// 3. Предефиниране на операции
// -- Въведение, основни понятия. Ограничения при предефинирането на 
 операции. 
// -- Функции за предефиниране на операции: членове на клас или приятелски 
 функции. 


// -- Предефиниране на потоковите операции за вход и изход. 
//
// fig08_03.cpp
// Overloading the stream-insertion and 
// stream-extraction operators.
#include <iostream.h>
#include <iomanip.h>

class PhoneNumber {
   friend ostream &operator<<( ostream&, const PhoneNumber & );
   friend istream &operator>>( istream&, PhoneNumber & );

private:
   char areaCode[ 4 ];  // 3-digit area code and null
   char exchange[ 4 ];  // 3-digit exchange and null
   char line[ 5 ];      // 4-digit line and null
};

// Overloaded stream-insertion operator (cannot be 
// a member function if we would like to invoke it with
// cout << somePhoneNumber;).
ostream &operator<<( ostream &output, const PhoneNumber &num )
{
   output << "(" << num.areaCode << ") "
          << num.exchange << "-" << num.line;
   return output;     // enables cout << a << b << c;
}

istream &operator>>( istream &input, PhoneNumber &num )
{
   input.ignore();                     // skip (
   input >> setw( 4 ) >> num.areaCode; // input area code
   input.ignore( 2 );                  // skip ) and space
   input >> setw( 4 ) >> num.exchange; // input exchange
   input.ignore();                     // skip dash (-)
   input >> setw( 5 ) >> num.line;     // input line
   return input;      // enables cin >> a >> b >> c;
}

int main()
{
   PhoneNumber phone; // create object phone

   cout << "Enter phone number in the form (123) 456-7890:\n";

   // cin >> phone invokes operator>> function by 
   // issuing the call operator>>( cin, phone ).
   cin >> phone;

   // cout << phone invokes operator<< function by
   // issuing the call operator<<( cout, phone ). 
   cout << "The phone number entered was: " << phone << endl;
   return 0;
}
------------------------------------------------------------
//-- Създаване на клас Array 
//
// array1.h
// Simple class Array (for integers)
#ifndef ARRAY1_H
#define ARRAY1_H

#include <iostream.h>

class Array {
   friend ostream &operator<<( ostream &, const Array & );
   friend istream &operator>>( istream &, Array & );
public:
   Array( int = 10 );                   // default constructor
   Array( const Array & );              // copy constructor
   ~Array();                            // destructor
   int getSize() const;                 // return size
   const Array &operator=( const Array & ); // assign arrays
   bool operator==( const Array & ) const;  // compare equal

   // Determine if two arrays are not equal and
   // return true, otherwise return false (uses operator==).
   bool operator!=( const Array &right ) const  
      { return ! ( *this == right ); }
   
   int &operator[]( int );              // subscript operator
   const int &operator[]( int ) const;  // subscript operator
   static int getArrayCount();          // Return count of 
                                        // arrays instantiated.
private:
   int size; // size of the array
   int *ptr; // pointer to first element of array
   static int arrayCount;  // # of Arrays instantiated
};

#endif
------
// Fig 8.4: array1.cpp
// Member function definitions for class Array
#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>
#include <assert.h>
#include "array1.h"

// Initialize static data member at file scope
int Array::arrayCount = 0;   // no objects yet

// Default constructor for class Array (default size 10)
Array::Array( int arraySize )
{
   size = ( arraySize > 0 ? arraySize : 10 ); 
   ptr = new int[ size ]; // create space for array
   assert( ptr != 0 );    // terminate if memory not allocated
   ++arrayCount;          // count one more object

   for ( int i = 0; i < size; i++ )
      ptr[ i ] = 0;          // initialize array
}

// Copy constructor for class Array
// must receive a reference to prevent infinite recursion
Array::Array( const Array &init ) : size( init.size )
{
   ptr = new int[ size ]; // create space for array
   assert( ptr != 0 );    // terminate if memory not allocated
   ++arrayCount;          // count one more object

   for ( int i = 0; i < size; i++ )
      ptr[ i ] = init.ptr[ i ];  // copy init into object
}

// Destructor for class Array
Array::~Array()
{
   delete [] ptr;            // reclaim space for array
   --arrayCount;             // one fewer objects
}

// Get the size of the array
int Array::getSize() const { return size; }

// Overloaded assignment operator
// const return avoids: ( a1 = a2 ) = a3
const Array &Array::operator=( const Array &right )
{
   if ( &right != this ) {  // check for self-assignment
      
      // for arrays of different sizes, deallocate original
      // left side array, then allocate new left side array.
      if ( size != right.size ) {
         delete [] ptr;         // reclaim space
         size = right.size;     // resize this object
         ptr = new int[ size ]; // create space for array copy
         assert( ptr != 0 );    // terminate if not allocated
      }

      for ( int i = 0; i < size; i++ )
         ptr[ i ] = right.ptr[ i ];  // copy array into object
   }

   return *this;   // enables x = y = z;
}

// Determine if two arrays are equal and
// return true, otherwise return false.
bool Array::operator==( const Array &right ) const
{
   if ( size != right.size )
      return false;    // arrays of different sizes

   for ( int i = 0; i < size; i++ )
      if ( ptr[ i ] != right.ptr[ i ] )
         return false; // arrays are not equal

   return true;        // arrays are equal
}

// Overloaded subscript operator for non-const Arrays
// reference return creates an lvalue
int &Array::operator[]( int subscript )
{
   // check for subscript out of range error
   assert( 0 <= subscript && subscript < size );

   return ptr[ subscript ]; // reference return
}

// Overloaded subscript operator for const Arrays
// const reference return creates an rvalue
const int &Array::operator[]( int subscript ) const
{
   // check for subscript out of range error
   assert( 0 <= subscript && subscript < size );

   return ptr[ subscript ]; // const reference return
}

// Return the number of Array objects instantiated
// static functions cannot be const 
int Array::getArrayCount() { return arrayCount; }

// Overloaded input operator for class Array;
// inputs values for entire array.
istream &operator>>( istream &input, Array &a )
{
   for ( int i = 0; i < a.size; i++ )
      input >> a.ptr[ i ];

   return input;   // enables cin >> x >> y;
}

// Overloaded output operator for class Array 
ostream &operator<<( ostream &output, const Array &a )
{
   int i;

   for ( i = 0; i < a.size; i++ ) {
      output << setw( 12 ) << a.ptr[ i ];

      if ( ( i + 1 ) % 4 == 0 ) // 4 numbers per row of output
         output << endl;
   }

   if ( i % 4 != 0 )
      output << endl;

   return output;   // enables cout << x << y;
}
---------------
// fig08_04.cpp
// Driver for simple class Array
#include <iostream.h>
#include "array1.h"

int main()
{
   // no objects yet
   cout << "# of arrays instantiated = "
        << Array::getArrayCount() << '\n';

   // create two arrays and print Array count
   Array integers1( 7 ), integers2;
   cout << "# of arrays instantiated = "
        << Array::getArrayCount() << "\n\n";

   // print integers1 size and contents
   cout << "Size of array integers1 is "
        << integers1.getSize()
        << "\nArray after initialization:\n"
        << integers1 << '\n';

   // print integers2 size and contents
   cout << "Size of array integers2 is "
        << integers2.getSize()
        << "\nArray after initialization:\n"
        << integers2 << '\n';

   // input and print integers1 and integers2
   cout << "Input 17 integers:\n";
   cin >> integers1 >> integers2;
   cout << "After input, the arrays contain:\n"
        << "integers1:\n" << integers1
        << "integers2:\n" << integers2 << '\n';

   // use overloaded inequality (!=) operator
   cout << "Evaluating: integers1 != integers2\n";
   if ( integers1 != integers2 )
      cout << "They are not equal\n";

   // create array integers3 using integers1 as an
   // initializer; print size and contents
   Array integers3( integers1 );

   cout << "\nSize of array integers3 is "
        << integers3.getSize()
        << "\nArray after initialization:\n"
        << integers3 << '\n';

   // use overloaded assignment (=) operator
   cout << "Assigning integers2 to integers1:\n";
   integers1 = integers2;
   cout << "integers1:\n" << integers1
        << "integers2:\n" << integers2 << '\n';

   // use overloaded equality (==) operator
   cout << "Evaluating: integers1 == integers2\n";
   if ( integers1 == integers2 )
      cout << "They are equal\n\n";

   // use overloaded subscript operator to create rvalue
   cout << "integers1[5] is " << integers1[5] << '\n';

   // use overloaded subscript operator to create lvalue
   cout << "Assigning 1000 to integers1[5]\n";
   integers1[5] = 1000;
   cout << "integers1:\n" << integers1 << '\n';

   // attempt to use out of range subscript
   cout << "Attempt to assign 1000 to integers1[15]" << endl;
   integers1[15] = 1000;  // ERROR: out of range

   return 0;
}
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