effect-io-ai

Package: effect
Module: Reducer

Reducer.make

Creates a Reducer from a combine function and an initialValue.

When to use

Use when you have a custom reducing operation not covered by a pre-built reducer.

• You want to provide an optimized combineAll (e.g. short-circuiting on a known absorbing element like 0 for multiplication).

Details

• If combineAll is omitted, a default left-to-right fold starting from initialValue is used.
• If combineAll is provided, it completely replaces the default fold.

Example (Multiplying with short-circuit)

import { Reducer } from "effect"

const Product = Reducer.make<number>(
  (a, b) => a * b,
  1,
  (collection) => {
    let acc = 1
    for (const n of collection) {
      if (n === 0) return 0
      acc *= n
    }
    return acc
  }
)

console.log(Product.combineAll([2, 3, 4]))
// Output: 24

console.log(Product.combineAll([2, 0, 4]))
// Output: 0

See

• Reducer – the interface this creates
• flip – reverse the argument order

Signature

declare const make: <A>(combine: (self: A, that: A) => A, initialValue: A, combineAll?: (collection: Iterable<A>) => A) => Reducer<A>

Source

Since v4.0.0