thi-ng/umbrella

import type { Fn } from "@thi.ng/api";
import { iterator } from "./iterator.js";

export function* flattenWith(
    tx: Fn<any, any>,
    input: Iterable<any>
): IterableIterator<any> {
    let iter = iterator(input);
    let v: IteratorResult<any>, val, res;
    while (((v = iter.next()), !v.done)) {
        val = v.value;
        if (val != null && (res = tx(val)) !== undefined) {
            yield* flattenWith(tx, res);
        } else {
            yield val;
        }
    }
}