module.exports = class Sets {
  static and(set1, ...rest) {
    const output = new Set();
    for (const v of set1) {
      if (rest.every((set) => set.has(v))) {
        output.add(v);
      }
    }
    return output;
  }
  static or(...sets) {
    const output = new Set();
    for (const set of sets) {
      for (const v of set) {
        output.add(v);
      }
    }
    return output;
  }
  static xor(...sets) {
    if (sets.length !== 2) {
      throw new Error('xor is only meaningful on 2 sets');
    }
    const [l, r] = sets;
    const output = new Set();
    for (const v of l) {
      if (!r.has(v)) {
        output.add(v);
      }
    }
    for (const v of r) {
      if (!l.has(v)) {
        output.add(v);
      }
    }
    return output;
  }
  static counts(...sets) {
    const output = new Map();
    for (const set of sets) {
      for (const v of set) {
        output.set(v, (output.get(v) || 0n) + 1n);
      }
    }
    return output;
  }
};