description

# lookup method Null safety

E? lookup (

1. Object? object

)
override

If an object equal to `object` is in the set, return it.

Checks whether `object` is in the set, like contains, and if so, returns the object in the set, otherwise returns `null`.

If the equality relation used by the set is not identity, then the returned object may not be identical to `object`. Some set implementations may not be able to implement this method. If the contains method is computed, rather than being based on an actual object instance, then there may not be a specific object instance representing the set element.

## Implementation

    E? lookup(Object? object) {
      if (!_validKey(object)) return null;
      int comp = _splay(object as E);
      if (comp != 0) return null;
      return _root!.key;
    }