Microsoft KB Archive/156532

= How to use the remove_if STL function in Visual C++ =

Article ID: 156532

Article Last Modified on 7/22/2005

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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 Q156532

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SUMMARY
The sample code in this article illustrates how to use the remove_if, end, begin, and bind2nd STL functions in Visual C++.

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Prototype
template<class ForwardIterator, class Predicate> inline ForwardIterator remove_if(ForwardIterator first,

ForwardIterator last, Predicate pred) NOTE: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description
The remove_if algorithm removes all elements from the range (first, last) that cause the predicate to return true. It returns an iterator equal to last - N, where N = number of elements removed. The last N elements of the range have undefined values. The size of the container remains the same.

Sample Code
NOTE: The first line in the sample code section is: // Compile options needed: /GX

In VC++ .NET, /EHsc is set by default and is equivalent to /GX. ////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // remove_if.cpp : Illustrates how to use the remove_if function. // // Functions: // //  remove_if - remove all elements from the sequence that //              satisfies a predicate. //  bind2nd - Returns true for elements for which the condition is true //  begin - Returns an iterator that points to the first element in a //           sequence //  end - Returns an iterator that points one past the end of a sequence // // Written by Kalindi Sanghrajka // of Microsoft Product Support Services, // Software Core Developer Support. // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character, // okay to ignore


 * 1) pragma warning(disable: 4786)

// disable warning C4244: possible loss of data, // okay to ignore


 * 1) pragma warning(disable: 4244)


 * 1) include
 * 2) include
 * 3) include
 * 4) include

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

void main

{

const int VECTOR_SIZE = 8 ;

// Define a template class vector of integers typedef vector<int, allocator > IntVector ;

//Define an iterator for template class vector of integer typedef IntVector::iterator IntVectorIt ;

IntVector Numbers(VECTOR_SIZE) ;  //vector containing numbers

IntVectorIt start, end, it, last;

start = Numbers.begin ;  // location of first // element of Numbers

end = Numbers.end ;      // one past the location // last element of Numbers

//Initialize vector Numbers Numbers[0] = 10 ; Numbers[1] = 20 ; Numbers[2] = 10 ; Numbers[3] = 15 ; Numbers[4] = 12 ; Numbers[5] = 7 ; Numbers[6] = 9 ; Numbers[7] = 10 ;

cout << "Before calling remove_if" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// remove all elements from Numbers that <= 10 last = remove_if(start, end, bind2nd(less_equal, 10) ) ;

cout << "After calling remove_if" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ;

//print number of elements removed from Numbers cout << "Total number of elements removed from Numbers = " << end - last << endl ;

//print only the valid elements of Number cout << "Valid elements of Numbers { " ; for(it = start; it != last; it++) cout << *it << " " ; cout << " }\n" << endl ;

} Program output follows: <pre class="fixed_text">Before calling remove_if Numbers { 10 20 10 15 12 7 9 10 }

After calling remove_if Numbers { 20 15 12 15 12 7 9 10 }

Total number of elements removed from Numbers = 5 Valid elements of Numbers { 20 15 12 }

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