description

# 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 StateError('No such element');
      }
      if (_length > 1) {
        throw StateError('Too many elements');
      }
      return _first;
    }