Int , Float , String and Complex are the Object type equivalent of int , float , string and complex , respectively. TrueObject and FalseObject are the Object type of bool to support true and false conditions, while nilObject is the Object type of nil to support nil condition. The details of these data types will not be discussed in this section. HARK adapts to the C++ Standard Template Library (STL), where data types are re-declared as Object type. Re-declared Object types include Vector and Matrix , which will be described in details below.