Exercise 6.1

Rewrite the following class definition to make it a class template:

class example { 


public: 


      example( double min, double max ); 


      example( const double *array, int size ); 





      double& operator[]( int index ); 


      bool operator==( const example1& ) const; 





      bool insert( const double*, int ); 


      bool insert( double ); 





      double min() const { return _min; } 


      double max() const { return _max; } 





      void min( double ); 


      void max( double ); 





      int count( double value ) const; 


private: 


      int     _size; 


      double *_parray; 


      double  _min; 


      double  _max; 


}; 

To transform the example class into a template, we must identify and factor out each dependent data type. _size, for example, is of type int. Might that vary with different user-specified instances of example? No. _size is an invariant data member that holds a count of the elements addressed by _parray. _parray, however, may address elements of varying types: int, double, float, string, and so on. We want to parameterize the data type of the members _parray, _min, and _max, as well as the return type and signature of some of the member functions.

template <typename elemType> 


class example { 


public: 


      example( const elemType &min, const elemType &max ); 


      example( const elemType *array, int size ); 





      elemType& operator[]( int index ); 


      bool operator==( const example1& ) const; 





      bool insert( const elemType*, int ); 


      bool insert( const elemType& ); 





      elemType min() const { return _min; }; 


      elemType max() const { return _max; }; 





      void min( const elemType& ); 


      void max( const elemType& ); 





      int count( const elemType &value ) const; 


private: 


      int       _size; 


      elemType *_parray; 


      elemType  _min; 


      elemType  _max; 


}; 

Because elemType now potentially represents any built-in or user-defined class, I declare the formal parameters as const references rather than pass them by value.