Microsoft KB Archive/156807

= How to use the accumulate, copy, and vector::push_back STL functions in Visual C++ =

Article ID: 156807

Article Last Modified on 1/5/2006

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APPLIES TO


 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 4.2 Professional Edition
 * Microsoft Visual C++ 5.0 Professional Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition
 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition
 * Microsoft Visual C++ 2005 Express Edition

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This article was previously published under Q156807



Note Microsoft Visual C++ NET 2002 supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies to unmanaged Visual C++ code only.

Note Microsoft Visual C++ 2005 supports both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model.



SUMMARY
The sample code below illustrates how to use the accumulate, copy, and vector::push_back STL functions in Visual C++.



Prototype
template inline

_TYPE accumulate(InputIterator first, InputIterator last, _TYPE init)

template inline

_TYPE accumulate(InputIterator first, InputIterator last, _TYPE init,                      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
The accumulate function initializes an accumulator acc with an initial value init and then modifies it with acc = acc + *i or acc = binary_op(acc,*i) for every iterator i in the range [first, last) in order.

Normally, the accumulate function is used to sum the numeric elements of a vector. However, it can also be used to do other useful work such as concatenate a vector of strings.

Sample Code
///////////////////////////////////////////////////////////////////////   //    // Compile options needed: /GX //   // accumulate.cpp : Demonstrates the use of accumulate //   // Description of accumulate(first,last,init) //               accumulate(first,last,init,binary_op): //   //    Initializes the accumulator acc with the initial value init //       acc = init //   and then modifies it with //       acc  =  acc + *i //   or   //        acc = binary_op(acc, *i) //   for every iterator i in the range [first, last) in order.   //    // Written by Shaun Miller   // of Microsoft Product Support Services, Languages Developer Support.   // Copyright (c) 1996 Microsoft Corporation. All rights reserved.   ///////////////////////////////////////////////////////////////////////

// turn off warning about symbols too long for debugger #pragma warning (disable : 4786)

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

typedef vector < float, allocator > FloatArray; typedef vector < string, allocator > StringArray; typedef ostream_iterator  FloatOstreamIt;

void main {      // a vector of floats FloatArray rgFA;

// an ostream iterator that outputs a float to cout terminated // by a space FloatOstreamIt OstreamIt(cout," ");

// Initialize the array to 1,1/2,1/3,... for (int i=0; i<10; i++) rgFA.push_back(1.0f/(i+1));

// Print the array copy(rgFA.begin,rgFA.end,OstreamIt); cout << endl;

// Sum the array cout << "The sum of 1 + 1/2 + 1/3 + ... + 1/10 is " << accumulate(rgFA.begin,rgFA.end,0.0f) << endl;

// Compute the product of the array cout << "The product of 1 * 1/2 * 1/3 * ... * 1/10 is " << accumulate(rgFA.begin,rgFA.end,1.0f,multiplies ) << endl;

// Initialize array of strings StringArray rgs; rgs.push_back("This "); rgs.push_back("is "); rgs.push_back("one "); rgs.push_back("sentence. ");

// Concatenate the strings in the array & print the sentence cout << "The concatenated vector of strings: " << accumulate(rgs.begin,rgs.end,string("")) << endl; } Program Output is: 1 0.5 0.333333 0.25 0.2 0.166667 0.142857 0.125 0.111111 0.1 The sum of 1 + 1/2 + 1/3 + ... + 1/10 is 2.92897 The product of 1 * 1/2 * 1/3 * ... * 1/10 is 2.75573e-007 The concatenated vector of strings: This is one sentence.

