INFO: STL sample for deque: size and deque::resize Functions

ID: Q157065

The information in this article applies to:

The Standard C++ Library, used with:
- Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0, 6.0

SUMMARY

The sample code below illustrates how to use the deque::size, deque::resize, deque::max_size, deque::end, and deque::begin STL functions in Visual C++.

MORE INFORMATION

Required Header


   <deque>

Prototype


   size_type size() const;
   void resize(size_type n, T x = T());
   size_type max_size() 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 size returns the length of the controlled sequence.

The member function resize ensures that size() henceforth returns n. If it must make the controlled sequence longer, it appends elements with value x. If no value is supplied, the default value depends upon the type. For example, if it is a deque of chars, the default is a blank. If it is a deque of ints, the default is zero.

The member function max_size returns the length of the longest sequence that the object can control.

Sample Code


////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: -GX
// 
// deque.cpp :
// 
// Functions:
// 
//    size
//    resize
//    max_size
//    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 a  with  A, B, C and D
    CHARDEQUE  a;
    a.push_back('A');
    a.push_back('B');
    a.push_back('C');
    a.push_back('D');

    //print out the contents

    print_contents (a,"a");
    cout <<"max_size of a is " <<a.max_size() <<endl;
    cout <<"size of a is " <<a.size() <<endl;

    //let us increase the size to 10
    // and set the new elements to be 'X'
    a.resize(10,'X');
    print_contents (a,"a");
    cout <<"size of a is " <<a.size() <<endl;

    //let us resize it to 5
    a.resize(5);
    print_contents (a,"a");
    cout <<"size of a is " <<a.size() <<endl;
    cout <<"max_size of a is still " <<a.max_size() <<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:


The contents of a : A B C D
max_size of a is 4294967295
size of a is 4
The contents of a : A B C D X X X X X X
size of a is 10
The contents of a : A B C D X
size of a is 5
max_size of a is still 4294967295

NOTE: With Visual C++ 4.2, the max_size value is misleading because a sequence this long cannot be created. See the following Microsoft Knowledge Base article for further information:

Q160017 BUG: Access Violation Using deque class

REFERENCES

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

Additional query words: STL STLSample deque size resize max_size begin end

Keywords : kbcode kbVC420 kbVC500 kbVC600 kbDSupport STLIss
Version : winnt:4.2,5.0,6.0
Platform : winnt
Issue type : kbinfo