Microsoft KB Archive/156902

= INFO: Sample of deque: operator[] and deque::at Functions =

Article ID: 156902

Article Last Modified on 9/18/2003

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APPLIES TO


 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 4.2 Professional Edition
 * Microsoft Visual C++ 5.0 Professional Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition
 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition

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This article was previously published under Q156902



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++.



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
 * 1) include
 * 2) include
 * 1) include

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

typedef deque 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 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

