Prime number sieve using Effect streams

effect-prime-stream.ts

import * as Stream from '@effect/stream/Stream'
import * as Chunk from '@effect/data/Chunk'
import * as IO from '@effect/io/Effect'
import { pipe } from "~/lib";

const intsPlusPrimality = pipe(
  Stream.range(1, Number.MAX_SAFE_INTEGER),
  Stream.mapAccum(Chunk.empty<number>(), sieveChunk),
  Stream.flatten
)

export const primes = Stream.map(
  Stream.filter(intsPlusPrimality, ([,prime]) => prime),
  ([int]) => int
)

function sieveChunk(
  primes: Chunk.Chunk<number>,
  candidate: number,
): readonly [Chunk.Chunk<number>, Stream.Stream<never, never, [number, boolean]>] {
  return candidate > 1 && Chunk.every(primes, prime => candidate % prime !== 0)
    ? [primes.append(candidate), Stream.succeed([candidate, true])]
    : [primes, Stream.succeed([candidate, false])]
}

// Get 10 primes after the first 1000
export const main = pipe(
  primes,
  Stream.drop(1000),
  Stream.take(10),
  Stream.runCollect,
  IO.timed,
  IO.tap(([duration, [...ns]]) => IO.log(`collected
${ns.join(', ')}
duration: ${duration.millis}ms`)),
)
void IO.runSync(main)

output.txt

timestamp=XX level=INFO fiber=#642 message="collected
7927, 7933, 7937, 7949, 7951, 7963, 7993, 8009, 8011, 8017
duration: 762ms"