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

Last reviewed: October 9, 1997
Article ID: Q158573

The information in this article applies to:

The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

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>

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 : STLIss kbcode
Version : WINNT:4.2;
Platform : NT WINDOWS
Issue type : kbhowto

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Last reviewed: October 9, 1997
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