Search documentation

Search by topic, API name, or import path.

GitHub ↗

variable / @typed/fx

Push.mapAccum

Maps over the output (Fx) side of a Push with an accumulator: for each emitted value b, applies f(state, b) to get [nextState, emitted] and emits the second element. The first element is the initial state; subsequent states are updated by each step. It emits exactly one C per upstream value, in order. Accumulator state is private to each output subscription; the input Sink is unchanged.

Package version
2.0.0-beta.7
Category
Stateful outputs
Since
1.0.0
Member of
Push

Import

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

Access Push.mapAccum through the imported Push 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 mapAccum: {
    <S, B, C>(initial: S, f: (s: S, b: B) => readonly [
        S,
        C
    ]): <A, E, R, E2, R2>(push: Push<A, E, R, B, E2, R2>) => Push<A, E, R, C, E2, R2>;
    <A, E, R, B, E2, R2, S, C>(push: Push<A, E, R, B, E2, R2>, initial: S, f: (s: S, b: B) => readonly [
        S,
        C
    ]): Push<A, E, R, C, E2, R2>;
};

Why

Stateful output projection can derive running totals or protocol state without moving that state into the bidirectional input boundary.

Ownership and lifetime

Each run owns its own synchronous accumulator. It is discarded when that run completes or is interrupted and acquires no Scope or external resource.

Examples

import { Effect } from "effect"
import * as Fx from "@typed/fx/Fx"
import * as Push from "@typed/fx/Push"
import * as Sink from "@typed/fx/Sink"

const push = Push.make(Sink.make(() => Effect.void, (_: string) => Effect.void), Fx.fromIterable([1, 2, 3]))
const totals = Push.mapAccum(push, 0, (total, value) => [total + value, total + value] as const)

Other public imports

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

Source