichever callback Effects the producer attached to the run.

Examples

import { Effect, Ref } from "effect"
import { Fx } from "@typed/fx"
const program = Effect.gen(function* () {
  const checks = yield* Ref.make(0)
  const values = yield* Fx.collectAll(
    Fx.fromIterable([2, 3]).pipe(
      Fx.skipWhileEffect((n) => Ref.update(checks, (count) => count + 1).pipe(Effect.as(n < 2)))
    )
  )
  return { values, checks: yield* Ref.get(checks) } // { values: [2, 3], checks: 2 }
})

Other public imports

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

Source