Microsoft KB Archive/157392

= INFO: STL Sample for the inner_product Function =

Article ID: 157392

Article Last Modified on 9/23/2003

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APPLIES TO

 The Standard C++ Library, when used with:  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</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul> </li> Microsoft Visual C++ .NET 2002 Standard Edition</li> Microsoft Visual C++ .NET 2003 Standard Edition</li></ul>

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This article was previously published under Q157392

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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.

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SUMMARY
The sample code below illustrates how to use the inner_product STL function in Visual C++.

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Required Header
#include #include

Prototype
template<class InputIterator1, class InputIterator2, class _TYPE>

inline _TYPE inner_product(InputIterator first, InputIterator last,                          InputIterator first2, _TYPE init)

template<class InputIterator1, class InputIterator2, class _TYPE,

class BinaryOperator1, class BinaryOperator2> inline _TYPE inner_product(InputIterator1 first, InputIterator1 last,                          InputIterator2 first2, _TYPE init,                           BinaryOperator1 binary_op1,                           BinaryOperator2 binary_op2) 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
inner_product computes its result by initializing the accumulator acc with init and then modifying it with:

acc = acc + (*i1) * (*i2)

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acc = binary_op1(acc, binary_op2(*i1, *i2))

for every iterator i1 in the range [first, last) and iterator i2 in the range [first2, first2 + (last - first)) in order.

Sample Code
/////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // inner_product.cpp : Demonstrates the use of inner_product. // // Description of //        inner_product(first,last,first2,init) //        inner_product(first,last,first2,init,binary_op1,binary_op2): // //   Computes its result by initializing the accumulator acc with init //       acc = init //   and then modifying it with //       acc = acc  +  (*i1) * (*i2) //   or //        acc = binary_op1(acc, binary_op2(*i1, *i2)) //   for every iterator i1 in the range [first, last) and //    iterator  i2  in  the  range [first2, first2 + (last - first)) //   in order. // // Written by Shaun Miller // of Microsoft Product Support Services, Languages Developer Support. // Copyright (c) 1996 Microsoft Corporation. All rights reserved. ///////////////////////////////////////////////////////////////////////


 * 1) include
 * 2) include
 * 3) include
 * 4) include
 * 5) 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 ostream_iterator < float, char, char_traits > FloatOstreamIt;

void main

{

FloatOstreamIt itOstream(cout," ");

// Initialize the arrays FloatArray rgF1, rgF2; for (int i=1; i<=5; i++) { rgF1.push_back((float)i); rgF2.push_back((float)i*i); };

// Print the arrays cout << "Array 1: "; copy(rgF1.begin,rgF1.end,itOstream); cout << endl; cout << "Array 2: "; copy(rgF2.begin,rgF2.end,itOstream); cout << endl;

// Compute the inner_product of the arrays // This is the sum of the products (S.O.P) of the correspondingelements

float ip1 = inner_product(rgF1.begin,rgF1.end,rgF2.begin,0.0f); cout << "The inner product (S.O.P) of Array1 and Array2 is " << ip1 << endl;

// Compute the inner_product of the arrays // This is the product of the sums (P.O.S.) of the corresponding elements

float ip2 = inner_product(rgF1.begin,rgF1.end,rgF2.begin,1.0f,                           multiplies ,plus ); cout << "The inner product (P.O.S.) of Array1 and Array2 is " << ip2 << endl;

} Program Output is: <pre class="fixed_text">Array 1: 1 2 3 4 5 Array 2: 1 4 9 16 25 The inner product (S.O.P) of Array1 and Array2 is 225 The inner product (P.O.S.) of Array1 and Array2 is 86400

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