list1904.cpp

teach yourself C++ in 21 days 第五版

//Listing 19.4 Using Operator ostream
#include <iostream>
using namespace std;

const int DefaultSize = 10;

class Animal
{
  public:
     Animal(int);
    Animal();
    ~Animal() {}
    int GetWeight() const { return itsWeight; }
    void Display() const { cout << itsWeight; }
  private:
    int itsWeight;
};

Animal::Animal(int weight):
   itsWeight(weight)
{}

Animal::Animal():
   itsWeight(0)
{}

template <class T>  // declare the template and the parameter
class Array            // the class being parameterized
{
  public:
    // constructors
    Array(int itsSize = DefaultSize);
    Array(const Array &rhs);
    ~Array() { delete [] pType; }
 
    // operators
    Array& operator=(const Array&);
    T& operator[](int offSet) { return pType[offSet]; }
    const T& operator[](int offSet) const
       { return pType[offSet]; }
    // accessors
    int GetSize() const { return itsSize; }

    template <class T>
    friend ostream& operator<< (ostream&, Array<T>&);
  private:
    T *pType;
    int  itsSize;
};

template <class T>
ostream& operator<< (ostream& output, Array<T>& theArray)
{
   for (int i = 0; i < theArray.itsSize; i++)
   {
      output << "[" << i << "] " << theArray[i] << endl;
   }
   return output;
}

// implementations follow...

// implement the Constructor
template <class T>
Array<T>::Array(int size):
   itsSize(size)
{
   pType = new T[size];
   for (int i = 0; i < size; i++)
      pType[i] = 0;
}

// copy constructor
template <class T>
Array<T>::Array(const Array &rhs)
{
   itsSize = rhs.GetSize();
   pType = new T[itsSize];
   for (int i = 0; i < itsSize; i++)
      pType[i] = rhs[i];
}

// operator=
template <class T>
Array<T>& Array<T>::operator=(const Array &rhs)
{
   if (this == &rhs)
      return *this;
   delete [] pType;
   itsSize = rhs.GetSize();
   pType = new T[itsSize];
   for (int i = 0; i < itsSize; i++)
      pType[i] = rhs[i];
   return *this;
}

int main()
{
   bool Stop = false;       // flag for looping
   int offset, value;
   Array<int> theArray;

   while (Stop == false)
   {
      cout << "Enter an offset (0-9) ";
      cout << "and a value. (-1 to stop): ";
      cin >> offset >> value;

      if (offset < 0)
         break;

      if (offset > 9)
      {
         cout << "***Please use values between 0 and 9.***\n";
         continue;
      }

      theArray[offset] = value;
   }

   cout << endl << "Here's the entire array:" << endl;
   cout << theArray << endl;
   return 0;
}