std::remove_copy,std::remove_copy_if (3) - Linux Manuals

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

NAME

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