Holder value;
   static Holder length;
   static Holder roots;
   static Holder powers;
   
   Symbol (const Holder& value = Holder (0));
   Symbol (const Symbol& symbol);
   ~Symbol (void);
   Symbol operator ! (void) const;
   Symbol operator ~ (void) const;
   Symbol operator & (const Symbol& symbol) const;
   Symbol operator | (const Symbol& symbol) const;
   Symbol operator ^ (const Symbol& symbol) const;
   Symbol operator + (const Symbol& symbol) const;
   Symbol operator - (const Symbol& symbol) const;
   Symbol operator * (const Symbol& symbol) const;
   Symbol operator / (const Symbol& symbol) const;
   Symbol& operator = (const Holder& value);
   Symbol& operator = (const Symbol& symbol);
   Symbol& operator &= (const Symbol& symbol);
   Symbol& operator |= (const Symbol& symbol);
   Symbol& operator ^= (const Symbol& symbol);
   Symbol& operator += (const Symbol& symbol);
   Symbol& operator -= (const Symbol& symbol);
   Symbol& operator *= (const Symbol& symbol);
   Symbol& operator /= (const Symbol& symbol);
   operator Holder (void) const;