Q158573: STL Sample for the set::(key_, value_)comp Function

Article: Q158573
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

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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) 
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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::key_comp and
set::value_comp STL functions in Visual C++.

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

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

     <set>

Prototype
---------

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

        key_compare key_comp() const;

     // Function 2:
        value_compare value_comp() 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 key_comp function returns the stored function object that determines the
order of elements in the controlled sequence. The value_comp function returns
the same function that key_comp returns.

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

  ////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: -GX
  // 
  // SetComp.cpp:
  //      Illustrates how to use the key_comp function to obtain a
  //      function pointer that is the stored function object that
  //      determines the order of elements in the controlled sequence.
  //      It also illustrates how to use the value_comp function to
  //      obtain a function pointer that is the stored function object
  //      that determines the order of the elements in the controlled
  //      sequence (same as key_comp result).
  // 
  // Functions:
  // 
  //    key_comp     Returns a function pointer to the function that
  //                 determines the order of elements in the controlled
  //                 sequence.
  //    value_comp   Returns a function pointer to the function that
  //                 determines the order of elements in the controlled
  //                 sequence (same as key_comp).
  // 
  // 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.key_comp()(8,10) returned ";
    truefalse(s1.key_comp()(8,10));  // True

    cout << "s1.value_comp()(8,10) returned ";
    truefalse(s1.value_comp()(8,10));  // True

    cout << "s1.key_comp()(10,8) returned ";
    truefalse(s1.key_comp()(10,8));  // False

    cout << "s1.value_comp()(10,8) returned ";
    truefalse(s1.value_comp()(10,8));  // False

    cout << "s1.key_comp()(8,8) returned ";
    truefalse(s1.key_comp()(8,8));  // False

    cout << "s1.value_comp()(8,8) returned ";
    truefalse(s1.value_comp()(8,8));   // False
  }

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

  s1.key_comp()(8,10) returned True
  s1.value_comp()(8,10) returned True
  s1.key_comp()(10,8) returned False
  s1.value_comp()(10,8) returned False
  s1.key_comp()(8,8) returned False
  s1.value_comp()(8,8) returned False

REFERENCES
==========

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

Additional query words: STL STLSample value_comp key_comp

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

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