export const intersect = <A>(xs: Set<A>, ys: Set<A>): Set<A> => {
    const out: Set<A> = new Set()

    xs.forEach(x => {
        if (ys.has(x)) {
            out.add(x)
        }
    })

    return out
}

export const setEquals = <A>(xs: Set<A>, ys: Set<A>): boolean => {
    if (xs.size != ys.size) {
        return false
    }

    for (const x of Array.from(xs)) {
        if (!ys.has(x)) {
            return false
        }
    }

    return true
}

export const union = <A>(xs: Set<A>, ys: Set<A>): Set<A> =>
    new Set([
        ...Array.from(xs),
        ...Array.from(ys),
    ])