chapter10-39.cpp

C++STL程序员开发指南

//文件名:CHAPTER10-39.cpp
#include <map>
#include <iostream>
#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
#endif
void main( )
{
   map <int, int>::allocator_type m1_Alloc;
   map <int, int>::allocator_type m2_Alloc;
   map <int, double>::allocator_type m3_Alloc;
   map <int, int>::allocator_type m4_Alloc;
   // The following lines declare objects that use the default allocator.
   map <int, int> m1;
   map <int, int, allocator<int> > m2;
   map <int, double, allocator<double> > m3;
   m1_Alloc = m1.get_allocator( );
   m2_Alloc = m2.get_allocator( );
   m3_Alloc = m3.get_allocator( );
   cout << "The number of integers that can be allocated\n"
        << "before free memory is exhausted: "<< m2.max_size( ) << ".\n" << endl;
   cout << "The number of doubles that can be allocated\n"
        << "before free memory is exhausted: "<< m3.max_size( ) <<  ".\n" << endl;
   // The following line creates a map m4 with the allocator of map m1.
   map <int, int> m4( less<int>( ), m1_Alloc );
   m4_Alloc = m4.get_allocator( );
   // Two allocators are interchangeable if storage allocated from 
//each can be deallocated with the other
   if( m1_Alloc == m4_Alloc )   
   {      cout << "The allocators are interchangeable." << endl;   }
   else   
   { cout << "The allocators are not interchangeable." << endl;   }
}