Std::remove_copy,std::remove_copy_if (3) Linux Manual Page

std::remove_copy,std::remove_copy_if – std::remove_copy,std::remove_copy_if

Synopsis

Defined in header<algorithm>

    template <class InputIt, class OutputIt, class T>

    OutputIt remove_copy(InputIt first, InputIt last, OutputIt d_first, (until C++ 20)

                                                                            const T &value);

template <class InputIt, class OutputIt, class T>

constexpr OutputIt remove_copy(InputIt first, InputIt last, OutputIt d_first, (since C++ 20)

                                                                                  const T &value);

template <class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class T>

ForwardIt2 remove_copy(ExecutionPolicy &&policy, ForwardIt1 first, ForwardIt1 last, (2)(since C++ 17)

                                                                                        ForwardIt2 d_first,
                       const T &value);
(1)

    template <class InputIt, class OutputIt, class UnaryPredicate>

    OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, (until C++ 20)

                                                                               UnaryPredicate p);

template <class InputIt, class OutputIt, class UnaryPredicate>

constexpr OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, (3)(since C++ 20)

                                                                                     UnaryPredicate p);

template <class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class UnaryPredicate>

ForwardIt2 remove_copy_if(ExecutionPolicy &&policy, ForwardIt1 first, ForwardIt1 last, (4)(since C++ 17)

                                                                                           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. Source and destination ranges cannot overlap.
1) Ignores all elements that are equal to value.
3) Ignores all elements for which predicate p returns true.
2,4) Same as (1,3), but executed according to policy. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last – the range of elements to copy
d_first – the beginning of the destination range.
value – the value of the elements not to copy
policy – the execution policy to use. See execution_policy for details.

Type requirements

–
InputIt must meet the requirements of LegacyInputIterator.
–
OutputIt must meet the requirements of LegacyOutputIterator.
–
ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.
–
UnaryPredicate must meet the requirements of Predicate.

Return value

Iterator to the element past the last element copied.

Complexity

Exactly last – first applications of the predicate.
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

First version

  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;
  }

Second version

  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

The following code outputs a string while erasing the spaces on the fly.
// Run this code

#include <algorithm>

#include <iterator>

#include <string>

#include <iostream>

int main()

{
    std::string str = "Text with some   spaces";
    std::cout << "before: " << str << "\n";
    std::cout << "after:  ";
    std::remove_copy(str.begin(), str.end(),
                     std::ostream_iterator<char>(std::cout), ' ');
    std::cout << '\n';
}

Output:

before: Text with some spaces
after: Textwithsomespaces

std::remove_copy,std::remove_copy_if (3) Linux Manual Page