INFO: STL Sample for the partial_sum Function (157393)



The information in this article applies to:

  • The Standard C++ Library, when used with:
    • Microsoft Visual C++, 32-bit Enterprise Edition 4.2
    • Microsoft Visual C++, 32-bit Enterprise Edition 5.0
    • Microsoft Visual C++, 32-bit Enterprise Edition 6.0
    • Microsoft Visual C++, 32-bit Professional Edition 4.2
    • Microsoft Visual C++, 32-bit Professional Edition 5.0
    • Microsoft Visual C++, 32-bit Professional Edition 6.0
    • Microsoft Visual C++, 32-bit Learning Edition 6.0
    • Microsoft Visual C++ .NET (2003)
    • Microsoft Visual C++ .NET (2002)

This article was previously published under Q157393
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.

Modification Type:MajorLast Reviewed:9/22/2003
Keywords:kbcode kbinfo KB157393