Q156301: INFO: STL Sample for the partition Function

Article: Q156301
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): _IK
Last Modified: 07-MAY-2001

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

- The Standard C++ Library, used with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 4.2 
-------------------------------------------------------------------------------

SUMMARY
=======

The sample code below illustrates how to use the partition, begin, end, and
bind2nd STL functions in Visual C++.

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

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

  <algorithm>
   

Prototype
---------

     template<class BidirectionalIterator, class Predicate> inline
     BidirectionalIterator partition(BidirectionalIterator first,
                                     BidirectionalIterator last,
                                     Predicate predicate)

NOTE: The class/parameter names in the prototype do not match the version in the
header file. Some have been modified to improve readability.

Description
-----------

The partition algorithm arranges elements in the range [first, last) such that
the elements for which predicate returns true are before the elements for which
predicate returns false. The algorithm returns an iterator positioned at the
first element for which predicate returns false.

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

  ////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: /GX
  // 
  // partition.cpp : Illustrates how to use the partition function.
  // 
  // Functions:
  // 
  //   partition  - Partition a range using a predicate.
  // 
  //   begin      - Returns an iterator that points to the first element
  //                in a sequence.
  // 
  //   end        - Returns an iterator that points one past the end of
  //                a sequence.
  // 
  //   bind2nd    - Returns true for elements for which the condition
  //                is true.
  // 
  // Written by Kalindi Sanghrajka
  // of Microsoft Product Support Services,
  // Software Core Developer Support.
  // Copyright (c) 1996 Microsoft Corporation. All rights reserved.
  ////////////////////////////////////////////////////////////////////// 

  // disable warning C4786: symbol greater than 255 character,
  // okay to ignore
  #pragma warning(disable: 4786)

  #include <iostream>
  #include <vector>
  #include <algorithm>
  #include <functional>
  using namespace std;

  void main()
  {
      const int VECTOR_SIZE = 8 ;

      // Define a template class vector of integers
      typedef vector<int, allocator<int> > IntVector ;

      //Define an iterator for template class vector of integer
      typedef IntVector::iterator IntVectorIt ;

      IntVector Numbers(VECTOR_SIZE) ;   //vector containing numbers

      IntVectorIt start, end, it ;

      start = Numbers.begin() ;   // location of first
                                  // element of Numbers

      end = Numbers.end() ;       // one past the location
                                  // last element of Numbers

      //Initialize vector Numbers
      Numbers[0] = 6 ;
      Numbers[1] = 20 ;
      Numbers[2] = 10 ;
      Numbers[3] = 15 ;
      Numbers[4] = 12 ;
      Numbers[5] = 7 ;
      Numbers[6] = 9 ;
      Numbers[7] = 10 ;

      cout << "Before calling partition" << endl ;

      // print content of Numbers
      cout << "Numbers { " ;
      for(it = start; it != end; it++)
          cout << *it << " " ;
      cout << " }\n" << endl ;

      // partition the sequence such that all the elements
      // less than 11 appear before all the elements greater than 11
      it =  partition(start, end, bind2nd(less<int>(), 11)) ;

      cout << "After calling partition" << endl ;

      // print content of Numbers
      cout << "Numbers { " ;
      for(it = start; it != end; it++)
          cout << *it << " " ;
      cout << " }\n" << endl ;

  }

Output:

Before calling partition
Numbers { 6 20 10 15 12 7 9 10 }

After calling partition
Numbers { 6 10 10 9 7 12 15 20 }

REFERENCES
==========

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.

Additional query words: STL partition begin end bind2nd

======================================================================
Keywords          : _IK 
Technology        : kbVCsearch kbAudDeveloper kbVCLibrary
Version           : winnt:
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.