STL Sample for the operator == and operato

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

SUMMARY

The sample code below illustrates how to use the operator== and operator< STL functions for the deque container class in Visual C++.

MORE INFORMATION

Required Header

   < deque>

Prototype

   template<class T, class A>
       bool operator==(
           const deque <T, A>& lhs,
           const deque <T, A>& rhs);

   template<class T, class A>
       bool operator<(
           const deque <T, A>& lhs,
           const deque <T, A>& rhs);

Description

The first template function overloads operator== to compare two objects of template class deque. The function returns:

   lhs.size() == rhs.size() && equal(lhs. begin(), lhs. end(),
   rhs.begin()).

The second template function overloads operator< to compare two objects of template class deque. The function returns:

   lexicographical_compare(lhs. begin(), lhs. end(), rhs.begin(),
   rhs.end()).

Sample Code

   //////////////////////////////////////////////////////////////////////
   //
   // Compile options needed: -GX
   //
   // deque.cpp :
   //
   // Functions:
   //
   //    ==
   //    <
   //
   // Written by Bobby Mattappally
   // of Microsoft Product Support Services,
   // Copyright (c) 1996 Microsoft Corporation. All rights reserved.
   //////////////////////////////////////////////////////////////////////

   /* Compile options needed:-GX
   */
   #include <iostream>
   #include <deque>

   typedef deque<char, allocator<char> >  CHARDEQUE;
   void print_contents (CHARDEQUE  deque, char*);

   void main()
   {
       //create a  with  3 A's
       CHARDEQUE  a(3,'A');
       a.push_front('C');

       //create b with 4 B's.
       CHARDEQUE  b(6,'B');

       //print out the contents
       print_contents (a,"a");
       print_contents (b,"b");

       //compare a and b
       if (a==b)
           cout <<"a is equal to b"<<endl;
       else if(a<b)
               cout <<"a is less than b"<<endl;
       else
           cout <<"a is greater than b" <<endl;

       //assign the contents of b to a
       a.assign(b.begin(),b.end());
       print_contents (a,"a");
       print_contents (b,"b");

       //compare a and b again
       if (a==b)
           cout <<"a is equal to b"<<endl;
       else if(a<b)
               cout <<"a is less than b"<<endl;
       else
           cout <<"a is greater than b" <<endl;

   }

   //function to print the contents of deque
   void print_contents (CHARDEQUE  deque, char *name)
   {
       CHARDEQUE::iterator pdeque;

       cout <<"The contents of "<< name <<" : ";

           for(pdeque = deque.begin();
           pdeque != deque.end();
           pdeque++)
       {
           cout << *pdeque <<" " ;
       }
           cout<<endl;
   }

   The contents of a : C A A A
   The contents of b : B B B B B B
   a is greater than b
   The contents of a : B B B B B B
   The contents of b : B B B B B B
   a is equal to b

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.