Microsoft KB Archive/158575

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

Article ID: 158575

Article Last Modified on 12/30/2005

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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</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2002 Standard Edition</li></ul>

 Microsoft Visual C++ .NET 2003 Standard Edition</li></ul>

 Microsoft Visual C++ 2005 Express Edition</li></ul> </li></ul>

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This article was previously published under Q158575

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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.

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

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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 about 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 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. //////////////////////////////////////////////////////////////////////


 * 1) pragma warning(disable:4786)
 * 2) include
 * 3) include

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

typedef set<int,less ,allocator > 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

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