Difference between revisions of "cpp/algorithm/remove copy"

Revision as of 13:54, 23 April 2024

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

If *d_first = *first is invalid(until C++20)*first is not writable to d_first(since C++20), the program is ill-formed.

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

Parameters

Return value

Iterator to the element past the last element copied.

Complexity

Given \(\scriptsize N\)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>
constexpr //< since C++20
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 UnaryPred>
constexpr //< since C++20
OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, UnaryPred 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