std::remove_copy, std::remove_copy_if

template< class InputIt, class OutputIt, class T >
OutputIt remove_copy( InputIt first, InputIt last,
                      OutputIt d_first, const T& value );

template< class InputIt, class OutputIt, class T >
constexpr OutputIt remove_copy( InputIt first, InputIt last,
                                OutputIt d_first, const T& value );

template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class T >
ForwardIt2 remove_copy( ExecutionPolicy&& policy,
                        ForwardIt1 first, ForwardIt1 last,
                        ForwardIt2 d_first, const T& value );

template< class InputIt, class OutputIt, class UnaryPredicate >
OutputIt remove_copy_if( InputIt first, InputIt last,
                         OutputIt d_first, UnaryPredicate p );

template< class InputIt, class OutputIt, class UnaryPredicate >
constexpr OutputIt remove_copy_if( InputIt first, InputIt last,
                                   OutputIt d_first, UnaryPredicate p );

template< class ExecutionPolicy, class ForwardIt1,
          class ForwardIt2, class UnaryPredicate >
ForwardIt2 remove_copy_if( ExecutionPolicy&& policy,
                           ForwardIt1 first, ForwardIt1 last,
                           ForwardIt2 d_first, UnaryPredicate p );

Copies elements from the range [first, last), to another range beginning at d_first, omitting the elements which satisfy specific criteria.

If source and destination ranges overlap, the behavior is undefined.

Parameters

Return value

Iterator to the element past the last element copied.

Complexity

Given N as std::distance(first, last):

For the overloads with an ExecutionPolicy, there may be a performance cost if ForwardIt1's value_type is not MoveConstructible.

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

template<class InputIt, class OutputIt, class T>
OutputIt remove_copy(InputIt first, InputIt last, OutputIt d_first, const T& value)
{
    for (; first != last; ++first)
        if (!(*first == value))
            *d_first++ = *first;
    return d_first;
}

template<class InputIt, class OutputIt, class UnaryPredicate>
OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, UnaryPredicate p)
{
    for (; first != last; ++first)
        if (!p(*first))
            *d_first++ = *first;
    return d_first;
}

Example

#include <algorithm>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <string>
 
int main()
{
    std::string str = "#Return #Value #Optimization";
    std::cout << "before: " << std::quoted(str) << '\n';
 
    std::cout << "after:  \"";
    std::remove_copy(str.begin(), str.end(),
                     std::ostream_iterator<char>(std::cout), '#');
    std::cout << "\"\n";
}

before: "#Return #Value #Optimization"
after:  "Return Value Optimization"

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also