Hyperlinkv0.8.0-beta.28

← Stream

Stream.runFoldEffectconsteffect/Stream.ts:10760
<Z, A, EX, RX>(
  initial: LazyArg<Z>,
  f: (acc: Z, a: A) => Effect.Effect<Z, EX, RX>
): <E, R>(self: Stream<A, E, R>) => Effect.Effect<Z, E | EX, R | RX>
<A, E, R, Z, EX, RX>(
  self: Stream<A, E, R>,
  initial: LazyArg<Z>,
  f: (acc: Z, a: A) => Effect.Effect<Z, EX, RX>
): Effect.Effect<Z, E | EX, R | RX>

Runs the stream and folds elements using an effectful reducer.

When to use

Use when reducing stream elements needs Effects, services, or failures in the reducer.

Example (Effectfully folding stream values)

import { Console, Effect, Stream } from "effect"

const program = Effect.gen(function*() {
  const total = yield* Stream.runFoldEffect(
    Stream.make(1, 2, 3),
    () => 0,
    (acc, n) => Effect.succeed(acc + n)
  )
  yield* Console.log(total)
})

Effect.runPromise(program)
// 6
destructors
Source effect/Stream.ts:1076032 lines
export const runFoldEffect: {
  <Z, A, EX, RX>(
    initial: LazyArg<Z>,
    f: (acc: Z, a: A) => Effect.Effect<Z, EX, RX>
  ): <E, R>(
    self: Stream<A, E, R>
  ) => Effect.Effect<Z, E | EX, R | RX>
  <A, E, R, Z, EX, RX>(
    self: Stream<A, E, R>,
    initial: LazyArg<Z>,
    f: (acc: Z, a: A) => Effect.Effect<Z, EX, RX>
  ): Effect.Effect<Z, E | EX, R | RX>
} = dual(3, <A, E, R, Z, EX, RX>(
  self: Stream<A, E, R>,
  initial: LazyArg<Z>,
  f: (acc: Z, a: A) => Effect.Effect<Z, EX, RX>
): Effect.Effect<Z, E | EX, R | RX> =>
  Channel.runFoldEffect(self.channel, initial, (acc, arr) => {
    let i = 0
    let s = acc
    return Effect.map(
      Effect.whileLoop({
        while: () => i < arr.length,
        body: () => f(s, arr[i]),
        step(z) {
          s = z
          i++
        }
      }),
      () => s
    )
  }))