single property

E single
override

Checks that this iterable has only one element, and returns that element.

Throws a StateError if this is empty or has more than one element.

Implementation 

E get single {
  if (isEmpty) {
    throw new StateError('No such element');
  }
  if (_length > 1) {
    throw new StateError('Too many elements');
  }
  return _first;
}