# single property

Rectangle<num> 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

    Rectangle get single {
      int len = this.length;
      if (len == 1) {
        return JS('Rectangle', '#[0]', this);
      }
      if (len == 0) throw new StateError("No elements");
      throw new StateError("More than one element");
    }