Q156902: STL Sample for deque::operator[] and deque::at Functions

Article: Q156902
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbcode kbVC420 kbVC500 kbVC600 kbDSupport
Last Modified: 27-MAR-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
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NOTE: Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.

SUMMARY
=======

The sample code below illustrates how to use the deque::operator[], deque::at,
deque::empty, deque::push_back, and deque::end, STL functions in Visual C++.

MORE INFORMATION
================

Required Header
---------------

     < deque>

Prototype
---------

     const_reference operator[](size_type pos) const;
     reference operator[](size_type pos);
     const_reference operator[](difference_type _N) const;
     reference operator[](difference_type _N) const;

     const_reference at(size_type pos) const;
     reference at(size_type pos);

     bool empty() const;

NOTE: The class/parameter names in the prototype may not match the version in the
header file. Some have been modified to improve readability.

Description
-----------

The member function operator[] returns a reference to the element of the
controlled sequence at position pos. If that position is invalid, the behavior
is undefined.

The member function at returns a reference to the element of the controlled
sequence at position pos. If that position is invalid, the function throws an
object of class out_of_range.

The member function empty returns true for an empty controlled sequence.

Sample Code
-----------

  ////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: -GX
  // 
  // deque.cpp :
  // 
  // Functions:
  // 
  //    operator[]
  //    at
  //    empty
  //    push_back
  //    begin
  //    end
  // 
  // 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>

  #if _MSC_VER > 1020   // if VC++ version is > 4.2
     using namespace std;  // std c++ libs implemented in std
     #endif

  typedef deque<char, allocator<char> >  CHARDEQUE;

  void print_contents (CHARDEQUE  deque, char*);

  void main()

  {

      //create an empty deque a
      CHARDEQUE  a;

      //check whether it is empty
      if(a.empty())
          cout<<"a is empty"<<endl;
      else
          cout<<"a is not empty"<<endl;

      //inset A, B, C and D  to a
      a.push_back('A');
      a.push_back('B');
      a.push_back('C');
      a.push_back('D');

      //check again whether a is empty
      if(a.empty())
          cout<<"a is empty"<<endl;
      else
          cout<<"a is not empty"<<endl;

      //print out the contents

      print_contents (a,"a");

      cout <<"The first element of a is  " <<a[0] <<endl;
      cout <<"The first element of a is  " <<a.at(0) <<endl;

      cout <<"The last element of a is  " <<a[a.size()-1] <<endl;
      cout <<"The last element of a is  " <<a.at(a.size()-1) <<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;

  }

Program Output is:

a is empty
a is not empty
The contents of a : A B C D
The first element of a is  A
The first element of a is  A
The last element of a is  D
The last element of a is  D

REFERENCES
==========

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

Additional query words: STL STLSample deque operator[] at empty push_back begin end kbSTL kbTemplate

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Keywords          : kbcode kbVC420 kbVC500 kbVC600 kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVC420 kbVC500 kbVC600 kbVC32bitSearch kbVCNET kbVC500Search
Version           : :4.2,5.0,6.0
Issue type        : kbinfo

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