STL Sample for the remove_if Function

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

SUMMARY

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

MORE INFORMATION

Required Header

<algorithm>

Prototype

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

                             ForwardIterator last,
                             Predicate pred)

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

//////////////////////////////////////////////////////////////////////
//
// 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

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

void main()

    const int VECTOR_SIZE = 8 ;

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

Program output follows:

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 }

REFERENCES

Visual C++, version 4.2, Visual C++ Books Online; click Visual C++ Books, C/C++, and then Standard C++ Library Reference.