remove_copy_if

     Algorithm

Move desired elements to the front of a container, and return an iterator that describes where the sequence of desired elements ends.

Contents

• Synopsis
• Description
• Complexity
• Example
• Warning
• See Also

#include <algorithm>

template <class InputIterator,
          class OutputIterator,
          class Predicate>
 OutputIterator remove_copy_if (InputIterator first,
                                InputIterator last,
                                OutputIterator result,
                                Predicate pred);

The remove_copy_if algorithm copies all the elements referred to by the iterator i in the range [first, last) for which the following condition does not hold: pred(*i) == true. remove_copy_if returns the end of the resulting range. remove_copy_if is stable, that is, the relative order of the elements in the resulting range is the same as their relative order in the original range.

Exactly last1 - first1 applications of the corresponding predicate are done.

//
// remove.cpp
//
 #include <algorithm>
 #include <vector>
 #include <iterator>
 #include <iostream.h>
 template<class Arg>
 struct all_true : public unary_function<Arg, bool>
 {
   bool operator() (const Arg&) { return 1; }
 };
 int main ()
 {
   int arr[10] = {1,2,3,4,5,6,7,8,9,10};
   vector<int> v(arr+0, arr+10);
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   //
   // Remove the 7.
   //
   vector<int>::iterator result = remove(v.begin(), v.end(), 7);
   //
   // Delete dangling elements from the vector.
   //
   v.erase(result, v.end());
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   //
   // Remove everything beyond the fourth element.
   //
   result = remove_if(v.begin()+4, v.begin()+8, all_true<int>());
   //
   // Delete dangling elements.
   //
   v.erase(result, v.end());
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   //
   // Now remove all 3s on output.
   // 
   remove_copy(v.begin(), v.end(),                ostream_iterator<int>(cout," "), 3);

   cout << endl << endl;
   //
   // Now remove everything satisfying predicate on output.
   // Should yield a NULL vector.
   //
   remove_copy_if(v.begin(), v.end(),                   ostream_iterator<int>(cout," "),

                  all_true<int>());
 
   return 0;
 }

Output :
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 8 9 10
1 2 3 4
1 2 4

If your compiler does not support default template parameters, then you need to always supply the Allocator template argument. For instance, you will need to write :

vector<int, allocator>

instead of :

vector<int>

remove, remove_if, remove_copy