Apache C++ Standard Library Reference Guide

## remove_copy()

Library: Algorithms

    Function

- Local Index
- Summary
- Synopsis
- Description
- Complexity
- Example
- See Also
- Standards Conformance

### Local Index

No Entries

### Summary

Algorithm that copies all elements other than those that compare equal to a given value from one range to another

### Synopsis

    #include <algorithm>

    namespace std {
      template <class InputIterator,
                class OutputIterator,
                class T>
      OutputIterator remove_copy(InputIterator start,
                                 InputIterator finish,
                                 OutputIterator result,
                                 const T& value);
    }

### Description

The `remove_copy()` algorithm copies all the elements referred to by the iterator `i` in the range `[start, finish)` for which the following corresponding condition does not hold: `*i == value`. `remove_copy()` returns an iterator that points to the end of the destination range. `remove_copy()` is stable, which means that the relative order of the elements in the resulting range is the same as their relative order in the original range. The elements in the original sequence are not altered by `remove_copy()`.

### Complexity

Exactly `finish - start` applications of the corresponding predicate are done.

### Example

    //
    //  remove.cpp
    //

    #include <algorithm>    // for copy, remove, remove_copy, remove_if
    #include <functional>   // for unary_function
    #include <iostream>     // for cout, endl
    #include <iterator>     // for ostream_iterator
    #include <vector>       // for vector

    template<class Arg>
    struct not_zero: public std::unary_function<Arg, bool>
    {
        bool operator() (const Arg &a) const {
            return a != 0;
        }
    };

    int main ()
    {
        // For convenience.
        typedef std::vector<int, std::allocator<int> > Vector;
        typedef std::ostream_iterator<int, char,
                                      std::char_traits<char> >
                Iter;

        // Populate a vector with elements from an array.
        const Vector::value_type arr[] = { 1, 2, 3, 4, 5,
                                           6, 7, 8, 9, 10};
        Vector v (arr + 0, arr + sizeof arr / sizeof *arr);

        // Write out the contents to cout.
        std::copy (v.begin (), v.end (), Iter (std::cout," "));
        std::cout << std::endl << std::endl;

        // Move the 7 to the end of the vector.
        Vector::iterator result = std::remove (v.begin (),
                                               v.end (), 7);

        // Delete the 7 from the vector.
        v.erase (result, v.end ());

        std::copy (v.begin (), v.end (), Iter (std::cout, " "));
        std::cout << std::endl << std::endl;

        // Remove all non-zero elements beyond the fourth element.
        v.erase (std::remove_if (v.begin () + 4, v.end (),
                                 not_zero<int> ()), v.end ());

        std::copy (v.begin (), v.end (), Iter (std::cout, " "));
        std::cout << std::endl << std::endl;

        // Now remove all 3s on output.
        std::remove_copy (v.begin (), v.end (),
                          Iter (std::cout, " "), 3);
        std::cout << std::endl << std::endl;

        // Now remove everything satisfying predicate on output.
        std::remove_copy_if (v.begin (), v.end (),
                             Iter (std::cout, " "),
                             not_zero<int>());

        // Return 0 on success, a non-zero value on failure
        return !!v.empty ();
    }

    Program 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

### See Also

`remove()`, `remove_if()`, `remove_copy_if()`

### Standards Conformance

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.7