Q158575: STL Sample for the set::(empty, clear) Functions

Article: Q158575
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbcode kbtemplate kbSTL kbVC420 kbVC500 kbVC600 kbDSupport
Last Modified: 04-MAY-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- The Standard C++ Library, used with:
   - 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) 
-------------------------------------------------------------------------------

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 following sample code illustrates how to use the set::empty and set::clear
STL functions in Visual C++.

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

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

     <set>

Prototype
---------

     template<class _K, class _Pr, class _A>
     class set {
     public:
     // Function 1:

        bool empty() const;

     // Function 2:
        void clear();
     }

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 empty function returns true when there are no elements in the controlled
sequence. By calling erase(begin,end), the clear function removes all elements
in the controlled sequence. For more information on the erase function, please
see set::erase.

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

  ////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: -GX
  // 
  // SetEmpty&Clear.cpp:
  //      Illustrates how to use the empty function to determine if
  //      there are elements in the controlled sequence. It also
  //      illustrates how to use the clear function to remove all
  //      elements from the controlled sequence.
  // 
  // Functions:
  // 
  //    empty        Returns true if there are no elements in the
  //                 controlled sequence.
  //    clear        Removes all elements from the controlled sequence.
  // 
  // Written by Derek Jamison
  // of Microsoft Technical Support,
  // Copyright (c) 1996 Microsoft Corporation. All rights reserved.
  ////////////////////////////////////////////////////////////////////// 

  #pragma warning(disable:4786)

  #include <set>
  #include <iostream>

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

  typedef set<int,less<int>,allocator<int> > SET_INT;

  void truefalse(int x)
  {
    cout << (x?"True":"False") << endl;
  }

  void main() {

    SET_INT s1;

    cout << "s1.empty() returned ";
    truefalse(s1.empty());  // True

    cout << "s1.insert(5)" << endl;
    s1.insert(5);
    cout << "s1.insert(8)" << endl;
    s1.insert(8);

    cout << "s1.empty() returned ";
    truefalse(s1.empty());  // False

    cout << "s1.clear()" << endl;
    s1.clear();

    cout << "s1.empty() returned ";
    truefalse(s1.empty());  // True
  }

Program Output
--------------

  s1.empty() returned True
  s1.insert(5)
  s1.insert(8)
  s1.empty() returned False
  s1.clear()
  s1.empty() returned True

REFERENCES
==========

Visual C++ Books Online: Visual C++ Books; C/C++; Standard C++ Library Reference

Additional query words: STL STLSample empty clear string

======================================================================
Keywords          : kbcode kbtemplate kbSTL kbVC420 kbVC500 kbVC600 kbDSupport 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : :4.2,5.0,6.0
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.