array1.cpp

这是C＋＋编程经典的书上实例的源代码。 （英文名是《C＋＋ how to program》第3版）

// Fig 8.4: array1.cpp
// Member function definitions for class Array
#include <iostream>

using std::cout;
using std::cin;
using std::endl;

#include <iomanip>

using std::setw;

#include <cstdlib>
#include <cassert>
#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;
}


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