computational-combinatorics/set-partition

import {list} from '@iterable-iterator/list';
import {map} from '@iterable-iterator/map';

export default function* _enumerate(elements, n = elements.length) {
    if (n === 0) yield [];
    else {
        const last = elements[n - 1];
        for (const partition of _enumerate(elements, n - 1)) {
            yield partition.concat([[last]]);
            for (const part of partition) {
                yield list(map((p) => (p === part ? p.concat([last]) : p), partition));
            }
        }
    }
}