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remove_if (STL Samples) 

Illustrates how to use the remove_if Standard Template Library (STL) function in Visual C++.


template<class ForwardIterator, class Predicate> inline
   ForwardIterator remove_if(
      ForwardIterator First,
      ForwardIterator Last,
      Predicate Pred
   )

NoteNote

The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

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.

// remove_if.cpp
// compile with: /EHsc
// 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
//////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;


int main()
{
    const int VECTOR_SIZE = 8 ;

    // Define a template class vector of integers
    typedef vector<int > 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<int>(), 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 ;

}

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  }

Header: <algorithm>

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