Help and Support

Article ID: 158575 - Last Review: December 30, 2005 - Revision: 5.1

How to use the set::empty and set::clear STL functions in Visual C++

View products that this article applies to.
This article was previously published under Q158575
Note Microsoft Visual C++ .NET (2002) and Microsoft Visual C++ 2005 support 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.

On This Page

Expand all | Collapse all

SUMMARY

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

MORE INFORMATION

Required header

<set>
Back to the top

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.
Back to the top

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 about the erase function, please see set::erase.
Back to the top

Sample code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: -GX
// 
// SetEmpty&Clear.cpp:
//      Illustrates how to use the empty function to determine whether
//      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
}
Back to the top

Program output

s1.empty() returned True
s1.insert(5)
s1.insert(8)
s1.empty() returned False
s1.clear()
s1.empty() returned True
Back to the top

REFERENCES

For the same topic about set::empty and set::clear, visit the following MSDN Web site: http://msdn.microsoft.com/en-us/library/x6sxc0b1.aspx (http://msdn.microsoft.com/en-us/library/x6sxc0b1.aspx)
Back to the top
APPLIES TO
  • The Standard C++ Library, when used with:
    • 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++, 32-bit Learning Edition 6.0
    • Microsoft Visual C++ .NET 2002 Standard Edition
    • Microsoft Visual C++ .NET 2003 Standard Edition
    • Microsoft Visual C++ 2005 Express Edition
Back to the top
Keywords: 
kbcode kbinfo kbstl kbtemplate KB158575
Back to the top

Get Help Now

Contact a support professional by E-mail, Online, or Phone

Article Translations