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std::remove_copy, std::remove_copy_if

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< cpp‎ | algorithm
 
 
Algorithm library
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C library
 
Defined in header <algorithm>
template< class InputIt, class OutputIt, class T >

OutputIt remove_copy( InputIt first, InputIt last, OutputIt d_first,

                      const T& value );
(1)
template< class ExecutionPolicy, class InputIt, class OutputIt, class T >

OutputIt remove_copy( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt d_first,

                      const T& value );
(2) (since C++17)
template< class InputIt, class OutputIt, class UnaryPredicate >

OutputIt remove_copy_if( InputIt first, InputIt last, OutputIt d_first,

                         UnaryPredicate p );
(3)
template< class ExecutionPolicy, class InputIt, class OutputIt, class UnaryPredicate >

OutputIt remove_copy_if( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt d_first,

                         UnaryPredicate p );
(4) (since C++17)

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. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Contents

[edit] 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 InputIterator.
-
OutputIt must meet the requirements of OutputIterator.
-
UnaryPredicate must meet the requirements of Predicate.

[edit] Return value

Iterator to the element past the last element copied.

[edit] Complexity

Exactly last - first applications of the predicate.

[edit] 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, std::terminate is called.
  • If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] 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;
}

[edit] Example

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

#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

[edit] See also

removes elements satisfying specific criteria
(function template) [edit]
copies a range of elements to a new location
(function template) [edit]
parallelized version of std::remove_copy
(function template) [edit]
parallelized version of std::remove_copy_if
(function template) [edit]