dropLast method
Implementation
IVector<A> dropLast() => _length == 0 ? this : new IVector._internal(_elementsByIndex.remove(_offset+(_length-1)), _offset, _length-1);
IVector<A> dropLast() => _length == 0 ? this : new IVector._internal(_elementsByIndex.remove(_offset+(_length-1)), _offset, _length-1);