@effect-ts/system/_src/Experimental/Stream/_internal/api/unfold.ts

Effect-TS is a zero dependency set of libraries to write highly productive, purely functional TypeScript at scale.

// ets_tracing: off

import * as CK from "../../../../Collections/Immutable/Chunk/index.js"
import * as Tp from "../../../../Collections/Immutable/Tuple/index.js"
import * as O from "../../../../Option/index.js"
import type * as C from "../core.js"
import * as UnfoldChunk from "./unfoldChunk.js"

/**
 * Creates a stream by peeling off the "layers" of a value of type `S`
 */
export function unfold<S, A>(s: S, f: (s: S) => O.Option<Tp.Tuple<[A, S]>>): C.UIO<A> {
  return UnfoldChunk.unfoldChunk(s, (_) =>
    O.map_(f(_), ({ tuple: [a, s] }) => Tp.tuple(CK.single(a), s))
  )
}