export class Stream {
  _listeners = [];
  listen(caller) {
    this._listeners.push(caller);
  }
  ignore(caller) {
    if (~this._listeners.indexOf(caller)) {
      this._listeners.splice(this._listeners.indexOf(caller));
    }
  }
  add(value) {
    for (let caller of this._listeners) caller(value);
  }
}