Microsoft KB Archive/156809

= INFO: STL Sample for adjacent_difference, vector::push_back Function =

Article ID: 156809

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>

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

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

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This article was previously published under Q156809

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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 adjacent_difference and vector::push_back STL functions in Visual C++.

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Prototype
template<class InputIterator, class OutputIterator> inline

OutputIterator adjacent_difference(InputIterator first,           InputIterator last, OutputIterator result)

template<class InputIterator, class OutputIterator,

class BinaryOperator> inline OutputIterator adjacent_difference(InputIterator first,           InputIterator last, OutputIterator result,            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 element referred to by iterator i in the range [result + 1, result + (last - first)) a value correspondingly equal to *(first + (i - result)) - *(first + (i - result) - 1) or binary_op (*(first + (i - result)), *(first + (i - result) - 1)). Result gets the value of *first.

Sample Code
/////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // adj_diff.cpp : Demonstrates the use of adjacent_difference // // Description of adjacent_difference(first,last,result) //               adjacent_difference(first,last,result,binary_op): // //   Assigns to every element referred to by iterator i in the range //   [result + 1, result + (last - first)) //    a value correspondingly equal to //    *(first + (i - result)) - *(first + (i - result) - 1) //    or //    binary_op(*(first + (i - result)), *(first + (i - result) - 1)). //    Result gets the value of *first. // // 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 < int, allocator > IntegerArray; typedef ostream_iterator < int, char, char_traits > IntOstreamIt;

void main

{

// an ostream iterator that outputs an int to cout terminated // by a space IntOstreamIt itOstream(cout," ");

// Initialize the array // Suppose that you are taking a trip and can measure // the miles traveled from your city of origin // to the city you are traveling through IntegerArray rgIA; rgIA.push_back(5661); // San Francisco to Berlin rgIA.push_back(7456); // to Cairo rgIA.push_back(10995); // to Calcutta rgIA.push_back(17019); // to Cape Town rgIA.push_back(24394); // to Hong Kong rgIA.push_back(30376); // to London rgIA.push_back(35758); // to Los Angeles

// Print the array copy(rgIA.begin,rgIA.end,itOstream); cout << endl;

// Suppose that you now want the distance between each // of the cities that you traveled to. You can easily // find it with adjacent_difference IntegerArray rgDifferences(7); IntegerArray::iterator itDifferences = rgDifferences.begin; adjacent_difference(rgIA.begin,rgIA.end,itDifferences);

// Print the differences // Remember that the first item in the differences array is   // not a difference, but is unused space cout << "The adjacent differences are: "; copy(rgDifferences.begin+1,rgDifferences.end,itOstream); cout << endl;

// Suppose that you now want to know which adjacent differences // are greater. If you have [a,b,c], you would like [1,0] if a>b // and b<=c. // You are using less rather than greater because // adjacent_difference reverses the parameters. For example, // if a and b are adjacent, adjacent_difference calls // less(b,a). See the explanation at the top of this file // for a more exact description. IntegerArray rgGT(6); IntegerArray::iterator itGT = rgGT.begin; adjacent_difference(rgDifferences.begin+1,                       rgDifferences.end,                        itGT,                        less );

// Print the greater thans // Remember that the first item in the differences array is   // not a difference, but is unused space cout << "Which adjacent distances are greater:" << endl << "(If you have [a,b,c], then you have [1,0] if a>b and b<=c)" << endl; copy(rgGT.begin+1,rgGT.end,itOstream); cout << endl;

} Program Output is: <pre class="fixed_text">5661 7456 10995 17019 24394 30376 35758 The adjacent differences are: 1795 3539 6024 7375 5982 5382 Which adjacent distances are greater: (If you have [a,b,c], then you have [1,0] if a>b and b<=c) 0 0 0 1 1

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