Q157393: INFO: STL Sample for the partial_sum Function

Article: Q157393
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbcode kbVC420 kbVC500 kbVC600 kbDSupport
Last Modified: 27-MAR-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 sample code below illustrates how to use partial_sum STL function in Visual
C++.

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

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

     #include <numeric>
     #include <functional>

Prototype
---------

     template<class InputIterator, class OutputIterator> inline

         OutputIterator partial_sum(InputIterator first, InputIterator last,
                                    OutputIterator first2)

     template<class InputIterator, class OutputIterator,

              class BinaryOperator> inline
         OutputIterator partial_sum(InputIterator first, InputIterator last,
                                    OutputIterator first2,
                                    BinaryOperator binary_op)

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
-----------

Assigns to every iterator i in the range [result,result + (last - first)) a value
correspondingly equal to ((...(*first + *(first + 1)) + ...) + *(first + (i -
result)))

- or -

binary_op(binary_op(..., binary_op(*first, *(first + 1)),...), *(first + (i -
result)))

In other words, *(result+i) = init + *(first+0) + *(first+1) + ... + *(first+i)

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

  /////////////////////////////////////////////////////////////////////// 
  // 
  // Compile options needed: /GX
  // 
  // partial_sum.cpp : Demonstrates the use of partial_sum().
  // 
  // Description of partial_sum(first,last,first2,init)
  //                partial_sum(first,last,first2,init,binary_op):
  // 
  //    Assigns to every iterator i in the range
  //    [result,result + (last - first)) a value correspondingly equal to
  //    ((...(*first + *(first + 1)) + ...) + *(first + (i - result)))
  // 
  //     - or -
  // 
  //    binary_op(binary_op(..., binary_op(*first, *(first  +  1)),...),
  //    *(first + (i - result)))
  // 
  //    In other words,
  //    *(result+i) = init + *(first+0) + *(first+1) + ... + *(first+i)
  // 
  // Written by Shaun Miller
  // of Microsoft Product Support Services, Languages Developer Support.
  // Copyright (c) 1996 Microsoft Corporation. All rights reserved.
  /////////////////////////////////////////////////////////////////////// 

  #include <iostream>
  #include <numeric>
  #include <functional>
  #include <vector>
  #include <iterator>

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

  typedef vector < int, allocator < int > > IntArray;
  typedef ostream_iterator < int, char, char_traits<char> > IntOstreamIt;

  void main ()

  {

      IntOstreamIt itOstream(cout," ");

      // Initialize the array
      IntArray rgI;
      for (int i=1; i<=10; i++) rgI.push_back(i);

      // Print the arrays
      cout << "Array: ";
      copy(rgI.begin(),rgI.end(),itOstream);
      cout << endl;

      // The result array must be at least the same size as the data array
      IntArray rgIresult(rgI.size());

      // Compute the partial sum of the array
      partial_sum(rgI.begin(),rgI.end(),rgIresult.begin());

      // Print the array of partial sums
      cout << "Array of partial sums: ";
      copy(rgIresult.begin(),rgIresult.end(),itOstream);
      cout << endl;

      // Compute the partial product of the array
      partial_sum(rgI.begin(),rgI.end(),rgIresult.begin(),multiplies<int>());

      // Print the array of partial products
      cout << "Array of partial products: ";
      partial_sum(rgIresult.begin(),rgIresult.end(),itOstream);
      cout << endl;

  }

The program output is:

Array: 1 2 3 4 5 6 7 8 9 10
Array of partial sums: 1 3 6 10 15 21 28 36 45 55
Array of partial products: 1 3 9 33 153 873 5913 46233 409113 4037913

REFERENCES
==========

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

Additional query words: STL STLSample partial_sum kbSTL kbTemplate

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

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