effect-io-ai

Package: effect
Module: Struct

Struct.makeReducer

Creates a Reducer for a struct shape by providing a Reducer for each property. The initial value is derived from each property’s Reducer.initialValue. When reducing a collection of structs, each property is combined independently.

When to use

Use when you need to fold same-shape records by accumulating each property independently into one summary record.

Details

Pass omitKeyWhen to drop properties whose reduced value matches a predicate.

Example (Reducing a collection of structs)

import { Number, String, Struct } from "effect"

const R = Struct.makeReducer<{ readonly n: number; readonly s: string }>({
  n: Number.ReducerSum,
  s: String.ReducerConcat
})

const result = R.combineAll([
  { n: 1, s: "a" },
  { n: 2, s: "b" },
  { n: 3, s: "c" }
])
console.log(result) // { n: 6, s: "abc" }

See

• makeCombiner – like makeReducer but without an initial value

Signature

declare const makeReducer: <A>(reducers: { readonly [K in keyof A]: Reducer.Reducer<A[K]>; }, options?: { readonly omitKeyWhen?: ((a: A[keyof A]) => boolean) | undefined; }) => Reducer.Reducer<A>

Source

Since v4.0.0