This class represent values in calculator.

You can find more information in comments below.

class CVariable
    {
    public:
        virtual const String &getName() const; // Return name 
        VARIABLE_TYPE getType() const; // Return type 
        int getCount() const; // Return child item count 
        CVariable *getItem(const int index); // Return child item by index 
        CVariable *getItem(const String &name); // Return child item by name 
    
        // Constructors 
        CVariable(CVariable *parent = nullptr);
        CVariable(const String &value, CVariable *parent = nullptr);
        CVariable(const long long value, CVariable *parent = nullptr);
        CVariable(const double value, CVariable *parent = nullptr);
        CVariable(const bool value, CVariable *parent = nullptr);
        CVariable(const VARIABLE_TYPE type, CVariable *parent = nullptr);
        CVariable(const String &name, const String &value, CVariable *parent = nullptr);
        CVariable(const String &name, const long long value, CVariable *parent = nullptr);
        CVariable(const String &name, const double value, CVariable *parent = nullptr);
        CVariable(const String &name, const bool value, CVariable *parent = nullptr);
        CVariable(const String &name, const VARIABLE_TYPE type, CVariable *parent = nullptr);
        virtual ~CVariable(); // Destructor 
    
        // Manage child items 
        void Add(CVariable *item);
        CVariable *Add(const String &name);
        CVariable *Add(const String &name, const String &value);
        CVariable *Add(const String &name, const long long value);
        CVariable *Add(const String &name, const double value);
        void Delete(const int index);
        void Delete(CVariable *item);
        void Delete(const String &name);
        void Clear();
    
        // Clone and copy 
        CVariable *Clone() const;
        void Copy(CVariable *dest) const;
    
        // Assignment operators 
        const CVariable &operator=(const String &value);
        const CVariable &operator=(const long long value);
        const CVariable &operator=(const double value);
        const CVariable &operator=(const bool value);
    
        // Converting operators 
        operator String();
        operator long long();
        operator double();
        operator bool();
    };