Iterable.chunksOf — API

Iterable.chunksOfconsteffect/Iterable.ts:1154

(n: number): <A>(self: Iterable<A>) => Iterable<Array<A>>
<A>(self: Iterable<A>, n: number): Iterable<Array<A>>

Splits an Iterable into length-n pieces. The last piece will be shorter if n does not evenly divide the length of the Iterable.

Example (Chunking an iterable)

import { Iterable } from "effect"

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
const chunks = Iterable.chunksOf(numbers, 3)
console.log(Array.from(chunks).map((chunk) => Array.from(chunk)))
// [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

// Last chunk can be shorter
const uneven = [1, 2, 3, 4, 5, 6, 7]
const chunks2 = Iterable.chunksOf(uneven, 3)
console.log(Array.from(chunks2).map((chunk) => Array.from(chunk)))
// [[1, 2, 3], [4, 5, 6], [7]]

// Chunk size larger than iterable
const small = [1, 2]
const chunks3 = Iterable.chunksOf(small, 5)
console.log(Array.from(chunks3).map((chunk) => Array.from(chunk)))
// [[1, 2]]

// Process data in batches
const data = Iterable.range(1, 100)
const batches = Iterable.chunksOf(data, 10)
const batchSums = Iterable.map(
  batches,
  (batch) => Iterable.reduce(batch, 0, (sum, n) => sum + n)
)
console.log(Array.from(Iterable.take(batchSums, 3))) // [55, 155, 255]

splitting

Source effect/Iterable.ts:115430 lines

export const chunksOf: {
  (n: number): <A>(self: Iterable<A>) => Iterable<Array<A>>
  <A>(self: Iterable<A>, n: number): Iterable<Array<A>>
} = dual(2, <A>(self: Iterable<A>, n: number): Iterable<Array<A>> => {
  const safeN = Math.max(1, Math.floor(n))
  return ({
    [Symbol.iterator]() {
      let iterator: Iterator<A> | undefined = self[Symbol.iterator]()
      return {
        next() {
          if (iterator === undefined) {
            return { done: true, value: undefined }
          }

          const chunk: Array<A> = []
          for (let i = 0; i < safeN; i++) {
            const result = iterator.next()
            if (result.done) {
              iterator = undefined
              return chunk.length === 0 ? { done: true, value: undefined } : { done: false, value: chunk }
            }
            chunk.push(result.value)
          }

          return { done: false, value: chunk }
        }
      }
    }
  })
})